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Atmospheric Environment (v.59, #)

Editorial board (pp. i).

Seasonal and spatial variations of individual organic compounds of coarse particulate matter in the Los Angeles Basin by Kalam Cheung; Michael R. Olson; Brandon Shelton; James. J. Schauer; Constantinos Sioutas (pp. 1-10).

To study the organic composition of ambient coarse particulate matter (CPM; 2.5–10 μm), coarse particles were collected one day a week from April 2008 to March 2009 at 10 sampling sites in the Los Angeles Basin. Samples were compiled into summer (June 2008 to September 2008) and winter (November 2008 to February 2009) composites, and were subsequently analyzed for individual organic constituents using gas chromatography-mass spectrometry. n-alkanoic acids and medium molecular weight (MW) n-alkanes (C25 to C35) – the major constituents in the coarse size fraction – showed good associations with crustal materials. Polycyclic aromatic hydrocarbons (PAHs) and hopanes (both in low concentrations), as well as high MW n-alkanes (C37 and C38), were associated with traffic-related emissions. In the summer, when prevailing onshore winds were strong, the downwind/rural sites had higher concentrations of PAHs, n-alkanes and n-alkanoic acids. An opposite trend was observed at the urban sites, where the levels of PAHs, n-alkanes and n-alkanoic acids were higher in the winter, when the low wind speed limited long-range atmospheric transport. In general, the contribution of organic compounds to CPM mass was higher during wintertime, due to a reduction in the fraction of other CPM components (sea salt, secondary ions, etc.) and/or the increase in source strengths of organic compounds. The latter is consistent with the traffic-induced re-suspension of mineral and road dust, as previously observed in this basin. Overall, our results suggest that emissions from natural sources (soil and associated biota) constitute the majority of the organic content in coarse particles, with a more pronounced influence in the semi-rural/rural areas in Riverside/Lancaster compared with urban Los Angeles in the summer.► We examine the organic composition of ambient coarse particulate matter. ► Emissions from natural sources constitute the majority of the organic content in coarse particles. ► The predominant organic constituents correlated with crustal materials. ► PAHs, hopanes, and high MW n-alkanes were associated with traffic-related emissions.

Keywords: Coarse particle; Coarse particulate matter; Organic compounds; Organic composition; Mineral and road dust; Los Angeles Basin

Long-term atmospheric visibility trend in Southeast China, 1973–2010 by Junjun Deng; Ke Du; Kai Wang; Chung-Shin Yuan; Juanjuan Zhao (pp. 11-21).

Particulate matter (PM) pollution in Southeast China has been worsening because of the rapid industrial development and urbanization, which have significant negative effects on atmospheric visibility. Characterization of the trend in atmospheric visibility is important for evaluating the impact of PM pollution on the impairment of visual air quality in urban and rural areas. Long-term trend in atmospheric visibility in Southeast China was analyzed for the period of 1973–2010 based on the meteorological data from the National Climatic Data Center (NCDC) database using four statistical methods: annual mean visibility, percentages of “very good” visibility and “bad” visibility, ridit analysis, and cumulative percentiles. The relationship of atmospheric extinction with Air Pollution Index (API) was studied. In addition, the effects of recent environment policies on visibility were studied. The results showed that the visibility had decreased in 94% stations of this region and prefecture stations had the highest decreasing trend of −3.1 km/decade during the entire period. The average visibility of all the 17 stations (i.e., region-average) declined at a rate of −2.0 km/decade, with a 38-year average of 18.1 km. Decrease in the percentage of “very good” visibility and increase in the percentage of “bad” visibility existed in 14 and 16 stations, respectively. Region-average percentage of “bad” visibility was in the range of 2.2–21.5%, with an increasing rate of 5.0% per decade, and that of “very good” visibility was 24.4–71.8%, with a decreasing rate of −10.7% per decade. During the entire period, county and prefecture stations had similar changing patterns and trends in visibility, while town stations had the least worsening trends. Region-average visibility was better before 1988 while worse after 1993 when comparing to the entire period, with the transition period of 1988–1993. The worst 20%, 50% and best 20% of region-average visibility declined at a rate of −1.6, −2.0 and −2.4 km/decade, with the average of 13.1, 17.8 and 23.0 km, respectively. During 2000–2010, the daily dry extinction coefficients were positively correlated with API with linear R² values of 0.42 and 0.43 for Xiamen and Shantou, respectively, suggesting that the air pollution could be responsible for the visibility impairment in Southeast China. Analysis on the effects of recent policies suggested that visibility change was significantly positively correlated with environment treatment variables including Removed Industrial SO₂ (RISO2), Total Investment in Environmental Pollution Control (TIEPC), Area of Green Space (AGS) and Removed Industrial Dust (RID), but significantly negatively correlated with Emission of Industrial Dust (EID). Time-lag effect on the contribution of TIEPC to visibility was found. It is suggested that continuous and effective pollution control strategy, particularly increasing investment in environment control and pollutant emission reduction, is needed to counteract the degradation of atmospheric visibility in Southeast China.► Long-term atmospheric visibility trend in Southeast China was analyzed. ► Significant decreasing trend was found. ► The relationship of extinction coefficient with air pollution was presented. ► We evaluated the effects of recent environmental policies on visibility change. ► Time-lag effect of investment on environment pollution control was found.

Keywords: Atmospheric visibility; Visibility trend; Southeast China; Ridit analysis; Environmental policy

Long-term atmospheric visibility trend in Southeast China, 1973–2010 by Junjun Deng; Ke Du; Kai Wang; Chung-Shin Yuan; Juanjuan Zhao (pp. 11-21).

Keywords: Atmospheric visibility; Visibility trend; Southeast China; Ridit analysis; Environmental policy

Long-term atmospheric visibility trend in Southeast China, 1973–2010 by Junjun Deng; Ke Du; Kai Wang; Chung-Shin Yuan; Juanjuan Zhao (pp. 11-21).

Keywords: Atmospheric visibility; Visibility trend; Southeast China; Ridit analysis; Environmental policy

Identifying the effect of vehicle operating history on vehicle running emissions by Huan Liu; Matthew Barth (pp. 22-29).

This research aims to determine the overall effects that a vehicle's short-term operating history has on its subsequent emissions, and how Vehicle Specific Power (VSP)-based vehicle emission models could be improved to account for these effects. Current VSP-based emission models, such as the U.S. EPA's MOtor Vehicle Emission Simulator (MOVES), only predict emissions based on instantaneous vehicle activity and the corresponding VSP value; the past short-term vehicle operational activity is not taken into account (e.g., the last 10–20 s of operation). For example, instantaneous vehicle emissions could be affected by a hard acceleration vs. a deceleration event at that particular point in time. This paper attempts to determine the accuracy of VSP-based emission models, which may suffer due to the fact that the history effects are being overlooked.A number of experiments were carried out in order to determine the anomalies resulting from instantaneous estimation as opposed to taking short-term vehicle operating history into account. These experiments compare model estimates with actual emission measurements. A quantitative analysis shows that the higher power operating modes (such as modes 33, 35, 37, 38, and 40 in MOVES) had the greatest variability – sometimes in the range of 60–100% – due to the effects that vehicle operating history has on carbon monoxide (CO). Hydrocarbons (HC) in higher power operating modes also vary 40–60% depending on the driving cycle. For lower power operating modes (e.g., MOVES modes 1–30), the uncertainty for all pollutants was significantly less. It was also established that the carbon dioxide (CO₂) and nitrogen oxide (NO_x) estimations conducted by MOVES were least affected by the vehicle operational history effects compared with other emissions. As such, MOVES emission results are more accurate for mild to normal driving cycles, but there is greater uncertainty for higher power driving cycles.► We compared dynamometer tested vehicle emission pattern with MOVES project-level simulated pattern. ► The history effect of vehicle running does indeed change emissions. ► The VSP-based model predicts emissions without taking history effects into account. ► The higher the power, the greater variability of emissions due to the history effect.

Keywords: Vehicle emissions; Operating history effects; Vehicle-specific power; MOVES; Driving cycle

Identifying the effect of vehicle operating history on vehicle running emissions by Huan Liu; Matthew Barth (pp. 22-29).

Keywords: Vehicle emissions; Operating history effects; Vehicle-specific power; MOVES; Driving cycle

Identifying the effect of vehicle operating history on vehicle running emissions by Huan Liu; Matthew Barth (pp. 22-29).

Keywords: Vehicle emissions; Operating history effects; Vehicle-specific power; MOVES; Driving cycle

Statistical analysis of 4-year observations of aerosol sizes in a semi-rural continental environment by Vijay P. Kanawade; David R. Benson; Shan-Hu Lee (pp. 30-38).

We have made long-term observations of particle size distributions in a semi-rural continental environment of the United States (Kent, Ohio) over a 4-year period, to investigate the seasonal trend of new particle formation (NPF). NPF events occurred throughout the year, but more frequently during the spring (∼40%) and fall (∼32%) than in the summer (∼19%) and winter (∼17%). The particle nucleation rates were also highest in the spring (with the median and standard deviation value of 6.8 ± 1.3 cm⁻³ s⁻¹) and lowest in the winter (1.0 ± 0.9 cm⁻³ s⁻¹). Particle growth rates were highest in the summer (6.4 ± 0.4 nm h⁻¹) and lowest in the winter (4.2 ± 0.3 nm h⁻¹), a trend different from nucleation rates, indicating that different chemical species may be involved in particle nucleation and growth processes. Backward trajectory calculations show that NPF events were often associated with air masses originated from the east–southeast where numerous large size power plants are located, containing high sulfur dioxide (SO₂). The NPF events in general had lower relative humidity, lower surface area of pre-existing particles, and higher solar radiation.► We provide long-term observations of new particle formation in a semi-rural continental environment of the U.S. ► Seasonal frequency of new particle formation is higher in the spring and fall than in summer and winter. ► Nucleation and growth rates show different seasonal variations. ► The frequent occurrence of new particle formation is related to the transported air masses from polluted power plants.

Keywords: Ultrafine particles; Particle size distribution; Nucleation; Growth; Air mass history

Statistical analysis of 4-year observations of aerosol sizes in a semi-rural continental environment by Vijay P. Kanawade; David R. Benson; Shan-Hu Lee (pp. 30-38).

Keywords: Ultrafine particles; Particle size distribution; Nucleation; Growth; Air mass history

Statistical analysis of 4-year observations of aerosol sizes in a semi-rural continental environment by Vijay P. Kanawade; David R. Benson; Shan-Hu Lee (pp. 30-38).

Keywords: Ultrafine particles; Particle size distribution; Nucleation; Growth; Air mass history

Commuters' exposure to PM₁ by common travel modes in Shanghai by Qi Yu; Yi Lu; Shan Xiao; Junxiu Shen; Xun Li; Weichun Ma; Limin Chen (pp. 39-46).

A study on commuter's exposure to PM₁ in Shanghai was presented. Commuters' real-time exposure concentrations by the common travel modes (bus, walking, cycling, taxi and subway) were measured by DustTrak™ dust monitors, and the average exposure concentrations and inhalation doses were analyzed. The lengths of the routes were designed to be within 30-min walking distance. The average PM₁ exposure concentrations during commuting were 0.147 ± 0.092 mg m⁻³, 0.145 ± 0.088 mg m⁻³, 0.140 ± 0.086 mg m⁻³, 0.139 ± 0.086 mg m⁻³ and 0.122 ± 0.077 mg m⁻³ for the bus, walking, cycling, taxi and subway trips respectively. The concentrations in the microenvironments were 0.147 ± 0.096 mg m⁻³, 0.155 ± 0.098 mg m⁻³, 0.142 ± 0.092 mg m⁻³ and 0.079 ± 0.051 mg m⁻³ for the bus station, bus, taxi and train respectively. The concentrations in the microenvironments were close to those in Guangzhou and higher compared to the results in London, Sydney, Florence, etc. The combined effect of exposure concentration, travel time and inhalation rate led to different inter-mode relationship of inhalation doses compared to that of exposure concentrations. The inhalation doses were 54.5 ± 38.9 μg, 45.2 ± 30.1 μg, 29.2 ± 25.4 μg, 28.6 ± 25.9 μg and 12.8 ± 13.4 μg for the cycling, walking, bus, subway and taxi trips respectively. The outdoor fractions of the inhalation doses by bus, taxi and subway were much higher than the indoor fractions.► Commuters in Shanghai were exposed to a high level of fine particulate matters. ► The exposure level in bus was the highest among the concerned modes. ► The doses by bike or by walking were higher compared to those by other modes. ► The outdoor inhala dose fraction was much higher than the indoor fractions.

Keywords: Particulate matter; Exposure; Road traffic; Travel mode; ShanghaiAbbreviations; AEC; average exposure concentration; MAEC; the mean value of the AEC data for several trips; OFCTS; Office of the Fourth Comprehensive Traffic Survey of Shanghai; SMBS; Shanghai Municipal Bureau of Statistics; USEPA; US Environmental Protection Agency

Commuters' exposure to PM₁ by common travel modes in Shanghai by Qi Yu; Yi Lu; Shan Xiao; Junxiu Shen; Xun Li; Weichun Ma; Limin Chen (pp. 39-46).

One way coupling of CMAQ and a road source dispersion model for fine scale air pollution predictions by Sean D. Beevers; Nutthida Kitwiroon; Martin L. Williams; David C. Carslaw (pp. 47-58).

In this paper we have coupled the CMAQ and ADMS air quality models to predict hourly concentrations of NO_X, NO₂ and O₃ for London at a spatial scale of 20 m × 20 m. Model evaluation has demonstrated reasonable agreement with measurements from 80 monitoring sites in London. For NO₂ the model evaluation statistics gave 73% of the hourly concentrations within a factor of two of observations, a mean bias of −4.7 ppb and normalised mean bias of −0.17, a RMSE value of 17.7 and an r value of 0.58. The equivalent results for O₃ were 61% (FAC2), 2.8 ppb (MB), 0.15 (NMB), 12.1 (RMSE) and 0.64 ( r). Analysis of the errors in the model predictions by hour of the week showed the need for improvements in predicting the magnitude of road transport related NO_X emissions as well as the hourly emissions scaling in the model. These findings are consistent with recent evidence of UK road transport NO_X emissions, reported elsewhere. The predictions of wind speed using the WRF model also influenced the model results and contributed to the daytime over prediction of NO_X concentrations at the central London background site at Kensington and Chelsea. An investigation of the use of a simple NO–NO₂–O₃ chemistry scheme showed good performance close to road sources, and this is also consistent with previous studies. The coupling of the two models raises an issue of emissions double counting. Here, we have put forward a pragmatic solution to this problem with the result that a median double counting error of 0.42% exists across 39 roadside sites in London. Finally, whilst the model can be improved, the current results show promise and demonstrate that the use of a combination of regional scale and local scale models can provide a practical modelling tool for policy development at intergovernmental, national and local authority level, as well as for use in epidemiological studies.► We coupled the CMAQ and ADMS air quality models. ► We predicted hourly NO_X, NO₂ and O₃ in London at 20 m × 20 m. ► Model evaluation has demonstrated reasonable agreement with 80 monitoring sites in London. ► Improvements are required in predicting the magnitude of road transport NO_X emissions. ► The combination of regional and local scale models is a practical modelling tool.

Keywords: Road source modelling; CMAQ; Air quality; Model evaluation; London

One way coupling of CMAQ and a road source dispersion model for fine scale air pollution predictions by Sean D. Beevers; Nutthida Kitwiroon; Martin L. Williams; David C. Carslaw (pp. 47-58).

Keywords: Road source modelling; CMAQ; Air quality; Model evaluation; London

One way coupling of CMAQ and a road source dispersion model for fine scale air pollution predictions by Sean D. Beevers; Nutthida Kitwiroon; Martin L. Williams; David C. Carslaw (pp. 47-58).

Keywords: Road source modelling; CMAQ; Air quality; Model evaluation; London

Importance of monoterpenes and isoprene in urban air in northern Europe by H. Hellén; T. Tykkä; H. Hakola (pp. 59-66).

The sources, concentration levels and potential effects of isoprene and the monoterpenes on local atmospheric chemistry were studied in urban background air in Helsinki, Finland. Ambient air concentration measurements were conducted using an in-situ gas chromatograph with a mass spectrometer at an urban background station during different seasons in 2011.The highest concentrations of isoprene and monoterpenes were measured in summer (990 ng m⁻³), but concentrations were also clearly above the detection limit in winter (230 ng m⁻³). The concentrations of aromatic hydrocarbons were higher during all seasons, but when viewed in terms of reactivity-scaled concentrations the data showed that also isoprene and monoterpenes have a strong influence on local atmospheric chemistry in urban air. While they explain 71% of the potential hydroxyl radical reactivity of air masses in summer, they still explain 32% of the reactivity also in winter.In winter and spring the urban background concentrations were higher than at a forested site in Finland, indicating anthropogenic sources of isoprene and monoterpenes. Source estimates obtained with the Unmix multivariate receptor model showed that traffic and wood combustion are the main local contributors to the measured concentration levels in winter, spring and November, but in July and October biogenic sources are dominant.► Urban concentrations of monoterpenes are sometimes higher than at a forested site. ► Isorpene and monoterpenes have an important effect on reactivity in urban air. ► Monoterpenes have also anthropogenic sources.

Keywords: Air quality; Monoterpenes; Isoprene; Urban air; Receptor modeling; BVOCs

Importance of monoterpenes and isoprene in urban air in northern Europe by H. Hellén; T. Tykkä; H. Hakola (pp. 59-66).

Keywords: Air quality; Monoterpenes; Isoprene; Urban air; Receptor modeling; BVOCs

Importance of monoterpenes and isoprene in urban air in northern Europe by H. Hellén; T. Tykkä; H. Hakola (pp. 59-66).

Keywords: Air quality; Monoterpenes; Isoprene; Urban air; Receptor modeling; BVOCs

Integration of population mobility in the evaluation of air quality measures on local and regional scales by S. Dhondt; C. Beckx; B. Degraeuwe; W. Lefebvre; B. Kochan; T. Bellemans; L. Int Panis; C. Macharis; K. Putman (pp. 67-74).

By focussing on air pollutant concentration levels only, the variation in population mobility is not taken into account when assessing the exposure. Transportation policies have an impact on both concentration levels and mobility patterns. The impact of a fuel price increase policy on population exposure to elemental carbon (EC) was evaluated and compared to the base scenario (current situation), taking into account time-activity patterns – including time in commute. We assessed the effect on exposure of both the change in concentrations and whereabouts. The decrease in exposure due to the fuel price increase using residential information only was limited to areas near highways and urban centres. Integrating population movement, exposures to EC were higher and the decrease in exposure was no longer limited to areas near traffic hotspots. For inhabitants of urban areas, the exposure integrating time-activity patterns was more similar to the residential exposure, as they spent more time in their own neighbourhood. For people living further away from traffic hotspots, the estimated impact of the policy was higher than expected for residential exposure. These people profited both from the higher decrease in concentrations at their work/shop/leisure destinations in more urban areas and, as they have to travel longer, also had a larger gain from the high decrease in concentrations during transport. Therefore, the impact of changing concentrations is underestimated when using residential exposure only. These results show the importance of taking into activity-travel patterns when planning future actions.► Population movement was integrated in the evaluation of a policy on EC exposure. ► Using residential exposure, decrease in concentrations was limited to major roads. ► Including population movement, a larger decrease in EC exposure was seen. ► Largest differences between exposure approaches were seen for non-urban areas. ► Concentrations at non-home based activities and in transport affect exposure.

Keywords: Elemental carbon; Time-activity; Exposure modelling; Scenario analysis; Traffic

Predicting velocities and turbulent momentum exchange in isolated street canyons by T.C. Hall; R.E. Britter; L.K. Norford (pp. 75-85).

A simplified way of studying the transport of mass and momentum through dense neighborhoods is to consider the flow field as a combination of a mainly horizontal flow along street canyons and a vertical flow into and out of street canyons. In this paper, we derive a simple, semi-analytical model for calculating the expected wind speeds in narrow, isolated, idealized street canyons of uniform height that are aligned with and at an angle to the wind through the introduction of a non-dimensional parameterization of the vertical turbulent exchange of horizontal momentum between the urban canopy layer (UCL) and the urban boundary layer (UBL). The model is closed and evaluated using computational fluid dynamics (CFD) in a generic way. The RMSE of the normalized bulk velocity in the street canyon in the direction of the freestream flow is 1.8 × 10⁻⁴, 2.3 × 10⁻² and 9.4 × 10⁻² for variations in façade roughness, aspect ratio and canyon orientation, respectively.We argue that there is a need for a fast, simple methodology to assess the impact of urban form on neighborhood microclimate, especially in dense neighborhoods, and specifically for use in the early phases of design. This methodology should be able to predict areas in a neighborhood that are prone to low wind speeds or weak mass and momentum exchange rates with the UBL above because these areas may be particularly susceptible to pollutant retention and the urban heat island (UHI) effect. Current methodologies are often inadequate for this purpose because they use computationally intensive techniques to solve for flow through a neighborhood and often require a strong technical background to support their use. The work in this paper addresses this problem for an idealized, narrow street canyon, and we discuss the need for parameterizations for urban form that are relevant to mass and momentum exchange rates to extend this model beyond a single street canyon. Finally, we discuss how this work could be further developed into generalized planning guidelines and incorporated into a comprehensive urban planning methodology that aims to passively mitigate the UHI effect and pollutant retention through the clever design of urban form.► We derive a semi-analytical model to predict velocities in ideal street canyons. ► We parameterize the turbulent momentum exchange using plume entrainment theory. ► Aspect ratio, façade roughness and orientation to the wind affect these values. ► The model is evaluated using computational fluid dynamics in a generic way. ► The exchange velocity can be used to calculate heat and species fluxes.

Keywords: Street canyons; Turbulent momentum exchange; Urban airflow; Exchange velocity; Exchange coefficient

Predicting velocities and turbulent momentum exchange in isolated street canyons by Terianne C. Hall; Rex E. Britter; Leslie K. Norford (pp. 75-85).

Keywords: Street canyons; Turbulent momentum exchange; Urban airflow; Exchange velocity; Exchange coefficient

Predicting velocities and turbulent momentum exchange in isolated street canyons by Terianne C. Hall; Rex E. Britter; Leslie K. Norford (pp. 75-85).

Keywords: Street canyons; Turbulent momentum exchange; Urban airflow; Exchange velocity; Exchange coefficient

Oxidation of gaseous elemental mercury in the presence of secondary organic aerosols by A.P. Rutter; K.M. Shakya; R. Lehr; J.J. Schauer; R.J. Griffin (pp. 86-92).

Gaseous elemental mercury (GEM; Hg⁰_(g)) was oxidized by ozone and secondary hydroxyl radicals generated by the chemistry associated with the formation of secondary organic aerosols. The reaction was investigated in a 9-m³ Teflon^® batch reactor.The losses of GEM in ozone-only experiments compared well with numerical model predictions based on published reaction rates, and a second order rate analysis gave a reaction rate of (7.4 ± 0.5) × 10⁻¹⁹ cm³ molecules⁻¹ s⁻¹, which was statistically indistinct from recent publications. Furthermore, the net oxidation of GEM observed in the SOA reaction system agreed well with a numerical model based on the GEM-ozone reaction rate determined in this study and a published GEM-OH oxidation rate.Recent modeling studies of mercury atmospheric cycling have found that use of laboratory-based GEM-ozone reaction rate coefficients caused overestimation of GEM oxidation, while theoretical studies cast doubt over the viability of the GEM-ozone oxidation reaction in the real atmosphere. The results presented here suggest that the reaction is viable in the atmosphere and that recent published reaction rates for GEM and ozone are pertinent for use in atmospheric models. An average of GEM-ozone rates determined during this and recent studies was 6.9 ± 0.9 × 10⁻¹⁹ cm³ molecules⁻¹ s⁻¹. This value is recommended for use in future modeling studies.► Gaseous elemental mercury was oxidized by ozone amidst secondary organic aerosol. ► Observed GEM oxidation corroborated published rate coefficients. ► Numerical model simulations compared well to the observed GEM oxidation. ► Study results indicate the GEM-ozone reaction pathway to be viable in the atmosphere.

Keywords: Mercury; Ozone; Secondary organic aerosol; Oxidation; Dry deposition; Residence time; Chamber

Oxidation of gaseous elemental mercury in the presence of secondary organic aerosols by A.P. Rutter; K.M. Shakya; R. Lehr; J.J. Schauer; R.J. Griffin (pp. 86-92).

Keywords: Mercury; Ozone; Secondary organic aerosol; Oxidation; Dry deposition; Residence time; Chamber

Oxidation of gaseous elemental mercury in the presence of secondary organic aerosols by A.P. Rutter; K.M. Shakya; R. Lehr; J.J. Schauer; R.J. Griffin (pp. 86-92).

Keywords: Mercury; Ozone; Secondary organic aerosol; Oxidation; Dry deposition; Residence time; Chamber

Comparison of the predicted concentration of outdoor originated indoor polycyclic aromatic hydrocarbons between a kinetic partition model and a linear instantaneous model for gas–particle partition by Shanshan Shi; Bin Zhao (pp. 93-101).

Polycyclic aromatic hydrocarbons (PAHs) of outdoor origin can enter indoor environment via infiltration or ventilation, and lead to human exposure. This study presents a kinetic partition model for the prediction of indoor PAH concentrations that are of outdoor origin. The model was verified with the previous published measurement conducted in a chamber. Indoor gas-phase, particle-phase and airborne concentrations (the sum of the gas- and particle-phases concentrations) of 16 species of PAHs listed by United States Environmental Protection Agency (EPA) as priority pollutants were calculated over a two-year period by the kinetic partition model. The predicted concentrations were compared with those calculated using a simple linear instantaneous model. Uncertainty in the differences between the predicted results by these two models caused by uncertain parameters was further conducted. For some PAHs, remarkable differences existed between the predicted indoor gas- and particle-phases concentrations of outdoor originated PAHs by the kinetic partition model and by the linear instantaneous model. The average relative differences of gas-phase PAHs ranged from 3.60 × 10⁻⁶ to 6.31 × 10¹ while those of particle-phase PAHs were between 5.47 × 10⁻² and 9.15 × 10⁻¹. However, there was no obvious average relative difference between the predicted airborne concentrations, which maximized to 6.52 × 10⁻². The average relative differences for both the gas- and particle-phases PAHs were even larger when particle deposition rate was at its maximum.► A kinetic partition model to predict indoor PAHs of outdoor origin was proposed. ► The model was verified by measured data and compared with a simple model. ► Results may guide model selection to predict/analyse indoor PAHs of outdoor origin.

Keywords: PAHs; SVOCs; Kinetic partition model; Linear instantaneous model; Exposure; Particle; Indoor air quality

Attributing ozone to NO_x emissions: Implications for climate mitigation measures by Volker Grewe; Katrin Dahlmann; Sigrun Matthes; Wolfgang Steinbrecht (pp. 102-107).

Emissions of nitrogen oxides (NO_x) lead to formation of ozone, which is an important greenhouse gas. Despite its relevance, little emphasis was previously given on verifying approaches to calculate contributions of individual emissions to ozone and hence to climate change. Basically two methods (perturbation method and tagging method) were used in the past. We demonstrate that both methods are valid and have their area of application, but only tagging calculates contributions of emissions to concentrations, whereas the perturbation method identifies changes in the ozone concentrations due to emission changes. Our results show that the contribution of road traffic emissions to climate change is underestimated by a factor of 5 in the perturbation method. This is caused by non-linear compensating effects from other emission sectors, which are concealed in the perturbation method but disclosed with tagging. Consequently, the effectiveness of mitigation measures for individual sectors (i.e. concentrating on road traffic induced ozone) is only correctly expressed by the tagging method. The perturbation method provides accurately the total impact (i.e. total ozone) of a mitigation measure. However, current approaches, which evaluate the effectiveness of a mitigation measure based on the perturbation approach, do not reflect changes in the chemical state of the atmosphere (i.e. ozone production rates). These largely affect the effectiveness of subsequent measures and hence make the evaluation of the effectiveness of two measures dependent on their chronology of application. We show that also in this regard, the tagging method is better suited to evaluate the effectiveness of a mitigation measure than the perturbation method.► We calculate contribution of NO_x emissions to ozone concentrations. ► The perturbation method largely underestimates the road traffic contribution to ozone. ► Combination of perturbation and tagging methods improves understanding. ► We propose to use the tagging method to evaluate mitigation measures.

Keywords: NO; _x; emissions; Climate change mitigation; Ozone chemistry; Tagging

Attributing ozone to NO_x emissions: Implications for climate mitigation measures by Volker Grewe; Katrin Dahlmann; Sigrun Matthes; Wolfgang Steinbrecht (pp. 102-107).

Keywords: NO; _x; emissions; Climate change mitigation; Ozone chemistry; Tagging

Attributing ozone to NO_x emissions: Implications for climate mitigation measures by Volker Grewe; Katrin Dahlmann; Sigrun Matthes; Wolfgang Steinbrecht (pp. 102-107).

Keywords: NO; _x; emissions; Climate change mitigation; Ozone chemistry; Tagging

Seasonal and altitudinal variations of legacy and current-use pesticides in the Brazilian tropical and subtropical mountains by Rodrigo Ornellas Meire; Sum Chi Lee; Yuan Yao; Admir C. Targino; João Paulo M. Torres; Tom Harner (pp. 108-116).

Polyurethane foam (PUF) disk passive air samplers were deployed over summer (December–March) and winter (June–August) periods in 2007–2008 along altitudinal gradients in Brazilian southeastern and southern mountain regions. As part of the Global Atmospheric Passive Sampling (GAPS) Network, this work was initiated to address the lack of knowledge on the fate of legacy and current-use pesticides in South America, particularly in mountainous regions. Of the pesticides measured, concentrations in air were dominated by the current-use pesticides (CUPs) endosulfan (and its metabolite, endosulfan sulphate (EndoSO₄)) and chlorpyrifos. Other pesticides that were regularly detected included α- and γ-hexachlorocyclohexanes (HCHs), dieldrin, heptachlor epoxide and p, p′-DDE. Highest air concentrations were observed for total endosulfan (Endo I + Endo II + EndoSO₄) (100s–1000s pg m⁻³), followed by chlorpyrifos, ΣDDT (mainly o, p′-DDT + p, p′-DDE), ΣHCH ( α-HCH + γ-HCH), dieldrin and heptachlor epoxide. Seasonal variations did not show any clear trends for pesticides, except for endosulfan which reached concentration values one order of magnitude higher during summer at all sites compared to levels during winter. Along the altitudinal gradients, some pesticides showed higher atmospheric concentrations at sites above 1500 m which may indicate efficient high-altitude transport from regional sources. Northerly and southerly air back trajectories appeared to be the main continental influences at the two highest-altitude sites in both mountain regions. These trajectories travelled over extended crop areas from central Brazil to Argentina. A strong, positive correlation between air concentration and altitude was observed (Spearman's correlation, p < 0.05) for endosulfan, consistent with previous studies of endosulfan in mountainous regions in South America.► Seasonal applications are the main source of current-use pesticides over upland sites. ► Some pesticides show high atmospheric concentrations at elevated altitude sites. ► The results reinforce the potential of mountains as pesticides conversion zones.

Keywords: Global Atmospheric Passive Sampling (GAPS) Network; Long range atmospheric transport (LRAT); Persistent toxic substances (PTS); Current-use pesticides (CUPs); Endosulfan; Chlorpyrifos; Mountainous regions; Brazil

Dissolved organic carbon in the precipitation of Seoul, Korea: Implications for global wet depositional flux of fossil-fuel derived organic carbon by Ge Yan; Guebuem Kim (pp. 117-124).

Precipitation was sampled in Seoul over a one-year period from 2009 to 2010 to investigate the sources and fluxes of atmospheric dissolved organic carbon (DOC). The concentrations of DOC varied from 15 μM to 780 μM, with a volume-weighted average of 94 μM. On the basis of correlation analysis using the commonly acknowledged tracers, such as vanadium, the combustion of fossil-fuels was recognized to be the dominant source. With the aid of air mass backward trajectory analyses, we concluded that the primary fraction of DOC in our precipitation samples originated locally in Korea, albeit the frequent long-range transport from eastern and northeastern China might contribute substantially. In light of the relatively invariant organic carbon to sulfur mass ratios in precipitation over Seoul and other urban regions around the world, the global magnitude of wet depositional DOC originating from fossil-fuels was calculated to be 36 ± 10 Tg C yr⁻¹. Our study further underscores the potentially significant environmental impacts that might be brought about by this anthropogenically derived component of organic carbon in the atmosphere.► We investigated the source and flux of DOC in precipitation of Seoul. ► Fossil fuel combustion was the dominant source. ► DOC originated predominantly from local emissions. ► The contribution by long-range transport from China was substantial. ► Global flux of wet depositional fossil-fuel DOC was estimated to be 36 ± 10 Tg C yr⁻¹.

Keywords: Rainwater DOC; Seoul; Fossil-fuel; Wet depositional flux; Long-range transport

Dissolved organic carbon in the precipitation of Seoul, Korea: Implications for global wet depositional flux of fossil-fuel derived organic carbon by Ge Yan; Guebuem Kim (pp. 117-124).

Keywords: Rainwater DOC; Seoul; Fossil-fuel; Wet depositional flux; Long-range transport

Dissolved organic carbon in the precipitation of Seoul, Korea: Implications for global wet depositional flux of fossil-fuel derived organic carbon by Ge Yan; Guebuem Kim (pp. 117-124).

Keywords: Rainwater DOC; Seoul; Fossil-fuel; Wet depositional flux; Long-range transport

Release of PCDD/PCDF to air and land during open burning of sugarcane and forest litter over soil fortified with mass labelled PCDD/PCDF by Robert R. Black; Carl P. (Mick) Meyer; Alan Yates; Lukas Van Zwieten; Brock G. Chittim; Jochen F. Mueller (pp. 125-130).

The contribution of PCDD/PCDF emissions from soil during open burning of biomass was examined. Mass labelled PCDD/PCDF was added to soil containing native PCDD/PCDF and biomass was laid out on this soil and burnt, simulating sugarcane trash and forest fires. Smoke samples were collected using a high volume portable field sampler. After each fire the concentration of all mass labelled PCDD/PCDF congeners in the surface soil decreased, however, the concentration of some native 2,3,7,8 substituted congeners increased, indicating that formation was occurring. Mass labelled PCDD/PCDF congeners were detected in all ash samples, mean 2.8 pg g⁻¹ (range 0.5–8 pg g⁻¹), demonstrating release from the soil. Additionally, mass labelled PCDD/PCDF congeners were detected in all air samples mean 1.2 μg (t fuel)⁻¹ (range 0.2–2.0 μg (t fuel)⁻¹), again demonstrating release from the soil. Native 2,3,7,8 substituted congeners detected in the air samples were dominated (in terms of contribution to total congener mass) by Cl₈DD (90% for forest litter and 77% for sugarcane). The major contributor to TEQ of emissions from both forest litter and sugarcane was 1, 2, 3, 7, 8-Cl₅DD (40–64% and 57–75%, respectively). These results demonstrate that release of PCDD/PCDF from soil to air and land occurs during open burning of biomass when soil temperatures are sufficiently elevated.► We measured release of native and mass labelled PCDD/PCDF from soil heated by fire. ► We found the mass labelled PCDD/PCDF in both ash and smoke samples. ► We found more natives were released than expected based on release of mass labelled. ► We found soil concentrations of some PCDD/PCDF congeners increased on soil heating.

Keywords: Polychlorinated dibenzo-p-dioxins; Polychlorinated dibenzofurans; Persistent organic pollutants; Bushfires; Forest fires; Emission factors

On the magnetic characterization and quantification of the superparamagnetic fraction of traffic-related urban airborne PM in Rome, Italy by Leonardo Sagnotti; Aldo Winkler (pp. 131-140).

The magnetic properties of traffic-related airborne particulate matter (PM) in the city of Rome, Italy, have been previously analyzed and interpreted as suitable proxies to discriminate between different vehicular sources. In this study, we carried out a new set of measurements and analyses specifically devoted to the identification and evaluation of the contribution of ultrafine superparamagnetic (SP) particles to the overall magnetic assemblage of traffic-related PM in Rome. In particular, the presence and the concentration of SP particles have been estimated on powders collected from disk brakes and gasoline exhaust pipes of circulating vehicles and from Quercus ilex leaves grown along high-traffic roads, measuring their hysteresis parameters in a range of temperatures from 293 K to 10 K and measuring the time decay of their saturation remanent magnetization ( M_RS) at room temperature. The SP fraction contributes for the 10–15% to the overall room temperature M_RS and causes the observed changes in the hysteresis properties measured upon cooling down to 10 K. In all the analyzed samples the SP fraction is associated to a generally prevailing population of larger ferrimagnetic multidomain (MD) particles and we suppose that in traffic-related PM the SP fraction mainly occurs as coating of MD particles and originated by localized stress in the oxidized outer shell surrounding the unoxidized core of magnetite-like grains. Under this hypothesis, the estimate of SP content in traffic-related PM cannot be considered a robust proxy to estimate the overall concentration of nanometric particles.► We studied the superparamagnetic (SP) fraction of traffic-related PM. ► The SP fraction makes the hysteresis properties at 10 K different from those at 293 K. ► The SP fraction carries a viscous 10–15% of the total saturation remanence. ► The SP fraction is mostly associated to larger multidomain particles.

Keywords: PM; Air pollution; Environmental magnetism; Superparamagnetic particles; Hysteresis properties

On the magnetic characterization and quantification of the superparamagnetic fraction of traffic-related urban airborne PM in Rome, Italy by Leonardo Sagnotti; Aldo Winkler (pp. 131-140).

Keywords: PM; Air pollution; Environmental magnetism; Superparamagnetic particles; Hysteresis properties

On the magnetic characterization and quantification of the superparamagnetic fraction of traffic-related urban airborne PM in Rome, Italy by Leonardo Sagnotti; Aldo Winkler (pp. 131-140).

Keywords: PM; Air pollution; Environmental magnetism; Superparamagnetic particles; Hysteresis properties

Modeling ozone formation from alkene reactions using the Carbon Bond chemical mechanism by Gookyoung Heo; Elena McDonald-Buller; William P.L. Carter; Greg Yarwood; Gary Z. Whitten; David T. Allen (pp. 141-150).

Predictions of ozone formation, due to oxidation of alkenes in presence of NOx, generated by the Carbon Bond 2005 (CB05) and CB05-TU (CB05 with an updated toluene scheme) condensed chemical mechanisms were tested by simulating 138 environmental chamber experiments carried out in 7 different environmental chambers and by running box modeling with four cases. CB05 and CB05-TU reasonably simulated ozone formation from propene under typical urban conditions and for cases with moderately elevated propene concentrations. Chamber simulations of 47 propene – NOx and 5 isobutene – NOx experiments and box modeling for four cases (1 for propene and 3 for isobutene) showed that the performance of CB05 and CB05-TU in simulating ozone formation from propene and isobutene can be improved by modeling propene and isobutene using the new condensed reactions for propene and isobutene developed in this work. The results of this study indicate that the capability of condensed chemical mechanisms in simulating ozone formation can be improved by (1) examining the relative importance of VOCs based on their emissions and reactivity, (2) separately representing relatively important VOCs in the mechanism, (3) modeling less important compounds using reactions of lumped model species shared by multiple compounds, and (4) evaluating mechanisms with experimental data such as environmental chamber data.► The CB05 chemical mechanism is used widely in photochemical air quality models. ► New reactions are developed to explicitly model propene and isobutene within CB05. ► Modeling shows that explicit propene and isobutene reactions change oxidant predictions. ► Using the new explicit reactions is recommended in circumstances where propene and isobutene dominate oxidant production.

Keywords: Alkene; Alkene chemistry; Ozone; Chemical mechanism; CB05

A travel mode comparison of commuters' exposures to air pollutants in Barcelona by Audrey de Nazelle; Scott Fruin; Dane Westerdahl; David Martinez; Anna Ripoll; Nadine Kubesch; Mark Nieuwenhuijsen (pp. 151-159).

Daily commutes may contribute disproportionately to overall daily inhalations of urban air contaminants. Understanding factors that explain variability of exposures during travel, and especially differences across transportation modes, is essential to accurately assess health impacts of traffic emissions and to develop effective mitigating measures. We evaluated exposures and inhaled doses of air pollution and assessed factors that contributed to their variability in different travel modes in Barcelona. Black carbon (BC), ultrafine particles (UFP), carbon monoxide (CO), fine particle mass (PM_2.5) and carbon dioxide (CO₂) were measured and compared across walk, bike, bus, and car modes for a total of 172 trips made on two different round trip routes. On average, the car mode experienced highest concentrations for all contaminants. In pairwise t-tests between concurrent mode runs, statistically significant differences were found for cars compared to walking and biking. Car-to-walk or car-to-bike concentration ratios ranged from 1.3 for CO₂ to 25 for CO and were 2–3 for PM_2.5, BC, and UFP. In multivariate analyses, travel mode explained the greatest variability in travel exposures, from 8% for PM_2.5 to 70% for CO. Different modal patterns emerged when estimating daily inhaled dose, with active commuters' two to three times greater total inhalation volume during travel producing about equal UFP and BC daily inhaled doses to car commuters and 33–50% higher UFP and BC doses compared to bus commuters. These findings, however, are specific to the bike and pedestrian lanes in this study being immediately adjacent to the roadways measured. Dedicated bike or pedestrian routes away from traffic would lead to lower active travel doses.► We measured air pollution in travel microenvironments in a Southern European city. ► Travel modes explained much more of commuters' exposure variability than meteorology. ► Particulate pollutants in cars were 2–3 times higher than in active modes (walk, bike). ► Contrasts between modes were greatest for primary pollutants (CO then BC and UFP). ► Accounting for inhalation rate differences, pedestrians and cyclists pollution doses were comparable to car drivers.

Keywords: Travel mode; Traffic air pollution; Inhalation dose; Active transportation; Near-road exposure

Development and evaluation of Vehicular Air Pollution Inventory model by Ajay Singh Nagpure; B.R. Gurjar (pp. 160-169).

Estimating emissions by road traffic is a key-issue for air pollution management in many regions. Emission models are important tools to help compute vehicular exhausts. There are several vehicular emission models available worldwide, though most of them have been developed in countries with advanced economies. Due to substantial differences in conditions and available datasets, application of these models in developing countries like India might be misleading. To bridge the gap between the available models and the tools needed in developing countries, the Vehicular Air Pollution emission Inventory (VAPI) model has been developed and evaluated. The proposed VAPI model is based on a simple approach incorporating emission factors and correction factors. This model can be used for estimating emissions for exhaust, evaporative and non-exhaust conditions in Indian cities. The temporal trend of emission estimates calculated with the VAPI model show reasonable agreement with ambient air concentrations monitored at locations significantly influenced by vehicular activity.► First time a simple model is proposed to estimate vehicular emissions in India. ► Climatic correction factors are incorporated to make estimations more realistic. ► Model emission estimates show fair agreement with air quality observations. ► The proposed model is more suitable for developing countries.

Keywords: Emission inventory; Emission model; Traffic emission; Vehicle exhausts; Non-exhaust emission

Development and evaluation of Vehicular Air Pollution Inventory model by Ajay Singh Nagpure; B.R. Gurjar (pp. 160-169).

Keywords: Emission inventory; Emission model; Traffic emission; Vehicle exhausts; Non-exhaust emission

Development and evaluation of Vehicular Air Pollution Inventory model by Ajay Singh Nagpure; B.R. Gurjar (pp. 160-169).

Keywords: Emission inventory; Emission model; Traffic emission; Vehicle exhausts; Non-exhaust emission

Simulation of the interannual variations of biogenic emissions of volatile organic compounds in China: Impacts on tropospheric ozone and secondary organic aerosol by Yu Fu; Hong Liao (pp. 170-185).

We use the MEGAN (Model of emissions of Gases and Aerosols from Nature) module embedded within the global three-dimensional Goddard Earth Observing System chemical transport model (GEOS-Chem) to simulate the interannual variations in biogenic volatile organic compound (BVOC) emissions and concentrations of ozone and secondary organic aerosols (SOA) in China over years 2001–2006. To have better representation of biogenic emissions, we have updated in the model the land cover and leaf area index in China using Moderate Resolution Imaging Spectroradiometer (MODIS) satellite measurements, and we have developed a new classification of vegetation with 21 plant functional types. Estimated annual BVOC emission in China averaged over 2001–2006 is 18.85 Tg C yr⁻¹, in which emissions of isoprene, monoterpenes, and other reactive volatile organic compounds account for 50.9%, 15.0%, and 34.1%, respectively. The simulated BVOC emissions in China have large interannual variations. The values of regionally averaged absolute percent departure from the mean (APDM) of isoprene emissions are in the range of 21–42% in January and 15–28% in July. The APDM values of monoterpene emissions are 14–32% in January and 10–21% in July, which are generally smaller than those of isoprene emissions. Model results indicate that the interannual variations in isoprene emissions are more dependent on variations in meteorological fields, whereas the interannual variations in monoterpene emissions are more sensitive to changes in vegetation parameters. With fixed anthropogenic emissions, as a result of the variations in both meteorological parameters and vegetation, simulated O₃ concentrations show interannual variations of 0.8–5 ppbv (or largest APDM values of 4–15%), and simulated SOA shows APDM values of 5–15% in southwestern China in January as well as 10–25% in southeastern and 20–35% in northeastern China in July. On a regional mean basis, the interannual variations in BVOCs alone can lead to 2–5% differences in simulated O₃ and SOA in summer.► We have updated land cover and leaf area index in China in MEGAN to estimate BVOCs. ► Simulated isoprene emissions in China have large interannual variations of 15–42%. ► Simulated monoterpene emissions in China have large interannual variations of 10–32%. ► Interannual variations of BVOCs can lead to 2–5% differences in O₃ and SOA in July.

Keywords: Biogenic emissions; Tropospheric ozone; Secondary organic aerosol; Interannual variations

Simulation of the interannual variations of biogenic emissions of volatile organic compounds in China: Impacts on tropospheric ozone and secondary organic aerosol by Yu Fu; Hong Liao (pp. 170-185).

Keywords: Biogenic emissions; Tropospheric ozone; Secondary organic aerosol; Interannual variations

Simulation of the interannual variations of biogenic emissions of volatile organic compounds in China: Impacts on tropospheric ozone and secondary organic aerosol by Yu Fu; Hong Liao (pp. 170-185).

Keywords: Biogenic emissions; Tropospheric ozone; Secondary organic aerosol; Interannual variations

Atmospheric BTEX and carbonyls during summer seasons of 2008–2010 in Beijing by Yujie Zhang; Yujing Mu; Peng Liang; Zhu Xu; Junfeng Liu; Hongxin Zhang; Xiaoke Wang; Jian Gao; Shulan Wang; Fahe Chai; Abdelwahid Mellouki (pp. 186-191).

The atmospheric concentrations of carbonyls and BTEX (benzene, toluene, ethylbenzene, m,p-xylene and o-xylene) were measured simultaneously in summers of Beijing from year 2008 to 2010. The total concentrations of formaldehyde, acetaldehyde and acetone in the consecutive summers, which were 33.4 μg m⁻³, 36.7 μg m⁻³ and 48.6 μg m⁻³, respectively, were much lower than those reported in the summers of 2005 (58.4 μg m⁻³) and 2006 (77.4 μg m⁻³). The concentrations of BTEX in the summers were 16 μg m⁻³, 21.5 μg m⁻³ and 15.4 μg m⁻³, respectively. The maximal contributions of photochemical reactions to atmospheric formaldehyde and acetaldehyde in the summers were estimated to be around 47.6–60.3%. The average ozone formation potentials (OFPs) for carbonyls and BTEX as well as carbon monoxide in summer of Beijing were calculated as 166.1 μg m⁻³, 65.4 μg m⁻³ and 100.8 μg m⁻³, respectively.► The atmospheric carbonyls and BTEX during summer seasons of 2008–2010 were reported. ► The yearly variations and sources origination of carbonyls and BTEX were analyzed. ► The OFPs of the pollutants were estimated and compared. ► The OFP of CO accounted for the largest proportion as individual species.

Keywords: Carbonyls; BTEX; Beijing; Photochemical activity; Ozone formation potential

Influence of airborne particles on the acidity of rainwater during wash-out process by Mingqun Huo; Qian Sun; Yuhua Bai; Jinlong Li; Peng Xie; Zhaorong Liu; Xuesong Wang (pp. 192-201).

Rainwater and airborne particles were sampled at five sites, including Beijing and Mazhuang Town in the northeast of China, Chongqing in the southwest of China, Shenzhen and Mangdang Mountain in the south of China. The pollution of airborne particles in winter at Chongqing and Beijing were the worst and the following was in summer at Mazhuang town and atmosphere quality in spring at Mangdang Mountain was the best. The ratios of fine particles to coarse particles were high among all the sampling sites. The contribution from soluble components to particulate mass was important and the main ions both on PM₁₀ and PM_2.5 were SO₄²⁻, NO₃⁻ and NH₄⁺. Both inorganic and organic soluble components on particles were mainly enriched on fine particles. The average pH values in rainwater at Beijing, Mazhuang Town, Shenzhen and Mangdang Mountain were 6.02, 5.97, 4.72 and 4.81 respectively.A new methodology to determine the neutralizing capacity of airborne particles was established in this study. The pH values and water-soluble ion concentrations in particulate matter extract were measured, then the ionization balance and charge conservation principle were adopted to determine the amount of acid-basic compositions on particle. The amount of H⁺ in rainwater neutralized by airborne particles per unit mass was used to denote the neutralizing capacity of particles. The neutralizing capacity of airborne particles was lower if both of the concentrations of particles and ratio of fine to coarse particles were higher. The neutralizing capacity of airborne particles was inverse proportion to the acidity of rainwater and the rain intensity. The neutralizing effect of particles accounted for 4%–28% of the reduction of rainwater acidity during wash-out process among different sites, and it was deduced that NH₃ was the major neutralizing species especially for rainwater from sites in the northeast of China.► Determination of the amounts of all weak acid and basic components on particles. ► Definition of neutralizing capacity of airborne particles. ► Spatial distribution character of neutralizing capacity of airborne particles. ► Influence factors of neutralizing capacity of airborne particles. ► Quantitative evaluation of influence on acidity of rainwater by scavenging particles.

Keywords: Airborne particles; Neutralizing capability; Acidity of rainwater; Wash-out process; Acid and basic gases

Influence of airborne particles on the acidity of rainwater during wash-out process by Mingqun Huo; Qian Sun; Yuhua Bai; Jinlong Li; Peng Xie; Zhaorong Liu; Xuesong Wang (pp. 192-201).

Keywords: Airborne particles; Neutralizing capability; Acidity of rainwater; Wash-out process; Acid and basic gases

Influence of airborne particles on the acidity of rainwater during wash-out process by Mingqun Huo; Qian Sun; Yuhua Bai; Jinlong Li; Peng Xie; Zhaorong Liu; Xuesong Wang (pp. 192-201).

Keywords: Airborne particles; Neutralizing capability; Acidity of rainwater; Wash-out process; Acid and basic gases

Phosphorus availability as a primary constraint on methane emission from a freshwater wetland by Changchun Song; Guisheng Yang; Deyan Liu; Rong Mao (pp. 202-206).

Human activities have increased phosphorus (P) loading in wetland ecosystems worldwide. However, little is known about the effect of P enrichment on CH₄ emissions from these ecosystems. In this study, a 4-year P addition experiment was conducted to examine the effects of increased P availability on CH₄ emission in a Deyeuxia angustifolia-dominated freshwater marsh in the Sanjiang Plain in northeastern China. Phosphorus was added at four rates (0, 1.2, 4.8 and 9.6 g P m⁻² year⁻¹). We investigated CH₄ emission during the growing season (early May to late September) using opaque chamber and gas chromatography method. Our results indicated that the effect of P enrichment on CH₄ emission was time-dependent. Increased P availability did not affect CH₄ emission in 2007 and 2008, but decreased in 2009 and 2010. Notably, four years of P addition decreased cumulative CH₄ emission during the growing season in the freshwater marsh, and the effect did not change with fertilization rates. From 2007 to 2010, P additions of 1.2, 4.8 and 9.6 g P m⁻² year⁻¹ caused a decline in growing-season CH₄ emissions by averages of 23%, 38% and 26%, respectively. Our results suggest that long-term P enrichment driven by agricultural activities would reduce CH₄ emission from temperate freshwater wetlands. This study also highlights the impact of experimental duration on accurate assessments of the effect of P addition on wetland CH₄ budget.► The effect of P enrichment on CH₄ emission is unclear in wetlands. ► 4-year P addition decreased CH₄ emissions in a temperate freshwater marsh. ► P addition's effect on CH₄ emissions was time-dependent. ► P addition's effect on CH₄ emissions did not vary with fertilization rates. ► Elevated P loading would suppress CH₄ emissions in freshwater wetlands.

Keywords: Deyeuxia angustifolia; Methane; Trace-gas flux; P enrichment; Eutrophication; Temperate wetlands; The Sanjiang Plain

Phosphorus availability as a primary constraint on methane emission from a freshwater wetland by Changchun Song; Guisheng Yang; Deyan Liu; Rong Mao (pp. 202-206).

Keywords: Deyeuxia angustifolia; Methane; Trace-gas flux; P enrichment; Eutrophication; Temperate wetlands; The Sanjiang Plain

Phosphorus availability as a primary constraint on methane emission from a freshwater wetland by Changchun Song; Guisheng Yang; Deyan Liu; Rong Mao (pp. 202-206).

Keywords: Deyeuxia angustifolia; Methane; Trace-gas flux; P enrichment; Eutrophication; Temperate wetlands; The Sanjiang Plain

Personal PM_2.5 and indoor CO in nomadic tents using open and chimney biomass stoves on the Tibetan Plateau by Chaoliu Li; Shichang Kang; Pengfei Chen; Qianggong Zhang; Junming Guo; Jue Mi; Puchi Basang; Quzhen Luosang; Kirk R. Smith (pp. 207-213).

Yak dung is the primary source of energy for cooking and heating of nomadic Tibetan herders. Personal PM_2.5 and indoor CO concentrations and time-activity patterns were investigated in nomadic tents with open stoves and locally available chimney stoves. Personal PM_2.5 monitoring using a light-scattering datalogger was performed with women in five tents with open fires and four with chimney stoves over 3 days. Meanwhile, indoor CO variation was also measured. Results showed that 24 h average concentrations of PM_2.5 and CO in the tents with open stoves were 1.42 mg m⁻³ ( n = 5, SD = 3.26) and 6.69 mg m⁻³ ( n = 4; SD = 9.11), respectively, which were significantly higher than the tents with chimney stoves having 0.14 mg m⁻³ ( n = 4; SD = 0.65) and 0.12 mg m⁻³ ( n = 4; SD = 1.01) of PM_2.5 and CO, respectively. Although chimney stoves significantly reduced indoor air pollution, the concentration of PM_2.5 was still higher than annual WHO Air Quality Guideline (0.035 mg m⁻³). Diurnal variability of PM_2.5 and CO was similar and had multiple peaks. This phenomenon was closely connected with behaviors of the participants within the tents. Average 1-h peak concentrations of PM_2.5 and CO exceed 24-h mean values by a factor of 5.0 and 4.3, respectively. Significant correlation between hourly PM_2.5 and CO concentrations was revealed. Generally, women and children spent 7 h longer than other family members within the tent each day and were thus exposed to higher levels of pollutants. Secondhand tobacco smoke and burning of yak oil lamps are also present in many households, but are much smaller contributors to the exposures. Therefore, yak dung combustion contributes substantially to the personal exposure of householders in this setting even during the warmest time of year in this setting and that although exposures are greatly reduced with chimney stoves; they are still high by comparison to national standards or WHO guidelines.► PM_2.5 and CO variations within 9 tents of nomadic Tibetan herders were measured. ► Time-activity patterns of these herders were recorded. ► Diurnal variability of PM_2.5 and CO was similar and had multiple peaks. ► Average concentrations of PM_2.5 and CO in tents using open stove were high. ► Women and children were exposed to higher levels of pollutants than other residents.

Keywords: Indoor air pollution; Household air pollution; Yak dung; CO/PM ratio; Time-activity

China's CO₂ emissions estimated from the bottom up: Recent trends, spatial distributions, and quantification of uncertainties by Yu Zhao; Chris P. Nielsen; Michael B. McElroy (pp. 214-223).

China's emissions of anthropogenic CO₂ are estimated using a bottom-up emission inventory framework based on a detailed categorization of economic sectors and provincial economic and energy data. It includes a newly compiled database of CO₂ emission factors employing the latest field study results from China. Total annual emissions are estimated to have risen from 7126 to 9370 Mt CO₂ from 2005 to 2009. Recent policies to conserve energy and reduce emissions have been effective in limiting CO₂ emissions from power and iron & steel plants, but have had little effect on those from cement production. The uncertainties of China's CO₂ emissions are quantified for the first time using Monte-Carlo simulation, producing a 95% confidence interval (CI) of −9% to +11% for total emissions in 2005. The largest contributors to sector-level emission uncertainty are emission factors for most industrial sources and activity levels for power plants, transportation, and residential & commercial sources. Application of province-level energy consumption and China-specific emission factors in some sectors results in higher annual emission estimates for 2005-2008 as compared with other studies, although most of those are within the 95% CIs of this study.► A database of CO₂ emission factors specific to China is established by sector. ► China's CO₂ emissions are estimated based on a bottom-up method for 2005–2009. ► The uncertainty of China's CO₂ emissions is quantified with Monte-Carlo simulation. ► Improved energy efficiency slows the increase of CO₂ emissions for certain sectors.

Keywords: Carbon dioxide; Emission factor; Uncertainty; China

China's CO₂ emissions estimated from the bottom up: Recent trends, spatial distributions, and quantification of uncertainties by Yu Zhao; Chris P. Nielsen; Michael B. McElroy (pp. 214-223).

Keywords: Carbon dioxide; Emission factor; Uncertainty; China

China's CO₂ emissions estimated from the bottom up: Recent trends, spatial distributions, and quantification of uncertainties by Yu Zhao; Chris P. Nielsen; Michael B. McElroy (pp. 214-223).

Keywords: Carbon dioxide; Emission factor; Uncertainty; China

Effect of ammonia on ozone-initiated formation of indoor secondary products with emissions from cleaning products by Yu Huang; Shun Cheng Lee; Kin Fai Ho; Steven Sai Hang Ho; Nanying Cao; Yan Cheng; Yuan Gao (pp. 224-231).

Biogenic volatile organic compounds (BVOCs) emitted from cleaning products and air fresheners indoors are prone to oxidation resulting in the formation of secondary pollutants that can pose health risks on residents. Ammonia (NH₃) is ubiquitous in ambient and indoor environments. In this study, we investigated the effect of ammonia (NH₃) on secondary pollutants formation from the ozonolysis of BVOCs emitted from cleaning products including floor cleaner (FC), kitchen cleaner (KC) and dishwashing detergent (DD) in a large environmental chamber. Our results demonstrated that the presence of NH₃ (maximum concentration is 240 ppb) could significantly enhance secondary organic aerosols (SOAs) formation from the ozonolysis of all the three categories of cleaning products. For example, for the FC sample, the maximum total particle concentration was up to 2.0 × 10⁴ # cm⁻³ in the presence of NH₃, while it was 1.3 × 10⁴ # cm⁻³ which was 35% lower without NH₃. However, it was found that the extent of NH₃ effect on SOAs formation from the ozonolysis of BVOCs emissions was component-dependent. The presence of NH₃ in the reaction systems could increase the consumptions of d-limonene that is the dominant BVOC species as identified in cleaning products. The percent yields (%) of secondary carbonyl compounds generated from the ozonolysis of BVOCs emitted from three categories of cleaning products were identified in the presence and absence of NH₃, respectively. The increase in SOAs particle number concentration can be attributed to the formation of condensable salts from reactions between NH₃ and organic compounds generated from the BVOCs ozonolysis processes. By investigating the NH₃ effect on the ozonolysis of BVOCs mixtures in contrast to the chemistry of individual compounds, a better assessment can be made of the overall impact cleaning products have on real indoor environments.► We studied the effect of NH₃ on indoor secondary pollutants formation. ► The presence of NH₃ could significantly enhance SOAs formation. ► The consumptions of d-limonene in the reaction systems increased with NH₃ presence. ► The percent yields (%) of secondary carbonyl compounds were quantified.

Keywords: Indoor secondary pollutants; Cleaning products; Biogenic volatile organic compounds; Ozonolysis; Ammonia effect

Non-exhaust PM emission measurements of a light duty vehicle with a mobile trailer by Marcel Mathissen; Volker Scheer; Ulf Kirchner; Rainer Vogt; Thorsten Benter (pp. 232-242).

A trailer-based mobile measurement approach for analyzing non-exhaust emissions of a light duty vehicle is presented. Based on a tracer gas experiment which allowed a mapping of the particle dispersion within the wake of the vehicle, emission factors were estimated. A combination of the results from tracer gas experiment, wind tunnel tests and local airflow measurements was taken into account to characterize the vehicle wake and optimize the position of the measurement devices in the wake of the vehicle. Diffuser type inlet devices were employed to correct for anisokinetic sampling. Measurements on unpaved and dust loaded agricultural paved roads as well as more than 800 km of real world driving were conducted with estimated PM₁₀ emission factors varying over several orders of magnitude (10–42,000 mg vehicle⁻¹ km⁻¹ (mg vkm⁻¹)). Emission factors were found to increase with increasing vehicle velocity. The lowest emission factors were measured on motorways. The coefficient of variation for the measurements varied from 10% to 30%.► Trailer based mobile measurement setup to estimate non-exhaust emissions. ► Diffuser type inlet used to assure isokinetic sampling. ► High spatial road dust variability found on real world routes. ► Estimated PM₁₀ emission factors for unpaved and paved roads.

Keywords: Resuspension; Road dust; Emission factor; PM; ₁₀; TRAKER; SCAMPER

Non-exhaust PM emission measurements of a light duty vehicle with a mobile trailer by Marcel Mathissen; Volker Scheer; Ulf Kirchner; Rainer Vogt; Thorsten Benter (pp. 232-242).

Keywords: Resuspension; Road dust; Emission factor; PM; ₁₀; TRAKER; SCAMPER

Non-exhaust PM emission measurements of a light duty vehicle with a mobile trailer by Marcel Mathissen; Volker Scheer; Ulf Kirchner; Rainer Vogt; Thorsten Benter (pp. 232-242).

Keywords: Resuspension; Road dust; Emission factor; PM; ₁₀; TRAKER; SCAMPER

Organic compounds in aerosols from selected European sites – Biogenic versus anthropogenic sources by Célia Alves; Ana Vicente; Casimiro Pio; Gyula Kiss; Andras Hoffer; Stefano Decesari; André S.H. Prevôt; María Cruz Minguillón; Xavier Querol; Risto Hillamo; Gerald Spindler; Erik Swietlicki (pp. 243-255).

Atmospheric aerosol samples from a boreal forest (Hyytiälä, April 2007), a rural site in Hungary (K-puszta, summer 2008), a polluted rural area in Italy (San Pietro Capofiume, Po Valley, April 2008), a moderately polluted rural site in Germany located on a meadow (Melpitz, May 2008), a natural park in Spain (Montseny, March 2009) and two urban background locations (Zurich, December 2008, and Barcelona, February/March 2009) were collected. Aliphatics, polycyclic aromatic hydrocarbons, carbonyls, sterols, n-alkanols, acids, phenolic compounds and anhydrosugars in aerosols were chemically characterised by gas chromatography–mass spectrometry, along with source attribution based on the carbon preference index (CPI), the ratios between the unresolved and the chromatographically resolved aliphatics, the contribution of wax n-alkanes, n-alkanols and n-alkanoic acids from plants, diagnostic ratios of individual target compounds and source-specific markers to organic carbon ratios. In spite of transboundary pollution episodes, Hyytiälä registered the lowest levels among all locations. CPI values close to 1 for the aliphatic fraction of the Montseny aerosol suggest that the anthropogenic input may be associated with the transport of aged air masses from the surrounding industrial/urban areas, which superimpose the locally originated hydrocarbons with biogenic origin. Aliphatic and aromatic hydrocarbons in samples from San Pietro Capofiume reveal that fossil fuel combustion is a major source influencing the diel pattern of concentrations. This source contributed to 25–45% of the ambient organic carbon (OC) at the Po Valley site. Aerosols from the German meadow presented variable contributions from both biogenic and anthropogenic sources. The highest levels of vegetation wax components and biogenic secondary organic aerosol (SOA) products were observed at K-puszta, while anthropogenic SOA compounds predominated in Barcelona. The primary vehicular emissions in the Spanish city accounted for around 25–30% of the OC in aerosols. Besides the traffic input (10% of OC), residential wood burning was found to be another dominant emission source contributing to the atmospheric aerosol (up to 38% of OC) at the Swiss urban location. It was estimated that around 10% of the OC mass in the urban sites originates from cooking emissions. Aerosols from the urban area of Zurich presented a much higher PAH content, and benzo(a)pyrene equivalent concentrations sometimes exceeding the mandatory limit.► The organic characterisation of aerosols from 7 contrasting European sites was made. ► Vehicle, cooking and biomass burning emissions represent major inputs to OC. ► In urban sites, the winter carcinogenic content may constitute an issue of concern.

Keywords: European aerosol; Organic compounds; Tracers; Diagnostic ratios; Benzo(a)pyrene equivalent carcinogenicity; Sources

The atmospheric lifetime of black carbon by J.N. Cape; M. Coyle; P. Dumitrean (pp. 256-263).

Black carbon (BC) in the atmosphere contributes to the human health effects of particulate matter and contributes to radiative forcing of climate. The lifetime of BC, particularly the smaller particle sizes (PM_2.5) which can be transported over long distances, is therefore an important factor in determining the range of such effects, and the spatial footprint of emission controls. Theory and models suggest that the typical lifetime of BC is around one week.The frequency distributions of measurements of a range of hydrocarbons at a remote rural site in southern Scotland (Auchencorth Moss) between 2007 and 2010 have been used to quantify the relationship between atmospheric lifetime and the geometric standard deviation of observed concentration. The analysis relies on an assumed common major emission source for hydrocarbons and BC, namely diesel-engined vehicles. The logarithm of the standard deviation of the log-transformed concentration data is linearly related to hydrocarbon lifetime, and the same statistic for BC can be used to assess the lifetime of BC relative to the hydrocarbons. Annual average data show BC lifetimes in the range 4–12 days, for an assumed OH concentration of 7 × 10⁵ cm⁻³. At this site there is little difference in BC lifetime between winter and summer, despite a 3-fold difference in relative hydrocarbon lifetimes. This observation confirms the role of wet deposition as an important removal process for BC, as there is no difference in precipitation between winter and summer at this site. BC lifetime was significantly greater in 2010, which had 23% less rainfall than the preceding 3 years.Display Omitted► Hydrocarbon and black carbon concentrations are log-normally distributed. ► Standard deviation of log(concentration) of hydrocarbons correlates with lifetime. ► Black carbon lifetimes, by analogy, are between 4 and 12 days at this site. ► Black carbon lifetime is determined by rainfall, and similar in summer and winter.

Keywords: Air quality monitoring; Global climate models; Aethalometer; Hydrocarbon lifetime

The atmospheric lifetime of black carbon by J.N. Cape; M. Coyle; P. Dumitrean (pp. 256-263).

Keywords: Air quality monitoring; Global climate models; Aethalometer; Hydrocarbon lifetime

The atmospheric lifetime of black carbon by J.N. Cape; M. Coyle; P. Dumitrean (pp. 256-263).

Keywords: Air quality monitoring; Global climate models; Aethalometer; Hydrocarbon lifetime

Chemical nature and molecular weight distribution of the water-soluble fine and ultrafine PM fractions collected in a rural environment by J. Pavlovic; P.K. Hopke (pp. 264-271).

PM_1–2.5, PM_0.1–1, and PM_<0.1 water-soluble organic carbon (WSOC) fractions of aerosol samples collected during summer and fall 2009 were analyzed by UV/VIS spectroscopy and electrospray ionization–mass spectrometry (ESI/MS). The focus of this study was to compare optical properties, chemical nature, and molecular weight distribution in samples extracted from different size fractions and collected during different seasons (fall vs. summer). Diurnal patterns were also investigated. An increase in absorptivity, aromaticity, and average molecular weight (AMW) in all size fractions found in the fall samples indicates different formation processes for the organic carbon between the summer and fall periods. The fall ultrafine fraction (PM_<0.1) demonstrated characteristics different from the other two PM size fractions and more similar to aquatic fulvic acids. It had the highest HULIS/WSOC ratio, molar absorptivity, and AMWs up to about 700 Da when analyzed by the UV/VIS method and about 475 Da by the ESI/MS. Higher concentrations of organosulfate (OS) compounds and polycarboxylic acids were detected in the summer samples while organonitrate (ON) compounds and monocarboxylic acids were higher in the fall samples.► Water-soluble organic carbon (WSOC) in different size PM fractions. ► WSOC in the PM_1–2.5 fraction ranged from 37% to 47%. ► PM_<0.1 contribute the least to the WSOC content (19%–31%). ► Average molecular weights ranged from 560 Da to 700 Da. ► Tandem MS found carboxylic, polycarboxylic acids, organosulfates, and -nitrates.

Keywords: Water-soluble organic carbon; HULIS; Organosulfates; Organonitrates; Ultrafine PM

Chemical nature and molecular weight distribution of the water-soluble fine and ultrafine PM fractions collected in a rural environment by J. Pavlovic; P.K. Hopke (pp. 264-271).

Keywords: Water-soluble organic carbon; HULIS; Organosulfates; Organonitrates; Ultrafine PM

Chemical nature and molecular weight distribution of the water-soluble fine and ultrafine PM fractions collected in a rural environment by J. Pavlovic; P.K. Hopke (pp. 264-271).

Keywords: Water-soluble organic carbon; HULIS; Organosulfates; Organonitrates; Ultrafine PM

Intraurban concentrations, spatial variability and correlation of ambient polycyclic aromatic hydrocarbons (PAH) and PM_2.5 by Angelos T. Anastasopoulos; Amanda J. Wheeler; Deniz Karman; Ryan H. Kulka (pp. 272-283).

To investigate the intraurban spatial variability of air toxics associated with respirable particulate matter (PM), ambient PM_2.5 and 16 polycyclic aromatic hydrocarbons (PAH) species (vapour phase plus 2.5 μm particle phase) were sampled over a dense network of sites in Hamilton, Ontario, Canada in June/July 2009 and December 2009. PM_2.5 levels ranged from 2.46 to 11.0 μg m⁻³ in the summer campaign and 6.52 to 13.4 μg m⁻³ in the winter campaign. Total sampled PAH (Σ₁₆PAH) levels ranged from 10.2 to 83.7 ng m⁻³ in the summer campaign and 8.31 to 52.1 ng m⁻³ in the winter campaign. Ambient PM_2.5 and PAH concentrations were greater below the city's escarpment with a below/above escarpment difference in concentration much greater for PAH than for PM_2.5 in both summer and winter sampling campaigns. Elevated levels of both pollutants were observed to occur near or downwind of the central business district and industrialized harbourfront area, suggesting the contribution of local sources. Ambient PAH exhibited a substantially greater degree of intraurban variability than PM_2.5 (coefficient of variation approximately three times greater in summer campaign, four times greater in winter campaign) both above and below the escarpment, particularly for heavy MW species found predominantly in the particle phase. Benzo(a)Pyrene-equivalent toxicity (BaP-TEQ) associated with ambient PAH showed a generally similar spatial distribution to Σ₁₆PAH; however, several sites with relatively low Σ₁₆PAH had high BaP-TEQ (enriched in more toxic heavy MW species), indicating potential hotspots for elevated PAH exposures and local source contributions. Co-located field sampling data showed that central site monitoring was a poor proxy for PM_2.5 and particularly for PAH and associated toxicity (BaP-TEQ) across the urban centre, underestimating levels at many sites, likely due to the significant number of locally distributed sources and mixed land use. The much greater intraurban variability of PAH relative to PM_2.5, particularly for toxic heavy MW species predominantly in particle phase, demonstrated variability in PM_2.5 composition and confirmed the importance of the local scale for PAH exposure health risk assessment.► Ambient PM_2.5 and 16 PAH were sampled in a dense intraurban network in two seasons. ► PAH showed much greater intraurban variability than PM_2.5 in both seasons. ► Central monitoring was a poor intraurban proxy for PM_2.5 and especially for PAH. ► ΣPAH/PM_2.5 and BaP-TEQ indicated potential exposure hot spots near local sources. ► Local scale differences are important in exposure assessment of light and heavy PAH.

Keywords: Air quality; Intraurban; Spatial variability; Fine particulate matter (PM; _2.5; ); Polycyclic aromatic hydrocarbons (PAH); Hamilton

Coupled turbulence and aerosol dynamics modeling of vehicle exhaust plumes using the CTAG model by Yan Jason Wang; K. Max Zhang (pp. 284-293).

This paper presents the development and evaluation of an environmental turbulent reacting flow model, the Comprehensive Turbulent Aerosol Dynamics and Gas Chemistry ( CTAG) model. CTAG is designed to simulate transport and transformation of multiple air pollutants, e.g., from emission sources to ambient background. For the on-road and near-road applications, CTAG explicitly couples the major turbulent mixing processes, i.e., vehicle-induced turbulence ( VIT), road-induced turbulence ( RIT) and atmospheric boundary layer turbulence with gas-phase chemistry and aerosol dynamics. CTAG's transport model is referred to as CFD-VIT-RIT. This paper presents the evaluation of the CTAG model in simulating the dynamics of individual plumes in the “tailpipe-to-road” stage, i.e., VIT behind a moving van and aerosol dynamics in the wake of a diesel car by comparing the modeling results against the respective field measurements. Combined with sensitivity studies, we analyze the relative roles of VIT, sulfuric acid induced nucleation, condensation of organic compounds and presence of soot-mode particles in capturing the dynamics of exhaust plumes as well as their implications in vehicle emission controls.► This paper introduces CTAG, an environmental turbulent reacting flow model. ► The structure and components of CTAG are described. ► CTAG is evaluated against the turbulence and aerosol measurements. ► The relative roles of VIT and different aerosol processes are analyzed.

Keywords: Air quality; Computational fluid dynamics (; CFD; ); Emissions; Particle size distribution; Transportation

Coupled turbulence and aerosol dynamics modeling of vehicle exhaust plumes using the CTAG model by Yan Jason Wang; K. Max Zhang (pp. 284-293).

Keywords: Air quality; Computational fluid dynamics (; CFD; ); Emissions; Particle size distribution; Transportation

Coupled turbulence and aerosol dynamics modeling of vehicle exhaust plumes using the CTAG model by Yan Jason Wang; K. Max Zhang (pp. 284-293).

Keywords: Air quality; Computational fluid dynamics (; CFD; ); Emissions; Particle size distribution; Transportation

Sources of nickel, vanadium and black carbon in aerosols in Milwaukee by Benjamin de Foy; Alison M. Smyth; Samantha L. Thompson; Deborah S. Gross; Michael R. Olson; Nicholas Sager; James J. Schauer (pp. 294-301).

Detailed analysis of the health effects of particulate matter shows that metals and black carbon have significant impacts of their own. A summer intensive study was performed in Milwaukee, Wisconsin in July and August 2010 to identify potential sources of nickel, vanadium and black carbon in the atmosphere. An Aerosol Time-of-Flight Mass Spectrometer (ATOFMS) was used to collect single-particle mass spectra and an Aethalometer was used to measure black carbon. Comparison with the National Emissions Inventory was performed using mesoscale meteorological simulations based on the Weather Research and Forecasting model (WRF) and the Comprehensive Air-quality Model with eXtensions (CAMx). The analysis suggests that nickel and vanadium are primarily emitted by industrial point sources in the Menomonee valley and that black carbon is primarily associated with mobile sources and emissions of nitrogen oxides. Evaluation of ship emissions from the port of Milwaukee suggest that they are responsible for approximately 5% of nickel and vanadium and approximately 10% of black carbon in Milwaukee. Elevated concentrations of air pollutants were found to occur mainly during wind stagnation events suggesting that local sources dominate over regional transport.► Nickel and vanadium in aerosols are due to local industrial point sources. ► Local power plants are not a significant source of Ni, V and BC. ► Local mobile sources emit most of the black carbon. ► Ships account for less than 10% of Ni, V and BC in Milwaukee.

Keywords: Aerosols; Black carbon; Nickel; Vanadium; Urban air quality; Emissions inventory

Contribution of leaf and needle litter to whole ecosystem BVOC fluxes by J.P. Greenberg; D. Asensio; A. Turnipseed; A.B. Guenther; T. Karl; D. Gochis (pp. 302-311).

Biogenic volatile organic compound (BVOC) emissions come from a variety of sources, including living above-ground foliar biomass and microbial decomposition of dead organic matter at the soil surface (litter and soil organic matter). There are, however, few reports that quantify the contributions of each component. Measurements of emission fluxes are now made above the vegetation canopy, but these include contributions from all sources. BVOC emission models currently include detailed parameterization of the emissions from foliar biomass but do not have an equally descriptive treatment of emissions from litter or other sources. We present here results of laboratory and field experiments to characterize the major parameters that control emissions from litter.Litter emissions are exponentially dependent on temperature. The moisture content of the litter plays a minor role, except during and immediately following rain events. The percentage of carbon readily available for microbial and other decomposition processes decreases with litter age. These 3 variables are combined in a model to explain over 50% of the variance of individual BVOC emission fluxes measured. The modeled results of litter emissions were compared with above-canopy fluxes. Litter emissions constituted less than 1% of above-canopy emissions for all BVOCs measured. A comparison of terpene oil pools in litter and live needles with above-canopy fluxes suggests that there may be another canopy terpene source in addition to needle storage or that some terpene emissions may be light-dependent.Ground enclosure measurements indicated that compensation point concentrations of BVOCs (equilibrium between BVOC emission and deposition) were usually higher than ambient air concentrations at the temperature of the measurements.► Litter BVOC fluxes were measured by gradient flux and enclosure techniques. ► Emissions were shown to have exponential dependence on temperature and moisture. ► A litter BVOC emissions model was developed which successfully reproduced the emission measurements. ► Litter BVOC emissions make only a small contribution to the whole ecosystem flux of the BVOCs measured.

Keywords: Biogenic emissions; Litter; Ecosystem fluxes; Methanol; Acetaldehyde; Acetone; Terpene; Compensation point

Contribution of leaf and needle litter to whole ecosystem BVOC fluxes by J.P. Greenberg; D. Asensio; A. Turnipseed; A.B. Guenther; T. Karl; D. Gochis (pp. 302-311).

Keywords: Biogenic emissions; Litter; Ecosystem fluxes; Methanol; Acetaldehyde; Acetone; Terpene; Compensation point

Contribution of leaf and needle litter to whole ecosystem BVOC fluxes by J.P. Greenberg; D. Asensio; A. Turnipseed; A.B. Guenther; T. Karl; D. Gochis (pp. 302-311).

Keywords: Biogenic emissions; Litter; Ecosystem fluxes; Methanol; Acetaldehyde; Acetone; Terpene; Compensation point

An observational study of the atmospheric ultra-fine particle dynamics by C. Varotsos; J. Ondov; C. Tzanis; F. Öztürk; M. Nelson; H. Ke; J. Christodoulakis (pp. 312-319).

This paper presents results derived from ultra-fine particle observations conducted in urban and semi-rural areas of the Athens basin in Greece. Aerosol particle size spectra were collected at 2.5-min time resolution with a Scanning Mobility Particle Sizer for approximately two months, along with standard meteorological, NO, NO₂ and O₃ measurements. The results obtained showed that a 10-fold less maximum number concentration of the mean spectrum was noticed at the semi-rural site compared with that at the urban site. The corresponding maximum for the median spectrum of urban site was only 20% less, indicating that extreme cases had little effect, at least in maximum mean concentration of 9.8 nm particles. The largest number concentration maximum in the mean size distribution spectrum for each area occurred at a modal diameter ≤9.8 nm. For particles ≥13.4 nm, the mean spectrum for Patision contained prominent accumulation particle populations at number median diameters of 13.4, 29.7, and 43.7 nm. In contrast, the major features of the accumulation region of the mean semi-rural spectrum were fit with 5 distribution functions of nearly the same amplitude. The most dominant feature occurred at a number median diameter of 70.1 nm, and thus substantially greater than the 43.7 nm most-dominant in the mean urban spectrum. High ultra-fine particle concentrations at the urban site generally coincided with periods of high NO concentrations and were well correlated with benzene, signifying emissions from motor vehicles.► Ultrafine particle observations were obtained in Athens in urban and semi-rural areas. ► Distribution parameters of component particle populations are provided. ► LNDF parameters of component particle populations are provided.

Keywords: Ultra-fine particles; Aerosols; Air quality; Emissions; Athens–Greece

An observational study of the atmospheric ultra-fine particle dynamics by C. Varotsos; J. Ondov; C. Tzanis; F. Öztürk; M. Nelson; H. Ke; J. Christodoulakis (pp. 312-319).

Keywords: Ultra-fine particles; Aerosols; Air quality; Emissions; Athens–Greece

An observational study of the atmospheric ultra-fine particle dynamics by C. Varotsos; J. Ondov; C. Tzanis; F. Öztürk; M. Nelson; H. Ke; J. Christodoulakis (pp. 312-319).

Keywords: Ultra-fine particles; Aerosols; Air quality; Emissions; Athens–Greece

Particles and gaseous emissions from realistic operation of residential wood pellet heating systems by Kaung Myat Win; Tomas Persson; Chris Bales (pp. 320-327).

Gaseous and particulate emissions from six residential wood pellet heating systems are determined at a realistic six day operation sequence. The study aims to investigate the total emissions from a realistic operation of the heating systems including start-up and stop phases. Five combined solar and pellet heating systems and one reference boiler without solar system with an integrated DHW preparation was tested in a laboratory at realistic operation conditions. The investigated emissions comprised carbon monoxide (CO), nitrogen oxide (NO), total organic carbon (TOC) and particulate matter (PM2.5). In this study, the emissions are presented as accumulated total emissions from the whole six days period and the emissions from start-up and stop phases are also presented separately to evaluate the influence of the emissions from these phases on the total emissions. Emission factors of the measured systems from the six day period are between 192 and 547 mg MJ⁻¹ for the CO emissions, between 61 and 95 mg MJ⁻¹ for the NO, between 6 and 45 mg MJ⁻¹ for the TOC, between 31 and 116 mg MJ⁻¹ for the particulate matter and between 2.1 × 10¹³ and 4 × 10¹³ for the number of particles. The emissions from the start-up and stop phases are significantly high for the CO (63–95 %) and the TOC (48–93 %). NO and particles emissions are shown to dominate during stationary operation. However, 30–40 % of the particle emissions arise from the start and stop periods. It is also shown that the average emissions of CO, TOC and particles under the realistic annual conditions were higher than the limit values of two eco labels.► Emissions from realistic operation of six domestic pellet heating systems are studied. ► Emissions from start-up and stop phases are significantly high for CO and TOC. ► NO and particles emissions dominates during stationary operation. ► Average annual CO, TOC and particles emissions were higher than two eco labels limits.

Keywords: Wood pellet; Combustion; Emissions; Pellet stove; Pellet boiler; Start-up phase; Stop phase

Particles and gaseous emissions from realistic operation of residential wood pellet heating systems by Kaung Myat Win; Tomas Persson; Chris Bales (pp. 320-327).

Keywords: Wood pellet; Combustion; Emissions; Pellet stove; Pellet boiler; Start-up phase; Stop phase

Particles and gaseous emissions from realistic operation of residential wood pellet heating systems by Kaung Myat Win; Tomas Persson; Chris Bales (pp. 320-327).

Keywords: Wood pellet; Combustion; Emissions; Pellet stove; Pellet boiler; Start-up phase; Stop phase

Comparison of biogenic methane emissions from unmanaged estuaries, lakes, oceans, rivers and wetlands by M.J. Ortiz-Llorente; M. Alvarez-Cobelas (pp. 328-337).

A literature review of quantitative data was carried out to conduct a cross-system study on methane emissions relating peak emissions (PE) and annual emissions (AE) in five types of non-managed ecosystems: estuaries, lakes, oceans, streams and wetlands. PE spanned eight orders of magnitude (0.015 μg CH₄ m⁻² h⁻¹–300 mg CH₄ m⁻² h⁻¹) while AE spanned seven (0.078–19044 g CH₄ m⁻² yr⁻¹). PE and AE were strongly related worldwide ( r² = 0.93). There was no relationship between AE and latitude, with highly variable PE across latitudes and climates. The coefficient of variation (CV) was greatest for emissions in oceans and estuaries, while the highest emission rate was recorded in wetlands and lakes. Efflux from coastal areas and estuaries was higher than that from upwelling areas and deep seas. Concerning wetland types, marshes showed the highest PE with the highest wetland emissions occurring in sites dominated by big helophytes. Non-stratifying- and eutrophic lakes displayed more emissions than other lake types, but there was no environmental variable that might predict methane emissions from lakes on a worldwide basis. Generally, most ecosystem types followed a seasonal pattern of emissions, with a maximum in summer, except in estuaries which did not show any distinct pattern. Regarding the importance of hot spots within most ecosystems, more spatial variability of CH₄ emissions was observed in lakes than in wetlands and oceans; however, no relationship between emissions and spatial variability was found. A positive relationship, albeit weak, was found between methane flux and either temperature or irradiance in wetlands; a narrow range of both negative and positive values of the water table promoted CH₄ emissions. Previously, little was known about the factors controlling efflux from river and marine environments. Our study suggests that local conditions are important in controlling CH₄ emissions, because the variability explained by the more commonly studied abiotic factors is low worldwide. This precludes the use of these variables to develop models to predict emissions at regional scales or wider, despite the many attempts made in the past. This makes local assessments of emissions essential, particularly in warm, temperate and tropical areas of the world. Future research aiming to shed light on CH₄ fluxes from estuaries, lakes, oceans, rivers and wetlands must: 1) produce more detailed data on controlling factors; 2) increase efforts to fully characterize spatial and temporal heterogeneity; 3) combine bottom-up (measurements) and top-down (modelling) approaches.► We report maximal and yearly CH₄ emissions in different latitudes, climates and ecosystem types. ► We outline how CH₄ emissions vary among different wetland- and marine ecosystem types. ► Seasonality of emissions in different aquatic environments has been described. ► The influence of spatial variability on emissions has been taking into account. ► We assess the influence of abiotic factors in aquatic environments and how different types of plants affect emissions.

Keywords: Seasonal emissions; Global emissions; Environmental factors; Scale of observation; Spatial heterogeneity

Comparison of biogenic methane emissions from unmanaged estuaries, lakes, oceans, rivers and wetlands by M.J. Ortiz-Llorente; M. Alvarez-Cobelas (pp. 328-337).

Keywords: Seasonal emissions; Global emissions; Environmental factors; Scale of observation; Spatial heterogeneity

Comparison of biogenic methane emissions from unmanaged estuaries, lakes, oceans, rivers and wetlands by M.J. Ortiz-Llorente; M. Alvarez-Cobelas (pp. 328-337).

Keywords: Seasonal emissions; Global emissions; Environmental factors; Scale of observation; Spatial heterogeneity

Measurement of the atmospheric aerosol particle size distribution in a highly polluted mega-city in Southeast Asia (Dhaka-Bangladesh) by Abdus Salam; Hassan Al Mamoon; Md. Basir Ullah; Shah M. Ullah (pp. 338-343).

Aerosol particle size distribution was measured with an aerodynamic particle sizer (APS) spectrometer continuously from January 21 to April 24, 2006 in Dhaka, Bangladesh. Particles number, surface and mass distributions data were stored automatically with Aerosol Instrument Manager (AIM) software on average every half an hour in a computer attached to the APS. The grand total average of number, surface and mass concentrations were 8.2 × 10³ ± 7.8 × 10³ particles cm⁻³, 13.3 × 10³ ± 11.8 × 10³ μm² cm⁻³ and 3.04 ± 2.10 mg m⁻³, respectively. Fine particles with diameter smaller than 1.0 μm aerodynamic diameter (AD) dominated the number concentration, accounted for 91.7% of the total particles indicating vehicular emissions were dominating in Dhaka air either from fossil fuel burning or compressed natural gas (CNGs). The surface and mass concentrations between 0.5 and 1.0 μm AD were about 56.0% and 26.4% of the total particles, respectively. Remarkable seasonal differences were observed between winter and pre-monsoon seasons with the highest monthly average in January and the lowest in April. Aerosol particles in winter were 3.79 times higher for number, 3.15 times for surface and 2.18 times for mass distributions than during the pre-monsoon season. Weekends had lower concentrations than weekdays due to less vehicular traffic in the streets. Aerosol particles concentrations were about 15.0% (ranging from 9.4% to 17.3%) higher during traffic peak hours (6:00am–8:00pm) than off hours (8:00pm–6:00am). These are the first aerosol size distribution measurements with respect to number, surface and mass concentrations in real time at Dhaka, Bangladesh.► Aerosol particle size distributions were measured in Southeast Asia Mega city (Dhaka, Bangladesh). ► Elevated concentrations of the number, surface and mass distributions were observed in Dhaka, Bangladesh. ► Fine particles (0.5–1.0 μm) were dominating the aerosol particles number concentrations. ► Remarkable daily, monthly, seasonal variations were observed. ► Aerosol particle concentrations showed significant correlation with the traffic peak and off hours.

Keywords: Aerosol size distribution; Number concentration; Aerodynamic particle sizer (APS)

Dust layer effects on the atmospheric radiative budget and heating rate profiles by Maria Rita Perrone; A.M. Tafuro; S. Kinne (pp. 344-354).

The effect of mineral aerosol optical properties and vertical distribution on clear-sky, instantaneous and daily-average aerosol direct radiative effects (DREs) and heating rates (HRs) is analyzed in the solar (S, 0.3–4 μm) and terrestrial (T, 4–80 μm) spectral domain, respectively. The used radiative transfer model is based on lidar, sun-sky photometer, and radiosonde measurements. The study focuses on the Sahara dust outbreak of July 16, 2009 which advected dust particles from north-western Africa over south-eastern Italy. Clear-sky, instantaneous aerosol DREs and HRs undergo large changes within few hours, for the variability of the dust aerosol properties and vertical distribution. The daily-average, clear-sky aerosol S-DRE is near −5 Wm⁻² and −12 Wm⁻² at the top of the atmosphere (ToA) and surface (sfc), respectively. The daily-average aerosol T-DRE offsets the S-DRE by about one third at the ToA and by about one half at the surface. The daily average aerosol HR integrated over the whole aerosol column is 0.5 and −0.3 K day⁻¹ in the S and T domain, respectively. Thus, the all-wave integrated HR is 0.2 K day⁻¹. These results highlight the importance of accounting for the interaction of dust particles with T and S radiation. Sensitivity tests indicate that the uncertainties of the aerosol refractive index, size distribution, and vertical distribution have on average a large impact on aerosol HRs in the S and T domain, respectively. Refractive index and aerosol size distribution uncertainties also have a large impact on S- and T-DREs. The aerosol vertical distribution that has a negligible impact on aerosol S-DREs, is important for aerosol T-DREs. It is also shown that aerosol HRs and DREs in the terrestrial domain are affected by the water vapour vertical distribution.► Dust aerosol direct radiative effects and heating rates. ► Radiative transfer calculations in the solar and terrestrial domain. ► Instantaneous and daily average radiative transfer calculations. ► Effects of aerosol properties on heating rates and direct radiative effects.

Keywords: Aerosol direct radiative effects; Aerosol heating rates; Desert dust properties; Aerosol vertical profiles

Dust layer effects on the atmospheric radiative budget and heating rate profiles by Maria Rita Perrone; A.M. Tafuro; S. Kinne (pp. 344-354).

Keywords: Aerosol direct radiative effects; Aerosol heating rates; Desert dust properties; Aerosol vertical profiles

Dust layer effects on the atmospheric radiative budget and heating rate profiles by Maria Rita Perrone; A.M. Tafuro; S. Kinne (pp. 344-354).

Keywords: Aerosol direct radiative effects; Aerosol heating rates; Desert dust properties; Aerosol vertical profiles

Calculation scheme for a Gaussian parameterization of the Thompson 1991 wind tunnel building downwash dataset by G. Cosemans; W. Lefebvre; C. Mensink (pp. 355-365).

In Flanders, the northern part of Belgium, several non-ferro industries face difficulties in meeting the upcoming air quality standards for Pb, Ni, As and Cd due to building downwash causing high pollutant concentrations within a distance equal to a few building heights from the building. Current models perform poorly at this very short distance (). Therefore, we invested in the development of a new building downwash model. The resulting model is able to reproduce the centre-line ground level concentration profiles measured by in the US-EPA meteorological wind tunnel for 320 different stack-building configurations. The model consists of the Gaussian transport and diffusion equation, in which the variables x_R (distance source-receptor) and H_s (stack height) have been replaced with functions that define a receptor dependent virtual origin. The found virtual source functions account for the impact of building downwash 1) by changing the height of the plume, 2) by using an upwind displacement of the plume origin and 3) by accounting for the entrainment of clean air into the plume by increasing the distance between the virtual source and the receptor point. The resulting peak values of the ground level centre-line concentration profiles are well reproduced with a R² = 0.96 and a regression equation of y = 1.095 x.► Modified bi-Gaussian formulation for building downwash. ► Thompson wind tunnel dataset well reproduced. ► Creating an opportunity for practical implementation of the scheme in existing models.

Keywords: Building downwash; Gaussian modeling; Wind tunnel; Ground level concentration profiles

Calculation scheme for a Gaussian parameterization of the Thompson 1991 wind tunnel building downwash dataset by G. Cosemans; W. Lefebvre; C. Mensink (pp. 355-365).

Keywords: Building downwash; Gaussian modeling; Wind tunnel; Ground level concentration profiles

Calculation scheme for a Gaussian parameterization of the Thompson 1991 wind tunnel building downwash dataset by G. Cosemans; W. Lefebvre; C. Mensink (pp. 355-365).

Keywords: Building downwash; Gaussian modeling; Wind tunnel; Ground level concentration profiles

Roles of surface wind, NDVI and snow cover in the recent changes in Asian dust storm occurrence frequency by Jong-Jae Lee; Cheol-Hee Kim (pp. 366-375).

This paper describes the recent variations in dust outbreak during the period from 1996 to 2007 over the Asian dust source regions. The Asian dust source regions were divided into four sub-regions; S1, Taklamakan; S2, Gobi; S3, Inner Mongolia-Manchuria; and S4, Loess, and the WMO SYNOP observation and satellite data were employed to analyze the features of recently changed dust outbreak frequencies (DOFs). There was no particular variation in region S1, but the recent spatiotemporal variations in DOFs over S2–S4 were well characterized by a severe and widespread increase in 2001–2002, and significant decreasing in 2003–2004 over the most source regions, with a steadily increasing trend again during 2005–2007. Seasonal features showed that the highest DOFs occurred in March–April before 2002, but was delayed by a month toward April–May during the next five years because of the shift in the month of highest strong wind-speed frequencies (SWFs). A secondary peak of DOF was also found, occurring in October–November since the year 2000. Over all the source regions, the primary controlling factor for explaining the spatiotemporal DOF patterns was the SWF, with a pattern correlation coefficient (PCC) of 0.66–0.76. Other secondary controlling factors varied from region to region. For example, the DOFs observed in region S2–S3 showed relatively greater sensitivity to the snow-cover fraction, and region S4 showed a better correlation with the normalized difference vegetation index (NDVI) than the other regions. Other recent significant changes in DOFs over the Asian dust source regions and their causes are also discussed in this study.► This study describes the recent dust occurrences over source regions. ► Severe dust activation (2000–2002) and decrease (2003–2004) were well contrasted. ► Higher dust occurrence area has been shifting toward northwest since 2003. ► Highest month has been delayed and secondary peaks were newly found. ► Strong wind speed, NDVI, and snow cover are main factors in dust occurrence.

Keywords: Asian dust; Dust source regions; NDVI; Snow-cover

Roles of surface wind, NDVI and snow cover in the recent changes in Asian dust storm occurrence frequency by Jong-Jae Lee; Cheol-Hee Kim (pp. 366-375).

Keywords: Asian dust; Dust source regions; NDVI; Snow-cover

Roles of surface wind, NDVI and snow cover in the recent changes in Asian dust storm occurrence frequency by Jong-Jae Lee; Cheol-Hee Kim (pp. 366-375).

Keywords: Asian dust; Dust source regions; NDVI; Snow-cover

Characteristics of 2-methyltetrols in ambient aerosol in Beijing, China by Linlin Liang; Guenter Engling; Fengkui Duan; Yuan Cheng; Kebin He (pp. 376-381).

PM₁₀ and PM_2.5 samples were collected from November, 2010 to October, 2011 at Tsinghua University in Beijing. Various carbohydrates were quantified by high-performance anion exchange chromatography with pulsed amperometric detection (HPAEC–PAD), including the 2-methyltetrols (2-methylthreitol and 2-methylerythritol). A clear seasonal variation in the ambient 2-methyltetrol concentrations was observed, with the highest levels occurring in the summer, followed by autumn, spring and winter. The average concentrations of the 2-methyltetrols in PM₁₀ and PM_2.5 were 17.5 ± 15.4 ng m⁻³ and 13.8 ± 12.2 ng m⁻³, respectively. The 2-methyltetrols exhibited significant positive correlations with ambient relative humidity and temperature, likely due to the higher isoprene emission strength and enhanced formation yield under higher temperature and humidity conditions. In contrast, there was no relationship between the concentration of 2-methyltetrols and sunshine duration. The significant positive correlation ( R² = 0.76) between 2-methyltetrols and SO₄²⁻ indicated that high concentrations of SO₄²⁻ can increase the formation rate of 2-methyltetrols from isoprene. Moreover, 2-methyltetrols were also observed in the winter time in Beijing, illustrating the enhancement of the 2-methyltetrol formation rate by high concentrations of pollutants in ambient aerosol.► First ambient aerosol measurements of 2-methyltetrols by HPAEC. ► A clear seasonal variation of 2-methyltetrol levels observed in PM_2.5 and PM₁₀. ► 2-Methyltetrols can still be detected during the winter in Beijing, China. ► Meteorological factors have various effects on the concentrations of 2-methyltetrols. ► Aerosol acidity may promote the formation of 2-methyltetrols in urban areas.

Keywords: 2-Methyltetrols; Seasonal variation; Biogenic SOA; Isoprene oxidation; HPAEC

Characteristics of 2-methyltetrols in ambient aerosol in Beijing, China by Linlin Liang; Guenter Engling; Fengkui Duan; Yuan Cheng; Kebin He (pp. 376-381).

Keywords: 2-Methyltetrols; Seasonal variation; Biogenic SOA; Isoprene oxidation; HPAEC

Characteristics of 2-methyltetrols in ambient aerosol in Beijing, China by Linlin Liang; Guenter Engling; Fengkui Duan; Yuan Cheng; Kebin He (pp. 376-381).

Keywords: 2-Methyltetrols; Seasonal variation; Biogenic SOA; Isoprene oxidation; HPAEC

Geochemical evidence on the source regions of Tibetan Plateau dusts during non-monsoon period in 2008/09 by Chaoliu Li; Shichang Kang; Qianggong Zhang; Shaopeng Gao (pp. 382-388).

Geochemical characteristics, source regions and related transport patterns of dust over the Tibetan Plateau (TP) are still unclear. To address these issues, major (Na, Mg, Al, K and Ca), trace (e.g. Li, Cr, Ni, As, Cd, Cs, Pb and U) and rare earth elements of dust samples from five snow-pits over the TP and its fringe areas during the non-monsoon period in 2008/2009 were analyzed. The results indicate that rare earth element compositions of snow-pit dust are similar to those of the upper continental crust. Enrichment factors of all the elements of snow-pit dust are identical to those of the <20 μm fraction of TP surface soils, especially for typical pollution elements (e.g. Cu and Ni) and elements like Li, As and Cs that are concentrated in surface soils. In contrast, concentrations of some typical pollution elements (e.g. Cr and Cd) of snow-pit dust are lower than those of dusts derived from the Sahara Desert and the Thar Desert surrounding the TP. Additionally, the compositions of rare earth elements and high field strength elements (Hf, Zr and Nb) of snow-pit dust are also similar to those of surface soils and different from dusts of these two deserts. The combined evidence, including dust transport patterns around the TP, supports the conclusion that the TP itself is the main source region of snow-pit dusts of the inner TP. It is unlikely that those particle-bound pollutants are transported into the TP from outside sources during the non-monsoon period.► Dust of five snow-pits across the Tibetan Plateau (TP) was measured for elements. ► Elemental compositions of dust are similar to those of top soil of the TP. ► Elemental compositions of dust are different with that of deserts surrounded the TP. ► Dust transport patterns also show outside dust can not be transported into the TP. ► Particle-bound pollutants can barely be transported into the TP from outside.

Keywords: Snow-pit; Dust transportation; Geochemical composition

Geochemical evidence on the source regions of Tibetan Plateau dusts during non-monsoon period in 2008/09 by Chaoliu Li; Shichang Kang; Qianggong Zhang; Shaopeng Gao (pp. 382-388).

Keywords: Snow-pit; Dust transportation; Geochemical composition

Geochemical evidence on the source regions of Tibetan Plateau dusts during non-monsoon period in 2008/09 by Chaoliu Li; Shichang Kang; Qianggong Zhang; Shaopeng Gao (pp. 382-388).

Keywords: Snow-pit; Dust transportation; Geochemical composition

Effect of isothermal dilution on emission factors of organic carbon and n-alkanes in the particle and gas phases of diesel exhaust by Yuji Fujitani; Katsumi Saitoh; Akihiro Fushimi; Katsuyuki Takahashi; Shuich Hasegawa; Kiyoshi Tanabe; Shinji Kobayashi; Akiko Furuyama; Seishiro Hirano; Akinori Takami (pp. 389-397).

To investigate the effect of isothermal dilution (30 °C) on emission factors (EFs) of semivolatile and nonvolatile compounds of heavy-duty diesel exhaust, we measured EFs for particulate matter (PM), organic carbon (OC), and elemental carbon (EC) in the particle phase, and EFs for n-alkanes in both the particle phase and the gas phase of exhaust produced under high-idle engine operating conditions at dilution ratios (DRs) ranging from 8 to 1027. The EC EFs did not vary with DR, whereas the OC EFs in the particle phase determined at DR = 1027 were 13% of the EFs determined at DR = 8, owing to evaporation of organic compounds. Using partitioning theory and n-alkane EFs measured at DR = 14 and 238, we calculated the distributions of compounds between the particle and gas phases at DR = 1760, which corresponds to the DR for tailpipe emissions as they move from the tailpipe to the roadside atmosphere. The gas-phase EF of a compound with a vapor pressure of 10⁻⁷ Pa was 0.01 μg kg⁻¹-fuel at DR = 14, and this value is 1/330 the value derived at DR = 1760. Our results suggest that the EFs of high-volatility compounds in the particle phase will be overestimated and that the EFs of low-volatility compounds in the gas phase will be underestimated if the estimates are derived from data obtained at the low DRs and they are applied to the real world. Therefore, extrapolation from EFs derived at low DR values to EFs at atmospherically relevant DRs will be a source of error in predictions of the concentrations of particulate matter and gas-phase precursors to secondary organic aerosols in air quality models.► We measured emission factors of semivolatile compounds in diesel exhaust. ► Partitioning between the particle and gas phases of n-alkanes were measured. ► Dilution ratios affects on emission factors of semivolatile compounds. ► Emission factor determined at low dilution is an error when it applies to real-world.

Keywords: Emission factor; Chemical composition; n; -Alkane; Semivolatile compound; Dilution ratio; Partitioning

Self organizing ozone model for Empty Quarter of Saudi Arabia: Group method data handling based modeling approach by Syed Masiur Rahman; A.N. Khondaker; Radwan Abdel-Aal (pp. 398-407).

In arid regions primary pollutants contribute to the increase of ozone levels, which cause negative effects on biotic health. This study investigates the use of abductive networks based on the group method data handling (GMDH) for ozone prediction. Abductive network models are automatically synthesized from a database of inputs and outputs. The models are developed for a location in the Empty Quarter, Saudi Arabia, first using only the meteorological data and derived meteorological data. In the subsequent efforts, NO and NO₂ concentrations and their transformations were incorporated as additional inputs. Another model forecasted ozone level after 1 h using mainly meteorological data, NO, and NO₂ concentrations. Models built for specific period of day are simpler compared to the generic models. Finally, ensemble modeling approach was also investigated. A time specific model produced mean absolute percentage error (MAPE) of 3.82%. The proposed models are self-organizing in nature and require less intervention from the users, and can be implemented easily by the interested practitioners.► Investigation of ozone levels at the Empty Quarter, Saudi Arabia. ► Development of self organizing abductive network using group method data handling. ► Use of meteorological data, NO and NO₂ concentrations as input. ► Models built for specific period of day are simpler than the generic model. ► Investigation of ensemble modeling approach.

Keywords: Abductive networks; Group method data handling (GMDH); Ozone modeling; Prediction; Machine learning; Empty Quarter

Self organizing ozone model for Empty Quarter of Saudi Arabia: Group method data handling based modeling approach by Syed Masiur Rahman; A.N. Khondaker; Radwan Abdel-Aal (pp. 398-407).

Keywords: Abductive networks; Group method data handling (GMDH); Ozone modeling; Prediction; Machine learning; Empty Quarter

Self organizing ozone model for Empty Quarter of Saudi Arabia: Group method data handling based modeling approach by Syed Masiur Rahman; A.N. Khondaker; Radwan Abdel-Aal (pp. 398-407).

Keywords: Abductive networks; Group method data handling (GMDH); Ozone modeling; Prediction; Machine learning; Empty Quarter

Retrieved actual ET using SEBS model from Landsat-5 TM data for irrigation area of Australia by Weiqiang Ma; Mohsin Hafeez; Umair Rabbani; Hirohiko Ishikawa; Yaoming Ma (pp. 408-414).

The idea of ground-based evapotranspiration (ET) is of the most interesting for land–atmosphere interactions, such as water-saving irrigation, the performance of irrigation systems, crop water deficit, drought mitigation strategies and accurate initialization of climate prediction models especially in arid and semiarid catchments where water shortage is a critical problem. The recent year's drought in Australia and concerns about climate change has prominent the need to manage water resources more sustainably especially in the Murrumbidgee catchment which utilizes bulk water for food security and production.This paper discusses the application of a Surface Energy Balance System (SEBS) model based on Landsat-5 TM data and field observations has been used and tested for deriving ET over Coleambally Irrigation Area (CIA), located in the southwest of NSW, Australia. 16 Landsat-5 TM scenes were selected covering the time period of 2009, 2010 and 2011 for estimating the actual ET in CIA. To do the validation the used methodology, the ground-measured ET was compared to the Landsat-5 TM retrieved actual ET results for CIA. The derived ET value over CIA is much closer to the field measurement. From the remote sensing results and observations, the root mean square error (RMSE) is 0.74 and the mean APD is 7.5%. The derived satellite remote sensing values belong to reasonable range.► The idea of ET is of the most interesting for land–atmosphere interactions. ► SEBS model for deriving ET over Coleambally Irrigation Area (CIA). ► In-situ ET was compared to RS retrieved ET results.

Keywords: Evapotranspiration; Murrumbidgee; Coleambally Irrigation Area; TM5; SEBS

Retrieved actual ET using SEBS model from Landsat-5 TM data for irrigation area of Australia by Weiqiang Ma; Mohsin Hafeez; Umair Rabbani; Hirohiko Ishikawa; Yaoming Ma (pp. 408-414).

Keywords: Evapotranspiration; Murrumbidgee; Coleambally Irrigation Area; TM5; SEBS

Retrieved actual ET using SEBS model from Landsat-5 TM data for irrigation area of Australia by Weiqiang Ma; Mohsin Hafeez; Umair Rabbani; Hirohiko Ishikawa; Yaoming Ma (pp. 408-414).

Keywords: Evapotranspiration; Murrumbidgee; Coleambally Irrigation Area; TM5; SEBS

A high-order model for accurately simulating the size distribution of ultrafine particles in a traffic tunnel by Peter E.J. Vos; Irina Nikolova; Stijn Janssen (pp. 415-425).

We present a computational model for simulating the dispersion of traffic emitted particulate matter inside a road tunnel, with an emphasis on the number concentration of ultrafine particles (UFP). The model primarily calculates the size distribution of the particle number concentration at each location inside the tunnel. The proposed model differs from existing models in the sense that it uses a continuous representation of the size distribution based upon the high-order finite element method and that it solves the governing equations using the state-of-the-art discontinuous Galerkin method. Next to the traditional transport processes, the model also implements the most important aerosol transformation processes such as coagulation, condensation and dry deposition. It is shown that based upon parametrisations found in literature, the process of condensation in a traffic tunnel cannot properly be modelled. Therefore, we present a correction factor that allows for a better parametrisation. The adequate performance of the model is demonstrated by both a verification study and a validation study. For the verification we show that the discretisation error converges consistently while for the validation we compare the modelled results with a suitable set of data from a UFP measurement campaign in a Taiwanese traffic tunnel. The model is shown to correctly simulate the observed behaviour and by applying a statistical model evaluation we demonstrate that the proposed model meets widely accepted air quality model acceptance criteria.Display Omitted► We present a model for simulating the particle number distributions in a road tunnel. ► The model combines the high-order finite element method with the discontinuous Galerkin method. ► The parametrisation of condensation appears to be a critical uncertainty. ► Validation against measurements gives R² = 0.85, NMSE = 0.18, FB = −0.025, FAC2 = 83%.

Keywords: Ultrafine particles; Size-resolved; Traffic tunnel; Coagulation; Condensation; Dry deposition; UFP emissions; Discontinuous Galerkin; High-order finite elements

A high-order model for accurately simulating the size distribution of ultrafine particles in a traffic tunnel by Peter E.J. Vos; Irina Nikolova; Stijn Janssen (pp. 415-425).

Keywords: Ultrafine particles; Size-resolved; Traffic tunnel; Coagulation; Condensation; Dry deposition; UFP emissions; Discontinuous Galerkin; High-order finite elements

A high-order model for accurately simulating the size distribution of ultrafine particles in a traffic tunnel by Peter E.J. Vos; Irina Nikolova; Stijn Janssen (pp. 415-425).

Keywords: Ultrafine particles; Size-resolved; Traffic tunnel; Coagulation; Condensation; Dry deposition; UFP emissions; Discontinuous Galerkin; High-order finite elements

Source apportionment of indoor, outdoor and personal PM_2.5 exposure of pregnant women in Barcelona, Spain by M.C. Minguillón; A. Schembari; M. Triguero-Mas; A. de Nazelle; P. Dadvand; F. Figueras; J.A. Salvado; J.O. Grimalt; M. Nieuwenhuijsen; X. Querol (pp. 426-436).

Exposure to air pollution has been shown to adversely affect foetal development in the case of pregnant women. The present study aims to investigate the PM composition and sources influencing personal exposure of pregnant women in Barcelona. To this end, indoor, outdoor and personal exposure measurements were carried out for a selection of 54 pregnant women between November 2008 and November 2009. PM_2.5 samples were collected during two consecutive days and then analysed for black smoke (BS), major and trace elements, and polycyclic aromatic hydrocarbons (PAHs) concentrations. Personal information such as commuting patterns and cosmetics use was also collected.PM_2.5 concentrations were higher for personal samples than for indoor and outdoor environments. Indoor, outdoor and personal BS and sulphate concentrations were strongly correlated, although some specific indoor and outdoor sulphate sources may exist. Average trace elements concentrations were similar indoor, outdoor and for personal exposure, but the correlations were moderate for most of them. Most of the PAHs concentrations showed strong correlations indoor–outdoor.A source apportionment analysis of the PM composition data by means of a Positive Matrix Factorization (PMF) resulted in the identification of six sources for the outdoor and indoor environments: secondary sulphate, fueloil + sea salt (characterized by V, Ni, Na and Mg), mineral, cigarette (characterized by K, Ce, Cd, benzo(k)fluoranthene and benzo(ghi)perylene), road traffic (characterized by BS and low weight PAHs), and industrial (characterized by Pb, Sn, Cu, Mn and Fe). For personal exposure two specific sources were found: cosmetics (characterized by abundance of Ca, Li, Ti and Sr and the absence of Al) and train/subway (characterized by Fe, Mn, Cu and Ba). The contribution of the sources varied widely among women, especially for cigarette (from zero to up to 4 μg m⁻³), train/subway (up to more than 6 μg m⁻³) and cosmetics (up to more than 5 μg m⁻³). The source contributions showed generally strong correlations indoor–outdoor although the infiltration efficiencies varied among homes. This study emphasizes the importance of relying on personal exposure in epidemiological studies assessing the impact of air pollution on human health.► PM measurements and source apportionment indoor, outdoor and personal exposure. ► PM_2.5 concentrations higher for personal exposure than for indoor and outdoor. ► Specific sources for personal exposure: cosmetics and train/subway. ► Importance of relying on personal exposure in epidemiological studies.

Keywords: Personal exposure; Trace elements; PAHs; PMF; Pregnancy

‘Erratum to “Urban NH₃ levels and sources in a Mediterranean environment” [Atmos. Environ. 57 (2012) 153–164]’ by Cristina Reche; Mar Viana; Marco Pandolfi; Andrés Alastuey; Teresa Moreno; Fulvio Amato; Anna Ripoll; Xavier Querol (pp. 437-437).

Analysis of motorcycle fleet in Hanoi for estimation of air pollution emission and climate mitigation co-benefit of technology implementation by Nguyen Thi Kim Oanh; Mai Thi Thuy Phuong; Didin Agustian Permadi (pp. 438-448).

A fleet of over two million motorcycles (MC) in Hanoi is believed to contribute a substantial emission of air pollutants and climate forcers but has not been thoroughly characterized. This study conducted a survey of the MC technologies and activities in Hanoi using questionnaires, GPS monitoring, and video camera in 2008. The data were collected for three typical road types (highways, arterials, residential streets) in 3 zones of the city. Majority of MC in Hanoi were relatively new (3.6 years), had 4-stroke engine, but only 6% was equipped with catalyst exhaust control devices. About 35% of the fleet did not comply with any EURO standards. The MC daily driving was 20 km, mostly done on arterial streets. The main driving features in Hanoi arterials and residential streets were of low speeds with frequent starts/stops and idling. International Vehicle Emissions (IVE) model produced adjusted emission factors (EFs) that were compared with the limited available measurement data. The fleet emission was estimated for 2008 as a base case and for two “what-if” faster technology implementation scenarios: scenario 1 assumed that the entire fleet in 2008 conformed at least EURO2 and scenario 2 assumed 100% MC met the EURO3 standard. Total emissions from the fleet in 2008 of CO, VOC, NO_x, SO₂, PM₁₀, and CH₄ were 158, 51.5, 9.5, 0.17, 2.4 and 9.5 kt, respectively. Emissions of 1,3-butadiene, acetaldehydes, formaldehydes and benzene were 0.26, 1.2, 4.9 and 2.1 kt, respectively. Faster EURO3 technology intrusion in scenario 2 would significantly reduce the emission of pollutants (by 53–94%) and climate forcers in CO₂-equivalent (53% for 20-year and 38% for 100-year horizon), which tripled the reductions obtained under scenario 1. Substantial co-benefits for air quality and climate forcer mitigation could be achieved by the faster technology implementation.► Motorcycle fleet technologies and driving activities in Hanoi were analyzed. ► Questionnaire, GPS and video camera survey were conducted to collect relevant data. ► IVE2.0 was used to generate the base case emission for 2008. ► Faster EURO2 and EURO3 technology intrusion scenarios were considered. ► Air quality and climate co-benefit under the scenarios were quantified.

Keywords: Motorcycle fleet; Hanoi; IVE model; Emission inventory; Climate co-benefit

A tunnel study to characterize PM_2.5 emissions from gasoline-powered vehicles in Monterrey, Mexico by Yasmany Mancilla; Alberto Mendoza (pp. 449-460).

One of the main sources of air pollution in the Monterrey Metropolitan Area (MMA), Mexico, is vehicle exhaust. In this study, emission factors (EFs) for PM_2.5, organic carbon (OC), elemental carbon (EC), trace metals (Na to Pb), cations (Na⁺, K⁺, NH₄⁺) and anions (Cl⁻, NO₃⁻, SO₄²⁻) from mobile sources operating under real-world conditions were determined using the Loma Larga Tunnel (LLT) as the experimental set-up. At each station, low-volume devices were deployed to collect 2.5 h-average PM_2.5 samples. From the samples collected, PM_2.5 EFs as well as chemical profiles were estimated. During the sampling periods conducted for this study, a fleet of 108,569 vehicles crossed the tunnel with average speeds that ranged from 43 km h⁻¹ to 76 km h⁻¹. 97% of the vehicle samples were gasoline-powered vehicles. Average emission rates of 22.8 ± 7.4 mg veh⁻¹ km⁻¹ and 187 ± 144 mg L⁻¹ for PM_2.5 were obtained. Contribution of dust resuspension to the total PM_2.5 EFs was analyzed using silicon (Si) as a key marker and main component of fugitive dust. Based on this analysis, we estimated a contribution of dust resuspension of 20%–25%. Trace metals linked to brake-wear emissions indicate a clear distinction between down-slope and up-slope emission profiles. Even though PM_2.5 EFs tended to be higher during downhill driving conditions, statistically we found no difference between these two driving modes. This could probably be caused by the cancellation of contributions between species that are preferentially emitted during downhill driving (more metal species and less OC and EC) and those emitted during uphill driving (more OC and EC, and less metals). Vehicular PM_2.5 emissions were dominated mainly by OC and EC, species which represented 55.2 ± 2.8% and 16.3 ± 1.6% of the total dust-corrected emitted mass. The OC/EC ratio was 2.85 ± 0.79 and 1.19 ± 0.65 for heavy traffic and moderate traffic conditions, respectively. The results obtained match those of other tunnel studies and can be complementary to the results obtained by other techniques to derive a better emissions inventory for the MMA.► We separate contributions from the exhaust, dust resuspension, and break wear. ► PM_2.5 emission factors were independent of the tunnel grade. ► Emission profiles change as the tunnel grade changes. ► Emission profiles were dominated by organic and elemental carbon. ► The data reported here is the first found in the literature for Monterrey, Mexico.

Keywords: Mobile source; Emission factor; Chemical profile; Particulate matter; On-road emissions

A tunnel study to characterize PM_2.5 emissions from gasoline-powered vehicles in Monterrey, Mexico by Yasmany Mancilla; Alberto Mendoza (pp. 449-460).

Keywords: Mobile source; Emission factor; Chemical profile; Particulate matter; On-road emissions

A tunnel study to characterize PM_2.5 emissions from gasoline-powered vehicles in Monterrey, Mexico by Yasmany Mancilla; Alberto Mendoza (pp. 449-460).

Keywords: Mobile source; Emission factor; Chemical profile; Particulate matter; On-road emissions

Long-term trends of sulfur deposition in East Asia during 1981–2005 by Masatoshi Kuribayashi; Toshimasa Ohara; Yu Morino; Itsushi Uno; Jun-ichi Kurokawa; Hiroshi Hara (pp. 461-475).

We used a chemical transport model to investigate the long-term trends of sulfur deposition in East Asia during 1981–2005. The model reproduced the observed spatial distributions in East Asia of the rate of wet deposition of non-seasalt sulfate (nss-SO₄²⁻), volume-weighted mean concentrations of nss-SO₄²⁻ in precipitation, precipitation, and concentrations in air of gaseous sulfur dioxide and particulate nss-SO₄²⁻. The model also reproduced well observed seasonal variations and long-term trends of wet deposition of nss-SO₄²⁻ in Japan from 1988 to 2005. The increasing rate of wet deposition of nss-SO₄²⁻ in Japan during 1991–2005 was demonstrated with 99.9% significance for both observed and modeled data. The annual rate of total (wet + dry) sulfur deposition in Japan increased from 15.6 Gmol S y⁻¹ in 1981–1985 to 23.9 Gmol S y⁻¹ in 2001–2005 in response to both increasing contributions from Chinese emissions and the eruption of Miyakejima volcano in 2000. During that 25-year period, approximately 2.1% of the sulfur from Chinese emissions was deposited in Japan. Over the same period, the rate of deposition of sulfur in East Asia increased gradually from 14.2 mmol S m⁻² y⁻¹ to 24.0 mmol S m⁻² y⁻¹, and the contribution of emissions from China to total sulfur deposition in East Asia increased from 65% to 77%. The contribution of Miyakejima volcano was 3% during 2001–2005. The increase in the sulfur deposition rate was remarkably high on the North China Plain, around Guangzhou, and south of Chongqing. The rate of increase in East Asia was greatest in winter, although the rate of sulfur deposition was highest in summer. Sulfur flux from China to Japan increased by a factor of 2.5 at altitudes of 0–3000 m from 1981 to 2005.Display Omitted► Our modeled data was consistent with observed data. ► Wet deposition rates increased significantly in Japan during 1991–2005. ► Sulfur deposition in East Asia increased from 14.2 to 24.0 mmol S m⁻² y⁻¹. ► China's contribution increased from 65% to 77% during the 25 years. ► The contribution of Miyakejima volcano was 3% during 2001–2005.

Keywords: Sulfur deposition; Long-term trends; East Asia; Chemical transport model; China; Miyakejima volcano

Long-term trends of sulfur deposition in East Asia during 1981–2005 by Masatoshi Kuribayashi; Toshimasa Ohara; Yu Morino; Itsushi Uno; Jun-ichi Kurokawa; Hiroshi Hara (pp. 461-475).

Keywords: Sulfur deposition; Long-term trends; East Asia; Chemical transport model; China; Miyakejima volcano

Long-term trends of sulfur deposition in East Asia during 1981–2005 by Masatoshi Kuribayashi; Toshimasa Ohara; Yu Morino; Itsushi Uno; Jun-ichi Kurokawa; Hiroshi Hara (pp. 461-475).

Keywords: Sulfur deposition; Long-term trends; East Asia; Chemical transport model; China; Miyakejima volcano

Performance criteria to evaluate air quality modeling applications by P. Thunis; A. Pederzoli; D. Pernigotti (pp. 476-482).

A set of statistical indicators fit for air quality model evaluation is selected based on experience and literature: The Root Mean Square Error (RMSE), the bias, the Standard Deviation (SD) and the correlation coefficient ( R). Among these the RMSE is proposed as the key one for the description of the model skill. Model Performance Criteria (MPC) to investigate whether model results are ‘good enough’ for a given application are calculated based on the observation uncertainty ( U). The basic concept is to allow for model results a similar margin of tolerance (in terms of uncertainty) as for observations. U is pollutant, concentration level and station dependent, therefore the proposed MPC are normalized by U. Some composite diagrams are adapted or introduced to visualize model performance in terms of the proposed MPC and are illustrated in a real modeling application. The Target diagram, used to visualize the RMSE, is adapted with a new normalization on its axis, while complementary diagrams are proposed. In this first application the dependence of U on concentrations level is ignored, and an assumption on the pollutant dependent relative error is made. The advantages of this new approach are finally described.► New method to evaluate air quality models based on observation uncertainty. ► The same margin of tolerance is allowed for models as for observations. ► New criteria and diagrams to visualize fulfillment zones are described. ► Various dependencies (pollutant, concentrations level…) can be considered. ► Example diagrams and criteria values from measurements are provided.

Keywords: Statistical model evaluation; Performance criteria; Air quality modeling; Quality objectives; Observation uncertainty

Performance criteria to evaluate air quality modeling applications by P. Thunis; A. Pederzoli; D. Pernigotti (pp. 476-482).

Keywords: Statistical model evaluation; Performance criteria; Air quality modeling; Quality objectives; Observation uncertainty

Performance criteria to evaluate air quality modeling applications by P. Thunis; A. Pederzoli; D. Pernigotti (pp. 476-482).

Keywords: Statistical model evaluation; Performance criteria; Air quality modeling; Quality objectives; Observation uncertainty

Factors controlling sea salt abundances in the urban atmosphere of a coastal South American megacity by Marina Dos Santos; Laura Dawidowski; Patricia Smichowski; Ana Graciela Ulke; Darío Gómez (pp. 483-491).

The South Atlantic oceanic influence in the ambient air of Buenos Aires was studied on the basis of the measured concentrations of Cl⁻, Mg²⁺ and Na⁺, as chemical markers of marine aerosols. A total of 113 fine (PM_2.5) and 113 coarse (PM_2.5–10) samples were collected over a one-year period in an inland sampling site located ∼250 km from the open sea and ∼7.5 km from the shore of the La Plata River, which flows into the Atlantic Ocean. The ratio r_ion-PM between the added concentrations of the three ions and the corresponding aerosol mass concentration was also used as a sea salt indicator. The behavior of these indicators under various meteorological conditions was used to identify and characterize the presence of sea salt in the urban aerosol. The influence of regional meteorological conditions was assessed by means of the Potential Source Contribution Function (PSCF) while that of local conditions was assessed by categorized percentile distributions analysis. The pattern of the PSCF for different ranges of the four sea salt indicators, exhibiting a transition from lowest values under continental influence to highest values under oceanic influence, provided robust evidence that the marine aerosol from the South Atlantic Ocean reaches the city of Buenos Aires. The r_ion-PM ratio, which combines the opposite effects of wind speed on the aerosol mass and ion concentrations, was identified as the most sensitive indicator of sea salt aerosol variations. Percentile distributions of the r_ion-PM ratio, disaggregated according to onshore (NE, E, SE, S) and offshore (N, NW, W, SW) winds and speeds above and below the median (4.3 m s⁻¹), clearly indicated that the highest levels of marine aerosol occurred under onshore winds and wind speeds > 4.3 m s⁻¹. In addition to characterizing the oceanic influence in Buenos Aires, we reported the expected sea salt levels under different conditions and estimated the magnitude of chloride depletion. This is the first study on sea salt levels in the urban atmosphere of this coastal megacity that reports and makes available a set of consistent concentrations of marine aerosol markers measured over a one-year period.► Sea salt is always present in PM_2.5 and PM_2.5–10 of the Buenos Aires aerosol. ► Oceanic influence under local and regional meteorological conditions is ratified. ► The ratio {[Cl⁻]+[Mg²⁺]+[Na⁺]}/PM best expresses variability in sea salt levels. ► Simple mathematical tools provide robust results to characterize sea salt patterns. ► Significant Cl⁻ depletion was registered from both, PM_2.5 and PM_2.5–10.

Keywords: Marine aerosols; Sea salt chemical markers; Sodium chloride; Chloride depletion; Back-trajectory analysis; Buenos Aires; Argentina

Land use to characterize spatial representativeness of air quality monitoring stations and its relevance for model validation by Stijn Janssen; Gerwin Dumont; Frans Fierens; Felix Deutsch; Bino Maiheu; David Celis; Elke Trimpeneers; Clemens Mensink (pp. 492-500).

The spatial representativeness of air quality monitoring stations is a crucial parameter when the observed concentration levels are used in an air quality assessment. Spatial representativeness defines to what extent the monitoring data is meaningful and useful in a spatial context. Within this paper a generic and robust methodology is presented for the assessment of the spatial representativeness of air pollution monitoring sites. The methodology relies on a statistical approach that links annual averaged concentration levels with land use characteristics. The methodology is demonstrated for the monitoring sites in the Belgian telemetric air quality network and then applied to define a set of zones with a given confidence level. Within such a zone the concentrations deviate to a maximum percentage from the measured values at the monitoring sites. Furthermore, the relevance of spatial representativeness for model validation is addressed and the technique is illustrated for the validation of the results of the regional air quality model BelEUROS. In general, the overall improvement of the model validation by taking into account spatial representativeness can be quantified as in the order of 20%.► A generic and robust methodology for spatial representativeness is presented. ► Methodology can be used to define a zone of a given confidence level. ► The relevance of spatial representativeness for model validation is addressed. ► Overall improvement of model validation can be quantified as in the order of 20%.

Keywords: Spatial representativeness; Land use; Air quality monitoring stations; Model validation

Isoprene and terpenoid emissions from Abies alba: Identification and emission rates under ambient conditions by Olga Pokorska; Jo Dewulf; Crist Amelynck; Niels Schoon; Maja Šimpraga; Kathy Steppe; Herman Van Langenhove (pp. 501-508).

In this study, biogenic volatile organic compound (BVOC) emissions from Abies alba were studied under ambient conditions in Flanders (Belgium). Emission patterns and rates were investigated from April till November 2010 by using the dynamic branch enclosure technique. The present work revealed that A. alba is an isoprene emitter, with isoprene accounting for 86–93% of total BVOC emissions, except during budburst (67%) in May. The emission spectrum of A. alba consisted of 27 compounds. Next to isoprene, the main emitted compounds were α-pinene, β-pinene, camphene and limonene. BVOC emissions showed a peak in June after development of the young needles, followed by a constant emission during summer months and September and a decrease in October. In all the samples isoprene was the most abundant compound with standardized emission rates between 27 μg g_(dw)⁻¹ h⁻¹ in June and 4.6 μg g_(dw)⁻¹ h⁻¹ in October, while the total standardized terpenoid emission rates ranged from 2.85 μg g_(dw)⁻¹ h⁻¹ in June to 0.26 μg g_(dw)⁻¹ h⁻¹ in October. The obtained average β coefficients according to the temperature dependent algorithm of during April–June, July, August and September–October were as follows: for terpenoids 0.12 ± 0.03, 0.11 ± 0.05, 0.12 ± 0.04, 0.24 ± 0.01 K⁻¹ and sesquiterpenes (SQTs) 0.09 ± 0.02, 0.11 ± 0.01, 0.10 ± 0.05, 0 K⁻¹, respectively. Overall, isoprene detected in this study was never quantified in previous studies on A. alba and this finding could have a significant impact on the regional BVOCs budget. Therefore, the result of this study is very important for modeling and local air quality.► Seasonal variation of BVOC emissions from Abies alba trees under ambient conditions in Flanders (Belgium). ► Isoprene was the main emitted compound (86–93% of the total BVOC emissions), which was never quantified. ► Emission spectrum consisted of 27 compounds including 7 SQT.

Keywords: Biogenic volatile organic compounds; Isoprene; Abies alba; Seasonal variations; Emission rates; Belgium

Net atmospheric mercury deposition to Svalbard: Estimates from lacustrine sediments by Paul E. Drevnick; Handong Yang; Carl H. Lamborg; Neil L. Rose (pp. 509-513).

In this study we used lake sediments, which faithfully record Hg inputs, to derive estimates of net atmospheric Hg deposition to Svalbard, Norwegian Arctic. With the exception of one site affected by local pollution, the study lakes show twofold to fivefold increases in sedimentary Hg accumulation since 1850, likely due to long-range atmospheric transport and deposition of anthropogenic Hg. Sedimentary Hg accumulation in these lakes is a linear function of the ratio of catchment area to lake area, and we used this relationship to model net atmospheric Hg flux: preindustrial and modern estimates are 2.5 ± 3.3 μg m⁻² y⁻¹ and 7.0 ± 3.0 μg m⁻² y⁻¹, respectively. The modern estimate, by comparison with data for Hg wet deposition, indicates that atmospheric mercury depletion events (AMDEs) or other dry deposition processes contribute approximately half (range 0–70%) of the net flux. Hg from AMDEs may be moving in significant quantities into aquatic ecosystems, where it is a concern because of contamination of aquatic food webs.► We measured mercury in sediment cores collected from lakes in Svalbard (Norway). ► Sedimentary mercury accumulation has increased twofold to fivefold since 1850. ► We estimate a modern net atmospheric mercury flux of 7 ± 3 μg m⁻² y⁻¹. ► Atmospheric mercury depletion events may contribute, on average, half of the net flux.

Keywords: Mercury; Atmospheric deposition; Arctic; Svalbard; Lake sediments

Net atmospheric mercury deposition to Svalbard: Estimates from lacustrine sediments by Paul E. Drevnick; Handong Yang; Carl H. Lamborg; Neil L. Rose (pp. 509-513).

Keywords: Mercury; Atmospheric deposition; Arctic; Svalbard; Lake sediments

Net atmospheric mercury deposition to Svalbard: Estimates from lacustrine sediments by Paul E. Drevnick; Handong Yang; Carl H. Lamborg; Neil L. Rose (pp. 509-513).

Keywords: Mercury; Atmospheric deposition; Arctic; Svalbard; Lake sediments

Detailed modeling of the atmospheric degradation mechanism of very-short lived brominated species by G. Krysztofiak; V. Catoire; G. Poulet; V. Marécal; M. Pirre; F. Louis; S. Canneaux; B. Josse (pp. 514-532).

Detailed chemical reaction schemes for the atmospheric degradations of the very short-lived species (VSLS) bromoform (CHBr₃) and dibromomethane (CH₂Br₂) have been established. These degradation schemes have been implemented in the meteorological/tracer transport model CATT-BRAMS used in the present case as pseudo one-dimensional model with chemistry of CH₄, CO, HO_x, NO_x, NO_y and O_x. They include the main possible reactions of the intermediate brominated peroxy radicals RO₂ (with R = CH₂Br, CHBr₂ and CBr₃) for which the most likely reaction pathways with HO₂ have been found using ab initio computational calculations. The full degradation schemes have been run for two well-defined realistic scenarios, “clean” atmosphere and “moderately” NO_y-polluted atmosphere, as representative of a tropical coastal region where these VSLS natural emissions are expected to be important. The Henry’s law constants of the brominated organics products have been estimated by using the Bond Contribution Method (BCM; ) or the Molecular Connectivity Index (MCI; ). Using these constants, the least soluble species formed from the VSLS degradation are found to be CBr₂O, CHBrO, CBr₃O₂NO₂, CHBr₂O₂NO₂, BrO, BrONO₂ and HOBr, which leads those to be potentially transported into the tropical tropopause layer (TTL) in case of deep convection and contribute to stratospheric bromine additionally to the original substances. For bromoform and dibromomethane degradation, the moderate NO_y pollution increases the production of the least soluble species and thus approximately doubles the bromine quantity potentially able to reach the TTL (from 22.5% to 43% for CHBr₃ and from 8.8% to 20.2% for CH₂Br₂). The influence of the reactions of the RO₂ radicals with HO₂, CH₃O₂ and NO₂ on the nature and abundance of the stable intermediate and end-products has been tested for CHBr₃ degradation. As a result, the reactions of the RO₂ radicals with NO₂ have no impact. Taking into account the reaction between RO₂ and CH₃O₂ and modifying the branching ratios of the reaction between RO₂ and HO₂ lead to a small impact on the bromoform degradation by slightly decreasing (by 10%) the bromine quantity potentially able to reach the TTL. As a final point, in contrast to CHBr₃, CH₂Br₂ degradation produces negligible quantities of organics species and the effects of pollution increase only the inorganic species production. By taking into account the results of these tests, new simplified degradation schemes for CHBr₃ and CH₂Br₂ are proposed.► Detailed reaction schemes for the degradations of CHBr₃ and CH₂Br₂ are established. ► CHBr₃ and CH₂Br₂ degradations in clean and NO_x-polluted atmospheres are modeled. ► The importance of the different pathways is tested, leading to simplified schemes. ► Henry’s law constants of the degradation organics products are estimated. ► NO_x pollution increases the bromine quantities able to reach the TTL.

Keywords: Modeling; ab initio; Calculation; Bromine; Henry’s law constants; Chemical degradation mechanism; Very short-lived species; CHBr; ₃; CH; ₂; Br; ₂; Stratosphere; Tropical tropopause layer

Concentration and oxidative potential of on-road particle emissions and their relationship with traffic composition: Relevance to exposure assessment by Leigh R. Crilley; Luke D. Knibbs; Branka Miljevic; Xiaochun Cong; Kathryn E. Fairfull-Smith; Steve E. Bottle; Zoran D. Ristovski; Godwin A. Ayoko; Lidia Morawska (pp. 533-539).

Particles emitted by vehicles are known to cause detrimental health effects, with their size and oxidative potential among the main factors responsible. Therefore, understanding the relationship between traffic composition and both the physical characteristics and oxidative potential of particles is critical. To contribute to the limited knowledge base in this area, we investigated this relationship in a 4.5 km road tunnel in Brisbane, Australia.On-road concentrations of ultrafine particles (<100 nm, UFPs), fine particles (PM_2.5), CO, CO₂ and particle associated reactive oxygen species (ROS) were measured using vehicle-based mobile sampling. UFPs were measured using a condensation particle counter and PM_2.5 with a DustTrak aerosol photometer. A new profluorescent nitroxide probe, BPEAnit, was used to determine ROS levels. Comparative measurements were also performed on an above-ground road to assess the role of emission dilution on the parameters measured.The profile of UFP and PM_2.5 concentration with distance through the tunnel was determined, and demonstrated relationships with both road gradient and tunnel ventilation. ROS levels in the tunnel were found to be high compared to an open road with similar traffic characteristics, which was attributed to the substantial difference in estimated emission dilution ratios on the two roadways. Principal component analysis (PCA) revealed that the levels of pollutants and ROS were generally better correlated with total traffic count, rather than the traffic composition (i.e. diesel and gasoline-powered vehicles).A possible reason for the lack of correlation with HDV, which has previously been shown to be strongly associated with UFPs especially, was the low absolute numbers encountered during the sampling. This may have made their contribution to in-tunnel pollution largely indistinguishable from the total vehicle volume. For ROS, the stronger association observed with HDV and gasoline vehicles when combined (total traffic count) compared to when considered individually may signal a role for the interaction of their emissions as a determinant of on-road ROS in this pilot study. If further validated, this should not be overlooked in studies of on- or near-road particle exposure and its potential health effects.► Reactive oxygen species might cause several adverse health effects of particles. ► We measured particle associated ROS on under and above-ground roads. ► Particle associated ROS was best correlated with total traffic volume. ► Non-diesel vehicles shouldn't be overlooked in exposure assessment and modelling.

Keywords: Toxicity; Diesel; Gasoline; Sampling; Exposure

Relationship between water-soluble ions in PM_2.5 and their precursor gases in Seoul megacity by Zang-Ho Shon; Ki-Hyun Kim; Sang-Keun Song; Kweon Jung; Nam-Jin Kim; Jun-Bok Lee (pp. 540-550).

In this study, fine-particle (PM_2.5) ionic composition in the city of Seoul was investigated using short-term measurement data (1 h interval) collected during the year 2010. The partitioning of semi-volatile inorganic species and phase state of aerosols were studied using ISORROPIA II thermodynamic equilibrium model. The analysis of ionic composition identified the relative dominance ofNO3−,SO42−, andNH4+ in the fine particles. The presence of strong correlation between these components indicates similarity of their formation pathways. Seasonal patterns of these ionic components and their gas-phase precursors were somewhat different from each other. The observedSO42−/SO2 mass ratio indicated a significant role of the gas-phase oxidation of SO₂ (to H₂SO₄) in theSO42− formation. Moreover, both SO₄²⁻ and NO₃⁻ were almost completely neutralized by NH₄⁺ to form (NH₄)₂SO₄ and NH₄NO₃. The formation of NO₃⁻ aerosol would be ammonia-sensitive (i.e., deficit ammonia), as evidenced by smaller total ammonia concentration than the sum of total sulfate and nitrate concentrations. The uptake of SO₂ on dust particles during Asian dust event is also likely to exert controls on SO₄²⁻ concentrations.► Chemical composition analysis of urban aerosols has been made over hourly intervals. ► We evaluated the interactions between the target gases and aerosol components. ► Based on this analysis, we accounted for many aspects of fine PM behavior in urban air.

Keywords: Aerosol; Fractionation; Sulfate; Nitrate; Ammonium

Relationship between water-soluble ions in PM_2.5 and their precursor gases in Seoul megacity by Zang-Ho Shon; Ki-Hyun Kim; Sang-Keun Song; Kweon Jung; Nam-Jin Kim; Jun-Bok Lee (pp. 540-550).

Keywords: Aerosol; Fractionation; Sulfate; Nitrate; Ammonium

Relationship between water-soluble ions in PM_2.5 and their precursor gases in Seoul megacity by Zang-Ho Shon; Ki-Hyun Kim; Sang-Keun Song; Kweon Jung; Nam-Jin Kim; Jun-Bok Lee (pp. 540-550).

Keywords: Aerosol; Fractionation; Sulfate; Nitrate; Ammonium

Characterization of carbonaceous aerosol by the stepwise-extraction thermal–optical-transmittance (SE-TOT) method by Yuan Cheng; Ke-bin He; Feng-kui Duan; Zhen-yu Du; Mei Zheng; Yong-liang Ma (pp. 551-558).

Carbonaceous aerosol collected in Beijing, China was characterized by a stepwise-extraction thermal–optical-transmittance (SE-TOT) method which allows for a quantitative separation of organic aerosol into distinct fractions. About 55% of the total organic carbon (OC) could be extracted by a mixture of hexane, methylene chloride and acetone. The extractable OC was further isolated into non-polar, low-polar and high-polar OC which constituted 10%, 23% and 22% of the total OC, respectively. The sum of low-polar and high-polar OC was found to coincide well with the secondary OC predicted by the elemental carbon tracer method, indicating that the low-polar and high-polar OC are strongly associated with secondary organic aerosol. Moreover, it was suggested that high relative humidity could enhance the production of high-polar OC through aqueous-phase reactions, because high-polar OC correlated strongly with oxalate and the ratio of high-polar OC to low-polar OC was significantly higher during the sampling events with high relative humidity (1.23 ± 0.35) comparing with results from the low relative humidity days (0.79 ± 0.23). In addition, the extractable OC was shown to be light-absorbing. The results of this study suggest that the SE-TOT method could provide new insights into the characterization of carbonaceous aerosol.Display Omitted► OC is separated into extractable OC and un-extractable OC. ► Extractable OC is further isolated into non-polar, low-polar and high-polar OC. ► Low-polar and high-polar OC are strongly associated with SOA. ► Extractable OC is light-absorbing.

Keywords: Carbonaceous aerosol; SOA; Brown carbon; Biomass burning

Impacts of aerosol compositions on visibility impairment in Xi'an, China by Jun-ji Cao; Qi-yuan Wang; Judith C. Chow; John G. Watson; Xue-xi Tie; Zhen-xing Shen; Ping Wang; Zhi-sheng An (pp. 559-566).

Daily particle light scattering coefficient, PM_2.5 mass and chemical composition were measured in Xi'an from February to December 2009. Visibility was strongly affected by anthropogenic air pollution sources, resulting in an average visual range (VR) of 6.4 ± 4.5 km. The threshold PM_2.5 mass concentration, corresponding to VR <10 km, was ∼88 μg m⁻³. The revised IMPROVE equation was applied to estimate chemical extinction ( b_ext), which on average was ∼15% lower than measured b_ext. PM_2.5 ammonium sulfate was the largest contributor, accounting for ∼40% of b_ext, followed by organic matter (∼24%), ammonium nitrate (∼23%), and elemental carbon (∼9%), with minor contributions from soil dust (∼3%), and NO₂ (∼1%). High secondary inorganic aerosol contributions (i.e., SO₄²⁻ and NO₃⁻) were the main contributors for VR <5 km. A Positive Matrix Factorization (PMF) solution to the Chemical Mass Balance (CMB) receptor model showed that coal combustion was the dominant factor, accounting for ∼52% of the dry particle light scattering coefficient, followed by the engine exhaust factor (∼31%). Other factors included biomass burning (∼12%) and fugitive dust (∼5%).► Visibility was an average visual range of 6.4 km at Xi'an. ► PM_2.5 concentration, corresponding to the low visibility (<10 km), was ∼88 μg m⁻³. ► PM_2.5 ammonium sulfate accounted for ∼40% of light extinction.

Keywords: Visibility impairment; Light extinction coefficient; Chemical species; Source apportionment

Projected risk of high ozone episodes in 2050 by Hang Lei; Donald J. Wuebbles; Xin-Zhong Liang (pp. 567-577).

We investigate the effects of projected global changes in climate and human-related emissions for the year 2050 relative to 2000 for trends in the potential risk of hazardous ozone pollution episodes using a global climate chemistry model, CAM-Chem, driven by meteorology output from Community Climate System Model 3. Three distinct pathways from the Intergovernmental Panel on Climate Change Special Report on Emissions Scenarios A1FI, A1B and B1 are considered to address the range and uncertainty in projected climate and emission changes. The projected changes in extreme climate conditions are likely to intensify the associated extreme weather conditions that foster the risk of high ozone pollution episodes over many parts of the world. It is found that the changes in regional high surface ozone concentration by 2050 largely depends on changes in the anthropogenic emissions of ozone precursors. Our analysis under projected climate and emissions on the frequency of “hazardous ozone days” in which the peak ozone concentration exceed the limit in the summer of 2050, based on 8 and 1-h standards, show that the risk of hazardous ozone pollution episodes will likely increase in developing regions, but changes of risk in developed regions depend on scenarios. For three major pollutant regions, north America, Europe and East Asia under 8-h definition, the hazardous risk in all regions increases under the A1FI scenario with a potential rate of 39–79 days/summer by 2050, but it is likely to decrease over North America and Europe under the A1B and B1 scenarios. The risk on Europe under the A1B and B1 scenarios can be ignored, but a significant rate of 6–71 days/summer still occur on other regions. The relative variability in projected frequency of hazardous ozone days increase by using the 1-h definition, although it shows the highest risk of 17–59 days/summer under the A1FI scenario. The higher variability can be understood through statistical analysis of cumulative frequency distribution of daily peak ozone concentrations, which shows that the changes of surface ozone level are more significantly presented on the high value part.► Climate change tend to foster the risk of high ozone episodes over major industrial regions. ► The risk of hazardous episodes decrease in developed regions by 2050 (A1B/B1). ► But increase in developing regions by 2050 (A1B/B1). ► Under the A1FI scenario, the risk in all regions increases by 2050. ► The changes of ozone level are more significant on the high value part.

Keywords: High ozone episodes; Surface ozone; Future projection; Climate change; Air quality

Projected risk of high ozone episodes in 2050 by Hang Lei; Donald J. Wuebbles; Xin-Zhong Liang (pp. 567-577).

Keywords: High ozone episodes; Surface ozone; Future projection; Climate change; Air quality

Projected risk of high ozone episodes in 2050 by Hang Lei; Donald J. Wuebbles; Xin-Zhong Liang (pp. 567-577).

Keywords: High ozone episodes; Surface ozone; Future projection; Climate change; Air quality

Linking in-vehicle ultrafine particle exposures to on-road concentrations by Neelakshi Hudda; Sandrah P. Eckel; Luke D. Knibbs; Constantinos Sioutas; Ralph J. Delfino; Scott A. Fruin (pp. 578-586).

For traffic-related pollutants like ultrafine particles (UFP), a significant fraction of overall exposure occurs within or close to the transit microenvironment. Therefore, understanding exposure to these pollutants in such microenvironments is crucial to accurately assessing overall UFP exposure. The aim of this study was to develop models for predicting in-cabin UFP concentrations if roadway concentrations are known, quantifying the effect of vehicle characteristics, ventilation settings, driving conditions and air exchange rates (AER). Particle concentrations and AER were measured in 43 and 73 vehicles, respectively, under various ventilation settings and driving speeds. Multiple linear regression (MLR) and generalized estimating equation (GEE) regression models were used to identify and quantify the factors that determine inside-to-outside (I/O) UFP ratios and AERs across a full range of vehicle types and ages. AER was the most significant determinant of UFP I/O ratios, and was most strongly influenced by ventilation setting (recirculation or outside air intake). Further inclusion of ventilation fan speed, vehicle age or mileage, and driving speed explained greater than 79% of the variability in measured UFP I/O ratios.Display Omitted► Significant overall ultrafine particle (UFP) exposure occurs in vehicles. ► In-vehicle exposures depend on inside-to-outside UFP ratios (I/O). ► At outside air setting, I/O is determined mostly by fan strength. ► Under recirculation, I/O is determined by vehicle age and speed. ► Fleet-wide UFP exposure varies 10-fold.

Keywords: Ultrafine particles; In-vehicle; Exposure; Microenvironment; Air exchange rate; Model

Linking in-vehicle ultrafine particle exposures to on-road concentrations by Neelakshi Hudda; Sandrah P. Eckel; Luke D. Knibbs; Constantinos Sioutas; Ralph J. Delfino; Scott A. Fruin (pp. 578-586).

Keywords: Ultrafine particles; In-vehicle; Exposure; Microenvironment; Air exchange rate; Model

Linking in-vehicle ultrafine particle exposures to on-road concentrations by Neelakshi Hudda; Sandrah P. Eckel; Luke D. Knibbs; Constantinos Sioutas; Ralph J. Delfino; Scott A. Fruin (pp. 578-586).

Keywords: Ultrafine particles; In-vehicle; Exposure; Microenvironment; Air exchange rate; Model

Seasonal comparisons of single-particle chemical mixing state in Riverside, CA by Xueying Qin; Kerri A. Pratt; Laura G. Shields; Stephen M. Toner; Kimberly A. Prather (pp. 587-596).

The Study of Organic Aerosols in Riverside, CA (SOAR) field campaign, conducted in the summer and fall of 2005, focused on developing a stronger understanding of seasonal influences on the sources and processes contributing to some of the highest levels of particulate matter in the United States. On-line single-particle mass spectrometry measurements showed that carbonaceous particles generally dominated the submicron size range (>75% by number), compared to primarily aged sea salt and dust in the supermicron size range. During periods with high PM_2.5 (particulate matter <2.5 μm) mass and number concentrations, hygroscopic water-containing carbonaceous particles internally mixed with sulfate and nitrate extended up into the supermicron size mode. The mixing state of carbonaceous particles changed with season. In the summer, carbonaceous particles were primarily mixed with secondary (oxidized) organic carbon and sulfate; whereas in the fall, they were mixed mostly with ammonium nitrate. During each season, different processes contributed to the highest pollution levels. In the summer, photochemical production of highly aged secondary organic carbon resulted in daily peaks in both number and mass particle concentrations, followed by removal in the afternoon by the arrival of the clean marine air masses from the coast. In contrast, cooler, more stagnant meteorological conditions in the fall season resulted in the buildup over several days of submicron carbonaceous particles mixed with semivolatile ammonium, nitrate, and amines. In addition, Santa Ana wind events in the fall led to dust and biomass burning particles dominating both the submicron and supermicron size ranges.► Average PM_2.5 concentrations were similar in Riverside, CA in the summer and fall. ► Organic carbon and sulfate dominated aerosol mass concentrations in the summer. ► Santa Ana periods in the fall were characterized by high dust concentrations. ► Stagnation periods in the fall were characterized by organics and ammonium nitrate.

Keywords: PM; _2.5; Aerosol chemistry; Single-particle mass spectrometry; California

Seasonal comparisons of single-particle chemical mixing state in Riverside, CA by Xueying Qin; Kerri A. Pratt; Laura G. Shields; Stephen M. Toner; Kimberly A. Prather (pp. 587-596).

Keywords: PM; _2.5; Aerosol chemistry; Single-particle mass spectrometry; California

Seasonal comparisons of single-particle chemical mixing state in Riverside, CA by Xueying Qin; Kerri A. Pratt; Laura G. Shields; Stephen M. Toner; Kimberly A. Prather (pp. 587-596).

Keywords: PM; _2.5; Aerosol chemistry; Single-particle mass spectrometry; California

Airborne measurements of O₃, CO, CH₄ and NMHCs over the Bay of Bengal during winter by Shuchita Srivastava; S. Lal; S. Venkataramani; I. Guha; D. Bala Subrahamanyam (pp. 597-609).

As part of the Winter phase of Integrated Campaign for Aerosols, gases and Radiation Budget (WICARB), airborne measurements of ozone (O₃), carbon monoxide (CO), methane (CH₄), ethane (C₂H₆), ethene (C₂H₄), acetylene (C₂H₂), propane (C₃H₈) and n-butane (n-C₄H₁₀) were conducted over the Bay of Bengal (BoB) at two altitude levels, 750 m and 1500 m, from Visakhapatnam, Chennai and Port Blair during January 2009. Airborne measurements, first of its kind over the BoB, revealed distinct chemical characteristics at these two altitudes over the eastern sector of Visakhapatnam away from the coastline. This feature is attributed to the presence of marine boundary layer inversion between the two altitudes that inhibited the vertical mixing. A comparative study of trace gas distributions during all air sorties showed enhanced mixing ratios of these gases over east of Visakhapatnam and south of Port Blair in comparison to the north/north–east and west of Port Blair and east of Chennai. The back-trajectory analysis showed the outflow from the highly polluted Indo-Gangetic Plain over eastern side of Visakhapatnam. The air masses showed lower photochemical processing (higher C₂H₂/CO ratio ∼ 4–4.5 pptv ppbv⁻¹) with the age of ∼ 3–4 days over this location in comparison to other sorties. Chemical characteristics over south of Port Blair seem to be controlled by the outflow from Southeast Asian countries. The results presented in this work would serve as valuable inputs for the atmospheric chemistry transport models and will be helpful in reducing the uncertainty in the budget estimation of trace gases over tropical marine region.► Airborne measurements of O₃, CO, CH₄ and NMHCs over the Bay of Bengal (BoB). ► Transport of pollutants from Indo-Gangetic Plain and Southeast Asia over the BoB. ► Estimation of photochemical processing and age of air masses using NMHCs. ► Photo-chemically fresh pollution plume was observed over the northern BoB.

Keywords: Airborne measurements; Ozone; Carbon monoxide; NMHCs; Bay of Bengal; Transport

Airborne measurements of O₃, CO, CH₄ and NMHCs over the Bay of Bengal during winter by Shuchita Srivastava; S. Lal; S. Venkataramani; I. Guha; D. Bala Subrahamanyam (pp. 597-609).

Keywords: Airborne measurements; Ozone; Carbon monoxide; NMHCs; Bay of Bengal; Transport

Airborne measurements of O₃, CO, CH₄ and NMHCs over the Bay of Bengal during winter by Shuchita Srivastava; S. Lal; S. Venkataramani; I. Guha; D. Bala Subrahamanyam (pp. 597-609).

Keywords: Airborne measurements; Ozone; Carbon monoxide; NMHCs; Bay of Bengal; Transport

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