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Atmospheric Environment (v.45, #2)

Editorial board (pp. i).

Review of relationship between indoor and outdoor particles: I/O ratio, infiltration factor and penetration factor by Chun Chen; Bin Zhao (pp. 275-288).

Epidemiologic evidence indicates a relationship between outdoor particle exposure and adverse health effects, while most people spend 85–90% of their time indoors, thus understanding the relationship between indoor and outdoor particles is quite important. This paper aims to provide an up-to-date revision for both experiment and modeling on relationship between indoor and outdoor particles. The use of three different parameters: indoor/outdoor (I/O) ratio, infiltration factor and penetration factor, to assess the relationship between indoor and outdoor particles were reviewed. The experimental data of the three parameters measured both in real houses and laboratories were summarized and analyzed. The I/O ratios vary considerably due to the difference in size-dependent indoor particle emission rates, the geometry of the cracks in building envelopes, and the air exchange rates. Thus, it is difficult to draw uniform conclusions as detailed information, which make I/O ratio hardly helpful for understanding the indoor/outdoor relationship. Infiltration factor represents the equilibrium fraction of ambient particles that penetrates indoors and remains suspended, which avoids the mixture with indoor particle sources. Penetration factor is the most relevant parameter for the particle penetration mechanism through cracks and leaks in the building envelope. We investigate the methods used in previously published studies to both measure and model the infiltration and penetration factors. We also discuss the application of the penetration factor models and provide recommendations for improvement.

Keywords: Particle; Penetration; Infiltration; I/O ratio; Indoor environment; Outdoor environment

Review of relationship between indoor and outdoor particles: I/O ratio, infiltration factor and penetration factor by Chun Chen; Bin Zhao (pp. 275-288).

Keywords: Particle; Penetration; Infiltration; I/O ratio; Indoor environment; Outdoor environment

Review of relationship between indoor and outdoor particles: I/O ratio, infiltration factor and penetration factor by Chun Chen; Bin Zhao (pp. 275-288).

Keywords: Particle; Penetration; Infiltration; I/O ratio; Indoor environment; Outdoor environment

Comparing mesoscale chemistry-transport model and remote-sensed Aerosol Optical Depth by C. Carnevale; G. Finzi; G. Mannarini; E. Pisoni; M. Volta (pp. 289-295).

A comparison of modeled and observed Aerosol Optical Depth (AOD) is presented. 3D Eulerian multiphase chemistry-transport model TCAM is employed for simulating AOD at mesoscale, while MODIS satellite sensor and AERONET photometer AOD are used for comparing spatial patterns and temporal time series. For the estimation of AOD from TCAM model, an external mixing approach for chemical species is considered. Furthermore, a parametrization of the effect of moisture affecting both aerosol size and composition is used. TCAM simulations for year 2004 over a domain containing Po-Valley and nearly whole Northern Italy are employed. TCAM AOD reproduces spatial patterns similar to those retrieved from MODIS, but AOD values are generally underestimated. The comparison between model AOD and values at “Venise” AERONET site shows good agreement. The analysis of the extinction coefficient reveals the dominant role of the sub micron size inorganic over the domain. The results suggest encouraging perspectives in view of satellite AOD assimilation also at the mesoscale and not only at the global and regional scale as already tested in the literature.► An optical module for a multiphase mesoscale CTM (TCAM) has been developed. ► TCAM AOD has been compared to both MODIS and AERONET AOD, over Northern Italy. ► Moisture effects have been assessed. ► Results suggest perspectives for EO/nonEO AOD data assimilation at the mesoscale.

Keywords: Aerosol Optical Depth; Chemical Transport Model; TCAM; MODIS; Po-Valley; Remote-sensing

Comparing mesoscale chemistry-transport model and remote-sensed Aerosol Optical Depth by C. Carnevale; G. Finzi; G. Mannarini; E. Pisoni; M. Volta (pp. 289-295).

Keywords: Aerosol Optical Depth; Chemical Transport Model; TCAM; MODIS; Po-Valley; Remote-sensing

Comparing mesoscale chemistry-transport model and remote-sensed Aerosol Optical Depth by C. Carnevale; G. Finzi; G. Mannarini; E. Pisoni; M. Volta (pp. 289-295).

Keywords: Aerosol Optical Depth; Chemical Transport Model; TCAM; MODIS; Po-Valley; Remote-sensing

Sorption of a diverse set of organic chemical vapors onto XAD-2 resin: Measurement, prediction and implications for air sampling by Stephen J. Hayward; Ying D. Lei; Frank Wania (pp. 296-302).

The wide-spread use of styrene–divinylbenzene-copolymeric resin (XAD-2) in air sampling necessitates a quantitative understanding of its sorption characteristics for organic chemicals. Inverse Gas Chromatography (IGC) was used to measure the sorption of a diverse set of 52 organic chemicals to XAD-2 at temperatures between 40°C and 100°C and at relative humidities between 0 and 87%. Even though relative humidity has been shown to influence sorption to other sorbents, it did not significantly influence most chemicals’ sorption to XAD-2, indicating that water does not form a strong physical barrier to sorption on XAD-2 at high relative humidity. The resin–air partition coefficients ( K_XAD) determined by IGC and the enthalpies of sorption derived from them were regressed against solute descriptors to derive poly-parameter Linear Free Energy Relationships (ppLFERs) which allow the estimation of K_XAD for chemicals which are not sufficiently volatile to be amenable to IGC and for temperatures outside the experimental range. K_XAD values at 20°C estimated for a set of 296 chemicals for which solute descriptors are available, including polychlorinated biphenyls, polycyclic aromatic hydrocarbons, and pesticides, indicate that for many of the substances commonly found in the atmosphere sorption is higher to XAD-2 than to poly-urethane foam, another popular air sampling sorbent.► Sorption of a diverse set of 52 organic chemicals to XAD-2 was determined as a function of temperature. ► Sorption of organic vapors to XAD-2 was not dependent on relative humidity. ► A newly derived poly-parameter Linear Free Energy Relationships allows the estimation of sorption onto XAD-2 for all neutral organic chemicals. ► XAD-2 resin has a notably higher capacity for organic vapors than poly-urethane foam.

Keywords: XAD resin; Pesticides; PCBs; Air sampling

Sorption of a diverse set of organic chemical vapors onto XAD-2 resin: Measurement, prediction and implications for air sampling by Stephen J. Hayward; Ying D. Lei; Frank Wania (pp. 296-302).

Keywords: XAD resin; Pesticides; PCBs; Air sampling

Sorption of a diverse set of organic chemical vapors onto XAD-2 resin: Measurement, prediction and implications for air sampling by Stephen J. Hayward; Ying D. Lei; Frank Wania (pp. 296-302).

Keywords: XAD resin; Pesticides; PCBs; Air sampling

Spatial variability of atmospheric semivolatile organic compounds in Chile by Chubashini Shunthirasingham; Ricardo Barra; Gonzalo Mendoza; Monica Montory; Catherine E. Oyiliagu; Ying Duan Lei; Frank Wania (pp. 303-309).

In an effort to characterize the spatial variability of pesticides, polychlorinated biphenyls (PCBs), and polycyclic aromatic hydrocarbons (PAHs) in the Chilean atmosphere, XAD-based passive air samplers (PAS) were deployed for 12 months (2006–2007) along three elevational gradients in Northern, Central and Southern Chile, for a total of 20 sampling sites, ranging in elevation from 10 to 4400m and ranging over 26 degrees of latitude. Hexachlorobenzene (HCB) had largely uniform air concentrations with latitude and altitude, and is therefore used to derive sampler specific sampling rates, that account for differences in uptake kinetics due to environmental factors such as altitude and temperature. Levels of pesticides in the atmosphere of Chile are very low and only α- and γ-hexachlorocyclohexane, α-endosulfan and chlorothalonil were present in all of the samples. The concentrations of these four pesticides in air decreased from North to South, with much steeper gradients for chlorothalonil and endosulfan. Chlorothalonil levels were greatly elevated in air samplers deployed in urban locations. Endosulfan concentrations in air tend to increase with elevation. Since endosulfan is particularly susceptible to mountain cold-trapping, such gradients may reflect the re-volatilization of endosulfan that had been preferentially deposited at higher altitudes. Alternatively, increasing endosulfan concentrations with elevation could be the result of transport to higher altitude sites from the other side of Andes. Airshed analysis indeed indicates that air masses originating outside of Chile have a higher influence on the higher elevation sites, especially along the Northern transect. Concentrations of four-ring PAHs ranged from 0.3 to 1300pgm⁻³, with higher levels in air samplers deployed in urban areas and close to roads. PCB concentrations were low (0.7–27pgm⁻³), with slightly higher levels of volatile congeners in two urban sampling sites in Concepcion and Arica. PCB-52 is the only congener present in all samples, with levels that are remarkably uniform across the country.► Passive air samplers provide annual averaged air concentrations of PCBs, PAHs and pesticides at 20 sampling sites across Chile. ► Concentrations are low and generally represent Southern hemispheric background. ► Endosulfan concentrations in air tend to increase with elevation. ► Air masses originating outside of Chile have a higher influence on the higher elevation sites.

Keywords: Chile; Passive air sampling; Elevation gradients; Pesticides; PCBs; PAHs; Atmosphere

Resuspension of particulate matter and PAHs from street dust by D. Martuzevicius; L. Kliucininkas; T. Prasauskas; E. Krugly; V. Kauneliene; B. Strandberg (pp. 310-317).

Winter street sanding activities in northern countries are often associated with elevated pollution by particulate matter. There are indications that street dust may act as a source of particle-bound PAHs. However, very few studies have addressed the resuspension potential of PAHs from street dust. The purpose of this study was to quantitatively assess emissions of particulate matter and PAHs from street dust by laboratory-scale simulation of particle resuspension. Increases in air velocity caused proportional increases in air-borne PM_2.5, PM₁₀ and PM_total concentrations, while the concentrations of PAHs associated with resuspended particles did not show clear statistically significant dependence on air velocity. A substantial difference in particle and PAH resuspension was observed between dust from the city center street and dust from the connecting street. The data obtained in the present study indicate that street dust may be a significant source not only of PMs but also of particle-bound PAHs in ambient air.► Street dust composition affects particle aerosolization. ► Street dust may be a substantial source of air-borne PAHs. ► PAH resuspension from street dust does not directly depend on air velocity. ► PAHs in street dust do not adequately indicate resuspension potential.

Keywords: Air pollution; Traffic; Street Dust; PM; ₁₀; PM; _2.5; PAH(s); Resuspension

Resuspension of particulate matter and PAHs from street dust by D. Martuzevicius; L. Kliucininkas; T. Prasauskas; E. Krugly; V. Kauneliene; B. Strandberg (pp. 310-317).

Keywords: Air pollution; Traffic; Street Dust; PM; ₁₀; PM; _2.5; PAH(s); Resuspension

Resuspension of particulate matter and PAHs from street dust by D. Martuzevicius; L. Kliucininkas; T. Prasauskas; E. Krugly; V. Kauneliene; B. Strandberg (pp. 310-317).

Keywords: Air pollution; Traffic; Street Dust; PM; ₁₀; PM; _2.5; PAH(s); Resuspension

Characteristics of summertime PM_2.5 organic and elemental carbon in four major Chinese cities: Implications of high acidity for water-soluble organic carbon (WSOC) by Ravi Kant Pathak; Tao Wang; K.F. Ho; S.C. Lee (pp. 318-325).

Although laboratory studies suggest that aerosol acidity ([H⁺]) significantly enhances the production of secondary organic aerosol (SOA) through heterogeneous chemistry, field studies have provided limited evidence of such enhancement. In this study, correlation of strong aerosol acidity with WSOC was investigated using the 24-hr PM_2.5 samples collected at sites near four major cities of China – Beijing (BJ), Shanghai (SH), Lanzhou (LZ), and Guangzhou (GZ) – during the summers of 2004–2006. PM_2.5 samples were characterized by high atmospheric loadings of PM_2.5, OC, EC, sulfate, nitrate, aerosol acidity, and aerosol-water, especially in Beijing and Shanghai. On average, OC and EC were distributed in the ratio of approximately 2:1 among carbonaceous aerosols (TC = OC + EC) in all four cities. However, the WSOC fraction in OC differed across the four cities (BJ ∼ 55% of OC; SH ∼ 35%; LZ ∼ 40%; GZ ∼ 32%). We found an increased WSOC content in organic carbon (OC) fraction in the samples with elevated aerosol acidity (H⁺) and the WSOC was thought to be influenced by aerosol acidity. The WSOC/OC ratio showed a strong positive correlation with the normalized strong acid concentration ([H⁺]/[OC]) in the four cities. The higher WSOC fraction in OC at higher strong acidity is postulated to be linked to the conversion of OC to WSOC via heterogeneous acid-catalyzed chemistry.► High water-soluble organic compounds [WSOC] content in organic carbon [OC] fraction at high acidity (H⁺). ► [WSOC]/[OC] ratio showed a strong positive correlation with [H⁺]/[OC] ratio. ► At high acidity conversion of OC to WSOC via heterogeneous acid catalyzed chemistry is postulated.

Keywords: Acid catalyzed reaction; OC; EC; WSOC; Acidity; SOA

Influence of Arctic Oscillation on dust activity over northeast Asia by Rui Mao; Chang-Hoi Ho; Yaping Shao; Dao-Yi Gong; Jhoon Kim (pp. 326-337).

The northeast Asian dust process during the spring seasons in the years 1982–2006 was simulated by the Integrated Wind Erosion Modeling System (IWEMS). The influence of Arctic Oscillation (AO) on dust activities was investigated by analyzing surface observations and model simulations. There is a significant relationship between AO and dust activity; a positive AO phase is associated with decreased (increased) dust storm frequency in Mongolia (Taklimakan Desert) and enhanced anticyclonic (southeastward) dust transport over northwestern China (North China). The AO-dust relation is mainly due to changes in the westerly jet and geopotential height in the middle troposphere; a positive AO phase induces a northward shift of the polar jet, an intensified westerly jet over northern Tibetan Plateau, and a positive geopotential height anomaly over Mongolia. The northern shift of the polar jet reduces the frequency of intense cyclones in Mongolia, thereby causing a decrease in the dust storm frequency. The intensified westerly jet stream over the northern Tibetan Plateau increases the dust storm frequency in the Taklimakan Desert. The positive geopotential height anomaly over Mongolia initiates an anticyclonic dust transport anomaly in the middle troposphere over northwestern China. It also induces a southeastward dust transport anomaly over North China. The reverse situations are true for a negative AO phase.►AO shows a negative correlation with dust storm frequency in Mongolia. ► AO has a positive correlation with dust storm frequency in Taklimakan Desert. ► Positive AO phase enhances anitcyclonic dust transport over northwestern China. ► Positive AO phase increases southeastward dust transport over North China. ► AO-dust relation is due to changes in westerly jet and geopotential height

Keywords: Arctic oscillation; Asian dust; Northeast Asia; Integrated Wind Erosion Modeling System (IWEMS)

Influence of Arctic Oscillation on dust activity over northeast Asia by Rui Mao; Chang-Hoi Ho; Yaping Shao; Dao-Yi Gong; Jhoon Kim (pp. 326-337).

Keywords: Arctic oscillation; Asian dust; Northeast Asia; Integrated Wind Erosion Modeling System (IWEMS)

Influence of Arctic Oscillation on dust activity over northeast Asia by Rui Mao; Chang-Hoi Ho; Yaping Shao; Dao-Yi Gong; Jhoon Kim (pp. 326-337).

Keywords: Arctic oscillation; Asian dust; Northeast Asia; Integrated Wind Erosion Modeling System (IWEMS)

Evaluation of HVAC filters as a sampling mechanism for indoor microbial communities by Federico Noris; Jeffrey A. Siegel; Kerry A. Kinney (pp. 338-346).

HVAC filters are in place for extended periods of time and can serve as integrated air samplers. This paper presents a comparison of bacterial and fungal concentrations and communities in HVAC filter dust and other sampling locations in occupied residences and in the unoccupied UTest House. A DNA-based, culture-independent approach was utilized to characterize the microbial communities. Microbial concentrations and communities in HVAC filter dust samples were not statistically different from those in high surface dust samples in occupied homes. Despite the general similarity in the communities, Proteobacteria were present in greater proportion in HVAC filter dust samples than in surface dust samples suggesting the air origin of this phylum. Gram-positive bacteria were present in greater proportion in occupied residences than in an unoccupied test house, confirming the potential association of this group with occupants. HVAC filter microbial communities were not different from those present in a composited month-long indoor air sample providing preliminary evidence that filters could be a viable option for long-term investigation of airborne biological contaminants.► Microbial communities in HVAC filter dust not different from those in high surface dust in residences. ► Greater Proteobacteria in HVAC filters than on high surface samples. ► Greater gram-positive bacteria in residences than unoccupied test house. ► Microbial communities in HVAC filter not different from composited indoor air. ► HVAC filters show promise as integrated indoor samplers for microbiological contaminants.

Keywords: Bacteria; Fungi; Microbial community; HVAC filter; Settled dust; Air

Evaluation of HVAC filters as a sampling mechanism for indoor microbial communities by Federico Noris; Jeffrey A. Siegel; Kerry A. Kinney (pp. 338-346).

Keywords: Bacteria; Fungi; Microbial community; HVAC filter; Settled dust; Air

Evaluation of HVAC filters as a sampling mechanism for indoor microbial communities by Federico Noris; Jeffrey A. Siegel; Kerry A. Kinney (pp. 338-346).

Keywords: Bacteria; Fungi; Microbial community; HVAC filter; Settled dust; Air

Source–receptor relationships for fine particulate matter concentrations in the Eastern United States by Kristina M. Wagstrom; Spyros N. Pandis (pp. 347-356).

The Particulate Matter Source Apportionment (PSAT) method is used to quantify the impacts of different source regions on fine particulate matter (PM) concentrations in the Eastern United States. Our analysis focuses both on how far pollutants are transported and the impacts they have in the corresponding receptor areas. Towards this goal, several quantitative measures of impact and transport distance are proposed and calculated for ten source regions for all seasons. The long range source impacts are extremely variable in space and time and are often in directions different than that of the average prevailing winds. Transport distances were usually lower during the summer than in other seasons for this region. The average transport distance (distance from the source area to the center of the pollution plume) for elemental carbon and other primary fine PM components was found to be 100–200km for most source regions. On the other hand, the secondary PM species were found to be transported the furthest with sulfate and secondary organic aerosol (SOA) traveling on average over 350km. Maximum transport distances are significant higher, with sulfate impacts reaching as far as 2000km away from the SO₂ source region.The fractional contribution of a source region to fine PM ground level concentrations can be quite different (up to a factor of 3) than its emission contribution. This is mainly due to the height where the emissions are released. Regions with mainly ground level emissions contribute more while regions with elevated emissions less than the magnitude of their emissions suggests.► Computationally efficient approach to calculate long range transport contributions to PM levels of source areas. ► Extremely variable impacts in space and time. ► Secondary PM components travel much further than the primary ones. ► Effects of source regions on PM levels in other areas are not necessarily proportional to their emissions.

Keywords: Particulate matter; Secondary aerosol; Long range transport; Air quality

Source–receptor relationships for fine particulate matter concentrations in the Eastern United States by Kristina M. Wagstrom; Spyros N. Pandis (pp. 347-356).

Keywords: Particulate matter; Secondary aerosol; Long range transport; Air quality

Source–receptor relationships for fine particulate matter concentrations in the Eastern United States by Kristina M. Wagstrom; Spyros N. Pandis (pp. 347-356).

Keywords: Particulate matter; Secondary aerosol; Long range transport; Air quality

Analytical puff modelling of light-wind dispersion in stable and unstable conditions by Ashok K. Luhar (pp. 357-368).

The puff modelling technique can describe dispersion in light winds by accounting for streamwise diffusion. A simple analytical puff model is formulated for stable as well as unstable stratification. In the stable case, the model is a slight generalisation of the Gaussian puff model of , whereas in the unstable case it incorporates a probability density function approach to account for the observed skewness of the vertical turbulent velocities. An evaluation conducted using a well-known dataset collected under stable conditions suggests that the performance of the model is comparable to some of the top-performing models based on more complex techniques. However, it is apparent that some of the observed complex dispersion behaviour that arises due to the non-Gaussian characteristics of the wind direction distribution cannot be properly modelled by using the hourly-averaged meteorology. Since there are no suitable datasets for evaluation under unstable conditions, the puff model is benchmarked against a full three-dimensional Lagrangian particle model. The results show that the puff model is capable of describing most of the well-known features of convective dispersion observed under moderate winds, and that it simulates light-wind dispersion characteristics that are in good agreement with the particle model predictions. The results also highlight that the time since the start of tracer release is an important parameter in light winds. Quantitative estimates as to when the effects of streamwise diffusion in unstable flows can be neglected are also given.► The new model is comparable to the Gaussian plume model in its simplicity. ► It accounts for the vertical diffusion asymmetry in unstable conditions. ► The model performance is very similar to more complex, numerical models. ► The time since the start of emission is an important parameter in weak winds; hence the assumption of steady state in many models may be a serious problem. ► Quantitative estimates as to when the effects of streamwise diffusion can be neglected are given.

Keywords: Puff model; Low winds; Stable boundary layer; Convective boundary layer; Probability density function model; Gaussian plume model

Analytical puff modelling of light-wind dispersion in stable and unstable conditions by Ashok K. Luhar (pp. 357-368).

Keywords: Puff model; Low winds; Stable boundary layer; Convective boundary layer; Probability density function model; Gaussian plume model

Analytical puff modelling of light-wind dispersion in stable and unstable conditions by Ashok K. Luhar (pp. 357-368).

Keywords: Puff model; Low winds; Stable boundary layer; Convective boundary layer; Probability density function model; Gaussian plume model

The transferability of NO and NO₂ land use regression models between cities and pollutants by Ryan W. Allen; Ofer Amram; Amanda J. Wheeler; Michael Brauer (pp. 369-378).

Land use regression (LUR) models are commonly used for exposure assessment in epidemiologic studies of traffic-related air pollution. Models in different cities often contain similar predictors, suggesting that models may be transferable between cities with similar characteristics. LUR models of NO or NO₂ may also be useful for estimating exposure to other pollutants in the traffic pollution mixture. We evaluated the transferability of NO and NO₂ LUR models between Winnipeg, Manitoba and Edmonton, Alberta, and the ability of the Winnipeg NO and NO₂ LUR models to predict concentrations of benzene and toluene. In both cities, LUR models were developed based on measurements with Ogawa passive samplers at 50 locations during two 14-day sampling campaigns, while benzene and toluene concentrations in Winnipeg were measured at 46 independent locations using 3M #3500 passive badges during a single 14-day period. Locally calibrated LUR models explained more variability in NO₂ ( R²: 0.81–0.84) than NO ( R²: 0.55–0.56). Although models transferred to the opposite city did not perform as well as the locally calibrated models for NO₂ ( R²: 0.37–0.52) or NO ( R²: 0.24–0.41), the transferred models explained more variability than simple binary or continuous road proximity metrics ( R² ≤ 0.19), which are commonly used in epidemiologic studies. In Winnipeg, the NO₂ LUR model explained 34% and 19% of the variation in benzene and toluene, respectively, while road proximity metrics explained ≤19% of the variation in both pollutants. In conclusion, epidemiologic studies will achieve better exposure assessments by developing LUR models locally and for the pollutant of interest, though transferred LUR models may provide a cost-effective improvement over road proximity metrics for assessing exposure to traffic-related air pollution.► Locally calibrated land use regression models explained more variability in NO₂ than in NO. ► NO and NO₂ models transferred between cities did not perform as well as the locally calibrated models. ► NO and NO₂ models transferred between cities explained more variability in those pollutants than road proximity metrics. ► The NO₂ land use regression model explained more variability in benzene than road proximity metrics.

Keywords: Air pollution; Traffic; Geographic information systems (GIS); Benzene; TolueneAbbreviations; LOO; Leave one out; LOD; Limit of detection; LUR; Land use regression; NPRI; National pollutant release inventory; TRAP; Traffic-related air pollution; VOC; Volatile organic compounds

The transferability of NO and NO₂ land use regression models between cities and pollutants by Ryan W. Allen; Ofer Amram; Amanda J. Wheeler; Michael Brauer (pp. 369-378).

A Bayesian model of time activity data to investigate health effect of air pollution in time series studies by Marta Blangiardo ∗; Anna Hansell; Sylvia Richardson (pp. 379-386).

Air pollution studies such as time series use measures of ambient concentration to approximate aggregate personal exposures. The resulting difference in health effects can be evaluated using survey data on the time people spend in different environments, with differing concentrations of pollutants. We present a Bayesian hierarchical model that incorporates time activity data to obtain an adjusted distribution of air pollution exposure for categories of individuals (group exposure); its implementation is illustrated using ambient data from five large US cities (NMMAPS database) and diaries of daily activities from the CHAD database. We then quantify the differences on the relative risks that arise when ambient concentration is used instead of time activity adjusted group exposure through a simulation study. Ambient concentrations overestimate exposures compared with those suggested using time-activity data. The overestimate is higher for ≥65 years people than younger adults. The simulation study suggests that using time activity adjusted group exposure would result in observed relative risks 1.5–2.5 times higher than those estimated on the basis of ambient concentrations.► Time activity adjusted exposure is smaller than the ambient concentration. ► Ambient concentration leads to an attenuation of the relative risk of disease. ► The group exposure approach allows to easily compare several scenarios. ► The fully Bayesian approach leads to smaller exposure-larger relative risks

Keywords: Individual exposure; Group exposure; Bayesian model; Attenuation; PM10; Cutting feedback

A Bayesian model of time activity data to investigate health effect of air pollution in time series studies by Marta Blangiardo ∗; Anna Hansell; Sylvia Richardson (pp. 379-386).

Keywords: Individual exposure; Group exposure; Bayesian model; Attenuation; PM10; Cutting feedback

A Bayesian model of time activity data to investigate health effect of air pollution in time series studies by Marta Blangiardo ∗; Anna Hansell; Sylvia Richardson (pp. 379-386).

Keywords: Individual exposure; Group exposure; Bayesian model; Attenuation; PM10; Cutting feedback

Radiative forcing due to changes in ozone and methane caused by the transport sector by G. Myhre; K.P. Shine; G. Rädel; M. Gauss; I.S.A. Isaksen; Q. Tang; M.J. Prather; J.E. Williams; P. van Velthoven; O. Dessens; B. Koffi; S. Szopa; P. Hoor; V. Grewe; J. Borken-Kleefeld; T.K. Berntsen; J.S. Fuglestvedt (pp. 387-394).

The year 2000 radiative forcing (RF) due to changes in O₃ and CH₄ (and the CH₄-induced stratospheric water vapour) as a result of emissions of short-lived gases (oxides of nitrogen (NO_x), carbon monoxide and non-methane hydrocarbons) from three transport sectors (ROAD, maritime SHIPping and AIRcraft) are calculated using results from five global atmospheric chemistry models. Using results from these models plus other published data, we quantify the uncertainties. The RF due to short-term O₃ changes (i.e. as an immediate response to the emissions without allowing for the long-term CH₄ changes) is positive and highest for ROAD transport (31 mW m⁻²) compared to SHIP (24 mW m⁻²) and AIR (17 mW m⁻²) sectors in four of the models. All five models calculate negative RF from the CH₄ perturbations, with a larger impact from the SHIP sector than for ROAD and AIR. The net RF of O₃ and CH₄ combined (i.e. including the impact of CH₄ on ozone and stratospheric water vapour) is positive for ROAD (+16(±13) (one standard deviation) mW m⁻²) and AIR (+6(±5) mW m⁻²) traffic sectors and is negative for SHIP (−18(±10) mW m⁻²) sector in all five models. Global Warming Potentials (GWP) and Global Temperature change Potentials (GTP) are presented for AIR NO_x emissions; there is a wide spread in the results from the 5 chemistry models, and it is shown that differences in the methane response relative to the O₃ response drive much of the spread.► The emissions of compounds affecting the climate from the transport sector are substantial. There are also a variety of compounds from the transport sector that affect the climate. ► In this study the year 2000 radiative forcing (RF) due to changes in O₃ and CH₄ (and the CH₄-induced stratospheric water vapour) as a result of emissions of short-lived gases (oxides of nitrogen (NO_x), carbon monoxide and non-methane hydrocarbons) from three transport sectors (ROAD, maritime SHIPping and AIRcraft) are calculated using results from five global atmospheric chemistry models. This study uses a consistent and comprehensive approach. ► The net RF of O₃ and CH₄ combined (i.e. including the impact of CH₄ on ozone and stratospheric water vapour) is positive for ROAD (+16(±13) (one standard deviation) mW m⁻²) and AIR (+6(±5) mW m⁻²) traffic sectors and is negative for SHIP (−18(±10) mW m⁻²) sector in all five models.

Keywords: Radiative forcing; GWP; GTP; Shipping; Aviation; Road transport

Development of wildland fire particulate smoke marker to organic carbon emission ratios for the conterminous United States by Leigh A. Munchak; Bret A. Schichtel; Amy P. Sullivan; Amanda S. Holden; Sonia M. Kreidenweis; William C. Malm; Jeffrey L. Collett Jr. (pp. 395-403).

Biomass burning is a significant source of aerosols that impact the global radiation budget, human health, and visibility. Molecular marker – chemical mass balance models are frequently employed to estimate the contribution of biomass burning smoke to pollution at receptor sites. These models require information about emissions of smoke tracer compounds to determine the smoke apportionment. This study provides new information about smoke marker emissions by combining laboratory measurements of the chemical composition of smoke with a fuelbed model to create spatially variable maps of smoke markers for the conterminous United States. The analysis incorporates novel measurements of anhydrosugars and water-soluble potassium collected from burning different wildland fuels during the Fire Lab at Missoula Experiment (FLAME). Several patterns emerged from the analyses of these measurements, particularly that different biomass tissue types (e.g., leaves, needles, branches and grasses) produced significantly different smoke marker to organic carbon emission ratios. Smoke marker to carbon emission ratios of biomass tissue types were coupled with the Fuel Characteristic Classification System fuelbed model and published combustion efficiencies to calculate 113 fuelbed smoke marker to carbon ratios. These fuelbed ratios were then mapped across the conterminous United States at 1 km resolution to understand the spatial variability of anhydrosugars and water-soluble potassium.

Keywords: Biomass burning; Levoglucosan; Mannosan; Galactosan

Spatial heterogeneities in aerosol properties over Bay of Bengal inferred from ship-borne and MODIS observations during ICARB-W cruise campaign: Implications to radiative forcing by K. Raghavendra Kumar; K. Narasimhulu; G. Balakrishnaiah; B. Suresh Kumar Reddy; K. Rama Gopal; R.R. Reddy; L.S.S. Reddy; K. Krishna Moorthy; S. Suresh Babu; C.B.S. Dutt (pp. 404-412).

Comprehensive investigations during the last decade have clearly established that aerosols have a significant impact on the climate. This paper reports the results of the spatial variations in aerosol optical depth (AOD) and fine mode fraction (FMF) characteristics as a function of latitude and longitude over the Bay of Bengal (BoB) and the Northern Indian Ocean (NIO) during ICARB-W cruise period of 27th December 2008–30th January 2009 from onboard Sunphotometer and MODIS (Terra, Aqua) satellite measurements. Very high AOD₅₀₀ (0.7–0.8) occurred over the north head BoB adjacent to the northeastern Indian coast and the lowest AOD₅₀₀ (0.1–0.2) occurred in central BoB far away from the coasts, and in a small area in the northeastern part close to Myanmar coast as well as over NIO. The highest values (as high as 1.2) of Ångström exponent, α occurring over northeast BoB (regions close to Bangladesh and Myanmar) indicate relative abundance of accumulation mode particles and very low values of α (below 0.7) over central part of BoB as well as southern BoB/NIO suggesting dominance of coarse-mode sea spray aerosols. Terra/Aqua MODIS AOD₅₅₀ and cruise measured AOD₅₀₀ using Sunphotometer showed good agreement ( R²=0.92) over the BoB. The total mass concentrations over BoB during cruise period were remarkably high, with a mean value of 28.4±5.7μgm⁻³. Aerosol FMF was higher than 0.7 over the BoB, while FMF over NIO was about 0.5. NCEP reanalysis data on winds at 850hPa, along with 5-days airmass back trajectories via HYSPLIT model, suggested transport of continental aerosols from the central and northern India over the BoB by the strong westerly/northwesterly winds. Regionally averaged clear sky aerosol (net) forcing over BoB during the winter is −28.9Wm⁻² at the surface and −10.4Wm⁻² at the top of the atmosphere whereas, the ARF values estimated over NIO at TOA, surface and in the atmosphere are −6.4, −18.3 and +11.9Wm⁻², respectively.► The spatial variation of columnar measurements of AOD₅₀₀ observed high values over northern/northwestern parts of the BoB in which AODs were as high as ∼0.7; while the low values of AOD₅₀₀ (<0.2) were observed in the northeastern regions of BoB (Myanmar/Bangladesh coast) and southern BoB which opens to the vast Indian Ocean. ► α showed highest values of ∼1.5, even though generally high values prevailed over the eastern as well as northern coastal regions of India and β followed the pattern similar to that of AOD with a mean value of 0.17±0.09 over BoB. ► Total mass concentration showed low values over the central BoB and equatorial Indian Ocean with a mean value of 23.6±4.3μgm⁻³, high values over northern BoB (mean 45.4±10.2μgm⁻³) and moderate mass concentrations with a mean value of 32.3±7.1μgm⁻³, persisted along the east coast of India with higher values very near to the ports. ► FMF is found to be higher than 0.7 over BoB indicates the dominance of fine mode particles which were produced mainly due to manmade sources in the surrounding regions and got transported across the oceanic region. ► The diurnally averaged aerosol forcing over entire BoB at the surface is −28.9Wm⁻² and at the TOA is −10.4Wm⁻². The difference between the TOA and the surface forcing is +18.5Wm⁻² which is absorbed in the atmosphere. Similarly, the ARF values estimated over NIO at TOA, surface and in the atmosphere are −6.4, −18.3 and +11.9Wm⁻², respectively.

Keywords: ICARB-W; Aerosol optical depth; Fine mode fraction; Ångström coefficients; Direct aerosol radiative forcing

Chemical characteristics and sources of organic acids in precipitation at a semi-urban site in Southwest China by Y.L. Zhang; X.Q. Lee; F. Cao (pp. 413-419).

In order to investigate the chemical characteristics and sources of organic acids in precipitation in Southwest China, 105 rainwater samples were collected at a semi-urban site in Anshun from June 2007 to June 2008. Organic acids and major anions were analyzed along with pH and electrical conductivity. The pH values varied from 3.57 to 7.09 for all the rainfall events sampled, with an average of 4.67 which was typical acidic value. Formic, acetic and oxalic acids were found to be the predominant carboxylic acids and their volume weighted average (VWA) concentrations were 8.77, 6.93 and 2.84μmoll⁻¹, respectively. These organic acids were estimated to account for 8.1% to the total free acidity (TFA) in precipitation. The concentrations of the majority organic acids at studied site had a clear seasonal pattern, reaching higher levels during the non-growing season than those in growing season, which was attributed to dilution effect of heavy rainfall during the growing season. The seasonal variation of wet deposition flux of these organic acids confirmed higher source strength of biogenic emissions from vegetation during the growing season. Formic-to-acetic acids ratio (F/A), an indicator of primary versus secondary sources of these organic acids, suggested that primary sources from vehicular emission, biomass burning, soil and vegetation emissions were dominant sources. In addition, the lowest concentrations of organic acids were found under type S, when air masses originated from the marine (South China Sea) during Southern Asian Monsoon period. And the highest concentrations were observed in precipitation events from Northeast China (type NE), prevailing mostly during winter with the lowest rainfall.► The average of pH of precipitation at the sampling site was 4.67. ► Organic acids accounted for 8.1% to the total free acidity. ► The concentration of organic acids in the non-growing season was comparably higher. ► The calculation of F/A ratio implied the primary emissions were dominant sources. ► The highest concentrations were observed in rain events from Northeast China.

Keywords: Organic acids; Formic acid; Acetic acid; Precipitation; Sources

Chemical characteristics and sources of organic acids in precipitation at a semi-urban site in Southwest China by Y.L. Zhang; X.Q. Lee; F. Cao (pp. 413-419).

Keywords: Organic acids; Formic acid; Acetic acid; Precipitation; Sources

Chemical characteristics and sources of organic acids in precipitation at a semi-urban site in Southwest China by Y.L. Zhang; X.Q. Lee; F. Cao (pp. 413-419).

Keywords: Organic acids; Formic acid; Acetic acid; Precipitation; Sources

Use of diagnostic ratios for studying source apportionment and reactivity of ambient polycyclic aromatic hydrocarbons over Central Europe by Alice Dvorská; Gerhard Lammel; Jana Klánová (pp. 420-427).

Ratios of levels of 9 polycyclic aromatic hydrocarbons (PAHs) in air at central European sites during 1996–2008 were used to assess the suitability of 5 commonly used diagnostic ratios (DRs) for PAH source apportionment. DRs derived from a detailed literature study on emission factors were reflected in ambient air samples only at sites located near major sources. A significant seasonality was observed in a long-term time series of ambient DRs at a background site indicating possible capability of this method to reflect changes in source characteristics.The results of a mass balance study suggest that current knowledge of PAH reactivities is insufficient for a source apportionment based on DRs at receptor sites, even when limited to major types of PAH sources. However, DRs could be used to narrow down ozone and hydroxyl radical reaction rate coefficients’ uncertainties: kO_₃⁽²⁾ of pyrene and benzo(ghi)perylene in the particulate phase seem to be≤10% of the highest rate coefficient measured using model aerosols in the laboratory and kO_₃⁽²⁾ of indeno(1,2,3-cd)pyrene in the gas phase could be higher than previously estimated by three orders of magnitude.The suitability of DRs for source apportionment at (especially background) receptor sites cannot be expected in the general case. However, measurements carried out close to sources are in accordance with literature data suggesting that the ratios of benzo(a)anthracene/(benzo(a)anthracene+chrysene) and indeno(123cd)pyrene/(indeno(123cd)pyrene+benzo(ghi)perylene) are capable of distinguishing between traffic and residential heating, while the ratio of anthracene/(anthracene+phenanthrene) was the least useful DR due to its low variability.► Current knowledge of PAH reactivities is insufficient for a source apportionment based on diagnostic ratios. ► Diagnostic ratios were used to narrow down ozone and hydroxyl radical reaction rate coefficients’ uncertainties. ► Two diagnostic ratios were found capable of distinguishing between traffic and residential heating.

Keywords: Polycyclic aromatic hydrocarbons; Diagnostic ratios; Reactivity; Air pollution; Source apportionment

CFD simulation of near-field pollutant dispersion on a high-resolution grid: A case study by LES and RANS for a building group in downtown Montreal by P. Gousseau; B. Blocken; T. Stathopoulos; G.J.F. van Heijst (pp. 428-438).

Turbulence modeling and validation by experiments are key issues in the simulation of micro-scale atmospheric dispersion. This study evaluates the performance of two different modeling approaches (RANS standard k-ε and LES) applied to pollutant dispersion in an actual urban environment: downtown Montreal. The focus of the study is on near-field dispersion, i.e. both on the prediction of pollutant concentrations in the surrounding streets (for pedestrian outdoor air quality) and on building surfaces (for ventilation system inlets and indoor air quality). The high-resolution CFD simulations are performed for neutral atmospheric conditions and are validated by detailed wind-tunnel experiments. A suitable resolution of the computational grid is determined by grid-sensitivity analysis. It is shown that the performance of the standard k-ε model strongly depends on the turbulent Schmidt number, whose optimum value is case-dependent and a priori unknown. In contrast, LES with the dynamic subgrid-scale model shows a better performance without requiring any parameter input to solve the dispersion equation.Display Omitted► Near-field pollutant dispersion in urban areas is particularly challenging to predict. ► The accuracy of RANS models depends strongly on the value of the turbulent Schmidt number. ► The optimum value of Sc_t depends on the configuration under study. ► With LES, the dispersion equation can be solved without any parameter input. ► Prediction accuracy depends strongly on urban geometry and reference wind direction.

Keywords: Computational fluid dynamics (CFD); Large eddy simulation (LES); Gas pollution; Urban area; Wind flow

Using multiple type composition data and wind data in PMF analysis to apportion and locate sources of air pollutants by Yiu-chung Chan; Olga Hawas; Darryl Hawker; Peter Vowles; David D. Cohen; Eduard Stelcer; Rod Simpson; Gary Golding; Elizabeth Christensen (pp. 439-449).

In this study a small but comprehensive data set from a 24-hourly sampling program carried out during June 2001 in an industrial area in Brisbane was chosen to investigate the effect of inclusion of multiple type composition data and wind data on source apportionment of air pollutants using the Positive Matrix Factorisation model, EPA PMF 3.0. The combined use of aerosol, VOC, main gaseous pollutants composition data and wind data resulted in better values of statistical indicators and diagnostic plots, and source factors which could be more easily related to known sources. The number of source factors resolved was similar to those reported in the literature where larger data sets were used. Three source factors were identified for the coarse particle samples, including ‘crustal matter’, ‘vehicle emissions’ and ‘sea spray’. Seven source factors were identified for the fine particle and VOC samples, including ‘secondary and biogenic’, ‘petroleum refining’, ‘vehicle emissions’, ‘petroleum product wholesaling’, ‘evaporative emissions’, ‘sea spray’ and ‘crustal matter’. The factor loadings of the 16 wind sectors and the calm wind sector from the PMF analysis were also used to quantify the directional contribution of the source factors. While the contributions were higher in the prevailing wind directions as expected, calm winds were also found to contribute up to 17% of the pollutant mass on average. The factor loadings, normalised by the overall abundance of the wind sectors, were also used to assess the directional dependences of the source factors. The results matched well with the location of known sources in the area. There was also a higher contribution potential from calm winds for local sources compared to that for distant sources. The results of directional effect using the PMF factor loading approach were similar to those by using the other approaches. This approach, however, also provides estimates of the mass contribution of source factors by wind sector and also the uncertainty of the results.

Keywords: Particulate matter; VOC; Wind direction; Source apportionment; Positive matrix factorisation

Nanometric-sized atmospheric particulate studied by magnetic analyses by F. Saragnese; L. Lanci; R. Lanza (pp. 450-459).

The PM10 particulate collected on filters from four air-quality monitoring stations in the city of Torino (Italy) has been investigated by means of detailed magnetic measurements, transmission electron microscopy and energy-dispersive X-ray analysis. The magnetic fraction mainly consists of magnetite-like ferrimagnetic phase and a minor contribution from a high-coercivity phase, which probably results from oxidation of the smallest magnetite grains. The magnetic particles have a grainsize mostly comprised in the single-domain/superparamagnetic range with a large prevalence of the latter. A large fraction of superparamagnetic particles of nanometric dimension were identified in the particulate matter by magnetic techniques and directly observed by electron microscopy. Energy dispersive X-ray elemental analysis showed that ultrafine Fe-rich particles have a spherical shape and are often associated with other metals. The analysis of daily-average variations of magnetic particle concentration found a close correlation of magnetic moment with total nitrogen oxides suggesting that the largest part of magnetic minerals in particulate matter originates from anthropogenic combustion processes. A simple model linking total nitrogen oxides with magnetic particles, for the city of Torino, is proposed. The correlation of magnetic moments and PM10 mass is generally poor because of the different sources of the latter, therefore in the studied contest PM10 is not a good proxy for ultrafine magnetic particles.

Keywords: Particulate matter; Anthropogenic pollution; Environmental magnetism; Superparamagnetism

Nanometric-sized atmospheric particulate studied by magnetic analyses by F. Saragnese; L. Lanci; R. Lanza (pp. 450-459).

Keywords: Particulate matter; Anthropogenic pollution; Environmental magnetism; Superparamagnetism

Nanometric-sized atmospheric particulate studied by magnetic analyses by F. Saragnese; L. Lanci; R. Lanza (pp. 450-459).

Keywords: Particulate matter; Anthropogenic pollution; Environmental magnetism; Superparamagnetism

Day–night variability of EC, OC, WSOC and inorganic ions in urban environment of Indo-Gangetic Plain: Implications to secondary aerosol formation by Kirpa Ram; M.M. Sarin (pp. 460-468).

This manuscript reports on the day- and night-time variability of EC, OC, WSOC and inorganic ions in ambient aerosols (PM_2.5 and PM₁₀) sampled from an urban site (Kanpur) in the Indo-Gangetic Plain. The chemical data also provide evidence for the secondary aerosol formation and variability in the composition of particulate matter. The aerosol mass is dominated by fine-mode particles and PM_2.5/PM₁₀ mass ratio exhibit significant temporal variability (range: 0.46 to 0.86). The chemical composition suggests that total carbonaceous aerosols (TCA=1.6×OC+EC) and water-soluble inorganic species (WSIS) account for nearly 50 and 20% of the PM_2.5 mass, respectively. The mass concentrations of PM_2.5, EC and OC show about 30% increase during night-time. A significant linear relation between EC-OC ( R²=0.66) and OC-K⁺ ( R²=0.59) and their characteristic ratios suggest biomass burning emission as a dominant source. The average WSOC/OC ratio is relatively high in the day-time samples (0.66±0.11) compared to that in the night-time (0.47±0.07); suggesting increased contribution of secondary organic aerosols. The mass fraction of particulate NO₃^- increases by a factor of five during night-time due to relatively stable NH₄NO₃ and/or its secondary formation from the hydrolysis of N₂O₅. Although the concentration of SO₄²⁻ is noticeably higher during day-time (∼20%), the day-night variability of particulate-NH₄⁺ is insignificant. The concentrations of OC, EC and inorganic species (K⁺, NH₄⁺, NO₃⁻ and SO₄²⁻) show 2 to 4 fold increase during the haze events.

Keywords: Organic carbon; Elemental carbon; Secondary aerosols; Urban-haze; Indo-Gangetic Plain; Diurnal variability

Day–night variability of EC, OC, WSOC and inorganic ions in urban environment of Indo-Gangetic Plain: Implications to secondary aerosol formation by Kirpa Ram; M.M. Sarin (pp. 460-468).

Keywords: Organic carbon; Elemental carbon; Secondary aerosols; Urban-haze; Indo-Gangetic Plain; Diurnal variability

Day–night variability of EC, OC, WSOC and inorganic ions in urban environment of Indo-Gangetic Plain: Implications to secondary aerosol formation by Kirpa Ram; M.M. Sarin (pp. 460-468).

Keywords: Organic carbon; Elemental carbon; Secondary aerosols; Urban-haze; Indo-Gangetic Plain; Diurnal variability

Carbon footprint of shopping (grocery) bags in China, Hong Kong and India by Subramanian Senthilkannan Muthu; Y. Li; J.Y. Hu; P.Y. Mok (pp. 469-475).

Carbon footprint has become a term often used by the media in recent days. The human carbon footprint is professed to be a very serious global threat and every nation is looking at the possible options to reduce it since its consequences are alarming. A carbon footprint is a measure of the impact of human activities on earth and in particular on the environment; more specifically it relates to climate change and to the total amount of greenhouse gases produced, measured in units of carbon dioxide emitted. Effort of individuals in minimizing the carbon footprint is vital to save our planet. This article reports a study of the carbon footprint of various types of shopping bags (plastic, paper, non-woven and woven) using life cycle impact assessment (LCIA) technique in two stages. The first stage (baseline study), comprised the study of the impact of different types of shopping bags in the manufacturing phase, without considering their usage and disposal phases (cradle to gate stage). The LCIA was accomplished by the IPCC 2007 method, developed by the Inter Panel on Climate Change in SIMAPRO 7.2. The GWP (Global Warming Potential) values calculated by the IPCC 2007 method for 100 years were considered as a directive to compare the carbon footprint made by the different types of shopping bags under consideration. The next stage was the study of the carbon footprint of these bags including their usage and disposal phases (cradle to grave stage) and the results derived were compared with the results derived from the baseline study, which is the major focus of this research work. The values for usage and end-of-life phases were obtained from the survey questionnaire performed amongst different user groups of shopping bags in China, Hong Kong and India. The results show that the impact of different types of shopping bags in terms of their carbon footprint potential is very high if no usage and disposal options were provided. When the carbon footprint values from different disposal options were compared, the carbon footprint values were lower in the case where a higher percentage of reuse is preferred to recycling and disposing to landfill. The results indicate that a higher percentage of reuse could significantly scale down the carbon footprint. Once the shopping bags reached the point where they can no longer be reused, they must be forwarded to recycling options, rather than being disposed to landfill. At this juncture, consumer’s perceptions and behaviours in connection with the respective government’s policies in promoting & facilitating recycling systems could be critical in reducing the carbon footprint of various shopping bags.

Keywords: Plastic bags; Paper bags; Non-woven bags; Woven bags; Life cycle impact assessment; SIMAPRO; IPCC 2007; Carbon footprint; Recycle; Reuse; Disposal to landfill

Carbon footprint of shopping (grocery) bags in China, Hong Kong and India by Subramanian Senthilkannan Muthu; Y. Li; J.Y. Hu; P.Y. Mok (pp. 469-475).

Keywords: Plastic bags; Paper bags; Non-woven bags; Woven bags; Life cycle impact assessment; SIMAPRO; IPCC 2007; Carbon footprint; Recycle; Reuse; Disposal to landfill

Carbon footprint of shopping (grocery) bags in China, Hong Kong and India by Subramanian Senthilkannan Muthu; Y. Li; J.Y. Hu; P.Y. Mok (pp. 469-475).

Keywords: Plastic bags; Paper bags; Non-woven bags; Woven bags; Life cycle impact assessment; SIMAPRO; IPCC 2007; Carbon footprint; Recycle; Reuse; Disposal to landfill

Evaluating the national air toxics assessment (NATA): Comparison of predicted and measured air toxics concentrations, risks, and sources in Pittsburgh, Pennsylvania by Jennifer M. Logue; Mitchell J. Small; Allen L. Robinson (pp. 476-484).

The National Air Toxics Assessment (NATA) is an ongoing modeling effort by the Environmental Protection Agency to predict air toxics concentrations, sources, and risks at the census tract level throughout the continental United States. To evaluate NATA, archived data collected at seven sites in and around Pittsburgh, Pennsylvania were compared to 2002 NATA predictions. The sites represent 3 different source regimes (mobile dominated, industrial point source dominated, and background). The evaluation considered 49 air toxics (37 gas-phase organics, 10 metals, coke oven emissions and diesel particulate matter); NATA’s performance was judged based on model-measurement comparisons of concentrations, health risks, and source contributions. On a concentration basis, NATA performance varied widely ranging from excellent for carbon tetrachloride to differences of more than a factor of 100 for low concentration chlorinated compounds. However, predicted concentrations were generally within a factor of 2 of measured values for air toxics that were estimated to be the primary cancer risk drivers; therefore NATA provided reasonable estimates of the additive cancer risks and risk ranking of air toxics. NATA performs better on average in Pittsburgh than nationwide. Comparison of source apportionment results indicates that NATA consistently underestimated concentrations of compounds emitted by large point sources as well as concentrations of chlorinated compounds, but overestimated the risks from mobile sources in Pittsburgh. Therefore, in Pittsburgh, NATA sufficiently prioritizes air toxics that drive potential cancer risks, but does not identify the sources of these priority air toxics.

Keywords: NATA; Air toxics; Model evaluation; Hazardous air pollutants; Cancer risk; Social justice; Pollutant sources

Assimilation of OMI NO₂ retrievals into a regional chemistry-transport model for improving air quality forecasts over Europe by Xiaoni Wang; Vivien Mallet; Jean-Paul Berroir; Isabelle Herlin (pp. 485-492).

This paper presents the assimilation of satellite NO₂ observations into a chemistry-transport model (CTM). The NO₂ columns from Ozone Monitoring Instrument (OMI) aboard NASA Aura satellite are used during November–December 2005. These satellite observations are assimilated in an air quality model from Polyphemus, in order to better forecast NO₂ in Europe. The optimal-interpolation method is applied to produce analyzed columns, and these analyzed columns are mapped to model concentrations assuming that the model vertical profile is perfect. Good consistency is seen in the comparisons of model simulations, satellite data and ground observations before assimilation. The model results with and without assimilation are then compared with ground observations for evaluating the assimilation effects. It is found that the assimilation can improve the NO₂ forecasts by reducing their discrepancies against ground observations, indicating a better NO₂ forecast obtained with OMI observations. Such improvements are seen in a cold season rather than in a warm one probably due to the longer lifetime of NO_x and the initial condition changes having more impacts in winter. This also suggests that the assimilation of the short-lived species like NO₂ is a complicate problem.

Keywords: Air quality; Satellite data assimilation; CTM; Nitrogen dioxide; Regional scale

Characterization of particulate matter emission from open burning of rice straw by Nguyen Thi Kim Oanh; Bich Thuy Ly; Danutawat Tipayarom; Bhai Raja Manandhar; Pongkiatkul Prapat; Christopher D. Simpson; L.-J. Sally Liu (pp. 493-502).

Emission from field burning of crop residue, a common practice in many parts of the world today, has potential effects on air quality, atmosphere and climate. This study provides a comprehensive size and compositional characterization of particulate matter (PM) emission from rice straw (RS) burning using both in situ experiments (11 spread field burning) and laboratory hood experiments (3 pile and 6 spread burning) that were conducted during 2003-2006 in Thailand. The carbon balance and emission ratio method was used to determine PM emission factors (EF) in the field experiments. The obtained EF varied from field to hood experiments reflecting multiple factors affecting combustion and emission. In the hood experiments, EF were found to be depending on the burning types (spread or pile), moisture content and the combustion efficiency. In addition, in the field experiments, burning rate and EF were also influenced by weather conditions, i.e. wind. Hood pile burning produced significantly higher EF (20±8gkg⁻¹ RS) than hood spread burning (4.7±2.2gkg⁻¹ RS). The majority of PM emitted from the field burning was PM_2.5 with EF of 5.1±0.7gm⁻² or 8.3±2.7gkg⁻¹ RS burned. The coarse PM fraction (PM_10–2.5) was mainly generated by fire attention activities and was relatively small, hence the resulting EF of PM₁₀ (9.4±3.5gkg⁻¹ RS) was not significantly higher than PM_2.5. PM size distribution was measured across 8 size ranges (from <0.4μm to >9.0μm). The largest fractions of PM, EC and OC were associated with PM_1.1. The most significant components in PM_2.5 and PM₁₀ include OC, water soluble ions and levoglucosan. Relative abundance of some methoxyphenols (e.g., acetylsyringone), PAHs (e.g., fluoranthene and pyrene), organochlorine pesticides and PCBs may also serve as additional signatures for the PM emission. Presence of these toxic compounds in PM of burning smoke increases the potential toxic effects of the emission. For illustration, an estimation of the annual RS field burning in Thailand was made using the obtained in situ field burning EF and preliminary burning activity data.

Keywords: Rice straw field burning; Pile burning; PM composition; Levoglucosan; Methoxyphenols; Semi-VOC

On-road emission factor distributions of individual diesel vehicles in and around Beijing, China by Xing Wang; Dane Westerdahl; Ye Wu; Xiaochuan Pan; K. Max Zhang (pp. 503-513).

This paper reports findings of a recent field study that characterized the on-road emissions of individual diesel vehicles in and around Beijing, China during November and December of 2009. We successfully sampled 230 individual trucks on 4 major expressways around the city as well as 57 individual buses in the city using refined mobile chasing techniques and fast response instruments. Emission factors (EF) for carbon monoxide (CO), black carbon (BC) and particulate matter with diameters less than 0.5 μm (PM_0.5) are derived from the measurements, which are consistent with the results from laboratory dynamometer tests. The PM_0.5 number emission factor distributions demonstrate consistent bimodal modes with peaks around 10 nm and 80 nm, while the mass emission factor distributions demonstrate a unimodal maximum around 110 nm for a majority of the trucks. The BC emissions are shown to be highly correlated with the mass emission of particles with 100–250 nm diameters, which are in good agreement with the results from previous studies. A number of important policy implications are discussed based on the results from this study. First, we identified “heavy emitters” in the on-road fleet we encountered, finding that 5% of diesel trucks in this sample are responsible for 50% of total BC emissions, and 20% of the trucks are responsible for 50% CO and PM_0.5 number emissions, 60% PM_0.5 mass emissions and over 70% of BC emissions. This suggests that emissions control programs should include identifying and removing heavy emitters from the road or improving their emissions. Second, the BC and PM_0.5 number emission factors of trucks registered in regions outside Beijing are significantly higher than those of Beijing-registered trucks, suggesting that improving engine and fuel standards in Beijing alone is not sufficient in reducing the traffic-related air pollution in Beijing. Third, the significantly lower emissions from Euro IV and CNG buses compared to the Euro II and Euro III buses support that introducing clean-burning buses is an effective way to reduce the overall vehicle emissions for the pollutants studied. Fourth, our refined chasing method demonstrates a cost-effective approach to characterize the emissions from a large number of on-road diesel vehicles. Further studies with large sample sizes are critical to constructing more accurate mobile emission inventories to represent the on-road vehicle population.

Keywords: Climate change; Air quality; Diesel; Size distribution

On-road emission factor distributions of individual diesel vehicles in and around Beijing, China by Xing Wang; Dane Westerdahl; Ye Wu; Xiaochuan Pan; K. Max Zhang (pp. 503-513).

Keywords: Climate change; Air quality; Diesel; Size distribution

On-road emission factor distributions of individual diesel vehicles in and around Beijing, China by Xing Wang; Dane Westerdahl; Ye Wu; Xiaochuan Pan; K. Max Zhang (pp. 503-513).

Keywords: Climate change; Air quality; Diesel; Size distribution

Contributions of resuspended soil and road dust to organic carbon in fine particulate matter in the Midwestern US by Andrew P. Rutter; David C. Snyder; James J. Schauer; Rebecca J. Sheesley; Michael R. Olson; Jeff DeMinter (pp. 514-518).

Considerable uncertainty still exists regarding the contribution of resuspended soil and road dust to PM_2.5 organic carbon (OC) in US urban areas. Contributing factors are the limited knowledge of the OC content of resuspended soils and road dusts, and the variability of the ratio of OC to traditional soil markers such as silicon and aluminum. This study investigates the composition of resuspended soils and road dusts in the Midwestern US, and the contributions of these soils to atmospheric PM_2.5 OC. Paved road dust and soil samples were resuspended in a residence chamber from which PM_2.5 size fractions were collected and analyzed to generate source profiles. Differences significant to 1 standard deviation were observed in the mass ratios between OC, and silicon and aluminum across different soil types which were larger between soil types within each city (61–97%), than between samples of the same soil type collected in different cities (29–57%). CMB 8.2 source apportionment results revealed large biases in soil apportionments, but these did not greatly affect the overall OC apportionments in six Midwest cities due to the small contributions of soil to total OC (ranging between 0.01 and 0.1μgm⁻³). Apportionments of total PM_2.5 mass were more greatly affected: biases up to 0.7μgm⁻³ for total PM_2.5 masses ranging between 7 and 14μgm⁻³ were observed when soil profiles were interchanged.

Keywords: Chemical mass balance; Air pollution; Urban; Air quality; Endotoxin; Windblown; Dust; Soil; Source apportionment

The altitude of snow growth by riming and vapor deposition in mixed-phase orographic clouds by Douglas H. Lowenthal; Randolph D. Borys; William Cotton; Stephen Saleeby; Stephen A. Cohn; William O.J. Brown (pp. 519-522).

Oxygen isotopic ratios ( δ¹⁸O) and sulfate concentrations were measured in cloud water and snow collected at Storm Peak Laboratory (SPL) during winter, 2007. The rimed mass fraction (RMF) was estimated as the ratio of sulfate concentration in snow to that in cloud water. A sharp increase in the RMF at mean droplet diameters above 10μm confirmed the expected relationship between riming efficiency and cloud droplet size. The mass-weighted altitude of snow formation was inferred from δ¹⁸O in cloud water and snow and did not exceed 300m above SPL. The mass-weighted altitude of snow growth by vapor deposition alone was no higher than 900m above SPL. The results suggest that snow crystals nucleated under water-sub-saturated conditions at higher elevations attained a significant fraction of their water content as they grew by riming and vapor deposition in transit through the low-level orographic cloud near the mountain crest. This approach provides a direct means of validating model simulations of snow growth processes in cold mountain clouds.

Keywords: Snow growth; Accretion; Rimed mass fraction; Oxygen isotopic ratio; Orographic cloud

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Atmospheric Environment (v.45, #2)

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Atmospheric Environment (v.45, #2)