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Atmospheric Environment (v.49, #)

Editorial board (pp. i).

Critical review of receptor modelling for particulate matter: A case study of India by Pallavi Pant; Roy M. Harrison (pp. 1-12).

India is used as a case study in reviewing the application of receptor models for source apportionment. India has high concentrations of airborne particulate matter, and the application of effective abatement measures is a high priority, and demands confidence in the results of source apportionment studies. The many studies conducted are reviewed, and reveal a very wide range of conclusions, even for the same city. To some degree these divergences may be the result of using different sampling locations and/or seasons, but to a large extent differences probably arise from methodological weaknesses. The assignment of factors from multivariate receptor models to specific source categories is in many cases highly questionable as factors often include combinations of chemical constituents that are of low plausibility. This ambiguity in terms of presence of tracer elements may be the result of genuine collinearity of diverse sources, or more probably arises from methodological problems. Few studies have used either organic molecular markers or chemical mass balance (CMB) models, and there is a shortage of data on locally-derived emission source profiles, although recent work has begun to remedy this weakness. The conclusions include a number of recommendations for use in design of future studies.► Many studies in India have used multivariate statistical models and a few CMB. ► The results are diverse and not explained entirely by different sampling locations. ► Methodological issues are identified. ► Genuine overlaps in chemical composition between soil and road dust create problems. ► Recommendations are given for future studies.

Keywords: Receptor model; PM; Source apportionment; Chemical mass balance; Multivariate models; India

Critical review of receptor modelling for particulate matter: A case study of India by Pallavi Pant; Roy M. Harrison (pp. 1-12).

Keywords: Receptor model; PM; Source apportionment; Chemical mass balance; Multivariate models; India

An assessment of GHG emissions from small ruminants in comparison with GHG emissions from large ruminants and monogastric livestock by G. Zervas; E. Tsiplakou (pp. 13-23).

Greenhouse gas (GHG) emissions are expected to cause global warming which results in extreme weather changes that could affect crop yields and productivity, food supplies and food prices. It is also expected that climate change will have an impact on animal metabolism and health, reproduction and productivity. On the other hand, the expected increased demand of animal origin products in the coming years will increase the reared animal numbers and consequently GHG emissions. This paper outlines the main GHGs emitted from livestock which are CO₂, CH₄ and N₂O, coming from respiration, enteric fermentation and manure management respectively, with CH₄ and N₂O having the highest global warming potential. Ruminant livestock has the highest contribution to these GHG emissions with small ruminants share being 12.25% of the total GHG emissions from livestock's enteric and manure CH₄, and manure N₂O in CO₂ equivalent, producing 9.45 kg CO₂ equivalent per kg body weight with the respective values for cattle, pigs and poultry being 5.45, 3.97 and 3.25. Since the production systems significantly affect the GHG emissions, the grazing, livestock crop complex, and intensive ones account for 30.5%, 67.29% and 5.51% for total CH₄ emission (from enteric fermentation and manure management) and 24.32%, 68.11% and 7.57% for N₂O respectively. Taking into account the positive and negative impacts of small ruminant livestock production systems to the environmental aspects in general, it is recommended that a number of potentially effective measures should be taken and the appropriate mitigation technologies should be applied in order to reduce effectively and essentially the GHG emissions to the atmosphere, with no adverse effects on intensification and increased productivity of small ruminants production systems.► Ruminants have higher GHG emissions compared to monogastrics. ► Feeding system and manure management are the main factors affecting GHG emissions. ► Beef has the largest footprint followed by lamb, pork, chicken and milk. ► Grazing and livestock crop complex systems have higher carbon footprint than intensive. ► Mitigation strategies can be applied to livestock farming systems to reduce GHG.

Keywords: Greenhouse gas emissions; Mitigation; Ruminants; Monogastrics; Carbon footprint

An assessment of GHG emissions from small ruminants in comparison with GHG emissions from large ruminants and monogastric livestock by G. Zervas; E. Tsiplakou (pp. 13-23).

Keywords: Greenhouse gas emissions; Mitigation; Ruminants; Monogastrics; Carbon footprint

Air pollution retention within a complex of urban street canyons: A two-city comparison by Jennifer Richmond-Bryant; Adam Reff (pp. 24-32).

Uncharacterized microscale spatial and temporal variability in urban air pollutant concentration dynamics may contribute uncertainty or bias to epidemiological model results. In this study, a method for quantifying this variability is presented. Urban buildings were treated as a matrix of bluff bodies to estimate the retention of air pollution in the street canyons downstream of the buildings. This method was based primarily on bluff body theoretical work that derived functional relationships between nondimensional contaminant residence time ( H) within a wake and the following fluid properties of the air: 1) Reynolds Number (Re), 2) street canyon height ( D) to width ( W) aspect ratio ( D/ W), and 3) turbulence intensity, defined as the square root of turbulence kinetic energy ( k) divided by the freestream wind speed ( U). Empirical relationships between these variables were built from sulfur hexafluoride (SF₆) concentration and meteorological data collected during the Midtown Manhattan 2005 (MID05) Study held in August, 2005 in Manhattan, NY, along with geographical information system (GIS) data describing the building topography. Results were then compared with results from a similar previous analysis using data collected during the Joint Urban 2003 (JU2003) study in Oklahoma City, OK. For the MID05 data, Re ranged from 1.65 × 10⁶ to 7.74 × 10⁷, with a median of 1.13 × 10⁷. The range of Re was consistent with earlier observations from the JU2003 study, although the measured winds tended to be more turbulent (median k = 2.2 m² s⁻²) compared with JU2003 (median k = 0.45 m² s⁻²). Values for H ranged from 7.2 to 1186, with a median H of 80.9. The distribution of H was substantially wider for MID05 than for JU2003, with model estimates exceeding observations of H by an order of magnitude for single obstacle wind tunnel studies with Re ∼ 10⁴. Inverse relationships were validated between H and Re and between H and D/ W for the MID05 data and for a pooled data analysis from the MID05 and JU2003 studies. The model of H vs. Re for pooled MID05 and JU2003 data provided a good fit overall but produced a positively biased estimate of the Oklahoma City model results. The model of H vs. D/ W for pooled MID05 and JU2003 data did not provide a good fit, suggesting that the building topographies of the two cities are too different to produce a reasonable comparison. These inter-study comparisons suggest that the topographic relationships may contain underlying site-specific features that would require elucidation prior to generalizing to other urban sites. Overall, results from this work present a foundational method for generating estimates of H based on readily available sources of data such as building coordinates and dimensions and meteorological parameters.► A method to quantify variability in urban street canyon air pollutant concentration. ► Empirical equation for contaminant residence time based on meteorology, topography. ► Nondimensional contaminant residence time model provided a good fit to field data

Keywords: Air quality; Air pollution; Dispersion; Epidemiology; Street canyon; Urban

Air pollution retention within a complex of urban street canyons: A two-city comparison by Jennifer Richmond-Bryant; Adam Reff (pp. 24-32).

Keywords: Air quality; Air pollution; Dispersion; Epidemiology; Street canyon; Urban

Studies on the atmospheric fate of propachlor (2-chloro-N-isopropylacetanilide) in the gas-phase by Amalia Muñoz; Teresa Vera; Howard Sidebottom; Milagros Ródenas; Esther Borrás; Mónica Vázquez; Montserrat Raro; Abdelwahid Mellouki (pp. 33-40).

The gas-phase degradation of propachlor (2-chloro-N-isopropylacetanilide), a widely used herbicide, was investigated under atmospheric conditions at the large outdoor European simulation chamber (EUPHORE) in Valencia, Spain. The rate coefficient for the reaction of hydroxyl radicals with propachlor was measured using a conventional relative rate technique. A value of the rate coefficient for the reaction of OH radicals with propachlor, k_OH(propachlor) = (1.5 ± 0.3) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹ was determined at 300 ± 5 K and atmospheric pressure. Rate coefficient data for the reaction of OH radicals with N,N-diisopropylaniline and N-methylacetanilide, which have structural similarities to propachlor, were also obtained using the relative rate method, k_OH(N,N-diisopropylaniline) = (4.4 ± 0.5) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹ and k_OH(N-methylacetanilde) = (2.7 ± 0.2) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹, respectively. The rate coefficients for photolysis of propachlor, J(propachlor) < 2.0 × 10⁻⁵ s⁻¹, and reaction of ozone with propachlor,kO3(propachlor) < 1.5 × 10⁻¹⁹ cm³ molecule⁻¹ s⁻¹, under atmospheric conditions were also determined. The available kinetic data suggest that the gas-phase tropospheric degradation of propachlor will be mainly controlled by reaction with OH and possibly NO₃ radicals, and provide the basis of an estimate for the propachlor tropospheric lifetime of approximately 20 h. The atmospheric implications of the use of this species as a herbicide are discussed.Display Omitted► The gas-phase atmospheric degradation of propachlor was investigated at EUPHORE. ► Studies carried out under ambient conditions and natural sunlight irradiations. ► First experimental values for the reaction of propachlor with OH radicals in gas-phase. ► First experimental values for the reaction of propachlor with ozone in gas-phase. ► Gas-phase tropospheric lifetime for herbicide propachlor of approximately 10 hours.

Keywords: Herbicides; 2-chloro-N-isopropylacetanalide; Propachlor; N,N-diisopropylaniline; N-methylacetanilide; EUPHORE; Tropospheric lifetime

Asian dust storm as conveyance media of anthropogenic pollutants by Wonnyon Kim; Seong-Jae Doh; Yongjae Yu (pp. 41-50).

As conveyance media of natural minerals as well as anthropogenic pollutants, the Asian dust storm (ADS) marks a potential impact on human health in the world's most populated region and on the atmospheric energy budget by absorbing/reflecting the solar radiation in a hemispheric-scale. However, the physicochemical state of individual anthropogenic particulates in ADS including the average grain-size and volume concentrations, grain morphology, and the mixing states with natural minerals is not fully understood. Here we trace pollution features of ADS including the temporal atmospheric loadings of particulates carried by ADS using rock magnetic methods and intensive microscopic analyses. Magnetic concentration has coupled with the total suspended particulates in ADS and has increased ∼9% for the past four years (2004–2007), resulting mainly from the increasing fossil-fuel combustion in East Asia. Notably, most of the observed particles in ADS contain carbon as a major element and some also contain sulfur. In addition, other anthropogenic elemental signatures encompass iron-oxides of combustion origin and heavy metals (Cr, Pb and Zn). Based on the predominance of carbon contents, increasing the atmospheric temperature in East Asia by ADS loadings can be expected by absorbing solar radiation effectively.► Magnetic measurements identified annually increasing flux of particulates in ADS. ► We also presented detailed chemical compositions of individual particulates. ► Most of the particulates were from fossil-fuel combustions. ► Significant carbon concentration possibly increases the energy budget of the Earth.

Keywords: Anthropogenic particulates; Asian dust; Heavy metals; Iron-oxides; Sulfates

Asian dust storm as conveyance media of anthropogenic pollutants by Wonnyon Kim; Seong-Jae Doh; Yongjae Yu (pp. 41-50).

Keywords: Anthropogenic particulates; Asian dust; Heavy metals; Iron-oxides; Sulfates

Air quality diagnosis from comprehensive observations of total OH reactivity and reactive trace species in urban central Tokyo by Ayako Yoshino; Yoshihiro Nakashima; Koji Miyazaki; Shungo Kato; Jeeranut Suthawaree; Nobuo Shimo; Sou Matsunaga; Satoru Chatani; Eric Apel; James Greenberg; Alex Guenther; Hiroyuki Ueno; Hiroyuki Sasaki; Jun-ya Hoshi; Hisashi Yokota; Koichiro Ishii; Yoshizumi Kajii (pp. 51-59).

We have conducted a comprehensive observational study to determine the mixing ratios of atmospheric chemical species and total OH reactivity in central Tokyo, in order to diagnose the air quality during summer and winter 2007 and autumn 2009. Concentrations of over 70 reactive trace species were continuously measured throughout each season. The total OH reactivity was measured directly using a laser-induced pump and probe technique. The observed chemical species exhibited seasonal variations. There was a good correlation between NO and CO in winter, but not in summer. This indicates that during winter, vehicle exhaust provided a significant source of NO in central Tokyo, while photolysis of NO₂ was dominant in summer. Similar values (approximately 30 s⁻¹) for the averaged total OH reactivity were observed in both summer and autumn during the daytime. However, VOCs accounted for a larger percentage of the OH reactivity in summer, while NO_x was more dominant in autumn. We find that photochemical processes leading to oxidant production via VOCs dominated OH removal in summer, while the production of nitric acid from the reaction between OH and NO₂ was dominant in autumn, by-passing the oxidant production pathways and resulting in reduced oxidant formation.► Comprehensive observations in central Tokyo have conducted to diagnose air quality. ► Atmospheric trace species and total OH reactivity were observed simultaneously. ► NO_x accounted for a large contribution to OH reactivity in autumn. ► VOCs accounted for a large percentage of the OH reactivity in summer. ► Different dominant processes in atmospheric reactions depend on season are present.

Keywords: Urban air quality; Total OH reactivity; Tropospheric ozone; Volatile organic compounds

Influence of the sampling site, the season of the year, the particle size and the number of nucleation events on the chemical composition of atmospheric ultrafine and total suspended particles by Jose Ruiz-Jimenez; Jevgeni Parshintsev; Totti Laitinen; Kari Hartonen; Tuukka Petäjä; Markku Kulmala; Marja-Liisa Riekkola (pp. 60-68).

Twenty one organic compounds including three monocarboxylic and ten dicarboxylic acids, four aldehydes, three polyols and one amine were determined in 61 atmospheric aerosol particle samples with different sizes (30 ± 4-nm, 40 ± 5-nm, 50 ± 5-nm and total suspended particles) collected at two sampling sites, the SMEAR II and SMEAR III stations during different seasons of the year. Non supervised pattern recognition techniques, such as hierarchical cluster analysis and principal component analysis were used to study the influence of the collection place, the season of the year and the particle size on the concentration and behavior of the target compounds. The reliability of these results was proved using a supervised pattern recognition technique such as soft independent modeling of class analogy. The results achieved demonstrate that the chemical composition of the atmospheric aerosol particles is affected by the potential emission sources and the reactivity of the studied compounds under certain atmospheric conditions. In addition, from quantitative analysis methodologies partial least squares regression and principal component regression models were successfully used to clarify the influence of the number of nucleation events on the chemical composition of the particles.► 61 aerosol particle samples (30 nm, 40 nm, 50 nm, TSP) were studied. ► Twenty one compounds studied are important in atmospheric aerosol chemistry. ► Chemical composition in ultrafine and TSP samples differ in place and in time. ► Correlations were found between analyte profiles and nucleation event number. ► Statistical models used as data analysis tools successfully completed the study.

Keywords: Aerosol ultrafine particles; Biogenic organic compounds; Anthropogenic organic compounds; SMEAR II station; SMEAR III station; Statistical analysis; Nucleation eventAbbreviations; BSTFA; N,O-bis-(trimethylsilyl)-trifluoroacetamide; DEA; Diethylamine; DMA; Differential mobility analyzer; HCA; Hierarchical cluster analysis; PAH; Polycyclic aromatic hydrocarbons; PCA; Principal component analysis; PCR; Principal component regression; PEEK; Polyether ether ketone; PLSR; Partial least squares regression; PM; Particulate matter; TMCS; Trimethylchlorosilane; TSP; Total suspended particles; SIM; Selected ion monitoring; SIMCA; Soft independent modeling of class analogy; SMEAR; Station for measuring forest ecosystem atmosphere relations

Characteristics of total mercury (TM) wet deposition: Scavenging of atmospheric mercury species by Yong-Seok Seo; Young-Ji Han; Hyun-Deok Choi; Thomas M. Holsen; Seung-Muk Yi (pp. 69-76).

Total mercury (TM) in precipitation samples were collected with a modified MIC-B sampler on the roof of Graduate School of Public Health building in Seoul, Korea from January 2006 to December 2007 to determine the seasonal variations in TM wet deposition and to identify the contribution of reactive gaseous mercury (RGM) and particulate mercury (Hg_p) scavenging to mercury wet deposition. The volume weighted mean (VWM) TM concentrations in 2006 and 2007 were 10.1±17.0ngL⁻¹ and 16.3±16.5ngL⁻¹, respectively and the TM wet deposition flux in 2006 and 2007 were 16.8μgm⁻² and 20.2μgm⁻², respectively. Seasonal VWM TM concentrations in 2006 were highest in fall followed by winter, spring, and summer. In 2007, VWM TM concentrations were greatest in winter, followed by spring, summer, and fall. Nonparametric Mann–Whitney test revealed that there was no statistical difference between fall and summer in 2006 ( p=0.10), however, there was a statistical difference between winter and fall in 2007 ( p<0.01). The high VWM TM concentration in spring was probably due to the yellow sand events suggesting that RGM and Hg_p present in the rain were long-range transported from China during this period. The large wet deposition fluxes observed in summers were possibly due to the intense rainfall. Overall there was a significant positive correlation between rainfall depth and wet deposition flux ( r²=0.22) ( p<0.01) and a significant negative correlation between rainfall depth and TM concentration in precipitation ( r²=0.20) ( p<0.01) due to dilution effects. In addition, a weak positive correlation between TM concentration and wet deposition flux was shown ( r²=0.10) ( p<0.05). Multiple linear regression showed that scavenging coefficient (SC) for RGM was much higher than SC for Hg_p suggesting that RGM was more effectively scavenged by wet deposition than Hg_p (SC_RGM=750 andSCHgp=380).► Total mercury (TM) in precipitation was collected with a modified MIC-B sampler. ► Atmospheric mercury species were also measured to identify their contribution to TM. ► Multiple linear regression revealed RGM was more effectively scavenged than was Hg_p.

Keywords: Total mercury; Seasonal variations; Wet deposition flux; Multiple linear regression; Scavenging coefficient

Characteristics of total mercury (TM) wet deposition: Scavenging of atmospheric mercury species by Yong-Seok Seo; Young-Ji Han; Hyun-Deok Choi; Thomas M. Holsen; Seung-Muk Yi (pp. 69-76).

Keywords: Total mercury; Seasonal variations; Wet deposition flux; Multiple linear regression; Scavenging coefficient

Particle Exposure Assessment for Community Elderly (PEACE) in Tianjin, China: Mass concentration relationships by Jian Zhou; Bin Han; Zhipeng Bai; Yan You; Jiefeng Zhang; Can Niu; Yating Liu; Nan Zhang; Fei He; Xiao Ding; Bing Lu; Yandi Hu (pp. 77-84).

Particle Exposure Assessment for Community Elderly (PEACE) in Tianjin, China was to characterize personal PM₁₀ exposure, and provide data support for an epidemiological study investigating potential health effects of PM pollution on Chinese elderly population. In this study, a total of 80 elderly participants were recruited for a two-consecutive-day personal exposure measurement, and simultaneously residential indoor, residential outdoor and community PM₁₀ were monitored in the summer and winter of 2009. Personal PM₁₀ concentrations were 192.8 ± 100.6 μg m⁻³ in summer and 154.6 ± 105.4 μg m⁻³ in winter. Modeled personal exposures were less than measured personal exposures while a high coefficient of determination ( R²) of 0.71 was obtained. Based on measured and modeled exposures, a mean personal cloud of 30.2 μg m⁻³ was estimated in summer and 16.5 μg m⁻³ in winter. Moderate correlation emerged between personal and community PM₁₀ concentrations in summer ( r = 0.39), and stronger correlation was found in winter ( r = 0.82). Analysis of variance (ANOVA) shown that smoking, cooking and cleaning activities did not produce significant effect on personal exposures. Further more, multivariate regression analysis performed in this study revealed that community PM₁₀ level contributed most of personal PM₁₀ exposure, 32% in summer and 64% in winter, respectively. The findings of this study indicated that PM₁₀ personal exposures were considerably influenced by outdoor particulate matter rather than typical indoor sources, and ambient PM₁₀ level measured at community monitoring sites may be used as a surrogate of personal exposure to PM₁₀.► Personal PM₁₀ exposures for 80 elderly people were characterized. ► Time-activity patterns of the Chinese elderly were collected. ► Modeled and measured personal exposures were comparable. ► Mean personal cloud of 30.2 μg m⁻³ was estimated in summer and 16.5 μg m⁻³ in winter. ► PM₁₀ personal exposures were considerably influenced by outdoor particulate matter rather than typical indoor sources.

Keywords: Elderly population; Particulate matter; Personal exposure; Time-activity pattern; Personal cloud

Rain pattern analysis and forecast model based on GPS estimated atmospheric water vapor content by Andres Seco; Francisco Ramírez; Eduardo Serna; Eduardo Prieto; Rafael García; Aitor Moreno; Juan Carlos Cantera; Luis Miqueleiz; Jose Enrique Priego (pp. 85-93).

Rain is one of the fundamental processes of the hydrologic cycle as it can be the source of wealth or natural hazards. This experiment focuses in the relationship between rain occurrence and atmospheric pressure (Patm) and atmospheric water vapor content (PW), GPS estimated. The available nine years time series of each variable were analyzed. It allowed to state the existence of three rain patterns and monthly differences in the Patm-PW combinations. In spite of rain episodes take place only for some of the Patm-PW combinations, only these variables are unable to explain the rain occurrences because of not always they take place. This because a forecast sliding windows model with neural network was developed, to capture nonlinear relations that can not to be fully reflected by the lineal probabilistic ones based on the observed rains, Patm and PW series. This model stated a good correlation between the observed rains and the forecast, with a positive impact of the PW but negative of Patm. This model was able to predict the rain precipitation with a reasonable precision and reliable accuracy up to a 56h horizon.► We analyzed the GPS’ availability as atmospheric water vapor content estimator. ► Tree rain-water vapor content-atmospheric pressure patterns were established. ► A rain forecast model GPS PW-based has been developed.

Keywords: GPS; Water vapor; Rain; Forecast model; Meteorology

Atmospheric transport route determines components of Asian dust and health effects in Japan by Kazunari Onishi; Yasunori Kurosaki; Shinji Otani; Atsushi Yoshida; Nobuo Sugimoto; Youichi Kurozawa (pp. 94-102).

Asian dust (yellow sand) events are a frequent problem throughout Northeast Asia, where they produce a diverse range of health issues and symptoms in humans that have been widely reported. Asian dust includes soil-derived metals, anthropogenic metals, and many other air pollutants at various concentrations, depending on the atmospheric transport route. Here, we investigated the possible causes for the diversity in symptoms produced by Asian dust events, as reported in a questionnaire survey, on the basis of the dust components and estimated trajectories. Nine dust events were recorded and classified into three types on the basis of light detection and ranging (lidar) data: Type 1 events with high counts of non-mineral dust (spherical) particles, Type 2 events with high counts of mineral dust particles in comparison to non-mineral dust particles, and Type 3 events with very low counts of non-mineral dust particles as compared with other Asian dust events during the surveillance period. Ensemble backward trajectory analysis showed that the atmospheric transport route indeed accounted for the differences. Subjective symptom scores showed the greatest increase after exposure to Type 1 events and a decrease after exposure to Type 3 events. A variety of aerosols were detected concurrent with Asian dust events, and the link between health effects in humans and changes in pollutant levels was explored. The results suggest that the components of Asian dust should be considered when investigating related health effects.► Asian dust can be classified according to its atmospheric transport route. ► The metal content of Asian dust varies with the route. ► The health effects of Asian dust depend on the components and thus the route.

Keywords: Asian dust; Aerosol; Metal; Health survey; Dust transport route

CO emissions in China: Uncertainties and implications of improved energy efficiency and emission control by Yu Zhao; Chris P. Nielsen; Michael B. McElroy; Lin Zhang; Jie Zhang (pp. 103-113).

A bottom-up methodology and an improved database of emission factors combining the latest domestic field measurements are developed to estimate the emissions of anthropogenic CO from China at national and provincial levels. The CO emission factors for major economic sectors declined to varying degrees from 2005 to 2009, attributed to improved energy efficiency and/or emission control regulations. Total national CO emissions are estimated at 173 Tg for 2005 and have been relatively stable for subsequent years, despite fast growth of energy consumption and industrial production. While industry and transportation sources dominated CO emissions in developed eastern and north-central China, residential combustion played a much greater role in the less developed western provinces. The uncertainties of national Chinese CO emissions are quantified using Monte Carlo simulation at −20% to +45% (95% confidence interval). Due to poor understanding of emission factors and activity levels for combustion of solid fuels, the largest uncertainties are found for emissions from the residential sector. The trends of bottom-up emissions compare reasonably to satellite observation of CO columns and to ground observations of CO₂–CO correlation slopes. The increase in the ratio for emissions of CO₂ relative to CO suggests that China has successfully improved combustion efficiencies across its economy in recent years, consistent with national policies to improve energy efficiency and to control criteria air pollutants.► China's CO emissions are estimated based on a bottom-up method for 2005–2009. ► Improvement of energy efficiency and emission control reduces CO emission factors. ► CO emission trends are consistent with satellite and ground observations. ► Uncertainties come most from residential combustion and non-road transportation.

Keywords: CO; Emission factor; Uncertainty; Energy efficiency; China

CO emissions in China: Uncertainties and implications of improved energy efficiency and emission control by Yu Zhao; Chris P. Nielsen; Michael B. McElroy; Lin Zhang; Jie Zhang (pp. 103-113).

Keywords: CO; Emission factor; Uncertainty; Energy efficiency; China

Modeling and surface observations of arsenic dispersion from a large Cu-smelter in southwestern Europe by Bing Chen; Ariel F. Stein; Nuria Castell; Jesus D. de la Rosa; Ana M. Sanchez de la Campa; Yolanda Gonzalez-Castanedo; Roland R. Draxler (pp. 114-122).

Arsenic is a toxic element for human health. Consequently, a mean annual target level for arsenic at 6 ng m⁻³ in PM10 was established by the European Directive 2004/107/CE to take effect January 2013. Cu-smelters can contribute to one-third of total emissions of arsenic in the atmosphere. Surface observations taken near a large Cu-smelter in the city of Huelva (Spain) show hourly arsenic concentrations in the range of 0–20 ng m⁻³. The arsenic peaks of 20 ng m⁻³ are higher than values normally observed in urban areas around Europe by a factor of 10. The Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model has been employed to predict arsenic emissions, transport, and dispersion from the Cu-smelter. The model utilized outputs from different meteorological models and variations in the model physics options to simulate the uncertainty in the dispersion of the arsenic plume. Modeling outputs from the physics ensemble for each meteorological model driving HYSPLIT show the same number of arsenic peaks. HYSPLIT coupled with the Weather Research and Forecasting (WRF-ARW) meteorological output predicted the right number of peaks for arsenic concentration at the observation site. The best results were obtained when the WRF simulation used both four-dimensional data assimilation and surface analysis nudging. The prediction was good in local sea breeze circulations or when the flow was dominated by the synoptic scale prevailing winds. However, the predicted peak was delayed when the transport and dispersion was under the influence of an Atlantic cyclone. The calculated concentration map suggests that the plume from the Cu-smelter can cause arsenic pollution events in the city of Huelva as well as other cities and tourist areas in southwestern Spain.► We measured hourly As concentrations near a large Cu-smelter in SW Spain. ► The HYSPLIT model was used to predict arsenic emissions, transport, and dispersion from a Cu-smelter. ► The model used a variety of meteorological drivers. ▶ Best results were obtained when the WRF simulation used both four-dimensional data assimilation and surface analysis nudging.

Keywords: Arsenic; Emission and transport; HYSPLIT; WRF

Oligomer and SOA formation through aqueous phase photooxidation of methacrolein and methyl vinyl ketone by Yao Liu; Frank Siekmann; Pascal Renard; Atallah El Zein; Guillaume Salque; Imad El Haddad; Brice Temime-Roussel; Didier Voisin; Roland Thissen; Anne Monod (pp. 123-129).

This work investigates the ability of methacrolein (MACR) and methyl vinyl ketone (MVK) (the two main gas phase atmospheric oxidation products of isoprene) to form oligomers and secondary organic aerosol (SOA) upon aqueous phase OH-oxidation and subsequent water evaporation. For the two precursors, electrospray mass spectrometry (in infusion and coupled to liquid chromatography) analysis of the reacting solutions brought clear evidence for the formation of oligomer systems having a mass range of up to 1400 Da. More than 11 series of oligomers were found. For MVK, the intensity and masses of oligomers became increasingly important as MVK initial concentrations increased from 0.2 to 20 mM. For both precursors, the oligomers were responsible for the SOA formation during nebulization experiments. The evaluated SOA mass yield ranged from 3.9 to 9.9% for MVK. These yields were time dependent and were in good agreement with the range (1.6–11.7%) obtained for MACR under the same conditions by .► We show clear evidence for the formation of oligomer systems through the aqueous phase reactivity. ► Oligomers are able to form SOA upon water droplet evaporation and with the mass yield of this SOA. ► MACR and MVK can act as important contributors to SOA formation through atmospheric aqueous phase.

Keywords: Aqueous phase OH-oxidation; Methacrolein; Methyl vinyl ketone; Oligomers; Secondary organic aerosol

Characterization, sources and redox activity of fine and coarse particulate matter in Milan, Italy by Nancy Daher; Ario Ruprecht; Giovanni Invernizzi; Cinzia De Marco; Justin Miller-Schulze; Jong Bae Heo; Martin M. Shafer; Brandon R. Shelton; James J. Schauer; Constantinos Sioutas (pp. 130-141).

The correlation between health effects and exposure to particulate matter (PM) has been of primary concern to public health organizations. An emerging hypothesis is that many of the biological effects derive from the ability of PM to generate reactive oxygen species (ROS) within affected cells. Milan, one of the largest and most polluted urban areas in Europe, is afflicted with high particle levels. To characterize its ambient PM, fine and coarse PM (PM_2.5 and PM_2.5–10, respectively) samples were collected on a weekly basis for a year-long period. Samples were analyzed for their chemical properties and ROS-activity. A molecular marker chemical mass balance (MM-CMB) model was also applied to apportion primary and secondary sources to fine organic carbon (OC) and PM. Findings revealed that PM_2.5 is a major contributor to ambient particle levels in Milan, averaging 34.5 ± 19.4 μg m⁻³ throughout the year. Specifically, secondary inorganic ions and organic matter were the most dominant fine PM species contributing to 36 ± 7.1% and 34 ± 6.3% of its mass on a yearly-based average, respectively. Highest PM_2.5 concentrations occurred during December–February and were mainly attributed to poor atmospheric dispersion. On the other hand, PM_2.5–10 exhibited an annual average of 6.79 ± 1.67 μg m⁻³, with crustal elements prevailing. Source apportionment results showed that wood-smoke and secondary organic aerosol sources contribute to 4.6 ± 2.6% and 9.8 ± 11% of fine OC on a yearly-based average, respectively. The remaining OC is likely associated with petroleum-derived material that is not adequately represented by existing source profiles used in this study. Lastly, ROS-activity measurements indicated that PM_2.5-induced redox activity expressed per m³ of air volume is greatest during January (837 μg Zymosan equivalents m⁻³) and February (920 μg Zymosan equivalents m⁻³). Conversely, intrinsic (per PM mass) ROS-activity peaked in July (22,587 μg Zymosan equivalents mg⁻¹ PM) and August (25,161 μg Zymosan equivalents mg⁻¹ PM), suggesting the influence of specific components on oxidant properties of PM. A correlation analysis between ROS-activity and select PM chemical components showed that Ni, Cr, Cu and water-soluble OC are strongly associated with ROS.► PM levels in Milan are dominated by PM_2.5, which exceeded the EU annual mean limit. ► Secondary inorganic ions and organic matter mostly contributed to PM_2.5. ► Wood-smoke and SOA accounted for 4.6 and 9.8% of fine OC on a yearly-basis. ► Residual OC was mostly attributed to petroleum-based material. ► Reactive Oxygen Species (ROS)-activity strongly correlated with Ni, Cr, Cu, WSOC.

Keywords: PM; Chemical speciation; Source apportionment; CMB; Redox activity; Milan

Chemical composition and sources of aerosol particles at Zeppelin Mountain (Ny Ålesund, Svalbard): An electron microscopy study by Stephan Weinbruch; David Wiesemann; Martin Ebert; Katharina Schütze; Roland Kallenborn; Johan Ström (pp. 142-150).

Aerosol particles were collected at the Zeppelin Mountain Atmospheric Research Station (474m asl) near Ny Ålesund (Svalbard, Norway) on 27 different days between July 2007 and December 2008. The size, morphology and chemical composition of 57,617 individual particles were studied by high-resolution scanning electron microscopy and energy-dispersive X-ray microanalysis. Based on chemical composition, morphology, mixing state and stability under electron bombardment, the particles were assigned to one of the following groups: sea salt, aged sea salt, Ca sulphates, Na sulphates, carbonates, soot, silicates, fly ashes, secondary aerosol, secondary aerosol plus sodium, secondary aerosol plus soot, mixed particles and others.Sea salt, aged sea salt, silicates and mixed particles (mixtures of sea salt, silicates and Ca sulphates) are the most abundant groups for particles with aerodynamic diameters>0.5μm, secondary aerosol, mixed particles and secondary aerosol with soot inclusions below 0.5μm. Silicate fly ashes (major source coal burning) and metal fly ashes (from metallurgical high temperature processes) occur only at very low number concentrations. In contrast to previous work, the fly ash abundance is not correlated with air masses that crossed industrialized regions in Central and Eastern Europe, Scandinavia or Russia. These observations indicate a significant reduction of long-range transport of heavy metals to Svalbard. Soot (external and internally mixed with secondary aerosol) shows a pronounced seasonal pattern with a much lower abundance during summer compared to spring, autumn and winter. The soot abundance is not correlated with the air mass back-trajectories. During summer (July and August), soot was only observed when cruise ships were present in the area around Ny Ålesund (Kongsfjorden). Pronounced seasonal patterns were observed for the abundance of the mineral dust component which is generally lower in summer compared to the other seasons. The observed seasonal dependence of anthropogenic primary particles (soot, fly ashes) is in good agreement with the Arctic circulation pattern.► Chemical composition of aerosol particles in the Arctic background. ► Long-range transport of fly ashes from coal burning and metallurgy declined. ► Soot shows a pronounced seasonal concentration pattern (highest in winter/spring). ► The mineral dust abundance among coarse particles is lowest in summer.

Keywords: Aerosol particles; Polar aerosol; Source apportionment; Soot; Electron microscopy

Regional scale photochemical model evaluation of total mercury wet deposition and speciated ambient mercury by Kirk R. Baker; Jesse O. Bash (pp. 151-162).

Methylmercury is a known neurotoxin with deleterious health effects on humans and wildlife. Atmospheric deposition is the largest source of mercury loading to most terrestrial and aquatic ecosystems. Regional scale air quality models are needed to quantify mercury deposition resulting from complex emissions sources and physical and chemical processes that govern the fate of mercury in the atmosphere. Total mercury wet deposition estimates from multiple regional photochemical transport models applied at 12km grid resolution over the continental United States compare well with observations (CAMx fractional error=45%, CMAQ fractional error=33%) despite uncertainties in global mercury emissions inventories and certain chemical transformation pathways. In addition, both CMAQ and CAMx well represent observed diel and seasonal patterns of Hg(0) and tend to exaggerate the diel patter of Hg(II) at AMNet monitor locations. The observed fraction of particulate mercury to total oxidized mercury (sum of particulate mercury and Hg(II)) is generally greater in colder months and during overnight hours. The modeling systems tend to capture these patterns but have a systematically lower fraction of particulate mercury to total oxidized mercury, especially in winter months.Annual total mercury deposition from wet and dry processes is 65% greater in CMAQ compared to CAMx over the entire modeling domain. This is largely due to higher wet deposition in CMAQ and higher dry deposition of Hg(0), which is treated as equilibrium with mercury re-emissions and not modeled in CAMx. A sensitivity using CAMx with Hg(0) dry deposition treated similar to CMAQ resulted in more comparable total mercury deposition estimates. Modeled dry deposition velocities for Hg(II) compare well with the limited experimental data, while Hg(0) dry deposition velocities are lower than published experimental data. A mercury bi-directional flux sensitivity application in CMAQ had the overall effect of reducing total mercury dry deposition and slightly improving ambient Hg(0) performance. The range of the domain wide total deposition from all model sensitivities was within 25% of the mean but exhibited larger deviations in the individual wet and dry deposition budgets. The contribution of mercury initial conditions and lateral boundary inflow conditions were tracked separately using CAMx source apportionment. Initial contribution to total mercury deposition for the entire model domain falls below 5% after 2 weeks. Boundary contribution to total mercury deposition vary considerably across the continental United States, but ranges between 20 and 99% at MDN monitor locations.► Annual mercury 12km CAMx and CMAQ photochemical model simulations evaluated. ► Performance compared to wet deposition and ambient speciated mercury networks. ► Dry deposition velocities compared to experimental measurements.

Keywords: Mercury; Air quality modeling; CAMx; CMAQ; AMNet; MDN; Deposition

Regional scale photochemical model evaluation of total mercury wet deposition and speciated ambient mercury by Kirk R. Baker; Jesse O. Bash (pp. 151-162).

Keywords: Mercury; Air quality modeling; CAMx; CMAQ; AMNet; MDN; Deposition

Climate change mitigation strategies for mechanically controlled repositories: The case of The National Archives, Kew by Sung H. Hong; Matija Strlič; Ian Ridley; Konstantinos Ntanos; Nancy Bell; May Cassar (pp. 163-170).

A computer based building simulation model was developed to examine the energy load and environmental management in The National Archives Q1 repository building in Kew, UK to optimise environmental management and examine the impacts of climate change. The need to accurately simulate the hygrothermal environment inside the archive building which houses mainly paper-based records led to the choice of EnergyPlus as the modelling software. The study presents the simulation results of five environmental strategies which predict energy saving potential as high as 43% without significantly affecting the quality of the preservation environment. The effect of climate change is predicted to have little impact on the archive environment due to the filtering effect of the air conditioning system. On the other hand, an increase in total energy load by 15% and 24% is predicted under the worst case climate change scenario in 2050 and 2080, respectively, if the current environmental management practice is continued into the future. However, the identified energy saving strategies could represent possible mitigative solutions in reducing future energy load against the impact of climate change.► The indoor climate of The National Archives, Kew was modelled using EnergyPlus. ► The model was used to predict implications of climate change on energy load. ► The HVAC energy load may increase up to 24% until 2080 with current settings. ► Environmental set-points can be optimised to reduce this impact significantly. ► Optimised energy use and preservation outcome can be achieved this way.

Keywords: Heritage collections; Archival repositories; Climate change; Modelling; Energy consumption

Uncertainty in the relationship between criteria pollutants and low birth weight in Chicago by Naresh Kumar (pp. 171-179).

Using the data on all live births (∼400,000) and criteria pollutants from the Chicago Metropolitan Statistical Area (MSA) between 2000 and 2004, this paper empirically demonstrates how mismatches in the spatiotemporal scales of health and air pollution data can result in inconsistency and uncertainty in the linkages between air pollution and birth outcomes. This paper suggests that the risks of low birth weight associated with air pollution exposure changes significantly as the distance interval (around the monitoring stations) used for exposure estimation changes. For example, when the analysis was restricted within 3 miles distance of the monitoring stations the odds of LBW (births <2500 g) increased by a factor of 1.045 (±0.0285 95% CI) with a unit increase in the average daily exposure to PM₁₀ (in μg m⁻³) during the gestation period; the value dropped to 1.028 when the analysis was restricted within 6 miles distance of air pollution monitoring stations. The effect of PM₁₀ exposure on LBW became null when controlled for confounders. But PM_2.5 exposure showed a significant association with low birth weight when controlled for confounders. These results must be interpreted with caution, because the distance to monitoring station does not influence the risks of adverse birth outcomes, but uncertainty in exposure increases with the increase in distance from the monitoring stations, especially for coarse particles such as PM₁₀ that settle with gravity within short distance and time interval. The results of this paper have important implications for the research design of environmental epidemiological studies, and the way air pollution (and potentially other environmental) and health data are collocated to compute exposure. While this paper challenges the findings of pervious epidemiological studies that have relied on coarse resolution air pollution data (such as county level aggregated data), the paper also calls for time-space resolved estimate of air pollution to minimize uncertainty in exposure estimation.► How uncertainty in exposure affect risk estimates. ► Mismatch in the spatial scale of health and air pollution data. ► Hybrid approaches necessary to compute robust exposure. ► Challenges the finding of previous studies.

Keywords: Exposure uncertainty; Spatiotemporal misalignment; Health risks

Uncertainty in the relationship between criteria pollutants and low birth weight in Chicago by Naresh Kumar (pp. 171-179).

Keywords: Exposure uncertainty; Spatiotemporal misalignment; Health risks

Source identification of PM₁₀ pollution in subway passenger cabins using positive matrix factorization by Duckshin Park; Miseok Oh; Younghun Yoon; Eunyoung Park; Kiyoung Lee (pp. 180-185).

Monitoring the air quality in subway passenger cabins is important because of the large number of passengers and potentially high levels of air pollution. This report characterized PM₁₀ levels in subway cabins in Seoul, Korea, and identified PM₁₀ sources using elemental analysis and receptor modeling. PM₁₀ levels in subway cabins were continuously measured using a light scattering monitor during rush and non-rush hours. A total of 41 measurements were taken during rush and non-rush hours, and the measurements were repeated in all four seasons. Filter samples were also collected for elemental composition analysis. Major PM₁₀ sources were identified using positive matrix factorization (PMF). The in-cabin PM₁₀ concentrations were the highest in the winter at 152.8 μg m⁻³ during rush hours and 90.2 μg m⁻³ during non-rush hours. While PM₁₀ levels were higher during rush hours than during non-rush hours in three seasons (excluding summer), these levels were not associated with number of passenger. Elemental analysis showed that the PM₁₀ was composed of 52.5% inorganic elements, 10.2% anions, and 37.3% other. Fe was the most abundant element and significantly correlated ( p < 0.01) with Mn ( r = 0.97), Ti ( r = 0.91), Cr ( r = 0.88), Ni ( r = 0.89), and Cu ( r = 0.88). Fe, Mn, Cr, and Cu are indicators of railroad-related PM₁₀ sources. The PM₁₀ sources characterized by PMF were soil and road dust sources (27.2%), railroad-related sources (47.6%), secondary nitrate sources (16.2%), and a chlorine factor mixed with a secondary sulfate source (9.1%). Overall, railroad-related sources contributed the most PM₁₀ to subway cabin air.► PM₁₀ levels in subway cabins were highest during the winter. ► The in-cabin PM₁₀ levels were not associated with passenger number. ► Elemental analysis of PM₁₀ showed that Fe was the most abundant element. ► Four PM₁₀ sources in cabins were identified by positive matrix factorization. ► Railroad-related sources contributed the most PM₁₀ to subway cabin air.

Keywords: PM; ₁₀; Subway cabin; Positive matrix factorization; Source apportionment

Source identification of PM₁₀ pollution in subway passenger cabins using positive matrix factorization by Duckshin Park; Miseok Oh; Younghun Yoon; Eunyoung Park; Kiyoung Lee (pp. 180-185).

Keywords: PM; ₁₀; Subway cabin; Positive matrix factorization; Source apportionment

Trends in atmospheric nitrogen and sulphur deposition in northern Belgium by Jeroen Staelens; Karen Wuyts; Sandy Adriaenssens; Philip Van Avermaet; Hilde Buysse; Bo Van den Bril; Edward Roekens; Jean-Pierre Ottoy; Kris Verheyen; Olivier Thas; Ellen Deschepper (pp. 186-196).

Temporal trends (2002–2009) in air concentrations and wet and dry atmospheric deposition of inorganic nitrogen (N) and sulphur (S) were determined for nine stations in northern Belgium (Flanders). Wet deposition of NH₄⁺, NO₃⁻ and SO₄²⁻ was measured with wet-only precipitation collectors and air concentrations of NH₃, NO₂ and SO₂ with passive samplers. Dry deposition was calculated from the air concentrations and literature-based deposition velocities. Generalized additive models were used to assess seasonal and long-term trends of biweekly measurements. Kendall tests on annual data were also applied but found to be less powerful. There was no trend in wet N deposition, while wet deposition of SO₄²⁻ and air concentrations of NH₃ and SO₂ decreased significantly ( P < 0.05) at seven of the nine stations. For NO₂, no significant long-term trend was detected, but opposite to the other compounds, the NO₂ concentration tended to increase at all stations. Overall, inorganic N deposition and potentially acidifying deposition (N + S) to grassland decreased significantly at seven stations. The N and N + S deposition to grassland in 2009 was generally below deposition targets for 2010, but the difference was not significant when accounting for data uncertainty using a bootstrap resampling procedure. For most stations, atmospheric deposition to heathland and deciduous forest insignificantly exceeded the targets, while deposition to coniferous forest was significantly too high. Consequently, additional policy measures are needed to reach deposition targets in order to prevent further eutrophication and acidification of (semi)natural ecosystems and to protect groundwater layers in Flanders.► First reported time trends of atmospheric N and S deposition in Flanders (Belgium). ► Wet deposition and air concentrations measured at nine stations during 8 years. ► Trend analysis with generalized additive models. ► Deposition declined significantly for SO_x and NH_x, but not for NO_y. ► Long-term (2030) targets and critical loads are still significantly exceeded.

Keywords: Acidifying deposition; Air pollution; Eutrophication; Semiparametric models; Time trend

Mechanistic and kinetic study of the gas-phase reaction of vinyl acetate with ozone by Maoxia He; Haijie Cao; Yanhui Sun; Dandan Han; Jingtian Hu (pp. 197-205).

The reaction mechanisms of vinyl acetate with O₃ are investigated by performing Density Functional Theory (DFT) calculations as an attempt to investigate the photooxidation reaction of acetate in the atmosphere. The detailed reaction mechanisms are proposed. The potential energy surface profiles (PESs) are constructed. Several products (formaldehyde, heroperoxymethyl formate and formic acetic anhydride) resulting from the gas phase reactions are identified by comparing with the experimental results. The experimentally uncertain dominant product of CH₂OO is confirmed to be heroperoxymethyl formate. The experimentally unknown mechanism for the formation of formic acetic anhydride from CH₃OCHOO is proposed. Rate constants of the reaction over the temperature range of 200–2000K are obtained by using Rice–Ramsperger–Kassel–Marcus (RRKM) theory based on the above PES calculations. The rate constants are independent on pressure.► Mechanism and rate constants for ozonolysis reaction of VAC were investigated. ► Detailed potential energy surface and completed reaction mechanism were proposed. ► Formaldehyde, HPMF and formic acetic anhydride are the major products. ► Experimentally uncertain dominant product of CH₂OO is confirmed to be HPMF. ► Unknown mechanism for formation of formic acetic anhydride from IM4 is proposed.

Keywords: Vinyl acetate; Reaction mechanisms; Kinetic study; Quantum chemical method

Mechanistic and kinetic study of the gas-phase reaction of vinyl acetate with ozone by Maoxia He; Haijie Cao; Yanhui Sun; Dandan Han; Jingtian Hu (pp. 197-205).

Keywords: Vinyl acetate; Reaction mechanisms; Kinetic study; Quantum chemical method

Deposition of polychlorinated biphenyls and polybrominated diphenyl ethers in the vicinity of a steel manufacturing plant by Mingliang Fang; Sung-Deuk Choi; Song-Yee Baek; Guangzhu Jin; Yoon-Seok Chang (pp. 206-211).

Spatial distribution and seasonal variation of polychlorinated biphenyl (PCB) and polybrominated diphenyl ether (PBDE) bulk deposition were investigated at four sites at and around an iron and steel making plant in Pohang, South Korea from January 2008 to May 2009. The steel complex site showed the highest average deposition fluxes of 74.0, 2.1, and 41.6 ng m⁻² day⁻¹ for ∑_tri_-_decaPCBs (Tri-DecaCBs), ∑₁₂PCBs (dioxin-like PCBs), and ∑₈PBDEs (8 PBDE congeners), respectively, indicating the steel complex is an important source of PCBs and PBDEs. The PCB deposition was dominated by Tri-TetraCBs and BDE209 was the most abundant PBDE congener. No clear seasonal variation of PCB and PBDE deposition was observed except at the steel complex site. Precipitation appeared to play an important role in the deposition distribution of PCBs, especially when the lowly chlorinated homologues dominated. In addition, the contribution of DL PCBs (dioxin-like PCBs) to the total TEQ (toxicity equivalent quantity) showed a seasonal variation and should not be neglected in the vicinity of a steel complex.► This is one of the few reports on the PCB and PBDE bulk deposition. ► Deposition of persistent organic pollutants around steel complex was investigated. ► Deposition results showed that the steel making is an important source of POPs. ► Long-term seasonal observation was conducted.

Keywords: PCBs; PBDEs; Deposition; Steel complex; Seasonal variation

A comparison of observed and parameterized SO₂ dry deposition over a grassy clearing in Duke Forest by LaToya Myles; Mark W. Heuer; Tilden P. Meyers; Zakiya J. Hoyett (pp. 212-218).

Deposition of trace gases, such as sulfur dioxide (SO₂), can affect plant and soil chemistry in different ecosystems. Measurements over a complex ecosystem, like a forest clearing, are necessary to determine more accurate deposition rates that can be used to improve parameterizations and models. The flux-gradient technique was used to determine SO₂ fluxes over grass in a clearing at Duke Forest, North Carolina, USA on 25 June – 2 July 2008. The mean flux was −0.037 ± 0.024 μg m⁻² s⁻¹. Dew on the canopy enhanced the uptake of SO₂, which increased deposition rates. Deposition velocities (V _d) fluctuated greatly with a mean of 1.00 ± 0.48 cm s⁻¹. The large variation inV _d was not fully captured by estimates determined from a multilayer model (MLM) and a big-leaf model (BLM). Mean deposition velocities derived from the MLM and BLM were 1.25 ± 0.21 cm s⁻¹ and 0.63 ± 0.12 cm s⁻¹, respectively. The model estimations ofV _d in this study were probably affected by uncertainties associated with canopy resistance, particularly with stomatal and non-stomatal processes.► Stomatal and non-stomatal resistances were significant contributors to canopy resistance for SO₂ deposition. ► Deposition rates increased when the canopy was wet with rain or dew. ► Deposition velocities from a multilayer model generally agreed with observed deposition velocities.

Keywords: Sulfur dioxide; Flux-gradient technique; Biosphere/atmosphere interactions; Canopy resistance

A comparison of observed and parameterized SO₂ dry deposition over a grassy clearing in Duke Forest by LaToya Myles; Mark W. Heuer; Tilden P. Meyers; Zakiya J. Hoyett (pp. 212-218).

Keywords: Sulfur dioxide; Flux-gradient technique; Biosphere/atmosphere interactions; Canopy resistance

A noticeable shift in particulate matter levels after platform screen door installation in a Korean subway station by Ki-Hyun Kim; Duy Xuan Ho; Jae-Sik Jeon; Jo-Chun Kim (pp. 219-223).

The concentrations of PM₁₀ and PM_2.5 were measured continuously in both indoors and outdoors of the Seoul Metropolitan Subway network, Korea from Oct. 2007 to Apr. 2008. As the platform screen door (PSD) system was installed in the end of 2007 (8–16 Dec. 2007), these PM data were analyzed for the evaluation of its effectiveness on the control of PM levels. The results indicated that the mean PM₁₀ concentration in the later period (after PSD installation) was significantly reduced by 16% relative to the earlier period. In contrast, in the case of PM_2.5 distinctions were not statistically significant despite a 12% reduction ( P < 0.05). The overall results of this study suggest that the installation of the PSD and ventilating system should have served as one of the important components for maintaining the air quality in the model subway system.► PM₁₀ data were measured continuously both inside the platform and outside the subway stations. ► PM concentrations were compared between before and after the installation of platform screen door (PSD). ► The results were also analyzed to derive the effect of PSD installation on air quality. ► The effectiveness of the PSD is evaluated based on the PM concentration changes.

Keywords: Metro; Underground; Subway; Particulate matter (PM); Platform screen door (PSD)

A noticeable shift in particulate matter levels after platform screen door installation in a Korean subway station by Ki-Hyun Kim; Duy Xuan Ho; Jae-Sik Jeon; Jo-Chun Kim (pp. 219-223).

Keywords: Metro; Underground; Subway; Particulate matter (PM); Platform screen door (PSD)

PM_2.5-bound PAHs and hydroxy-PAHs in atmospheric aerosol samples: Correlations with season and with physical and chemical factors by Ana Isabel Barrado; Susana García; Enrique Barrado; Rosa María Pérez (pp. 224-232).

Over a one-year period, the concentrations of ten polycyclic aromatic hydrocarbons (PAHs) and two of their hydroxy derivatives (OH-PAHs) were monitored in a suburb of Madrid (Spain). The levels of other chemical indicators of urban pollution (nitrogen oxides, sulphur oxides, etc.), as well as a series of meteorological variables (temperature, atmospheric pressure, etc.) were determined simultaneously. PAH concentrations varied according to the environmental conditions such that depending on the wind direction and speed, levels exceeded those expected for outside the central city area. Concentrations of 2-hydroxyphenanthrene ranged from 12 to 200 pg m⁻³ and those of 1-hydroxypyrene from 3 to 60 pg m⁻³. Their variations were directly related to levels of phenanthrene and pyrene and also found to depend on the weather conditions, especially temperature and atmospheric pressure. Through multivariate analysis (factor and cluster analyses) a clear link was detected between the concentrations of PAHs or hydroxy-PAHs and those of other chemical pollutants (nitrogen and sulphur oxides). We also observed an inverse relationship with temperature, ozone concentration, solar radiation and UV radiation intensity. Changes in both PAHs and OH-PAHs were clearly seasonal, increasing in the colder months and undergoing a reduction in the warmer months of the year.► 10 PAH's and 2 OH-PHA's were monitored in PM_2.5 atmospheric samples in a suburban area. ► Variations were found to be related to weather conditions (temperature and pressure). ► Concentrations were higher for the colder months and lower for the warmer period. ► Increased concentrations of ozone/temperature caused disappearance of PAHs and OH-PAHs. ► Changes produced in OH-PAHs followed a similar pattern to that shown by PAHs.

Keywords: PAHs; OH-PAHs; Atmospheric aerosol; HPLC/Fluorescence; Season; Multivariate analysis

Impact of realistic hourly emissions profiles on air pollutants concentrations modelled with CHIMERE by Laurent Menut; Arnaud Goussebaile; Bertrand Bessagnet; Dmitry Khvorostiyanov; Anthony Ung (pp. 233-244).

Regional chemistry-transport models are used for atmospheric composition studies in several contexts: analysis of past events, scenarios studies, trends or forecast. Modelled concentrations are sensitive to many inputs data like anthropogenic surface emissions of NO x_, VOCs and particulate matter. These emissions are provided as annual masses of pollutants for several activity sectors and projected onto a spatial grid. To use these data, modellers must make important assumptions in order to estimate pollutants fluxes for their own model grid and time frequency. Among these hypotheses, the time resolution is crucial and the way to redistribute emissions from annual to hourly fluxes determines the modelled concentrations accuracy. The usual CTMs approaches handle the time distribution with averaged factors. The present study quantifies with the chemistry-transport model CHIMERE the benefit of improving the calculation of traffic emissions fluxes by using hourly NO₂ measurements nearby roadside areas as a proxy of road traffic sources. This work shows very different diurnal variation of emissions from country to country and suggests the use of a new hourly emission factor dataset for various countries. The induced changes are quantified for ozone, nitrogen dioxide and particulate matter surface concentrations over the whole Europe during the summer 2007. It is shown that the daily ozone peak remains relatively insensitive to this improvement whereas the pollutants concentrations during nighttime are closer to the measurements with the new profiles.► Regional atmospheric composition modelling. ► Optimization of anthropogenic hourly emissions profiles. ► Spatialization of traffic emissions over Europe. ► Improvement of the analysis/forecast CHIMERE model.

Keywords: Atmospheric composition; European air quality; Anthropogenic emissions

Five-year roadside measurements of ultrafine particles in a major Canadian city by Kelly Sabaliauskas; Cheol-Heon Jeong; Xiaohong Yao; Yun-Seok Jun; Parnian Jadidian; Greg J. Evans (pp. 245-256).

This study reports the diurnal, seasonal and annual variation of ultrafine particles (UFP) in a large city. Particle number (PN) concentrations were measured in Toronto, Canada on a major arterial roadway between March 2006 and May 2011 using a Fast Mobility Particle Sizer. The PN in the size range of 8–300 nm decreased during the measurement period primarily due to changes in the vehicle fleet. PN₅₀ (particles with diameters less than 50 nm) decreased by 21% between 2006 and 2010. Notably, the majority of the reduction occurred during the winter months. PN₅₀ exhibited the strongest seasonality and diurnal trend. PN_50–100 (particles between 50 and 100 nm) and PN_100–300 (particles between 100 and 300 nm) decreased by 17% and 24%, respectively. Correlation analysis between gas phase criteria pollutants showed good correlation between PN_50–100 and NO₂, SO₂, and PM_2.5. In contrast, PN₅₀ exhibited the highest correlation with temperature, NO and NO₂. A multiple linear regression model was developed for each size fraction. The model adequately explained the annual, seasonal and day-to-day variability of PN_50–100 ( R² = 0.64) and PN_100–300 ( R² = 0.83). The model captured the annual and seasonal variability of PN₅₀ but only partially explained the day-to-day variability ( R² = 0.52). The long-term reductions in PN₅₀ indicate that policy interventions are having some success in slowly decreasing UFP concentrations in Toronto.► Ultrafine particles (UFP) were measured near a roadway in downtown Toronto, Canada. ► The annual, seasonal and diurnal UFP trends were explored between 2006 and 2011. ► Particles with diameters <50 nm and 50–100 nm decreased by 21% and 17%, respectively. ► UFP exhibited correlation with NO, NO₂, SO₂, PM_2.5, temperature, and wind speed. ► A multiple linear regression model successfully predicted UFP concentrations.

Keywords: Ultrafine particles; Particle number concentration; Particle size distribution; Annual variation; Seasonal variation; Diurnal variation

Five-year roadside measurements of ultrafine particles in a major Canadian city by Kelly Sabaliauskas; Cheol-Heon Jeong; Xiaohong Yao; Yun-Seok Jun; Parnian Jadidian; Greg J. Evans (pp. 245-256).

Keywords: Ultrafine particles; Particle number concentration; Particle size distribution; Annual variation; Seasonal variation; Diurnal variation

Ecosystem carbon exchange over a warm-temperate mixed plantation in the lithoid hilly area of the North China by Xiaojuan Tong; Ping Meng; Jinsong Zhang; Jun Li; Ning Zheng; Hui Huang (pp. 257-267).

In recent decades, forest area in China increased rapidly by afforestation and reforestation, especially in its temperate parts. However, lack of information on carbon exchange in temperate plantations in China reduced the accuracy of estimation on regional carbon budget. In this study, CO₂ flux was measured using the eddy covariance method over a broadleaf dominant mixed plantation in the lithoid hilly area of the North China. The results showed that annual maximum photosynthetic capacity ( A_max) varied from 0.81 to 1.22 mg CO₂ m⁻² s⁻¹ and annual initial light use efficiency ( α) from 0.014 to 0.026. Net CO₂ uptake was depressed when vapor pressure deficit (VPD) was more than 2.5 kPa. Annual temperature sensitivity coefficient ( Q₁₀) for ecosystem respiration, ranged from 1.84 to 2.35, was negatively correlated with base ecosystem respiration ( R₀) ( P < 0.05). Annual R₀ decreased but Q₁₀ increased evidently when winter drought occurred. From 2006 to 2010, annual net ecosystem carbon exchange (NEE), Gross primary productivity (GPP) and ecosystem respiration ( R_ec) were −355 ± 34, 1196 ± 21 and 841 ± 43 g C m⁻² yr⁻¹, respectively. The warm-temperate mixed plantation in the lithoid hilly area of the North China was a strong carbon sink of the atmosphere, which was usually weaken when spring drought happened.► The mixed plantation in the lithoid hilly area of the North China was a strong carbon sink. ► Annual net CO₂ uptake declined evidently when spring drought happened. ► Annual base ecosystem respiration decreased but Q₁₀ increased markedly when winter drought occurred.

Keywords: Mixed plantation; Eddy covariance; Net ecosystem carbon exchange; Gross primary productivity; Ecosystem respiration

An analysis of direct-injection spark-ignition (DISI) soot morphology by Teresa L. Barone; John M.E. Storey; Adam D. Youngquist; James P. Szybist (pp. 268-274).

We have characterized particle emissions produced by a 4-cylinder, 2.0 L DISI engine using transmission electron microscopy (TEM) and image analysis. Analyses of soot morphology provide insight to particle formation mechanisms and strategies for prevention. Particle emissions generated by two fueling strategies were investigated, early injection and injection modified for low particle number concentration emissions. A blend of 20% ethanol and 80% emissions certification gasoline was used for the study given the likelihood of increased ethanol content in widely available fuel. In total, about 200 particles and 3000 primary soot spherules were individually measured. For the fuel injection strategy which produced low particle number concentration emissions, we found a prevalence of single solid sub-25nm particles and fractal-like aggregates. The modal diameter of single solid particles and aggregate primary particles was between 10 and 15nm. Solid particles as small as 6nm were present. Although nanoparticle aggregates had fractal-like morphology similar to diesel soot, the average primary particle diameter per aggregate had a much wider range that spanned from 7 to 60nm. For the early fuel injection strategy, liquid droplets were prevalent, and the modal average primary particle diameter was between 20 and 25nm. The presence of liquid droplets may have been the result of unburned fuel and/or lubricating oil originating from fuel impingement on the piston or cylinder wall; the larger modal aggregate primary particle diameter suggests greater fuel-rich zones in-cylinder than for the low particle number concentration point. However, both conditions produced aggregates with a wide range of primary particle diameters, which indicates heterogeneous fuel and air mixing.► We characterized direct-injection spark-ignition soot morphology. ► We analyzed solid sub-25nm spheres and aggregate primary particle sizes. ► The most abundant single solid spheres were 10–15nm diameter. ► Aggregate primary particle diameters ranged from 7 to 60nm.

Keywords: Nanoparticles; Morphology; Transmission electron microscopy; Gasoline exhaust; Emissions

An analysis of direct-injection spark-ignition (DISI) soot morphology by Teresa L. Barone; John M.E. Storey; Adam D. Youngquist; James P. Szybist (pp. 268-274).

Keywords: Nanoparticles; Morphology; Transmission electron microscopy; Gasoline exhaust; Emissions

Nucleation and Aitken mode atmospheric particles in relation to O₃ and NO _X at semirural background in Denmark by Jacob K. Nøjgaard; Quynh T. Nguyen; Marianne Glasius; Lise L. Sørensen (pp. 275-283).

Atmospheric oxidants (O₃, NO and NO₂) and particle size distributions (6–700nm) were studied at a semi-rural background location in Denmark during 2009 to evaluate the sources of particulate matter. Aitken mode particles (30–110nm) and accumulation mode particles (110–700nm) anti-correlated or showed no correlation with O₃. The lower Aitken mode (<30nm), also referred to as the nucleation mode, typically peaked around noon from April to September and correlated positively with O₃, which indicates that photochemistry is likely to be responsible for most of the nucleation mode particles in this period of the year. In the months with low global radiation (October–March), NO₂ correlated positively with the lower Aitken mode, which typically peaked in the morning and afternoon on working days, indicating that traffic is the most important source of nucleation mode particles in that period of the year. A strong correlation was observed for NO₂ and Aitken mode particles throughout the year, which indicate a common traffic source. We also observed growth of Aitken mode particles during high NO _X episodes. While photochemistry and traffic were major sources to Aitken mode particles, a source apportionment analysis identified Secondary Inorganic Aerosols (SIA), as the largest source to PM₁₀ (36% including secondary marine aerosols) in the semi-rural background troposphere in Denmark. Ammonium nitrate was a larger source than ammonium sulfate to the SIA mass fraction, where particulate nitrate exceeded that of sulfates by 2.6 times on a molar basis. Indications are that NO₂, as a precursor for e.g. ammonium nitrate is probably more important than SO₂, as a precursor for ammonium sulfate, in the formation of SIA. In this way, NO₂ from anthropogenic emissions and following conversion to particulate nitrates thus appeared to impact semi-rural atmospheric particulate matter in both the Aitken mode and mass wise in PM₁₀.► Sources to semi-rural atmospheric particles were studied in Denmark, North Europe. ► The correlation of O₃ and NO₂ with particle sizes depended strongly on season. ► Photochemistry and traffic were the most important sources to the nucleation mode. ► Secondary inorganic aerosols was the most important source to PM₁₀ (36%).

Keywords: Atmospheric particles; Oxidants; Nucleation mode; Aitken mode; Source apportionment

Concentrations and properties of airborne particles in the Mexico City subway system by V. Mugica-Álvarez; J. Figueroa-Lara; M. Romero-Romo; J. Sepúlveda-Sánchez; T. López-Moreno (pp. 284-293).

Samples of PM₁₀ and PM_2.5 were collected using High Vol and MiniVol devices on the platform of a subway station in Mexico City and in an outdoor location close to it, using such devices. Soluble extractable organic matter (SEOM) and water solubility of metals were determined. Elemental composition and solubility of trace metals were determined and individual aerosol particles were studied with scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDX). The concentration levels in both sizes were similar during all days with the exception of weekends, especially on Sunday when activity decreases due to lower trains’ frequency. The largest particles concentrations in the subway were found from 06:00 to 14:00 and the lowest concentrations were registered from 22:00 to 06:00. Concentrations of PM_2.5 ranging between 60 μg m⁻³ and 93 μg m⁻³ (10% and 90% percentile) in the subway were 6% larger than outside, whereas PM₁₀ were 20% larger than outside ranging from 88 μg m⁻³ to 145 μg m⁻³. Greater Fe, Cu, Ni, Cr and Mn concentrations were quantified in the subway samples as compared to the airborne particles by up to 2.5, 9, 1.8, 2.0 and 2.6 times, respectively. Even when the solubility percent of these metals in the subway PM was smaller than in the outdoor airborne particles, metals’ concentrations were greater. SEM and EDS exhibit the presence of many individual particles with a large metal content in the subway samples. Correlation analysis showed the influence of outdoor PM in the subway aerosols, but characterization revealed also important differences in the presence of metals and SEOM, due to underground sources such as friction, brake system, and metals from sparking. This means that a large number of commuters are exposed during labor days to large toxic metals concentrations as they transit.► First attempt to study in depth the air quality in the underground system in Mexico. ► Elemental speciation was done to assess the underground’s microenvironment. ► This is a comparative study broaching several world underground systems. ► Water solubility of the metals incorporated into the PM particles was determined. ► SEM micrographs and EDX analysis revealed important aspects of morphology.

Keywords: PM; _2.5; PM; ₁₀; Heavy metals; Subway; Soluble metals; Mexico City

Concentrations and properties of airborne particles in the Mexico City subway system by V. Mugica-Álvarez; J. Figueroa-Lara; M. Romero-Romo; J. Sepúlveda-Sánchez; T. López-Moreno (pp. 284-293).

Keywords: PM; _2.5; PM; ₁₀; Heavy metals; Subway; Soluble metals; Mexico City

Evaluation of a relationship between aerosols and surface downward shortwave flux through an integrative analysis of modeling and observation by Daisuke Goto; Shuhei Kanazawa; Teruyuki Nakajima; Toshihiko Takemura (pp. 294-301).

Although aerosols have great impacts on Surface Downward Shortwave Flux (SDSF), the relationship between aerosol loading and SDSF in global models has not yet been adequately investigated. In this study, we attempt to investigate the effects of aerosol optical thickness (AOT) and single scattering albedo (SSA) on SDSF through an integrative analysis of modeling and observation. At first, we compared the results obtained by a global aerosol model, SPRINTARS, with in-situ measurements, AERONET and BSRN. And then we estimated the impacts of AOT and SSA on SDSF through an offline radiative transfer model, Rstar. Through this study, we found that the difference in SDSF between SPRINTARS and BSRN is much larger over heavy aerosol regions than those over regions. Using the Rstar radiative transfer model, we demonstrated that the AOT difference usually has the strongest impact on the SDSF difference and the SSA difference has a moderate impact over heavy aerosol loading regions, whereas the effect of water vapor can be ignored. Finally, we generated a contour plot to demonstrate the relationships between AOT-SSA-SDSF. For example, at low AOT (e.g., 0.15), the 20 W m⁻² changes in SDSF are required to make more than 0.2 changes of SSA, whereas at high AOT (e.g., 0.85), the same changes in SDSF are required to have only 0.05 changes of SSA.► SDSF in our global aerosol model was evaluated by BSRN measurement. ► The difference in SDSF between the model and BSRN was large over heavy aerosol loading regions. ► Radiation calculation showed that the SDSF difference is primarily resulted from the AOT difference.

Keywords: Global aerosol model; Surface downward shortwave flux (SDSF); Aerosol optical thickness (AOT); Single scattering albedo (SSA); Aerosol radiative forcing (ARF); AERONET; BSRN; Radiation calculation

Re-suspension of lead contaminated urban soil as a dominant source of atmospheric lead in Birmingham, Chicago, Detroit and Pittsburgh, USA by Mark A.S. Laidlaw; Sammy Zahran; Howard W. Mielke; Mark P. Taylor; Gabriel M. Filippelli (pp. 302-310).

Soils in older areas of cities are highly contaminated by lead, due largely to past use of lead additives in gasoline, the use of lead in exterior paints, and industrial lead sources. Soils are not passive repositories and periodic re-suspension of fine lead contaminated soil dust particulates (or aerosols) may create seasonal variations of lead exposure for urban dwellers. Atmospheric soil and lead aerosol data from the Interagency Monitoring of Protected Visual Environments (IMPROVE) database were obtained for Pittsburgh (Pennsylvania), Detroit (Michigan), Chicago (Illinois), and Birmingham (Alabama), USA. In this study the temporal variations of atmospheric soil and lead aerosols in these four US cities were examined to determine whether re-suspended lead contaminated urban soil was the dominant source of atmospheric lead. Soil and lead-in-air concentrations were examined to ascertain whether lead aerosols follow seasonal patterns with highest concentrations during the summer and/or autumn. In addition, atmospheric soil and lead aerosol concentrations on weekends and Federal Government holidays were compared to weekdays to evaluate the possibility that automotive turbulence results in re-suspension of lead contaminated urban soil. The results show that the natural logs of atmospheric soil and lead aerosols were associated in Pittsburgh from April 2004 to July 2005 ( R²=0.31, p<0.01), Detroit from November 2003 to July 2005 ( R²=0.49, p<0.01), Chicago from November 2003 to August 2005 ( R²=0.32, p< 0.01), and Birmingham from May 2004 to December 2006 ( R²=0.47, p<0.01). Atmospheric soil and lead aerosols followed seasonal patterns with highest concentrations during the summer and/or autumn. Atmospheric soil and lead aerosols are 3.15 and 3.12 times higher, respectively, during weekdays than weekends and Federal Government holidays, suggesting that automotive traffic turbulence plays a significant role in re-suspension of contaminated roadside soils and dusts. In order to decrease urban lead aerosol concentrations, lead deposition and subsequent children’s seasonal exposure, lead contaminated urban soils need remediation or isolation because the legacy of lead continues to pose unnecessary and preventable health risks to urban dwellers.► This study evaluated re-suspension of Pb contaminated urban soil as a source of atmospheric Pb. ► Atmospheric soil and Pb aerosols were examined for Pittsburgh, Detroit, Chicago and Birmingham. ► Strongly associated soil and lead aerosol concentrations were highest in summer and/or autumn. ► Atmospheric soil and Pb are ∼3 times higher on weekdays than weekends/holidays. ► This finding demonstrates the role of vehicular traffic in soil and lead re-suspension.

Keywords: Exposure; Health risks; Lead; Re-suspension; Seasonality; Soil

Gaseous and particulate polycyclic aromatic hydrocarbons at the Gosan background site in East Asia by J.Y. Kim; J.Y. Lee; S.-D. Choi; Y.P. Kim; Y.S. Ghim (pp. 311-319).

The seasonal intensive field measurements of gaseous and particulate polycyclic aromatic hydrocarbons (PAHs) were carried out at the Gosan international background site from November 2001 to August 2003. The annual average concentrations of gaseous and particulate PAHs are 1.4ngm⁻³ and 2.9ngm⁻³ (∑₁₄PAH), respectively. Distinct seasonal variations exist with the highest concentration in winter and the lowest concentration in summer. In comparison with other places in Korea and other countries, the most distinguishing features at Gosan are the significantly low concentrations of low-molecular weight gaseous PAHs. In addition, noticeably high particulate PAH concentrations measured at urban and background areas in Korea could represent the regional characteristics of East Asia under the influence of high emission from China. The BaP equivalent concentrations (BaP_eq) at Gosan, which are based on the US EPA’s toxicity equivalency factors for carcinogenic PAHs, are much higher than those at coastal or background sites in USA and Europe, and even comparable with that at urban sites in Europe. The possibility of more aged PAHs in the atmosphere associated with the long range transport of PAHs during winter period was suggested. It was found that larger fraction of non-exchangeable PAHs had strong influence to the gas/particle partitioning of PAHs at Gosan.► Seasonal concentrations of both gaseous and particulate PAHs at Gosan. ► Significantly low concentrations of low-molecular weight gaseous PAHs at Gosan. ► High particulate PAHs concentrations at urban and background areas in Korea. ► Toxicity even comparable with that at urban sites in Europe. ► Variation in the gas/particle partitioning due to aging in the atmosphere.

Keywords: Seasonal variation; Background concentrations; Long-range transport; Toxicity

Gaseous and particulate polycyclic aromatic hydrocarbons at the Gosan background site in East Asia by J.Y. Kim; J.Y. Lee; S.-D. Choi; Y.P. Kim; Y.S. Ghim (pp. 311-319).

Keywords: Seasonal variation; Background concentrations; Long-range transport; Toxicity

The model SIRANE for atmospheric urban pollutant dispersion; PART II, validation of the model on a real case study by L. Soulhac; P. Salizzoni; P. Mejean; D. Didier; I. Rios (pp. 320-337).

We analyse the performance of the model SIRANE by comparing its outputs to field data measured within an urban district. SIRANE is the first urban dispersion model based on the concept of street network, and contains specific parametrical law to explicitly simulate the main transfer mechanisms within the urban canopy. The model validation is performed by means of field data collected during a 15 days measurement campaign in an urban district in Lyon, France. The campaign provided information on traffic fluxes and cars emissions, meteorological conditions, background pollution levels and pollutant concentration in different location within the district. This data set, together with complementary modelling tools needed to estimate the spatial distribution of traffic fluxes, allowed us to estimate the input data required by the model. The data set provide also the information essential to evaluate the accuracy of the model outputs.Comparison between model predictions and field measurements was performed in two ways. By evaluate the reliability of the model in simulating the spatial distribution of the pollutant and of their time variability.The study includes a sensitivity analysis to identify the key input parameters influencing the performance of the model, namely the emissions rates and the wind velocity. The analysis focuses only on the influence of varying input parameters in the modelling chain in the model predictions and complements the analyses provided by wind tunnel studies focussing on the parameterisation implemented in the model. The study also elucidates the critical role of background concentrations that represent a significant contribution to local pollution levels. The overall model performance, measured using the criteria can be considered as ‘good’ except for NO and some of BTX species. The results suggest that improvements of the performances on NO require testing new photochemical models, whereas the improvement on BTX could be achieved by correcting their vehicular emissions factors.► The model SIRANE is validated by means of field data collected in a district in Lyon. ► The overall model performance, according to criteria Hanna and Chang, is ‘good’. ► The study includes of a sensitivity analysis on the model outputs.

Keywords: Field measurement campaign; Numerical modelling; Pollutant dispersion; Urban canopy; Traffic emissions

The model SIRANE for atmospheric urban pollutant dispersion; PART II, validation of the model on a real case study by L. Soulhac; P. Salizzoni; P. Mejean; D. Didier; I. Rios (pp. 320-337).

Keywords: Field measurement campaign; Numerical modelling; Pollutant dispersion; Urban canopy; Traffic emissions

Aerosol optical depth trends over different regions of India by S. Ramachandran; Sumita Kedia; Rohit Srivastava (pp. 338-347).

Seasonal and annual mean trends in aerosol optical depths (AODs) for the last decade are derived using MODerate resolution Imaging Spectroradiometer (MODIS) Level 2 10 km × 10 km remote sensing data over different locations in India. AODs have increased across India in the last decade. AOD trends exhibit spatial, seasonal and annual mean variations. Annual mean AODs have increased by >40% during 2000–2009 in Jaipur, Hyderabad and Bengaluru. The increase in AODs over Hyderabad and Bengaluru, major high-tech cities, can be ascribed to the increase in urbanization. An increase in AODs over New Delhi where manmade aerosols are dominant can be attributed to an increase in the amount of aerosols from fossil fuel and biomass burning, while an increasing trend in AODs in the northeast, indicates an increase in the amount of aerosols produced from biomass burning and forest fires. AODs decreased in the high altitude sites of Shimla and Dehradun. AODs and wind speeds increased over Jaipur, while they decreased in Trivandrum during the last decade. An increase in wind speeds led to an increase in soil derived dust particles over Jaipur, an arid site, while a decrease in wind speeds over Trivandrum, contributed to a decrease in sea spray aerosols thereby causing a decrease in AOD. Annual rainfall increased by ≤1% in most locations. Both AODs and rainfall have increased in the last decade over most study locations. These findings become important and useful in the context of regional and global climate change due to aerosols.► Aerosol optical depths increased across India in the last decade. ► AOD trends exhibit spatial and seasonal differences. ► AODs increased over most urban areas. ► AODs increased over northeast India dominated by natural sources. ► AODs decreased over high altitude sites.

Keywords: Aerosols; Trends; India; Regional; Rainfall; Meteorology

Aerosol optical depth trends over different regions of India by S. Ramachandran; Sumita Kedia; Rohit Srivastava (pp. 338-347).

Keywords: Aerosols; Trends; India; Regional; Rainfall; Meteorology

An approach to characterize within-grid concentration variability in air quality models by Jason Ching; Mohammed A. Majeed (pp. 348-360).

A new methodology to obtain subgrid air quality concentration variability (SGV) as distribution functions is described. Grid-based air quality models provide deterministic single value outcomes and thus do not represent concentration spatial details which can vary widely especially within urban and highly industrialized areas. While such spatial details can be obtained by running grid-based regional-scale air quality models at finer resolution or by employing local-scale models, such implementation may be impractical for performing a variety of applications, e.g., health exposure assessments. Strategically we propose a paradigm that can provide operational AQ models with supplemental estimates of SGV distributions as analytic functions provided on hourly and grid-by-grid bases. We illustrate and discuss this prototype implementation for a case study of benzene for several 12-km grid cells in the Wilmington, Delaware area. For this effort the contribution to SGV is limited to that from fine grid emissions distributions.► Conceptual framework to provide subgrid details to air quality grid models. ► Paradigm fits two-parameter Weibull distribution to subgrid variance histograms. ► Regression of operational model outputs used to model Weibull parameters for Benzene. ► Methodology provides on-line capability for regional air quality models.

Keywords: Subgrid variability; Fine-scale AQ modeling; Concentration variability; Exposure assessments

An approach to characterize within-grid concentration variability in air quality models by Jason Ching; Mohammed A. Majeed (pp. 348-360).

Keywords: Subgrid variability; Fine-scale AQ modeling; Concentration variability; Exposure assessments

Atmospheric phosphorus deposition in a near-coastal rural site in the NE Iberian Peninsula and its role in marine productivity by Rebeca Izquierdo; Claudia R. Benítez-Nelson; Pere Masqué; Sonia Castillo; Andrés Alastuey; Anna Àvila (pp. 361-370).

In this study, African red-rains were collected at Montseny (NE Spain) on a weekly basis and analyzed for total particulate phosphorus (TPP), total dissolved P (TDP) and soluble reactive P (SRP) for the period 1996–2008. Wet and dry weekly deposition of TPP was analyzed for all provenances in 2002–2003. In this period, African sources were found to contribute 66% of the 576 μmol m⁻² y⁻¹ of total particulate phosphorus (TPP) deposited in Montseny, split almost evenly between dry and wet deposition. Measurement of this dry deposition further allowed a direct determination of deposition velocity (V_d), which suggested significant depositional differences between African (V_d = 3.1 ± 0.80 cm s⁻¹) and non-African events (V_d = 1.07 ± 0.13 cm s⁻¹). Measurement of TDP concentrations during the African rains suggests a solubility of 11.2% TPP. SRP solubility was lower (2.2%), highlighting the importance of understanding the composition of the atmospherically derived P component. Samples were collected 25 km from the Mediterranean coast and were assumed to represent the atmospheric P input to coastal waters. On an annual basis, atmospheric-derived soluble P contributed <1% of annual new primary production in the western Mediterranean. However, one strong African dust event (22–27 May, 2008) accounted for 24–33 % of the atmospheric P-induced annual new production. These results highlight the potential biogeochemical importance of seasonality, source, and composition of aerosols deposited in the Western Mediterranean Sea.► African sources contributed 66% TPP deposition to the NW Mediterranean. ► TPP deposition was split almost evenly between wet and dry deposition modes. ► Soluble P deposition was relevant for marine productivity only in big dust events.

Keywords: African dust; wet/dry deposition; Particulate matter; Phosphorus; Mediterranean; Marine productivity

On-board measurements of emissions from light-duty gasoline vehicles in three mega-cities of China by Hong Huo; Zhiliang Yao; Yingzhi Zhang; Xianbao Shen; Qiang Zhang; Yan Ding; Kebin He (pp. 371-377).

This paper is the second in a series of three papers aimed at understanding the emissions of vehicles in China by conducting on-board emission measurements. This paper focuses on light-duty gasoline vehicles. In this study, we measured 57 light-duty gasoline vehicles (LDGVs) in three Chinese mega-cites (Beijing, Guangzhou, and Shenzhen), covering Euro 0 through Euro IV technologies, and generated CO, HC, and NOx emission factors and deterioration rates for each vehicle technology. The results show that the vehicle emission standards have played a significant role in reducing vehicle emission levels in China. The vehicle emission factors are reduced by 47–81%, 53–64%, 46–71%, and 78–82% for each phase from Euro I to Euro IV. Euro 0 vehicles have a considerably high emission level, which is hundreds of times larger than that of Euro IV vehicles. Three old taxis and four other Euro I and Euro II LDGVs are also identified as super emitters with equivalent emission levels to Euro 0 vehicles. Of the measured fleet, 23% super emitters were estimated to contribute 50–80% to total emissions. Besides vehicle emission standards, measures for restricting super emitters are equally important to reduce vehicle emissions. This study is intended to improve the understanding of the vehicle emission levels in China, but some key issues such as emission deterioration rates are yet to be addressed with the presence of a sufficient amount of vehicle emission measurements.► 57 gasoline cars covering from Euro 0 to IV were measured in three Chinese cities. ► Emission factors drop by >47%, >53%, >46%, and >78% for each phase from Euro I to IV. ► Deterioration rates (DRs) of the test fleet are 5–60% lower than the U.S. EPA data. ► 23% super emitters can contribute 50–80% to total emissions from the measured fleet. ► Extensive tests are needed in future for reliable emission factors and DRs for China.

Keywords: On-board emission measurement; Emission factors; Deterioration rates; Super emitters; China

Implementation and evaluation of pH-dependent cloud chemistry and wet deposition in the chemical transport model REM-Calgrid by S. Banzhaf; M. Schaap; A. Kerschbaumer; E. Reimer; R. Stern; E. van der Swaluw; P. Builtjes (pp. 378-390).

The Chemistry Transport Model REM-Calgrid (RCG) has been improved by implementing an enhanced description of aqueous-phase chemistry and wet deposition processes including droplet pH. A sensitivity study on cloud and rain droplet pH has been performed to investigate its impact on model sulphate production and gas wet scavenging. Air concentrations and wet deposition fluxes of the model sensitivity runs have been analysed and compared to observations. It was found that droplet pH variation within atmospheric ranges affects modelled air concentrations and wet deposition fluxes significantly. Applying a droplet pH of 5.5 for July 2005, mean sulphate air concentrations increased by up to 10% compared to using a droplet pH of 5 while SO₂ domain wet deposition sum increased by 110%. Moreover, model results using modelled droplet pH for January and July 2005 have been compared to model results applying a constant pH of 5 and to observations. The comparison to observations has shown that using a variable droplet pH improves the model performance concerning air concentrations and wet deposition fluxes of the investigated sulphur and nitrogen compounds. For SO_x wet deposition fluxes the Root Mean Square Error (RMSE) decreased by 16% for July 2005 when using a variable droplet pH instead of a constant pH of 5. Concerning sulphate and SO₂ air concentrations the RMSE was reduced by 8% and 16% for July 2005, respectively. The results have revealed that applying a variable droplet pH is preferable to using a constant pH leading to better consistency concerning air concentrations and wet deposition fluxes.► We improved the CTM RCG by implementing pH dependent aqueous-phase chemistry. ► We integrated a pH dependent gas wet scavenging scheme in RCG. ► We investigated the impact of droplet pH variations on model results. ► pH variation within atmospheric ranges affects model results significantly. ► Using variable pH is preferable to using a fixed pH leading to better model results.

Keywords: Wet deposition; Aqueous-phase chemistry; Sulphate; Ammonia; Droplet pH sensitivity; Nitrogen deposition; Sulphur deposition; Model evaluation

Investigation of diesel ash particulate matter: A scanning electron microscope and transmission electron microscope study by A. Liati; P. Dimopoulos Eggenschwiler; E. Müller Gubler; D. Schreiber; M. Aguirre (pp. 391-402).

Investigation of ash PM deposited in a diesel particulate filter (DPF) operating on a light truck by means of SEM and TEM reveals the following: ash inside the DPF occurs in form of chemically very inhomogeneous, mostly brittle agglomerates accumulated at the plugged ends of inlet channels and deposited directly on the inlet channel walls all along the filter length. Ash agglomerates occur within pores of the channel walls. A minor part of ash PM may escape to the atmosphere. The individual ash phases are mostly crystalline with round outlines and sizes between ca. 170 and 60 nm, down to 7–12 nm, that is far below the breathable size range PM10. Aggregation of the predominantly finest fraction of ash particles leads to densification, which may translate to fewer breakouts from the DPF. EDX mapping and chemical analyses of the bulk ash reveal that ash consists mainly of Ca, Mg, P, Zn, S, O and minor Fe, Al and Si. Based on TEM diffraction data of ash single phases, combined with data on their chemistry, the diversity of ash phases is higher than previously presumed. Comparison with the ash particles of a heavily used DPF from a passenger car operating with Fe-based fuel-borne additives reveals characteristics very similar to those found for the light truck DPF with a tendency to generally lower sizes of the participating phases, mostly between 30 and 60 nm. 4–40 nm large, locally abundant Pt particles deriving from the coating material of the diesel oxidation catalyst (DOC) upstream the DPF occur within ash agglomerates of both DPFs. Ash collected from the exhaust gas at the exit of the light truck DPF under normal engine operation reveals that some fine particles, as well as a few of the larger (200–600 nm) ash-bearing agglomerates escape filtration. Very fine ash particles are reaching the atmosphere also attached onto soot agglomerates.► Ash agglomerates, up to a few μm large, escape filtration and reach the ambient air. ► The size of individual ash phases goes down to a few nanometers, far below PM10. ► Part of the finest ash particulates form larger aggregates and may thus be trapped by DPFs. ► Ash microscopic characteristics are independent of aftertreatment conditions and engine loading. ► Pt particles (4–40 nm) deriving from the oxidation catalyst surface may reach ambient air.

Keywords: Diesel ash; Diesel particulate filter; Particulate matter; Exhaust aftertreatmentAbbreviations; PM; particulate matter; DPF; diesel particulate filter; SEM; scanning electron microscope; TEM; transmission electron microscope; EDX; energy dispersive X-ray spectroscopy; DOC; diesel oxidation catalyst

Observations and modeling of formaldehyde at the PROPHET mixed hardwood forest site in 2008 by Melissa M. Galloway; Joshua P. DiGangi; John R. Hottle; Andrew J. Huisman; Levi H. Mielke; Marjan Alaghmand; Paul B. Shepson; Joanna Weremijewicz; Hugh Klavon; Fredrick M. McNeal; Mary Anne Carroll; Stephen Griffith; Robert F. Hansen; Sebastien Dusanter; Philip S. Stevens; Steven B. Bertman; Frank N. Keutsch (pp. 403-410).

We report the first field measurements of gas-phase formaldehyde (HCHO) via laser-induced fluorescence (LIF) obtained August 1–8, 2008 at the PROPHET mixed hardwood forest site at the University of Michigan Biological Station. HCHO mixing ratios above the canopy ranged from a nighttime minimum of ∼0.5 ppb_v to afternoon maxima of ∼4.2 ppb_v. Daytime HCHO mixing ratios were compared to two zero-dimensional box models: one based on the Master Chemical Mechanism v3.2 (MCM), the other using a simplified treatment of HCHO production. Both models over-predicted HCHO relative to observations. Sensitivity analyses demonstrated that increasing vertical dilution and/or decreasing OH concentrations would result in a significant reduction in this over-prediction for both models, as did reducing NO concentrations in the MCM based model. On average, the two models agreed to within 9%, though sensitivity analyses of changing NO and HO₂ concentrations result in significant deviation. This displays that modeled HCHO production is heavily-dependent on the yields and rates of RO₂ destruction pathways under low NO conditions, which may have implications for simplified mechanisms and global predictions of isoprene emission based on satellite HCHO measurements.► First atmospheric field measurements of formaldehyde by LIF. ► Implicit and explicit chemical models of HCHO similar at rural, isoprene-rich site. ► Models sensitive to OH, vertical mixing and, to lesser degree, deposition velocity. ► Explicit model not in low NO regime, but reduction of NO results in lower HCHO. ► Implicit model HCHO high at “low” NO, with implications for modeling remote forests.

Keywords: Formaldehyde; Laser-induced fluorescence; Forest; NO; _x; PROPHET; Isoprene

Preferential solvation of perfluorooctanoic acid (PFOA) by methanol in methanol–water mixtures: A potential overestimation of the dissociation constant of PFOA using a Yasuda–Shedlovsky plot by Shuzo Kutsuna; Hisao Hori; Takaaki Sonoda; Toru Iwakami; Akihiro Wakisaka (pp. 411-414).

Solvation of perfluorooctanoic acid (PFOA) in methanol–water mixed solvents was investigated by means of the mass spectrometric analyses of clusters in the solutions. The observed clusters were composed of PFOA, methanol, and water molecules. The molecular composition of the clusters showed that PFOA was preferentially solvated by methanol in the methanol–water mixed solvents, and that the ratio of methanol molecules in the PFOA solvation sphere was beyond 0.6 at the bulk methanol mole fraction ( x_MeOH) = 0.045. The microscopic environment of PFOA was almost occupied by the methanol from such lower x_MeOH ( x_MeOH ≥ 0.045), and hence the ratio of methanol in the PFOA solvation sphere did not change at x_MeOH ≥ 0.045 as much as the bulk x_MeOH. This preferential solvation of PFOA by methanol suggested a potential overestimation on the dissociation constant (p K_a) of PFOA extrapolated from a Yasuda–Shedlovsky plot.

Keywords: Preferential solvation; Perfluorooctanoic acid; PFOA; p; K; _a; Yasuda–Shedlovsky plot

Dioxin inhalation doses from wood combustion in indoor cookfires by Amanda L. Northcross; S. Katharine Hammond; Eduardo Canuz; Kirk R. Smith (pp. 415-418).

Approximately 3 billion people worldwide rely on solid biomass fuels for household cooking and space heating, and approximately 50–60% use wood, often indoors in poorly ventilated situations. Daily exposures to high concentrations of smoke from cookstoves inside kitchens create large smoke exposures for women cooks and their small children. The smoke from burning the wood fuel contains hundred of toxic compounds, including dioxins and furans some of the most toxic compounds known to science. Health effects from exposure to dioxins include reproductive and developmental problems, damage the immune system, interference with hormones and also cause cancer. This study measured concentrations of dioxins and furans in a typical Guatemalan village home during open cookfires. Measured concentrations averaged 0.32±0.07ngm⁻³ over 31 fires. A Monte Carlo simulation was conducted using parameter estimates based on 8 years of research experience in the study area. The estimated total daily intake of 17 particle phase dioxin and furans for women, a 5-year-old child and a 6-month-old infant were 1.2 (S.D.=0.4), 1.7 (S.D.=0.7) and 2.0 (S.D.=0.5) respectively. The 46% of babies have and estimated total daily intake (TDI) which exceed the WHO TDI guideline for dioxins and furans, 3% of women and 26% of 5-year-old children based solely inhalation of particle phase dioxins in woodsmoke from an open cooking fire. These values maybe underestimates, as they did not include gas phase concentrations or ingestion of dioxins and furans through food, which is the largest route of exposure in the developed world.

Keywords: Cookstoves; Indoor air pollution; Furans; Household energy

Dioxin inhalation doses from wood combustion in indoor cookfires by Amanda L. Northcross; S. Katharine Hammond; Eduardo Canuz; Kirk R. Smith (pp. 415-418).

Keywords: Cookstoves; Indoor air pollution; Furans; Household energy

New Directions: Understanding interactions of air quality and climate change at regional scales by Kiran Alapaty; Rohit Mathur; Jonathan Pleim; Christian Hogrefe; S. Trivikrama Rao; Venkatachalam Ramaswamy; Stefano Galmarini; Martijn Schaap; Paul Makar; Robert Vautard; Alexander Baklanov; George Kallos; Bernhard Vogel; Ranjeet Sokhi (pp. 419-421).

Air quality–climate change interactions; AQMEII; Metrics for model intercomparison; Global climate modeling; Regional air quality modeling; Lateral boundary conditions; Model evaluation; Global-to-regional models; Emissions uncertainty

Corrigendum to Atmospheric organic nitrogen deposition in China [Atmos. Environ. 46C (2011) 195–204] by Y. Zhang; L. Song; X.J. Liu; W.Q. Li; S.H. Lü; L.X. Zheng; Z.C. Bai; G.Y. Cai; F.S. Zhang (pp. 422-422).

Corrigendum to “Tracheobronchial and alveolar dose of submicrometer particles for different population age groups in Italy” [Atmos. Environ. 45 (2011) 6216–6224] by G. Buonanno; G. Giovinco; L. Morawska; L. Stabile (pp. 423-423).

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Atmospheric Environment (v.49, #)