Atmospheric Environment (v.62, #C)

Chemical and radioactive composition of bulk deposition in Málaga (Spain) by C. Dueñas; M.C. Fernández; E. Gordo; S. Cañete; M. Pérez (1-8).
Chemical and radioactive composition of bulk deposition samples, which were collected monthly over a 5 year period (January 2007 until 31 December 2011) at a site located 30 m.a.l. in Málaga (4°28′ 8″W; 36°43′ 40″N) have been analysed. All samples were analysed for pH, major ions and gamma radionuclides. The average pH of bulk deposition was 6.4. Cl and SO 4 2− were the main anions, while Ca+ and Na+ were the main cations. Significant correlations were found in soil-derived species among Ca2+, Mg2+ and K+ and sea-salt species between Na+ and Cl. Other relatively good correlations were also observed between acidic anions ( SO 4 2− and NO 3 − ) and crustal-derived cations (Ca2+, Na+, K+). Sources of the major ions were assessed based on the enrichment factor method. The radionuclides present in all samples are 7Be and 210Pb and 40K appears in 50% of the samples. Relatively poor correlations were observed between the specific activities of gamma radionuclides and the major ions. The temporal variations of major ions and radionuclides exhibit similar seasonal behaviour with low values in winter–autumn months and maximum values in spring–summer months. The fluxes of major ions and gamma radionuclides have been discussed with meteorological factors controlling depositions.► Chemistry and radioactive composition of bulk deposition. ► Seasonal variations of chemistry and radioactive composition in bulk deposition. ► Relationships between chemistry and radioactive composition in bulk deposition. ► Factors controlling the fluxes of major ions and radionuclides in bulk deposition.
Keywords: Bulk deposition; Major ions; Radionuclides; Atmospheric fluxes;

Wind tunnel measurements for dispersion modelling of vehicle wakes by Matteo Carpentieri; Prashant Kumar; Alan Robins (9-25).
Wind tunnel measurements downwind of reduced scale car models have been made to study the wake regions in detail, test the usefulness of existing vehicle wake models, and draw key information needed for dispersion modelling in vehicle wakes. The experiments simulated a car moving in still air. This is achieved by (i) the experimental characterisation of the flow, turbulence and concentration fields in both the near and far wake regions, (ii) the preliminary assessment of existing wake models using the experimental database, and (iii) the comparison of previous field measurements in the wake of a real diesel car with the wind tunnel measurements. The experiments highlighted very large gradients of velocities and concentrations existing, in particular, in the near-wake. Of course, the measured fields are strongly dependent on the geometry of the modelled vehicle and a generalisation for other vehicles may prove to be difficult. The methodology applied in the present study, although improvable, could constitute a first step towards the development of mathematical parameterisations. Experimental results were also compared with the estimates from two wake models. It was found that they can adequately describe the far-wake of a vehicle in terms of velocities, but a better characterisation in terms of turbulence and pollutant dispersion is needed. Parameterised models able to predict velocity and concentrations with fine enough details at the near-wake scale do not exist.► A car wake was characterised through wind tunnel measurements. ► Large gradients of velocities and tracer concentrations were found in the near-wake. ► Current wake models adequately describe the velocities in the far-wake. ► A better characterisation of turbulence and pollutant dispersion is needed. ► Near-wake models do not exist, yet they are necessary for some applications.
Keywords: Dispersion modelling; Near and far wake; Vehicle wake dispersion; Wind tunnel measurements; Mixing processes;

Estimates of major anthropogenic halocarbon emissions from China based on interspecies correlations by Xuekun Fang; Jing Wu; Shenshen Su; Jiarui Han; Yusheng Wu; Yehong Shi; Dan Wan; Xuezhi Sun; Jianbo Zhang; Jianxin Hu (26-33).
Halocarbon emissions from China are of great interest to both policy makers and academia. To estimate halocarbon emissions with interspecies correlation methods, previous studies adopted CO, HCFC-22 or other species as reference tracers. However, few of these studies compared the results using different reference tracers. In this study, chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs) and carbon monoxide (CO) concentrations were measured at a monitoring site in northern China in 2009/2010, and halocarbon emissions were estimated using an interspecies correlation method. A comparison was performed of the correlations between estimated halocarbon emissions and two reference tracers, CO and HCFC-22. The results show that both species are significantly correlated with most of the target species (P < 0.01), whereas HCFC-22 shows better correlations than does CO. Our estimated halocarbon emissions for 2009 agree within uncertainties with results obtained with other approaches, including inverse modeling and interspecies correlation methods. The emissions for 2001–2009 estimated in different studies (all using top–down approaches) show a clear decrease in the emissions of CFC-11 and CFC-12 and an increase in the emissions of HCFC-22, HCFC-141b and HCFC-142b in China. Moreover, the combined Ozone Depletion Potential weighted emissions of CFCs are much greater than the reported consumption, whereas the emissions of HCFC counterparts are not more than one-half of the reported consumption. This result suggests that HCFCs are being accumulated in banks and that these banks will sustain elevated in China.► HCFC-22 is better as a reference tracer than CO derived from comparisons. ► The estimated emissions agree well with other estimates within uncertainties. ► HCFC emissions from China contributed more than CFC/HFC emissions to global totals. ► CFC emissions are decreasing evidently and HCFC emissions are increasing during 2001–2009. ► HCFCs are being accumulated in banking time usages in China.
Keywords: Halocarbon; Emission; China; Interspecies correlation; Global perspective; Trend;

Lidar depolarization measurement of fresh volcanic ash from Mt. Etna, Italy by Gianluca Pisani; Antonella Boselli; Mauro Coltelli; Giuseppe Leto; Giulia Pica; Simona Scollo; Nicola Spinelli; Xuan Wang (34-40).
A small, portable, polarization lidar system with scanning capability was used to perform range resolved measurements of fresh erupted volcanic plume from Mount Etna in Italy. Measurements were carried out on November 15, 2010 during a volcanic plume emission event by placing the lidar very close to volcano summit craters. Depolarization measurements highlighted that aerosol of different shape and optical properties were emitted by the two involved vents, Bocca Nuova and North-East Craters. In the plume emitted from Bocca Nuova Crater the mean value of aerosol linear depolarization ratio resulted near to zero, corresponding to non depolarizing particles or liquid droplets, while values of (16 ± 2)% and (45 ± 3)% were observed in the ash plume emitted from North-East Crater, in the morning and in the afternoon, respectively. The retrieved values of volcanic aerosol depolarization ratio, aerosol backscattering and lidar-ratio allowed distinguishing the changes in the properties of the emitted aerosol. Furthermore, the ash mass concentration at source was estimated, reaching a maximum value of 24,000 ± 6000 μg m 3, with an additional systematic uncertainty of 50% related to the assumption of an effective radius of 10 μm for ash particles.► Ash emission from Mt Etna was followed by a polarization lidar. ► Particle depolarization of fresh volcanic ash was measured near the source. ► Depolarization and lidar ratio values of two plumes components were determined. ► Estimation of volcanic ash mass concentration at source was performed.
Keywords: Lidar; Volcanic ash; Mass concentration; Depolarization; Lidar-ratio;

The impacts of tropospheric ozone on conifer health in the Sierra Nevada of California, USA, and the Pyrenees of Catalonia, Spain, were measured using field assessments and GIS variables of landscape gradients related to plant water relations, stomatal conductance and hence to ozone uptake. Measurements related to ozone injury included visible chlorotic mottling, needle retention, needle length, and crown depth, which together compose the Ozone Injury Index (OII). The OII values observed in Catalonia were similar to those in California, but OII alone correlated poorly to ambient ozone in all sites. Combining ambient ozone with GIS variables related to landscape variability of plant hydrological status, derived from stepwise regressions, produced models with R 2 = 0.35, p = 0.016 in Catalonia, R 2 = 0.36, p < 0.001 in Yosemite and R 2 = 0.33, p = 0.007 in Sequoia/Kings Canyon National Parks in California. Individual OII components in Catalonia were modeled with improved success compared to the original full OII, in particular visible chlorotic mottling (R 2 = 0.60, p < 0.001). The results show that ozone is negatively impacting forest health in California and Catalonia and also that modeling ozone injury improves by including GIS variables related to plant water relations.► Ozone Injury Index (OII) values in Catalonia were similar to those in California. ► OII models improved by including GIS variables related to plant water relations. ► The OII visual component proved the most robust metric of ozone injury to conifers.Capsule: Models of ozone injury improve significantly when combining ambient ozone mixing ratios and field assessment of ozone impacts with GIS variables related to plant water relations.
Keywords: Pinus ponderosa; Pinus jeffreyi; Pinus uncinata; Ozone; GIS; Ozone Injury Index; Bioindicator; California; Catalonia; Mediterranean; Air pollution;

Impact of declining atmospheric deposition on forest soil solution chemistry in Flanders, Belgium by Arne Verstraeten; Johan Neirynck; Gerrit Genouw; Nathalie Cools; Peter Roskams; Maarten Hens (50-63).
Throughout Europe and the USA, forest ecosystem functioning has been impacted by long-term excessive deposition of acidifying compounds. In this study, we report on trends in stand deposition and soil solution fluxes of inorganic nitrogen (N) and sulphur (S) compounds over a 17-year period (1994–2010) in five ICP Forests monitoring plots in Flanders, northern Belgium. Deposition was dominated by N, and primarily NH4 +. Deposition of SO4 2− and NH4 + declined by 56–68% and 40–59% respectively. Deposition of NO 3 decreased by 17–30% in deciduous forest plots, but remained stable in coniferous forest plots. The decrease of N and S deposition was parallelled by a simultaneous decline in base cation (BC = Ca2+ + K+ + Mg2+) deposition, resulting in a 45–74% decrease of potentially acidifying deposition. Trends in soil solution fluxes of NH4 +, NO3 , SO4 2− and BC mirrored declining depositions. Nitrate losses below the rooting zone were eminent in both coniferous forest plots and in one deciduous forest plot, while net SO4 2− release was observed in two deciduous forest plots. Critical limits for BC/Al ratio were exceeded at the three plots on sandy soils with lower cation exchange capacity and base saturation. Soil solution acid neutralizing capacity increased but remained negative, indicating that soil acidification continued, as the start of recovery was delayed by a simultaneous decrease of BC depositions and short-term soil buffering processes. Despite substantial reductions, current N deposition levels still exceed 4–8 times the critical load for safeguarding sensitive lichen species, and are still 22–69% above the critical load for maintaining ground vegetation diversity.► Acidifying depositions were related to soil solution chemistry in Flanders forests. ► Depositions of N and S decreased significantly between 1994 and 2010. ► Lichen and ground vegetation based critical loads for N were still exceeded. ► Critical limits for BC/Al and ANC were exceeded and soil acidification continued. ► Recovery is delayed by soil buffering processes and decreasing BC depositions.
Keywords: Acidifying deposition; Soil solution; Forests; Acid neutralizing capacity; BC/Al ratio; Time trend;

Prediction of ozone levels using a Hidden Markov Model (HMM) with Gamma distribution by Hao Zhang; Weidong Zhang; Ahmet Palazoglu; Wei Sun (64-73).
Ground level ozone, generated by the photochemical reaction between nitrogen oxides and volatile hydrocarbons, is harmful to humans and the environment. Prediction and forecasting play an important role in the regulatory policies aimed at the control and reduction of surface ozone. Belonging to the family of model-driven statistical models, Hidden Markov Models (HMMs) provide a rich mathematical structure and perform well in many applications. While conventional HMM applications assume Gaussian distribution for the observation statistics, several key meteorological factors and most ozone precursors exhibit a non-Gaussian distribution, which would weaken the performance of a conventional HMM in modeling ozone exceedances. We propose a method based on a HMM with a Gamma distribution (HMM-Gamma) where each monitoring day is pre-labeled according to its maximum 8-h average ozone concentration and monitoring days are further grouped into zones with different ozone levels. Then, HMMs associated with each zone are trained using air quality monitoring data where the model parameters are estimated by a modified Expectation–Maximization (EM) algorithm. We derive a new re-estimation formula for the model parameters for observation sequences that exhibit a Gamma distribution. The trained HMM-Gamma models are used to predict ozone exceedances in two geographic areas, Livermore Valley near San Francisco, CA and Houston Metropolitan Area, TX. Compared to the conventional HMM (HMM-Gaussian), HMM-Gamma for the ground level ozone in Livermore Valley can reduce false alarms by 77% and HMM-Gamma for that in Houston Metropolitan Area can reduce false alarms by 32%.► A Hidden Markov Model with Gamma distribution is derived in this paper. ► It is applied on ozone prediction in Livermore Valley near San Francisco, CA and Houston Metropolitan Area, TX. ► Results show that HMM-Gamma can predict all exceedances correctly and reduce false alarms significantly.
Keywords: Ozone prediction; Model-driven models; Hidden Markov models; Wavelets;

This paper aims to advance regional worldwide source–receptor relationships, providing fate factors for acidifying and eutrophying air emissions (NO x , HNO3, SO2, SO4 and NH3) to be used within life cycle impact assessment. A simulation for the reference year 2005 of the three-dimensional global scale tropospheric GEOS-Chem model was used as the basis of a novel methodological approach to derive source–receptor matrices (SRMs) whose elements are fate factors at a global 2° × 2.5° grid. This new approach makes it possible to assess the impact of transboundary emissions while maintaining regional scale emission differentiation. These 2° × 2.5° grid resolution fate factors were later aggregated at continental and country resolutions using emission weighting. Continental fate factor results showed that 50–70% of nitrogen oxides (NO x , HNO3) and sulfur oxides (SO2, SO4) and approximately 80% of ammonia (NH3) emissions will deposit on the same continent. Results showed that the developed fate factor derivation approach was within a ±10% agreement with GEOS-Chem simulations in which fate factors were determined by withdrawing the regional emission inventory over Canada and in ±50% agreement with current state-of-the-art LCIA fate factors (calculated with the European Monitoring and Evaluation Programme (EMEP) model). The SRMs outlined in this paper facilitate further modeling developments without having to run the underlying tropospheric model, thus opening the door to the assessment of the regional life cycle inventories of a global economy.► We provide an approach to estimate regional fate factors at a global scale. ► Transboundary impacts can now be evaluated in life cycle impact assessment (LCIA). ► We favorably compared the approach results with direct GEOS-Chem outputs. ► The uncertainties and limitations of the approach are acceptable for LCIA purposes.
Keywords: Acidification; Eutrophication; Source–receptor relationship; Fate factors; Life cycle impact assessment;

Environmental tobacco smoke aerosol in non-smoking households of patients with chronic respiratory diseases by Marie-Cecile Chalbot; Ino-Christina Vei; Maria Lianou; Anastasia Kotronarou; Anna Karakatsani; Klea Katsouyanni; Gerard Hoek; Ilias G. Kavouras (82-88).
Fine particulate matter samples were collected in an urban ambient fixed site and, outside and inside residencies in Athens greater area, Greece. n-Alkanes, iso/anteiso-alkanes and polycyclic aromatic hydrocarbons (PAHs) were identified by gas chromatography and mass spectrometry. The values of concentration diagnostic ratios indicated a mixture of vehicular emissions, fuel evaporation, oil residues and environmental tobacco smoke (ETS) in outdoor and indoor samples. Particulate iso/anteiso-alkanes, specific tracers of ETS, were detected in both non-smoking and smoking households. The indoor-to-outdoor ratios of particulate iso/anteiso-alkanes and unresolved complex mixture (a tracer of outdoor air pollution) in non-smoking households were comparable to the measured air exchange rate. This suggested that penetration of outdoor air was solely responsible for the detection of tobacco smoke particulate tracers in indoor non-smoking environments. Overall, residential outdoor concentrations accounted for a large fraction (from 25 up to 79%) of indoor aliphatic and polyaromatic hydrocarbons. Open windows/doors and the operation of an air condition unit yielded also in higher indoor concentrations than those measured outdoors.► We analyzed indoor and outdoor PAHs and alkanes in the residencies of asthmatic and COPD patients. ► ETS tracers in non-smoking households were due to penetration of outdoor air. ► We identified the contribution of ETS, indoor activities and ventilation on indoor concentrations.
Keywords: Urban aerosol; Indoor aerosol; Environmental tobacco smoke; iso/anteiso-alkanes;

Seasonal cycles in short-lived hydrocarbons in baseline air masses arriving at Mace Head, Ireland by Richard G. Derwent; Peter G. Simmonds; Simon O'Doherty; Aoife Grant; Dickon Young; Michael C. Cooke; Alistair J. Manning; Steven R. Utembe; Michael E. Jenkin; Dudley E. Shallcross (89-96).
The observed seasonal cycles of a selection of reactive hydrocarbons in baseline air masses at Mace Head, Ireland are consistent with a simple picture of largely man-made sources and oxidation by hydroxyl (OH) radicals. As a result, the observed seasonal cycles become more pronounced the more reactive the species are with OH. For the pentanes, the assumption of little wintertime removal breaks down, leading to an apparent dampening of the seasonal cycles relative to ethane, propane and the butanes. A global chemistry-transport model is used to describe the seasonal cycles of the hydrocarbons at Mace Head and provided an accurate description of their observed amplitudes and phases. The model derived local OH concentrations in baseline air masses required to support the observed seasonal cycles of the hydrocarbons averaged 1.38 ± 1.1 × 106 molecule cm−3. Peak daytime levels during summertime reached 1.2 × 107 molecule cm−3.► The observed baseline seasonal cycles are driven by OH radical oxidation. ► A global CTM model described the observed amplitudes and phases. ► The CTM model derived local OH concentrations from the observations.
Keywords: C2–C5 hydrocarbons; Seasonal cycles; OH;

Extreme value theory, which characterizes the behavior of tails of distributions, is potentially well-suited to model exposures and risks of pollutants. In this application, it emphasizes the highest exposures, particularly those that may be high enough to present acute or chronic health risks. The present study examines extreme value distributions of exposures and risks to volatile organic compounds (VOCs).Exposures of 15 different VOCs were measured in the Relationship between Indoor, Outdoor and Personal Air (RIOPA) study, and ten of the same VOCs were measured in the nationally representative National Health and Nutrition Examination Survey (NHANES). Both studies used similar sampling methods and study periods. Using the highest 5 and 10% of measurements, generalized extreme value (GEV), Gumbel and lognormal distributions were fit to each VOC in these two large studies. Health risks were estimated for individual VOCs and three VOC mixtures. Simulated data that matched the three types of distributions were generated and compared to observations to evaluate goodness-of-fit. The tail behavior of exposures, which clearly neither fit normal nor lognormal distributions for most VOCs in RIOPA, was usually best fit by the 3-parameter GEV distribution, and often by the 2-parameter Gumbel distribution. In contrast, lognormal distributions significantly underestimated both the level and likelihood of extrema. Among the RIOPA VOCs, 1,4-dichlorobenzene (1,4-DCB) caused the greatest risks, e.g., for the top 10% extrema, all individuals had risk levels above 10−4, and 13% of them exceeded 10−2. NHANES had considerably higher concentrations of all VOCs with two exceptions, methyl tertiary-butyl ether and 1,4-DCB. Differences between these studies can be explained by sampling design, staging, sample demographics, smoking and occupation.This analysis shows that extreme value distributions can represent peak exposures of VOCs, which clearly are neither normally nor lognormally distributed. These exposures have the greatest health significance, and require accurate modeling.► Personal VOC exposures drawn from two studies, RIOPA and NHANES, were used. ► Generalized extreme value (GEV) and Gumbel distributions were fit to VOC extrema. ► The tail behavior of exposure was usually best fit by GEV and Gumbel distributions. ► Lognormal distributions underestimated both the level and likelihood of extrema. ► NHANES had considerably higher concentrations of most VOCs, including extrema.
Keywords: RIOPA; Extreme value analysis; Exposure; Risk; Volatile organic compounds;

Detailed predictions of particle aspiration affected by respiratory inhalation and airflow by Kiao Inthavong; Qin Jiang Ge; Xiang Dong Li; Ji Yuan Tu (107-117).
The effects of air pollution found in the atmosphere and exposure to airborne particles are an important problem in the interest of public health. Exposure to contaminated air under different flow conditions is studied using the latest computational fluid dynamics models. For the first time the upper respiratory airway is integrated into a human body and placed inside a room, facing different airflow speeds (0.05–0.35 m s 1). It was found that the airflow streamlines diverged as it approached the human body, at the torso and accelerated upwards past the face and head before separating at the rear of the head, forming recirculating regions in the wake behind the body. Inhaled particles were tracked backwards to determine its origins. At a plane upstream from the face the locations of particles inhaled form a region known as the critical area, which is presented. This study establishes a better understanding of particle inhalability and provides a step towards a more holistic approach in determining inhalation toxicology effects of exposure to atmospheric particles.► Integrated model of human respiratory airway, humanoid, and indoor room is modelled. ► Flow near the face shows accelerated flow into the nostril during inhalation. ► Recirculating flow in the wake created behind body can induce pollutants. ► Particle tracking reveals origin of particles and its fate in respiratory airway.
Keywords: Air pollution; Particle; Deposition; Nasal cavity; Inhalation; CFD;

GC–MS characterization of contemporary pesticides in PM10 of Valencia Region, Spain by Elizabeth Hart; Clara Coscollà; Agustín Pastor; Vicent Yusà (118-129).
Better knowledge of the occurrence of pesticides in the inhalable fraction of particulate matter (PM10) could be very useful for future exposure assessment in individuals of the general public. The present work studies the spatial and temporal distribution of the occurrence of currently used pesticides (CUPs) in PM10. Ambient air samples were collected from January through December 2010 at one remote, one urban and three rural sites in Valencia Region (Spain) and analyzed for 42 CUPs using a gas chromatography coupled to mass spectrometry in tandem (GC–MS/MS) approach. Overall, 24 pesticides were detected in the PM10 fraction, four of them currently banned pesticides. Among those detected, concentrations of two particle-bound pesticides (permethrin and pyrimethanil) were, to our knowledge, reported for the first time in air in the literature. The detected pesticides appeared at frequencies ranging from <1 to 47%, with chlorpyrifos, bifenthrin and diazinon presenting the highest frequencies. The concentrations detected ranged from a few to several hundred pg m−3, with ethoprophos showing the highest average concentration (149.2 pg m−3). Each station shows its own specific pesticide profile, which is linked to the different types of crops around each site. Seasonal patterns were observed in the rural stations of Alzira and Sant Jordi, correlating pesticide detection with their application in agricultural practices, mostly in spring and early summer. These findings suggest that more efforts are required to implement an extensive air monitoring network in Europe for pesticide control and to develop regulations or recommendations regarding pesticide levels in ambient air.► 42 current-use pesticides (CUPs) were monitored in PM10 in Valencia Region, Spain. ► A total of 24 pesticides were detected at frequencies up to 47%. ► Average pesticide concentrations ranged from 6 to 149 pg m−3. ► Seasonal patterns of pesticide air levels were observed in 2 rural stations. ► Some of the pesticides detected are currently banned in the EU.
Keywords: Pesticides; Temporal variations; PM10;

Attributing health effects to individual particulate matter constituents by Annette C. Rohr; Ronald E. Wyzga (130-152).
There is a general consensus in the scientific community that fine particulate matter (PM2.5) composition plays a significant role in the health effects attributed to PM; indeed, components may be more important than PM concentration alone in explaining health responses. As evidence linking composition to health impacts continues to accumulate in the epidemiological, toxicological, and controlled human exposure arenas, it is becoming more urgent from a policy perspective to determine which components or combination of components are most harmful to human health. While several reviews on this topic have focused on specific types of studies, such as source apportionment studies or those using concentrated ambient particles (CAPs), no review has been published that holistically examines the evidence from all component-based studies. In particular, while source apportionment is a useful tool for developing an understanding of potential contributing sources to PM2.5 in certain areas, it is also subject to significant limitations, and therefore results from those studies need to be interpreted with care. We reviewed published studies that (1) included at least two PM components; (2) did not only group them statistically into factors; and (3) quantitatively determined the relationship between the components and health effects. The majority of the studies examined yielded significant findings for specific components of PM, but not for PM concentration, demonstrating that PM alone does not drive health responses. Overall, the epidemiological studies did not fully exonerate any major component class of PM2.5 mass, but did demonstrate that more scrutiny needs to be given to carbon-containing PM components (elemental and organic carbon), as growing evidence suggests these are most strongly associated with adverse health outcomes. The results of controlled human exposure studies are consistent with this premise, although only two such studies were available for consideration. Toxicological studies suggest that several elements, including aluminum, silicon, vanadium, and nickel, are most closely associated with health impacts, although many other elements, as well as carbon-containing components, have been implicated as well. There are no PM components for which there is unequivocal evidence of zero health impact. However, care must be taken in interpreting these results as it is unclear whether a component per se is responsible for health impacts or is an index or surrogate for some other pollutant.► We review the literature on fine particulate matter components and health effects. ► No components show unequivocal evidence of zero health impact. ► Carbon-containing PM appears to be most strongly associated with health effects. ► Any given component could be an index for another pollutant.
Keywords: Particulate matter; Air pollution; Health; Components; Toxicology; Epidemiology;

The experimental data available for the photodissociation quantum yields of acetaldehyde are evaluated to derive formal expressions for their dependence on wavelength and pressure. The formulae are used to calculate the photodissociation coefficient of acetaldehyde as a function of altitude in the troposphere. The processes active in the photodecomposition of acetaldehyde are comparable to those in acetone, but the photodissociation coefficients of acetaldehyde (at room temperature) are six times greater. The dependence of the quantum yields on wavelength and pressure supports recent evidence of participation of both singlet and triplet states in the photodissociation process.► The photodissociation quantum yields (QY) of acetaldehyde are evaluated. ► Expressions of QY are derived as function of wavelengths and pressure. ► Participation of both singlet and triplet states in the photodissociation process. ► Photodissociation rates as a function of altitude in the troposphere are calculated.
Keywords: Acetaldehyde photolysis; Quantum yield; Wavelength dependence; Pressure dependence; Photodissociation coefficient;

Ground-based zenith-sky DOAS observation was carried out from October 1, 2009 to September 30, 2010 in Shanghai, China to measure the O4 and H2O absorption in visible band and to illustrate the dependence of their correlation slope on the aerosol pollution type. Good correlations between O4 and H2O DSCDs can be found through linear regression analysis whether it was sunny, cloudy, overcast, or rainy. The correlation slope varied seasonally in the order of summer < autumn, spring < winter. In particular, the correlation slope and fluctuation were small in the summer. It was found that slope values also relied on sky conditions generally in the sequence of dusty > sunny > cloudy > overcast > rainy. The implication of the variation of slope to the aerosol pollution type was discussed for typical heavy dust and haze episodes occurred in March 2010 and October 2009, respectively. As the correlation slope abruptly increased during the heavy dust due to low moisture content and enhanced O4 absorption caused by abundant suspended dry crustal particles, the slope dropped suddenly in the haze episode owing to the significant augment of H2O absorption. Thus, the much discrepant correlation patterns may be regarded as a characteristic signature for dust and haze events.► Correlation between O4 and H2O absorptions in vis-band is first proposed to implicate aerosol. ► Good correlations between O4 and H2O DSCDs can be found under different weather. ► The seasonal correlation slopes sequence was: summer < autumn < spring < winter. ► The slopes varied generally in sequence of dusty > sunny > cloudy > overcast > rainy. ► The slope abruptly increased in heavy dust while it dropped suddenly in haze episode.
Keywords: Aerosol remote sensing; O4; Dust; Haze; DOAS;

Differences of chemical species and their ratios between fine and ultrafine particles in the roadside environment by Shinji Kudo; Kazuhiko Sekiguchi; Kyung Hwan Kim; Masatoshi Kinoshita; Detlev Möller; Qingyue Wang; Hiroshi Yoshikado; Kazuhiko Sakamoto (172-179).
Chemical components of fine particles (FPs; aerodynamic diameter, Dp < 2.5 μm) and ultrafine particles (UFPs; Dp < 0.1 μm) at Japanese and German roadsides were investigated during summer. The UFPs/FPs ratio for organic carbon (OC) concentrations on weekdays was 34.5% and 25.0% at Japanese and German roadsides, respectively, whereas 3.3% and 6.4% for elemental carbon (EC) concentrations, respectively. These results thus indicate a higher OC and a lower EC contribution from UFPs at the Japanese roadside than at the German roadside. In particle samples, OC2 and OC3 constituted a high proportion of UFPs, and pyrolyzed OC and EC1 were predominant among FPs of 0.1 μm < Dp < 2.5 μm. Our results showed roadside environment exist not only primary FPs and UFPs but also secondary FPs and UFPs from photochemical reactions or long-range transport.► OC2 and OC3 constitute a high proportion of UFPs. ► POC and EC1 were dominant among of FPs 0.1 < Dp < 2.5 μm. ► EC2 contributed to the total EC of UFPs in roadside environment. ► Higher minimum OC/EC ratio of UFP is affected by secondary or background particles.
Keywords: Fine particles; Ultrafine particles; Roadside environment; Organic carbon/elemental carbon ratio;

Plant species richness enhanced the methane emission in experimental microcosms by Chong-Bang Zhang; Hong-Ying Sun; Ying Ge; Bao-Jing Gu; Hai Wang; Jie Chang (180-183).
Effect of plant species richness on the methane (CH4) flux was investigated in vertical flow microcosms fed with the modified Hoagland solution. The CH4 flux increased significantly with the plant species richness (Linear regression analysis, r 2 = 0.203, P = 0.010), with an average range from 1.59 to 4.30 mg m−2 d−1. Above-ground plant biomass followed the CH4 flux trend with the plant species richness (r 2 = 0.108, P = 0.023), but both methanogenic number and activity decreased to different extents with the plant species richness (r 2 = 0.103, P = 0.023; r 2 = 0.020, P = 0.337), respectively. Accordingly, the present study highlights the significance of plant species diversity and its biomass production in manipulating the CH4 flux in the constructed wetlands.
Keywords: Methane flux; Plant species diversity; Plant biomass; Methanogens; Methanogenic activity;

A case study of chlorine transport and fate following a large accidental release by Robert L. Buckley; Charles H. Hunter; David W. Werth; Morgana T. Whiteside; Kuo-Fu Chen; Carl A. Mazzola (184-198).
A train derailment that occurred in Graniteville, South Carolina during the early morning hours of 06 January, 2005 resulted in the prompt release of approximately 60 tons of chlorine to the environment. Comprehensive modeling of the transport and fate of this release was performed including the characterization of the initial three-phased chlorine release, a detailed determination of the local atmospheric conditions acting to generate, disperse, and deplete the chlorine vapor cloud, the establishment of physical exchange mechanisms between the airborne vapor and local surface waters, and local aquatic dilution and mixing.Previous studies of large chlorine releases have concluded that depletion of the resulting vapor cloud through physical and chemical reactions with sunlight, atmospheric constituents, and local surfaces can significantly reduce the areal extent over which the vapor poses a toxicological hazard. For Graniteville, modeling results were the most consistent with available data on human health effects, animal and fish mortality, and vegetation damage when an effective deposition velocity in the lower end of a range of values commonly cited in other studies (1 cm s−1) was applied. This relatively small deposition is attributed to a lack of sunlight, a limited uptake in vegetation due to rapid stomatal damage, and the limited presence of nearby man-made structures. Explicit simulations of chlorine deposition into adjacent surface waters were based on a modified Henry's Law approach and resulted in the transfer of an estimated 21 kg of chlorine into these waters.► A case study on a large accidental release of chlorine. ► This paper examines atmospheric transport and deposition onto nearby surfaces. ► The mass of chlorine transferred into nearby water bodies was estimated. ► Simulated dose compares well with available health effects and vegetative damage. ► Model-estimated chlorine concentrations compare well with available fish kill data.
Keywords: Atmospheric modeling; Dispersion; Chlorine release; Deposition velocity; Absorption;

Global climate, atmospheric chemistry, and air quality are affected by tropospheric particulate matter. Recent measurements suggest organic compounds present in this haze comprise roughly half of total aerosol fine mass concentration globally. Unlike the well-constrained processes which result in formation of nitrate or sulfate aerosol, the oxidation of volatile organics in the atmosphere can lead to thousands of stable compounds in the aerosol phase. Development of a tractable framework to consider the chemical and physical evolution of the organic aerosol is crucial for modeling its effect on global climate. Here we show coupling a 3-dimensional coordinate system defined by the molecular descriptors of molecular weight, heteroatom mass, and double bond equivalents (D.B.E.) with high-resolution molecular mass spectrometry is a powerful approach for describing key properties of the organic aerosol. The scheme is conceptually simple, yet maintains sufficient complexity to be compatible with quantitative structure–property relationships (QSPRs) used to predict chemical and physical properties that govern aerosol behavior. From available data, both ambient organic aerosol and laboratory generated organic aerosol frequently occupy the region characterized by <10 D.B.E. <600 M.W. and <200 heteroatom mass. A QSPR analysis conducted illustrates spatial trends within the 3D space for volatility and Henry's law constants for 31,000 organic compounds considered.► A 3D coordinate system for describing organic aerosol is described. ► Molecular descriptors of molecular weight, heteroatom mass, and double bond equivalents are used. ► The approach has been coupled to HR-ESI–MS measurements of organic aerosol. ► QSPRs can be used to estimate chemical and physical properties of organics. ► An organic compounds location in the coordinate system describes its properties.
Keywords: Atmospheric particles; Aerosols; Organic aerosol; Secondary organic aerosol; VOC; Aerosol aging; Air quality;

Regional differences of column aerosol parameters in western Iberian Peninsula by M.A. Obregón; S. Pereira; F. Wagner; A. Serrano; M.L. Cancillo; A.M. Silva (208-219).
This study presents a characterization of aerosols columnar properties measured at three different AERONET sites in the western part of the Iberian Peninsula, namely Évora and Cabo da Roca, in Portugal, and Cáceres, in Spain, during the period from 2005 to 2010. AERONET level 2.0 products have been analyzed. The comparison of these three stations has great interest because it has not been conducted yet and it allows to characterize the aerosols of a wide region in western Iberian Peninsula by a long-term analysis of their aerosol properties. In addition, it allows analyzing the possible differences in these properties between the three sites located at different distances from the coast. The results show differences between the aerosol optical depth at 440 and 1020 nm at the three stations, being the mean values in Cabo da Roca at 1020 and 440 nm (0.08 and 0.16) slightly higher than in the other two stations (Évora: 0.06 and 0.15; Cáceres: 0.05 and 0.14). Greater differences among the three stations are found for the Ångström exponent values. Thus, Cáceres shows the highest mean value (1.33), followed by Évora (1.14) and, finally, by Cabo da Roca (1.00) which exhibits the smallest median α values due to the presence of coarse sea salt particles and high atmospheric humidity. These values are consistent with the values of volume size distribution, exhibiting a greater value of large particles at Cabo da Roca. The mean values of the single scattering albedo (ω) have been also analyzed, obtaining higher results as the coast is approached: Cabo da Roca: ω (440) = 0.95; ω (1020) = 0.96, Évora: ω (440) = 0.93; ω (1020) = 0.95 and Cáceres: ω (440) = 0.88; ω (1020) = 0.83. The differences between the three stations are explained in terms of the distance to the coast and to the occasional arrival of diverse air masses transporting different aerosol types to each station. One classification method proposed for the study region has been applied to multi-year measurements performed at the three sites and verified by means of daily 120-h back-trajectory analyses of air masses. The most frequent situations observed at all sites include the clean, maritime and continental situations, which account for about 80% or more. The remaining percentage is accounted by the more episodic situations of desert dust (10–14%) and forest fires emissions (3–5%). The probability density plots calculated for the different classified aerosol situations show significant differences consistent with the different paths of the air masses corresponding to each aerosol situation.► Long-term characterization of aerosol properties from AERONET high quality measurements. ► First comparison of different locations in western Iberian Peninsula. ► Significance regional differences between the 3 stations explained in terms of the maritime influence. ► Reliable aerosol classification was accomplished based on Elias method and air masses trajectories.
Keywords: Atmospheric aerosol; Optical properties; Regional differences; AERONET;

Influence of palm oil biodiesel on the chemical and morphological characteristics of particulate matter emitted by a diesel engine by Maurin Salamanca; Fanor Mondragón; John R. Agudelo; Alexander Santamaría (220-227).
The influence on the chemical composition of the particle matter (PM) produced in an automotive diesel engine operated with palm biodiesel (PB) and its blends with diesel fuel were studied. The opacity index showed a decrease on the PM emitted by the engine when palm biodiesel amount increased in the fuel, a result that also agrees with the amount of PM collected in filters. Similarly, the PB concentration did not affect the average size of PM emitted compared to diesel. But, it seems to be that biodiesel and its blends tend to produce PM with a higher number of small particles. The chemical composition of PM obtained from PB blends and pure PB were similar to those reported before; however no correlation with biodiesel concentration was found, except for the evident reduction on sulfur content in particle matter, a fact that can be associated with a fuel dilution effect.► Palm biodiesel-PB changes chemical composition of the PM produced on an engine. ► Particle nucleation is reduced due to the reactions promoted by biodiesel oxygen content. ► The amount of PM emitted decreased as function of PB added to the fuel. ► PB and its blends tend to produce PM with a higher number of small particles. ► None correlation between chemical composition of PM and palm biodiesel was found.
Keywords: Biodiesel; Palm oil biodiesel; Particulate matter; Chemical composition; Particulate matter morphology;

Source apportionment of PM2.5 nitrate and sulfate in China using a source-oriented chemical transport model by Hongliang Zhang; Jingyi Li; Qi Ying; Jian Zhen Yu; Dui Wu; Yuan Cheng; Kebin He; Jingkun Jiang (228-242).
Nitrate and sulfate account for a significant fraction of PM2.5 mass and are generally secondary in nature. Contributions to these two inorganic aerosol components from major sources need to be identified for policy makers to develop cost effective regional emission control strategies. In this work, a source-oriented version of the Community Multiscale Air Quality (CMAQ) model that directly tracks the contributions from multiple emission sources to secondary PM2.5 is developed to determine the regional contributions of power, industry, transportation and residential sectors as well as biogenic sources to nitrate and sulfate concentrations in China in January and August 2009.The source-oriented CMAQ model is capable of reproducing most of the available PM10 and PM2.5 mass, and PM2.5 nitrate and sulfate observations. Model prediction suggests that monthly average PM2.5 inorganic components (nitrate + sulfate + ammonium ion) can be as high as 60 μg m−3 in January and 45 μg m−3 in August, accounting for 20–40% and 50–60% of total PM2.5 mass. The model simulations also indicate significant spatial and temporal variation of the nitrate and sulfate concentrations as well as source contributions in the country. In January, nitrate is high over Central and East China with a maximum of 30 μg m−3 in the Sichuan Basin. In August, nitrate is lower and the maximum concentration of 16 μg m−3 occurs in North China. In January, highest sulfate occurs in the Sichuan Basin with a maximum concentration of 18 μg m−3 while in August high sulfate concentration occurs in North and East China with a similar maximum concentration. Power sector is the dominating source of nitrate and sulfate in both January and August. Transportation sector is an important source of nitrate (20–30%) in both months. Industry sector contributes to both nitrate and sulfate concentrations by approximately 20–30%. Residential sector contributes to approximately 10–20% of nitrate and sulfate in January but its contribution is low in August.► The first CMAQ modeling on source contributions to inorganic aerosol in China. ► Significant spatial and temporal variations in the predicted concentrations. ► Power sector is the dominating source of nitrate and sulfate in both Jan. and Aug. ► Transportation sector is an important source of secondary nitrate in both months.
Keywords: Source-oriented air quality model; Source apportionment; Secondary particulate matter; INTEX-B Asian emission inventory; CMAQ;

Total OH reactivity measurements in laboratory studies of the photooxidation of isoprene by Yoshihiro Nakashima; Hiroshi Tsurumaru; Takashi Imamura; Iustinian Bejan; John C. Wenger; Yoshizumi Kajii (243-247).
The hydroxyl radical (OH) is the principal oxidizing agent in Earth's troposphere. Measurements of the total OH reactivity, defined as the reciprocal of the lifetime of OH, have been employed in field studies to estimate the entire amount of reactive trace gases in the atmosphere. Here, the OH reactivity technique has been employed in laboratory studies of the OH initiated atmospheric oxidation of the important biogenic volatile organic compound, isoprene. A significant discrepancy was observed between measured and calculated OH reactivity, indicating that OH was reacting with some oxidation products not measured in the experiment. The “missing” OH reactivity gradually increased as the oxidation progressed and contributed up to 40% of the total OH reactivity. In the presence of NO, the “missing” OH reactivity is likely due to a number of first-generation products produced in low yields, while in the absence of NO, alternative pathways that produce less reactive products are also occurring.This work demonstrates that OH reactivity measurements can be successfully incorporated into atmospheric simulation chamber studies of VOC degradation. The OH reactivity technique has the potential to be a powerful tool for elucidating finer details of VOC oxidation.
Keywords: Total OH reactivity; Isoprene photooxidation; Photochemical oxidation products; Photochemical smog chamber;

Modelling air quality impact of a biomass energy power plant in a mountain valley in Central Italy by Gabriele Curci; Giovanni Cinque; Paolo Tuccella; Guido Visconti; Marco Verdecchia; Marco Iarlori; Vincenzo Rizi (248-255).
In this study, we investigate the potential impact on local air quality of a biomass power plant, which is planned for installation near L'Aquila, a city of 70,000 people located in a mountain valley in Central Italy. The assessment is carried out by applying a one year simulation with the CALPUFF model, following the recommendations of the U. S. Environmental Protection Agency. Meteorological input is produced with CALMET model, fed with both MM5 meteorological fields at 3 km resolution and wind observations from a surface weather station. We estimate small (<0.5 μg m 3) annual average increments to SO2, NO2 and PM10 ambient levels over the domain of interest, but significant (up to 50% for NO2) enhancements and several violations (up to 141 for NO2) of hourly limits for human protection within 1.5 km from the source. These results anticipate a larger negative effect on local air quality than those published by the building firm of the plant. We also suggest that a minimum distance of 5 km from the nearest residential area would represent a significant decrease of population exposure.Display Omitted► Pollutant increments due to a biomass power plant simulated with CALPUFF. ► Violations of NO2 and SO2 limits are predicted within 1.5 km of the source. ► Population exposure is greatly reduced at more than 5 km from the source.
Keywords: Biomass energy; Air quality; CALPUFF; NO2; SO2; Particulate matter; Intake fraction; Complex terrain; Mountain valley;

Influences of fireworks on chemical characteristics of atmospheric fine and coarse particles during Taiwan's Lantern Festival by Hsieh-Hung Tsai; Li-Hsing Chien; Chung-Shin Yuan; Yuan-Chung Lin; Yi-Hsiu Jen; Iau-Ren Ie (256-264).
In recent years, the celebration activities of various folk-custom festivals have been getting more and more attention from the citizens in Taiwan. Festivities throughout the whole island are traditionally accompanied by loud and brightly colored firework displays. Among these activities, the firework displays during Taiwan's Lantern Festival in Kaohsiung harbor is one of the largest festivals in Taiwan each year. Therefore, it is of importance to investigate the influence of fireworks displays on the ambient air quality during the Taiwan's Lantern Festival. Field measurements of atmospheric particulate matter (PM) were conducted on February 9th–11th, 2009 during Taiwan's Lantern Festival in Kaohsiung City. Moreover, three kinds of fireworks powders obtained from the same manufacturing factory producing Kaohsiung Lantern Festival fireworks were burned in a self-designed combustion chamber to determine the physicochemical properties of the fireworks' particles and to establish the source profile of firework burning. Several metallic elements of PM during the firework display periods were notably higher than those during the non-firework periods. The concentrations of Mg, K, Pb, and Sr in PM2.5 during the firework periods were 10 times higher than those during the non-firework periods. Additionally, the Cl/Na+ ratio was approximately 3 during the firework display periods as Cl came from the chlorine content of the firework powder. Moreover, the OC/EC ratio increased up to 2.8. Results obtained from PCA and CMB receptor modeling showed that major sources of atmospheric particles during the firework display periods in Kaohsiung harbor were fireworks, vehicular exhausts, soil dusts and marine sprays. Particularly, on February 10th, the firework displays contributed approximately 25.2% and 16.6% of PM10 at two downwind sampling sites, respectively.
Keywords: Firework displays; Air quality monitoring; Physicochemical properties; Principal component analysis (PCA); CMB receptor modeling;

This study examined mercury (Hg) emissions from cement manufacturing facilities in Korea. Hg concentrations in stack gases from a kiln at the largest cement manufacturing facility (CMF) in Korea were measured using three different methods: a wet-chemical method and on-line measurements with two different types of conversion systems (SnCl2 and thermal) attached in front of each analyzer. The Hg concentrations of the feedstocks and fuels were then analyzed to determine the total amount of Hg input into CMFs and how much each material contributed to the Hg input. The total annual Hg input into all CMFs in Korea was estimated to be 1.71 tons, while the total annual Hg emissions estimated from the stack-gas measurement was 1.17–1.53 tons, indicating that 68–89% of total Hg input is released into the atmosphere. Therefore, more stringent regulation and effective control technologies should be applied to the CMFs to reduce Hg emissions.Display Omitted► Mercury concentrations of stack gases from cement kiln were measured. ► Feedstocks and fuels used in cement kiln were analyzed for their mercury contents. ► Majority of mercury input were released to the atmosphere without being controlled. ► Total annual mercury emissions from cement manufacturing facilities were estimated. ► Cement manufacturing facilities are one of major sources of mercury emissions.
Keywords: Mercury; Cement manufacturing facility; Cement kiln; Combustion flue gas; Ontario Hydro Method; Continuous emission monitor;

Snowpack samples were collected from a snow pit sequence (6 m in depth) at the Murodo-Daira site near the summit of Mt. Tateyama, central Japan, an outflow region of Asian dusts. The snow samples were analyzed for a homologous series of low molecular weight normal (C1–C10) and branched (iC4–iC6) monocarboxylic acids as well as aromatic (benzoic) and hydroxy (glycolic and lactic) acids, together with major inorganic ions and dissolved organic carbon (DOC). The molecular distributions of organic acids were characterized by a predominance of acetic (range 7.8–76.4 ng g−1-snow, av. 34.8 ng g−1) or formic acid (2.6–48.1 ng g−1, 27.7 ng g−1), followed by propionic acid (0.6–5.2 ng g−1, 2.8 ng g−1). Concentrations of normal organic acids generally decreased with an increase in carbon chain length, although nonanoic acid (C9) showed a maximum in the range of C5–C10. Higher concentrations were found in the snowpack samples containing dust layer. Benzoic acid (0.18–4.1 ng g−1, 1.4 ng g−1) showed positive correlation with nitrate (r = 0.70), sulfate (0.67), Na+ (0.78), Ca2+ (0.86) and Mg+ (0.75), suggesting that this aromatic acid is involved with anthropogenic sources and Asian dusts. Higher concentrations of Ca2+ and SO4 2− were found in the dusty snow samples. We found a weak positive correlation (r = 0.43) between formic acid and Ca2+, suggesting that gaseous formic acid may react with Asian dusts in the atmosphere during long-range transport. However, acetic acid did not show any positive correlations with major inorganic ions. Hydroxyacids (0.03–5.7 ng g−1, 1.5 ng g−1) were more abundant in the granular and dusty snow. Total monocarboxylic acids (16–130 ng g−1, 74 ng g−1) were found to account for 1–6% of DOC (270–1500 ng g−1, 630 ng g−1) in the snow samples.► We determined C1–C10 monocarboxylic acids in High Mountain snow in Japan. ► C1 or C2 was dominant acid followed by C3 and then C4. ► Benzoic acid was abundant in snow with dust layer. ► Formic acid may react with Asian dust during atmospheric transport.
Keywords: Formic acid; Acetic acid; Propionic acid; Lactic acid; Glycolic acid; High mountain snowpack; Sulfate; Calcium; Asian dust;

Size-resolved chemical constituents (organics, sulfate, nitrate, ammonium, and chloride) of nonrefractory submicrometer particles were measured in real time using a quadruple aerosol mass spectrometer (QAMS) at an urban area of Gwangju, Korea in the fall (8/30/2011–9/19/2011) and winter (12/19/2011–12/30/2011). Organics were found to be the most dominant chemical species (∼50%) in the total aerosol mass loading. The average mass concentrations of organics were 4.7 ± 1.8 μg m 3 and 6.3 ± 1.8 μg m 3 in the fall and winter, respectively. The organics increased in the morning and evening times, and decreased in the afternoon in both the fall and winter, with a more pronounced diurnal pattern observed in the winter. The ratio of m/z 44 to organics and sulfate increased significantly in the afternoon, which is contrary to the behavior of the total organics, suggesting that intense photochemical activity led to the production of oxidized organics and sulfate in the afternoon. The average sulfate concentration was 1.8 μg m 3, which was the lowest reported in East Asian countries due to there being few SO2 emission sources around the sampling site. The most significant difference in concentrations between the fall and winter was found for nitrate; the concentration was ∼4 times higher than in the fall (2.45 μg m 3 versus 0.62 μg m 3). It was also observed that sulfate, nitrate, and chloride were fully neutralized by the ammonium in the winter, whereas these anions were not fully neutralized in the fall. Size distribution data showed that sulfate had only one D va peak at 600 ± 100 nm, regardless of season, and that organics had one peak (600 ± 100 nm) in the fall and a bimodal distribution (200 ± 100 nm and 600 ± 100 nm) in the winter. The absence of the first mode (i.e., D va ∼200 nm) in organics in fall and the higher ratios of m/z 44 to organics in fall (0.10 ± 0.02) than winter (0.07 ± 0.01) suggest that oxidized organic species would be more dominant than hydrocarbon-like organics. Air-mass dependent concentrations of species showed that the northwest air mass (i.e., long-range transported from industrial areas in China) and southeast air mass (i.e., transported from industrial area in Korea) were mainly responsible for the high loadings of organics and sulfate.► Chemical constituents of submicrometer particles in Korea were measured in real time. ► Comparison of data among East Asia countries was conducted. ► Simultaneous production of oxidized organics and sulfate in the afternoon. ► High loadings of organics and sulfate were observed with air mass from industry.
Keywords: Aerosol mass spectrometer; Size distribution; Submicrometer particles; Chemical constituents;

Atmospheric mercury emissions in Australia from anthropogenic, natural and recycled sources by Peter F. Nelson; Anthony L. Morrison; Hugh J. Malfroy; Martin Cope; Sunhee Lee; Mark L. Hibberd; C.P. (Mick) Meyer; John McGregor (291-302).
The United Nations Environment Programme (UNEP) has begun a process of developing a legally binding instrument to manage emissions of mercury from anthropogenic sources. The UNEP Governing Council has concluded that there is sufficient evidence of significant global adverse impacts from mercury to warrant further international action; and that national, regional and global actions should be initiated as soon as possible to identify populations at risk and to reduce human generated releases. This paper describes the development of, and presents results from, a comprehensive, spatially and temporally resolved inventory of atmospheric mercury emissions from the Australian landmass. Results indicate that the best estimate of total anthropogenic emissions of mercury to the atmosphere in 2006 was 15 ± 5 tonnes. Three industrial sectors contribute substantially to Australian anthropogenic emissions: gold smelting (∼50%, essentially from a single site/operation), coal combustion in power plants (∼15%) and alumina production from bauxite (∼12%). A diverse range of other sectors contribute smaller proportions of the emitted mercury, but industrial emissions account for around 90% of total anthropogenic mercury emissions. The other sectors include other industrial sources (mining, smelting, and cement production) and the use of products containing mercury. It is difficult to determine historical trends in mercury emissions given the large uncertainties in the data. Estimates for natural and re-emitted emissions from soil, water, vegetation and fires are made using meteorological models, satellite observations of land cover and soil and vegetation type, fuel loading, fire scars and emission factors which account for the effects of temperature, insolation and other environmental variables. These natural and re-emitted sources comfortably exceed the anthropogenic emissions, and comprise 4–12 tonnes per year from vegetation, 70–210 tonnes per year from soils, and 21–63 tonnes per year from fires.► The first spatially resolved inventory of mercury emissions from Australia. ► The best estimate of anthropogenic emissions of mercury in 2006 was 15 ± 5 Mg. ► Natural and re-emitted sources comfortably exceed the anthropogenic emission. ► Emissions were ∼8, 140 and 42 Mg pa from vegetation, soils and fires respectively.
Keywords: Mercury; Emissions; Anthropogenic; Natural; Inventory;

Spatial variation of PM2.5, PM10, PM2.5 absorbance and PMcoarse concentrations between and within 20 European study areas and the relationship with NO2 – Results of the ESCAPE project by Marloes Eeftens; Ming-Yi Tsai; Christophe Ampe; Bernhard Anwander; Rob Beelen; Tom Bellander; Giulia Cesaroni; Marta Cirach; Josef Cyrys; Kees de Hoogh; Audrey De Nazelle; Frank de Vocht; Christophe Declercq; Audrius Dėdelė; Kirsten Eriksen; Claudia Galassi; Regina Gražulevičienė; Georgios Grivas; Joachim Heinrich; Barbara Hoffmann; Minas Iakovides; Alex Ineichen; Klea Katsouyanni; Michal Korek; Ursula Krämer; Thomas Kuhlbusch; Timo Lanki; Christian Madsen; Kees Meliefste; Anna Mölter; Gioia Mosler; Mark Nieuwenhuijsen; Marieke Oldenwening; Arto Pennanen; Nicole Probst-Hensch; Ulrich Quass; Ole Raaschou-Nielsen; Andrea Ranzi; Euripides Stephanou; Dorothee Sugiri; Orsolya Udvardy; Éva Vaskövi; Gudrun Weinmayr; Bert Brunekreef; Gerard Hoek (303-317).
The ESCAPE study (European Study of Cohorts for Air Pollution Effects) investigates relationships between long-term exposure to outdoor air pollution and health using cohort studies across Europe. This paper analyses the spatial variation of PM2.5, PM2.5 absorbance, PM10 and PMcoarse concentrations between and within 20 study areas across Europe.We measured NO2, NO x , PM2.5, PM2.5 absorbance and PM10 between October 2008 and April 2011 using standardized methods. PMcoarse was determined as the difference between PM10 and PM2.5. In each of the twenty study areas, we selected twenty PM monitoring sites to represent the variability in important air quality predictors, including population density, traffic intensity and altitude. Each site was monitored over three 14-day periods spread over a year, using Harvard impactors. Results for each site were averaged after correcting for temporal variation using data obtained from a reference site, which was operated year-round.Substantial concentration differences were observed between and within study areas. Concentrations for all components were higher in Southern Europe than in Western and Northern Europe, but the pattern differed per component with the highest average PM2.5 concentrations found in Turin and the highest PMcoarse in Heraklion. Street/urban background concentration ratios for PMcoarse (mean ratio 1.42) were as large as for PM2.5 absorbance (mean ratio 1.38) and higher than those for PM2.5 (1.14) and PM10 (1.23), documenting the importance of non-tailpipe emissions. Correlations between components varied between areas, but were generally high between NO2 and PM2.5 absorbance (average R 2 = 0.80). Correlations between PM2.5 and PMcoarse were lower (average R 2 = 0.39). Despite high correlations, concentration ratios between components varied, e.g. the NO2/PM2.5 ratio varied between 0.67 and 3.06.In conclusion, substantial variability was found in spatial patterns of PM2.5, PM2.5 absorbance, PM10 and PMcoarse. The highly standardized measurement of particle concentrations across Europe will contribute to a consistent assessment of health effects across Europe.► We used one method to measure PM2.5, PM2.5 absorbance & PM10 in 20 European areas. ► We studied contrasts of these metrics and PMcoarsewithin andbetweenall 20 areas.► Concentrationswerehigher in Southern than in Western and Northern European areas.► Within-area contrasts varied by area andwerelarger for PM2.5 absorbance & PMcoarse. ► Concentration ratios of particle metrics and NO2varied significantly across areas.
Keywords: Traffic; PM2.5; PM10; Coarse particle; Soot; Spatial variation;

Prevalence of wide area impacts downwind of freeways under pre-sunrise stable atmospheric conditions by Wonsik Choi; Meilu He; Vincent Barbesant; Kathleen H. Kozawa; Steve Mara; Arthur M. Winer; Suzanne E. Paulson (318-327).
In urban areas, a large fraction of the population typically lives within 1.5–2 km of a freeway. In an earlier study, Hu et al. (2009) showed that in the pre-sunrise hours, with stable, nocturnal meteorological conditions, the vehicle-related pollution from a freeway in southern California extended more than 2 km downwind. This was in striking contrast to earlier studies in the U.S. and Australia showing that during the daytime pollutant concentrations extended no more than ∼300 m downwind of major roadways. The present study was designed to explore the variability of the large downwind pollutant impact zone observed by Hu et al. (2009) in the pre-sunrise hours on a wider geographic scale. An instrumented mobile platform was employed to measure vehicle-related pollutant concentrations on transects running upwind and downwind of four freeways in the coastal, central and eastern areas of the California South Coast Air Basin (SoCAB) during the pre-sunrise period (04:30–06:30). Extended freeway plumes were observed for ultrafine particles (UFP), nitric oxide and particle-bound polycyclic aromatic hydrocarbons (PAH) at all four sites during stable pre-sunrise periods. Plume lengths were measured to be ∼2 km or more with a dilution rate coefficient about a factor of ten lower than commonly observed for daytime. An average of 39 and 19% (±8–9%) of freeway plume peak concentrations of UFP remained 500 and 1500 m downwind, respectively, from the freeways for the four transects studied here. Because a large fraction of UFP and other vehicle related pollutants typically penetrate into indoor environments, and nocturnal surface inversions are widespread across the globe, our findings have significant implications for more extensive human exposures to vehicle-related pollutants than previously indicated based on daytime measurements of roadway plumes.► Pollutant plumes from major roadways extend up to 2 km under stable conditions. ► Wide area impacts of freeway plumes are commonly observed in the SoCAB. ► Dilution rate coefficients in stable atmospheres are less than a tenth of daytime. ► Decay rates of UFP vary with size, changing size distributions. ► Mixed fleet emissions of UFP for a given traffic flow have decreased over time.
Keywords: Ultrafine particles; Traffic emissions; Freeway plume extension; Human exposure; Plume decay rates; Emissions reduction;

Greenhouse gas emissions from different wetlands during the snow-covered season in Northeast China by Yuqing Miao; Changchun Song; Xianwei Wang; Xiaoxin Sun; Henan Meng; Li Sun (328-335).
Emission of CO2, CH4 and N2O from the snowpack is an important component of annual C and N budgets in wetland ecosystems in mid- and high-latitude. However, there is little information about greenhouse gas fluxes during the snow-covered season in wetlands in Northeast China. In the present study, we investigated the trace gas fluxes from a peatland and a marsh using the methods of concentration gradient and diffusion model during the snow-covered season of 2010/2011 in this region. Estimates of CO2 efflux from a peatland and a marsh during this period were 4.179 and 5.026 g C m−2 season−1, respectively. The seasonal release of CH4 from the peatland (0.009 g C m−2 season−1) was much lower than that from the marsh (0.818 g C m−2 season−1). Intriguingly, we observed that the peatland acted as sink for N2O, and the marsh as a source for N2O during the snow-covered season. For the peatland, snowpack such as snow density is important for CO2 and CH4 fluxes, while N2O flux was controlled by soil–snow interface temperature. In the marsh, however, soil temperature was the primary parameter regulating greenhouse gas fluxes. Our results suggest that in mid- and high-latitude regions, greenhouse gas fluxes during the snow-covered season is an important part of C and N cycles in seasonally snow-covered wetland ecosystems. The difference in greenhouse gas emission from both peatland and marsh suggests that wetland types should be considered when evaluating regional gas budgets.► The natural wetlands in the middle latitude are source for CO2 and CH4 in the snow-covered season. ► During the snow-covered season, peatland acts as N2O sink and marshland acts as a N2O source. ► Soil temperature is the primary factor controlling marshland greenhouse gas fluxes in the snow-covered season.
Keywords: Marsh; Methane; Nitrous oxide; Winter flux; Peatland; Diffusion model;

Indoor PM2.5 exposure in London's domestic stock: Modelling current and future exposures following energy efficient refurbishment by C. Shrubsole; I. Ridley; P. Biddulph; J. Milner; S. Vardoulakis; M. Ucci; P. Wilkinson; Z. Chalabi; M. Davies (336-343).
Simulations using CONTAM (a validated multi-zone indoor air quality (IAQ) model) are employed to predict indoor exposure to PM2.5 in London dwellings in both the present day housing stock and the same stock following energy efficient refurbishments to meet greenhouse gas emissions reduction targets for 2050. We modelled interventions that would contribute to the achievement of these targets by reducing the permeability of the dwellings to 3 m3 m−2 h−1 at 50 Pa, combined with the introduction of mechanical ventilation and heat recovery (MVHR) systems. It is assumed that the current mean outdoor PM2.5 concentration of 13 μg m−3 decreased to 9 μg m−3 by 2050 due to emission control policies. Our primary finding was that installation of (assumed perfectly functioning) MVHR systems with permeability reduction are associated with appreciable reductions in PM2.5 exposure in both smoking and non-smoking dwellings. Modelling of the future scenario for non-smoking dwellings show a reduction in annual average indoor exposure to PM2.5 of 18.8 μg m−3 (from 28.4 to 9.6 μg m−3) for a typical household member. Also of interest is that a larger reduction of 42.6 μg m−3 (from 60.5 to 17.9 μg m−3) was shown for members exposed primarily to cooking-related particle emissions in the kitchen (cooks). Reductions in envelope permeability without mechanical ventilation produced increases in indoor PM2.5 concentrations; 5.4 μg m−3 for typical household members and 9.8 μg m−3 for cooks. These estimates of changes in PM2.5 exposure are sensitive to assumptions about occupant behaviour, ventilation system usage and the distributions of input variables (±72% for non-smoking and ±107% in smoking residences). However, if realised, they would result in significant health benefits.► We model the current (2010) and future (2050) domestic stock for London. ► We examine the effects of energy efficiency measures on indoor PM2.5 concentrations. ► Decreases in permeability combined with MVHR systems substantially reduce exposure. ► Occupant behaviour plays a critical role in determining PM2.5 exposure level.
Keywords: PM2.5; Indoor; Dwelling; CONTAM; Exposure; Modelling;

Evaluation of accuracy in measurements of VOC emissions with dynamic chamber system by Pasi Kolari; Jaana Bäck; Risto Taipale; Taina M. Ruuskanen; Maija K. Kajos; Janne Rinne; Markku Kulmala; Pertti Hari (344-351).
We determined the accuracy of the dynamic chamber system for measuring VOC emissions of trees and soil in the field at SMEAR II station, Hyytiälä, Southern Finland. The study was based on creating a known source of different VOCs inside the chamber and measuring the concentration dynamics in the chamber by a proton transfer reaction mass spectrometer (PTR-MS) connected to the chamber. The chamber system underestimated the artificially generated VOC emission rates at varying degree. In isoprene, monoterpene and many oxygenated VOCs the underestimation was 5–30% but in some compounds with protonated mass >100 amu the signal was almost completely lost. The underestimation mainly originated in the chamber but the length of the sample tubing also affected the observed magnitude of the standard gas emission. The systematic error was higher at high relative humidity than in drier conditions, which suggests that the thickness of the water film adsorbed on the chamber inner surfaces contributes to the VOC loss rate in the chamber. Increasing the length of the chamber closure time slightly reduced the systematic underestimation of emission in most of the studied compounds although the underestimation persisted for at least 10 min. A dynamic chamber setup enables measurement of VOC emissions with good accuracy and precision while minimising the disturbance of the chamber to the object being measured.► A dynamic chamber is suitable for measuring emissions of many VOC species. ► The chamber system consistently underestimated VOC emissions. ► The accuracy of the observed emission was best in light VOC species. ► Sample tubing affected the observed emission less than the chamber. ► The systematic error was higher at high relative humidity than in drier conditions.
Keywords: Volatile organic compounds (VOC); Dynamic chamber; PTR-MS; Accuracy; Field measurements;

Effect of rain events on the mobility of road dust load in two Dutch and Spanish roads by Fulvio Amato; Martijn Schaap; Hugo A.C. Denier van der Gon; Marco Pandolfi; Andrés Alastuey; Menno Keuken; Xavier Querol (352-358).
In spite of the high air quality and health relevance of PM emissions from road dust resuspension in large cities, very little is known on their temporal variability, severely hampering a reliable description of population exposure by dispersion models. We have experimentally monitored the mobile dust load (only inhalable fraction) in two different European urban environments resulting in the first empirical description of the temporal variation of road dust emission strength. In Central (The Netherlands) and Southern (Spain) European environments the loadings of mobile road dust particles <10 μm were found to be generally constant on a day-to-day scale, except during and in the hours immediately after rain events when the mobility of particles drops dramatically to values close to zero. After the rain event the mobile dust load increases exponentially tending to reach again the maximum value, result of the equilibrium between mobilization/buildup of dust and moistening/resuspension processes. The mobilization/buildup of particles smaller than 10 μm was found to be three times faster in Barcelona than in Utrecht, in relation to higher solar radiation. In Barcelona the recovery of mobile road dust reached 50%, 75%, and 90% of the maximum value after 8, 16 and 27 h, respectively. These values were independent of amounts of rain. In Utrecht the same thresholds were reached after, 28, 55 and 90 h, respectively. Our observations may suggest that, for reducing road dust emissions, light but frequent moistening of roads might be more effective than intensive occasional cleanings.► Loadings of inhalable mobile road dust were monitored in one Dutch and one Spanish city. ► After rain, mobile road dust load increase until a maximum value is reached. ► An equilibrium is reached between mobilization/buildup and, moistening/resuspension processes. ► The mobilization rate was ∼3 times faster in the Barcelona road than in the Utrecht road.
Keywords: PM10; Resuspension; Precipitation; Moisture; Emission factor; Time variability;

Mercury emissions from waste combustion in China from 2004 to 2010 by Dan Hu; Wei Zhang; Long Chen; Cen Chen; Langbo Ou; Yindong Tong; Wen Wei; Wenjing Long; Xuejun Wang (359-366).
An inventory of mercury emissions originating from waste incineration in China, including municipal solid waste, rural household waste and agricultural waste, was calculated for the period of 2004–2010. During this period, mercury emissions from waste incineration increased at an average annual rate of 3.9%, and reached 16.6 t y−1 by the end of 2010. From 2004 to 2010, the mercury emissions from rural household waste incineration accounted for 46.6% of the total waste emissions, followed by agricultural waste (30.7%) and municipal solid waste (22.7%). However, the growth rate of mercury emissions was largest for municipal solid waste incineration, with an annual rate of 37.3%, while the emissions from rural household waste showed a negative growth rate (−5.8%). The mercury emissions from waste combustion is projected to be 18.6 t y−1 by 2015, with the contribution of municipal solid waste, rural household waste and agricultural waste being 46.4%, 27.1% and 26.5%, respectively.► Inventory on mercury emission from waste incineration with high spatial resolution. ► Mercury emission from rural household waste incineration was large. ► Mercury emission from waste incineration was projected to 2015.
Keywords: Mercury emission inventory; Waste combustion; Municipal solid waste; Rural household waste; Agricultural waste;

Influence of aerosol composition on visibility degradation in megacity Delhi has been quantified using model-derived seasonal mean aerosol composition constrained by satellite-measured columnar aerosol optical depth spectrum. Aerosols contribute ∼90% to the observed visibility degradation in non-foggy condition, while its relative contribution decreases rapidly at RH ≥ 80% due to stronger relative influence of fog droplets on attenuation of radiation, especially during the winter season. Visibility is most sensitive to water-soluble particles and soot in all seasons. Sensitivity study shows that visibility does not respond strongly to reduction of mass concentration of insoluble, accumulation mode and coarse mode dust particles. Reduction of mass concentration of soot and water-soluble particles in the range of 10%–50% will lead to an increase in visibility by 2.4 ± 0.1%–11.3 ± 1.6% and 4.9 ± 2%–29 ± 12% respectively. Reduction of the last two anthropogenic components has co-benefits, as it may reduce fog formation and thus further enhance the visibility along with an improved air quality in terms of associated health and climatic effects.► Role of aerosols on visibility degradation in megacity Delhi is examined. ► Sensitivity of visibility to individual aerosol species is examined. ► Seasonally representative aerosol composition is derived. ► The quantitative estimates can help addressing the visibility problem in this region.
Keywords: Aerosol composition; Visibility; Sensitivity;

Variation of NO2 and NO x concentrations between and within 36 European study areas: Results from the ESCAPE study by Josef Cyrys; Marloes Eeftens; Joachim Heinrich; Christophe Ampe; Alexandre Armengaud; Rob Beelen; Tom Bellander; Timea Beregszaszi; Matthias Birk; Giulia Cesaroni; Marta Cirach; Kees de Hoogh; Audrey De Nazelle; Frank de Vocht; Christophe Declercq; Audrius Dėdelė; Konstantina Dimakopoulou; Kirsten Eriksen; Claudia Galassi; Regina Grąulevičienė; Georgios Grivas; Olena Gruzieva; Annika Hagenbjörk Gustafsson; Barbara Hoffmann; Minas Iakovides; Alex Ineichen; Ursula Krämer; Timo Lanki; Patricia Lozano; Christian Madsen; Kees Meliefste; Lars Modig; Anna Mölter; Gioia Mosler; Mark Nieuwenhuijsen; Michael Nonnemacher; Marieke Oldenwening; Annette Peters; Sabrina Pontet; Nicole Probst-Hensch; Ulrich Quass; Ole Raaschou-Nielsen; Andrea Ranzi; Dorothee Sugiri; Euripides G. Stephanou; Pekka Taimisto; Ming-Yi Tsai; Éva Vaskövi; Simona Villani; Meng Wang; Bert Brunekreef; Gerard Hoek (374-390).
The ESCAPE study (European Study of Cohorts for Air Pollution Effects) investigates long-term effects of exposure to air pollution on human health in Europe. This paper documents the spatial variation of measured NO2 and NO x concentrations between and within 36 ESCAPE study areas across Europe.In all study areas NO2 and NO x were measured using standardized methods between October 2008 and April 2011. On average, 41 sites were selected per study area, including regional and urban background as well as street sites. The measurements were conducted in three different seasons, using Ogawa badges. Average concentrations for each site were calculated after adjustment for temporal variation using data obtained from a routine monitor background site.Substantial spatial variability was found in NO2 and NO x concentrations between and within study areas; 40% of the overall NO2 variance was attributable to the variability between study areas and 60% to variability within study areas. The corresponding values for NO x were 30% and 70%. The within-area spatial variability was mostly determined by differences between street and urban background concentrations. The street/urban background concentration ratio for NO2 varied between 1.09 and 3.16 across areas. The highest median concentrations were observed in Southern Europe, the lowest in Northern Europe.In conclusion, we found significant contrasts in annual average NO2 and NO x concentrations between and especially within 36 study areas across Europe. Epidemiological long-term studies should therefore consider different approaches for better characterization of the intra-urban contrasts, either by increasing of the number of monitors or by modelling.► We measured NO2 and NO x in 36 European study areas using standardized method. ► Significant contrast in NO2 and NO x levels between and within areas were found. ► Concentrations were generally lower in Northern than in Southern Europe. ► Street/urban background contrast was higher than for the particle metrics. ► Epidemiological studies should characterize intra-urban contrasts.
Keywords: Air pollution; Long term; Traffic; Spatial variation; NO x ; NO2; ESCAPE study;

Primary source regions of polychlorinated biphenyls (PCBs) measured in the Arctic by Sandy Ubl; Martin Scheringer; Andreas Stohl; John F. Burkhart; Konrad Hungerbuhler (391-399).
We investigate the source regions of the three polychlorinated biphenyl congeners (PCBs) 28, 101, and 180 measured at the Arctic stations Alert and Zeppelin, and at Birkenes, which is located in southern Norway. Although the Arctic is remote from the main use areas of these chemicals, PCBs have been found in Arctic air, seawater and biota, which has caused concerns for human and environmental health. We used 20-day backward calculations of the Lagrangian Particle Dispersion Model FLEXPART to identify the origin of air masses associated with the 20% highest and lowest measured PCB concentrations. At Birkenes, high concentrations are clearly associated with air masses arriving from known source regions (primarily in Europe and Russia), whereas low concentrations are correlated with atmospheric transport from regions with low primary emissions. At Zeppelin, the influence from known source regions is also enhanced when high PCB-28 and PCB-101 concentrations were measured. At Alert, in contrast, there is no clear link between high/low PCB concentrations and atmospheric transport from source/non-source regions. Additionally, we combined the atmospheric transport patterns with PCB emission data to identify important source regions and their seasonal variability. For the Arctic stations, Western Russia is the dominant source region for PCB-28 and PCB-101. Central Europe is the most important source region for PCB-180, but sources in the US contribute up to 15% to PCB-180 measured at Alert.► Source regions of PCB concentrations measured in the Arctic are identified. ► PCB concentration peaks in the European Arctic are controlled by European emissions. ► Seasonal changes in PCB emissions and in atmospheric transport control PCB levels.
Keywords: PCBs; Long-range transport potential; Transport modeling; Arctic; FLEXPART;

Size fractionated airborne particle samples were collected from the top of the BT Tower and a ground-based site in Regents Park in London by deploying MOUDI instruments at the two locations. Particles were examined by Transmission Electron Microscope (TEM), Energy Dispersive X-Ray Analysis (EDX) and selected area electron diffraction patterns to determine the morphology, crystallinity and composition of individual particles in aggregated and non-aggregated forms. Eight different types of particles were observed which were common both to the ground-based location and some 160 m above the conurbation of London at the top of the BT Tower. Of these different types, amorphous carbonaceous aggregates (soot-like) containing C and O and often extending to the inclusion of Ca, K and Fe were the most common type of particles that occurred across all stages of the impactors but were most common in the fractions <1.2 μm. Other types of particles included beam-sensitive sulphur-rich particles containing Na and Cl that were present in crystalline and amorphous forms. Iron and titanium were common elements in other types of particles. Concurrent ATOFMS measurements were taken at the Regents Park site and 13 particle types were found. An intercomparison of the two techniques found three types of particle (out of eight) identified by the TEM, which had analogues (but not direct equivalents) in the ATOFMS clusters. Many of the particle types identified by the ATOFMS are vacuum-volatile (e.g. nitrates) and are therefore not seen by the TEM. The relative strengths and weaknesses of the two techniques are considered and it is concluded that both have major weaknesses but that they tend to complement one another.► Size-fractionated particles were collected at BT Tower and Regents Park, London. ► Characterization of particles was by TEM (EDX) and ATOFMS in real-time. ► TEM identified 8 types common to both sites with soot-like particles predominating. ► ATOFMS identified 13 types at Regents Park but only 3 were common to the 8 by TEM. ► TEM fails to identify semi-volatiles but traces involatile particles effectively.
Keywords: Transmission Electron Microscope; ATOFMS; Airborne particles; Particulate matter; Atmospheric aerosol;

Coupling of highly explicit gas and aqueous chemistry mechanisms for use in 3-D by Diana L. Ginnebaugh; Mark Z. Jacobson (408-415).
This study discusses the coupling of a near-explicit gas-phase chemical mechanism with an extensive aqueous-phase mechanism in an accurate chemical solver designed for use in 3-D models. The gas and aqueous mechanisms and the solver used are the Master Chemical Mechanism (MCM 3.1), the Chemical Aqueous Phase Radical Mechanism (CAPRAM 3.0i), and the SMVGEAR II ordinary differential solver, respectively. The MCM has over 13,500 reactions and 4600 species, whereas CAPRAM treats aqueous chemistry among 390 species and 829 reactions (including 51 gas-to-aqueous phase reactions). SMVGEAR II is a sparse-matrix Gear solver that reduces the computation time significantly while maintaining any specified accuracy. MCM has been used previously with SMVGEAR II in 3-D, and computer timings here indicate that coupling MCM with CAPRAM in SMVGEAR II is also practical. Gas- and aqueous-phase species are coupled through time-dependent dissolutional growth and dissociation equations. This method is validated with a smaller mechanism against results from a previous model intercomparison. When the smaller mechanism is compared with the full MCM-CAPRAM mechanism, some concentrations are still similar but others differ due to the greater detail in chemistry. We also expand the mechanism to include gas–aqueous transfer of two acids, glycolic acid and glyoxylic acid, and modify the glyoxal Henry's law constant from recent measurements. The average glyoxal partitioning in the cloud changed from 67% aqueous-phase to 87% aqueous-phase with the modifications. The addition of gas–aqueous transfer reactions increased the average gas-phase percentage of glycolic acid to 19% and of glyoxylic acid to 16%. This full gas-phase and aqueous-phase chemistry module is a potentially useful tool for studying air pollution in a cloud or a fog.► MCM 3.1 is coupled with CAPRAM 3.0i in SMVGEAR II. ► The module is compared to other model studies and mechanisms. ► Two gas-to-aqueous transfer reactions are added and one Henry's constant is modified. ► Computer timings confirm the module is practical for use in 3-D simulations.
Keywords: Chemical mechanism; Air pollution; Aqueous mechanism; MCM; CAPRAM; Gas mechanism;

Biomass burning in Siberia as a source of BrO to the Arctic free troposphere by M. Pommier; C.A. McLinden; J.A. Neuman; J.B. Nowak (416-423).
During the ARCPAC (Aerosol, Radiation, and Cloud Processes affecting Arctic Climate) campaign in April 2008, several flights of the WP-3D research aircraft over the Arctic Ocean and Alaska sampled relatively rich bromine monoxide (BrO > 5 pptv) air masses in the free troposphere. In most cases air masses were identified as either stratospheric intrusions or as being recently in contact with sea-ice and thereby pointing to an established BrO source. However, in at least two instances there was a strong indication that the BrO originated, directly or as a secondary product from forest fires in Siberia. In all cases the origin of the air masses studied (polluted or stratospheric influenced) was confirmed by trajectories calculations and carbon monoxide (CO), ozone (O3), water vapor (H2O), bromine monochloride (BrCl), and acetonitrile (CH3CN) measurements on-board the aircraft. In spite of this finding, the mechanisms of BrO release in the free troposphere, possibly involving heterogeneous reactions, remain unclear.► A new interpretation of the BrO budget over the Arctic is provided. ► A possible link between forest fire and BrO in the Arctic free troposphere is found. ► The new source could affect Arctic O3 chemistry. ► This result means new fire emissions investigations are required.
Keywords: Artic; Free troposphere; BrO plume; Biomass burning; O3 depletion;

Aerosol properties over two urban sites in South Spain during an extended stagnation episode in winter season by H. Lyamani; J. Fernández-Gálvez; D. Pérez-Ramírez; A. Valenzuela; M. Antón; I. Alados; G. Titos; F.J. Olmo; L. Alados-Arboledas (424-432).
Columnar and ground level aerosol properties as well as mass concentrations of some gaseous pollutants were measured at two urban sites (Granada and Málaga, South Spain) before, during and after an extended stagnation episode from 7 to 13 February 2011. This long lasting event was associated with a very strong and persistent blocking high-pressure system over the Iberian Peninsula, together with very intense and persistent temperature inversions near the ground level. The columnar aerosol load at Granada showed a significant increase during this stagnation episode as indicated by aerosol optical depth at 440 nm, reaching values four times higher (0.6) than before and after the event. A significant increase in aerosol load at night time was also evidenced by star photometer measurements. Similarly, pronounced enhancement in columnar aerosol load was observed at Málaga, indicating the regional extension of this event. Analysis of ground level measurements obtained at Granada showed a significant increase in aerosol scattering coefficients and aerosol number concentrations during the stagnation episode. Furthermore, the analysis of aerosol size distribution measurements has evidenced the large contribution of fine particles at ground level as well as in the atmospheric column during the stagnation period. The fine mode radius measured at Granada showed a large displacement towards larger sizes together with a pronounced increase in the geometric standard deviation of the fine mode during the high pollution event in the morning hours on 9 February. This was attributed to the growth of aerosol particles due to coagulation and condensation processes as a result of the high fine aerosol load next to the surface favoured by the high pressure system and thermal inversion on that day. This increases in the radius and width of the fine mode results in more efficient scattering in the 440–1020 nm spectral range which, in combination with nearly constant and low imaginary refractive index (0.002) leads to high single scattering albedo with neutral spectral dependency. During the persistent temperature inversion episode the daily European PM10 mass concentration limit (50 μg m−3) was exceeded in Granada for most days and in Málaga for three consecutive days. Nevertheless, the mass concentrations of NO2, CO and O3 were below the European thresholds with a noticeable decrease in O3 mass concentration at both sites.► Study of an intensive and long-lasting aerosol event at regional level. ► Characterization of the atmospheric thermodynamic structure during this event. ► Drastic increase in the aerosol fine concentration during the stagnation episode. ► Increase in modal radius and width of fine particles mode due to growth processes. ► Unusual high single scattering albedo with neutral spectral dependence.
Keywords: Aerosol size distribution; Aerosol growth; Atmospheric dynamic;

Effect of ozone on the visible injury, nitrogen metabolism of rice leaves, and sugar and protein contents in rice grain was carried out by the open-top chamber. The results indicated that ozone stress caused obvious injury in rice leaves. The increase in ozone concentration had significant influence on the nitrate reductase activity in rice leaves. At the ozone concentration of 40, 80 and 120 nL L−1, the nitrate reductase activities in rice leaves in the tillering stage, the jointing stage, the heading stage and milk stage were separately reduced by 25.3–86.3%, 57.4–97.8%, 91.0–99.3% and 89.5–96.7% compared with those in the control treatment. As ozone concentration increased, the contents of ammonium nitrogen and nitrate nitrogen in rice leaves were obviously reduced. Ozone stress also had an influence on the contents of sugar and protein in rice grain. The stress of high ozone concentration (120 nL L−1) caused the starch content in grain to reduce by 15.8% than that in the control treatment, but total soluble sugars in grain was actually enhanced by 47.5% compared to that in the control treatment. The contents of albumin and glutenin in rice grain increased with increasing the ozone concentration, and prolamin and crude protein contents in rice grain increased only at the higher ozone concentration. Under ozone concentration of 120 nL L−1, the contents of albumin, glutenin and crude protein in rice grain were increased respectively by 23.1%, 21.0% and 21.1% compared with those in the control treatment. The result suggested that ozone tress has an influence on nitrogen metabolism of rice leaves and grain quality.► Ozone stress caused obvious injury in rice leaves. ► Ozone stress had significant influence on the nitrate reductase activity in rice leaves. ► Sugar and protein contents in rice grain are influenced by ozone stress. ► The contents of albumin and glutenin in rice grain increased with increasing the ozone concentration.
Keywords: Ozone; Rice; Nitrate reductase; Starch; Protein; Grain;

The spatial and temporal variability in ambient atmospheric ammonia (NH3) concentration was evaluated across southern Ontario, Canada, during the period August 2007–December 2010 using the Willems badge diffusive passive sampler (under a two week measurement frequency). A network of 11 monitoring sites was established across a land use transect reflecting low to high agricultural activity based on agricultural statistics and reported emissions. Ambient two-week average NH3 concentrations were lowest during the winter and highest during the spring consistent with seasonal agricultural activity; the largest range in observed NH3 concentrations at an individual site was 0.4–15.8 μg m−3 (winter–spring; intensive agricultural site). Annual average ambient NH3 concentrations ranged from 0.3 μg m−3 at low agricultural intensity (background) sites (n = 4) to 2.8 μg m−3 at intensive agricultural sites (n = 3); the largest range in biweekly NH3 concentrations across the 11 monitoring sites (during one exposure period) was ∼16 μg m−3 (spring season). Annual average concentrations ranged from 0.1 μg m−3 to 3.0 μg m−3 across sites; nonetheless, there was strong temporal coherence among all sites suggesting a common regional ‘footprint’ from agricultural emissions. Regional agricultural statistics correlated well with NH3 concentrations, cattle and pig numbers being the best predictors of annual average NH3 concentrations across southern Ontario.► Ambient annual NH3 concentrations across Ontario ranged from <0.5 to >3.0 μg m−3. ► Largest two week variability in NH3 concentrations was during the spring ∼16 μg m−3. ► Ambient NH3 concentrations highly correlated to animal numbers in southern Ontario. ► Agricultural NH3 emissions leave a regional footprint across southern Ontario. ► Forest ecosystems may have reduced biodiversity due to predicted NH3 >1 μg m−3.
Keywords: Agricultural emissions; Critical levels; Diffusive passive sampler; Willems badge;

Impacts of future air pollution mitigation strategies on the aerosol direct radiative forcing over Europe by J.C. Péré; A. Colette; P. Dubuisson; B. Bessagnet; M. Mallet; V. Pont (451-460).
Projections of aerosol emissions for 2030 have been recently generated and implemented in a comprehensive chemistry-transport model to analyse the future evolution of the aerosol radiative forcing over Europe. In this study, numerical developments based on an off-line coupling between the regional chemistry-transport model CHIMERE (extended by an aerosol optical module) and the radiative transfer code GAME have been implemented in order to simulate the interaction of physico-chemically resolved aerosols with radiation at regional scale. This novel approach is used to examine the shortwave aerosol direct radiative forcing response to two air pollution reduction scenarios for 2030 over Europe. Our study suggests that measures introduced to improve future air quality could have large implication on the aerosol climate forcing over Europe. Results of simulations indicate that abatement of aerosols in the near future could lead to a decrease of the aerosol cooling effect at the surface and at the top of the atmosphere over the main anthropogenic emission regions. Especially over the Moscow region, different strategies of reduction for scattering sulphate and absorbing black carbon aerosols between the two scenarios could result, however, in either a reduction or an enhancement in atmospheric radiative forcing.► We developed a coupling between chemistry-transport and radiative transfer models. ► We simulated the Aerosol Direct Radiative Forcing at regional scale. ► We studied the ADRF response to 2 emission reduction scenarios for 2030 over Europe. ► Measures to improve air quality could have implication on aerosol climate forcing.
Keywords: Aerosol; Air quality; Climate; Emission reduction; Direct radiative forcing; Cooling/warming effects;

Comparison of road traffic emission models in Madrid (Spain) by Rafael Borge; Isabel de Miguel; David de la Paz; Julio Lumbreras; Javier Pérez; Encarnación Rodríguez (461-471).
Many cities in Europe have difficulties to meet the air quality standards set by the European legislation, most particularly the annual mean Limit Value for NO2. Road transport is often the main source of air pollution in urban areas and therefore, there is an increasing need to estimate current and future traffic emissions as accurately as possible. As a consequence, a number of specific emission models and emission factors databases have been developed recently. They present important methodological differences and may result in largely diverging emission figures and thus may lead to alternative policy recommendations. This study compares two approaches to estimate road traffic emissions in Madrid (Spain): the COmputer Programme to calculate Emissions from Road Transport (COPERT4 v.8.1) and the Handbook Emission Factors for Road Transport (HBEFA v.3.1), representative of the ‘average-speed’ and ‘traffic situation’ model types respectively. The input information (e.g. fleet composition, vehicle kilometres travelled, traffic intensity, road type, etc.) was provided by the traffic model developed by the Madrid City Council along with observations from field campaigns. Hourly emissions were computed for nearly 15 000 road segments distributed in 9 management areas covering the Madrid city and surroundings. Total annual NOX emissions predicted by HBEFA were a 21% higher than those of COPERT. The discrepancies for NO2 were lower (13%) since resulting average NO2/NOX ratios are lower for HBEFA. The larger differences are related to diesel vehicle emissions under “stop & go” traffic conditions, very common in distributor/secondary roads of the Madrid metropolitan area.In order to understand the representativeness of these results, the resulting emissions were integrated in an urban scale inventory used to drive mesoscale air quality simulations with the Community Multiscale Air Quality (CMAQ) modelling system (1 km2 resolution). Modelled NO2 concentrations were compared with observations through a series of statistics. Although there are no remarkable differences between both model runs, the results suggest that HBEFA may overestimate traffic emissions. However, the results are strongly influenced by methodological issues and limitations of the traffic model. This study was useful to provide a first alternative estimate to the official emission inventory in Madrid and to identify the main features of the traffic model that should be improved to support the application of an emission system based on “real world” emission factors.► COPERT4 v.8.1 and HBEFA v.3.1 emissions models have been applied to the Madrid city. ► Total annual NOX emissions predicted by HBEFA were 21% higher than those of COPERT. ► Better results in urban-scale, high-resolution NO2 simulations with COPERT outputs. ► Large discrepancies for congestion situations (stop & go) and heavy vehicles. ► Strong influence of methodological issues (e.g. determination of service level).
Keywords: Emission inventory; Road traffic; Emission models; Air quality modelling; NO2; Madrid;

Polycyclic aromatic hydrocarbons (PAHs) are among the most toxic air pollutants in China. Efforts in assessing population inhalation exposure to PAHs, and its contribution to lung cancer risk for Chinese residents, have been limited due to insufficient data on measured indoor concentrations. A mass-balance model to predict indoor PAH concentrations was developed, along with estimated exposures and attributable lung cancer risks for residents in the Beijing region in 2006, with a 2-stage Monte Carlo simulation framework. The exposures and risks were split into three parts, based on the sources and places of exposure, to estimate the contributions of indoor and outdoor PAH sources and exposures, in order to better understand the source and place pattern of PAH exposure. PAHs bring considerable lung cancer risk to the population of Beijing region. The population attributable fraction (PAF) of lung cancer for Beijing's overall population is 2.99% [95% confidence interval (CI): 1.71%–4.26%]. Median contribution of indoor exposure to outdoor-originated PAHs (OUT–in) is 78% (CI: 73%–81%) in the overall population, for 97% (CI: 94%–99%) of whom OUT–in is the largest contributor. Rural residents are facing considerable exposure to indoor-originated PAHs (IN–in), which dominates the total exposure in 12% (CI: 2%–24%) of the rural population. This model framework could be used in quantitative comparison of different interventions on exposure to PAHs as well as other airborne pollutants.► We use Monte Carlo method to estimate PAH exposure with modeled indoor concentration. ► Uncertainty of the model is investigated with a 2-stage Monte Carlo technique. ► Key data pertinent to Beijing population is collected and presented in detail. ► Contributions of in/outdoor sources/exposures for urban/rural residents are analyzed. ► Population attributable fraction of lung cancer is calculated from exposure estimate.
Keywords: Polycyclic aromatic hydrocarbons (PAHs); Lung cancer risk; Population exposure assessment; Monte Carlo method; China; Semi-volatile organic compounds (SVOCs);

The spatial and temporal variation in ambient atmospheric concentrations of gaseous reactive nitrogen (Nr) species (ammonia [NH3], nitrogen dioxide [NO2] and nitric acid [HNO3]) were measured at four sites (spanning a transect in land use types: intensive agricultural, urban–agricultural transition, urban, and rural background) across southern Ontario, Canada. Atmospheric concentrations were measured with the Willems badge diffusive passive sampler for one year (April 2010–March 2011) at two-week exposure periods (biweekly integrated concentration measurements); dry deposition was estimated using the inferential method. There was high spatial and temporal variability in the ambient concentrations and estimated dry deposition of NH3, NO2 and HNO3 across the four study sites. Annual average Nr concentrations were greatest at the urban site owing to high NO2 concentrations (>25 μg m−3), while annual average ambient NH3 concentrations were greatest at the intensive agricultural site (>3 μg m−3) followed by the urban site (∼2 μg m−3) suggesting that outside of intensive agricultural areas, urban regions have the highest ambient NH3 concentrations in southern Ontario. The high ambient NH3 and NO2 concentrations resulted in high dry deposition of gaseous Nr (urban [>12 kg N ha−1 yr−1] and intensive agricultural [>8 kg N ha−1 yr−1]), accounting for 50–60% of estimated total Nr deposition (dry gaseous + wet ammonium and nitrate) at the study sites. Atmospheric NH3 and NO2 are significant components of total Nr deposition in southern Ontario and should be routinely monitored.► Intensive agricultural and urban sites have the highest NH3 concentrations. ► Nr deposition was highest at the high-density urban site owing to NO2. ► NH3 and NO2 account for 50–60% of total N deposition at urban and agricultural sites. ► Gaseous Nr concentrations were variable across the rural–urban–agricultural transect. ► Routine monitoring of NH3 and NO2 would better quantify N budgets in southern Ontario.
Keywords: Gaseous reactive nitrogen; Dry deposition; Agricultural emissions; Urban emissions; Passive diffusive sampler; Willems badge;

Aircraft measurements of SO2 and aerosols over northeastern China: Vertical profiles and the influence of weather on air quality by Can Li; Jeffrey W. Stehr; Lackson T. Marufu; Zhanqing Li; Russell R. Dickerson (492-501).
Aircraft measurements of SO2 and aerosol scattering coefficients (b sp) were made over Shenyang, an industrialized city in northeastern China in April 2005. Weather conditions were found to have strong impact on the area's air quality. Between two flights on April 10 and 11, the SO2 loading increased by an order of magnitude within 24 h, from ∼0.1 DU (Dobson Unit) to ∼1 DU. Meteorological observations and back trajectory analyses suggest that anthropogenic pollutants emitted from the area accumulated under stagnant conditions induced by a mid-latitude cyclone approaching from the west. The observed rapid buildup demonstrates that strong local emissions can expose the populace to high pollutant levels under unfavorable weather conditions. Ångström exponents determined from the aircraft and ground-based sun photometers are significantly smaller over China than over the U.S., suggesting the prevalence of dust particles in northern China, particularly in spring. The coarse mode became more pronounced with altitude, indicating dust-dominant aerosol layers in the lower free troposphere, which should be accounted for in the satellite remote sensing of surface pollution over the region. Information on the vertical distribution of aerosols and precursor gases over China will also help better understand their transport as well as effects on weather and climate.► Dramatic change in air quality caused by shift in weather pattern. ► Significant difference in aerosol properties between N China and E U.S. ► Prevalent dust layers in the free troposphere over N China.
Keywords: Aircraft measurements; SO2; Aerosols; Vertical profile; Weather and air quality;

Aqueous phase sulfate production in clouds in eastern China by Xinhua Shen; Taehyoung Lee; Jia Guo; Xinfeng Wang; Penghui Li; Pengju Xu; Yan Wang; Yu Ren; Wenxing Wang; Tao Wang; Yi Li; Simon A. Carn; Jeffrey L. Collett (502-511).
Clouds play an important role in the oxidation of sulfur dioxide to sulfate, since aqueous phase sulfur dioxide oxidation is typically much faster than oxidation in the gas phase. Important aqueous phase oxidants include hydrogen peroxide, ozone and oxygen (catalyzed by trace metals). Because quantities of emitted sulfur dioxide in China are so large, however, it is possible that they exceed the capacity of regional clouds for sulfate production, leading to enhanced long-range transport of emitted SO2 and its oxidation product, sulfate. In order to assess the ability of regional clouds to support aqueous sulfur oxidation, four field campaigns were conducted in 2007 and 2008 at Mt. Tai in eastern China. Single and 2-stage Caltech Active Strand Cloudwater Collectors were used to collect bulk and drop size-resolved cloudwater samples, respectively. Key species that determine aqueous phase sulfur oxidation were analyzed, including cloudwater pH, S(IV), H2O2, Fe, and Mn. Gas phase SO2, O3, and H2O2 were also measured continuously during the campaigns. A wide range of cloud pH values was observed, from 2.6 to 7.6; 60% of cloud samples had a pH between 3 and 5. H2O2 was found to be an important sulfur oxidant, especially at cloudwater pH lower than 5. H2O2 was the most important oxidant in 68% of the cloud sampling periods. High concentrations of residual H2O2 were observed in many periods, especially in summer, implying a substantial capacity for additional sulfur oxidation. O3 was an important oxidant when cloudwater pH was higher than approximately 5–5.3, and was the most important oxidant in 20% of the studied periods. Aqueous sulfur oxidation by O2 (catalyzed by Fe and Mn) was found to be the fastest sulfate production pathway in 12% of the cases. Observed chemical heterogeneity among cloud drop populations was found to enhance rates of S(IV) oxidation by ozone and enhance or slow metal-catalyzed S(IV) autooxidation rates in some periods. These effects were found to be only of minor importance for the total S(IV) oxidation rate, however, as H2O2 was the dominant S(IV) oxidant during most periods.► Aqueous phase sulfur chemistry is examined in clouds in east China. ► Spring and summer clouds were sampled and analyzed in 2007 and 2008. ► H2O2 was the dominant S(IV) oxidant. ► Ozone and oxygen (catalyzed by trace metals) were important oxidants in high pH clouds. ► Many summer clouds contained residual H2O2 suggesting additional capacity for aqueous sulfur oxidation.
Keywords: Sulfur dioxide; Sulfate; Aqueous phase oxidation; Clouds; Cloud chemistry; Mt. Tai; China;

Visibility trends in Tehran during 1958–2008 by Samaneh Sabetghadam; Farhang Ahmadi-Givi; Yahya Golestani (512-520).
Visibility, in the absence of certain weather conditions (e.g., fog and rain), is an excellent indicator of air quality because its impairment results from light scattering and absorption by atmospheric particles and gases. In this study, the historical airport visibility database is explored during the last five decades for the city of Tehran, Iran. Seasonal and long-term variations of the visibility are investigated using cumulative percentiles. The correlation of the long-term visibility trend with precipitation, fog and high relative humidity are also examined.The trends of visual range of the best, median, and worst visibilities at 10th, 50th and 90th percentiles of daily visibility data indicate an overall downward trend for all the percentiles. Results show a larger decrease in visibility for the Tehran metropolitan area than the sparsely populated and less polluted parts of the city. The largest trend in decreasing visibility is observed during winter time followed by spring, fall and summer. Decreasing trends in visibility occur for all stations and do not significantly depend on the special weather events.► Historical visibility database are explored to investigate visibility trend. ► We examined correlation of visibility trend with precipitation, fog and humidity. ► More decrease for Tehran metropolitan area than sparsely populated parts. ► The most decreasing trend of visibility is observed during winter time.
Keywords: Visibility; Trends; Visual air quality; Percentile; Tehran;

Thirty years of erosion and declining atmospheric pollution at St Paul's Cathedral, London by R.J. Inkpen; H.A. Viles; C. Moses; B. Baily; P. Collier; S.T. Trudgill; R.U. Cooke (521-529).
The relationship between limestone deterioration (in the form of recession or erosion rates) and changing air quality has been the subject of much debate. A 30-year record of limestone erosion rates from the balustrade of St Paul's Cathedral, London, UK has been obtained from five micro-erosion meter (MEM) sites (last remeasured in September 2010) providing a unique, long-term dataset with which to examine the nature and causes of changing deterioration, particularly the existence of a memory effect. Whilst atmospheric sulphur dioxide concentrations fell from a daily average of 80 ppb in the early 1980s to less than 3 ppb by the late 2000s, erosion rates (measured as surface lowering or recession) only declined from 0.049 mm a−1 to 0.035 mm a−1 over the same period. A more conservative measure of the rate of surface change (which includes both lowering and raising of the surface) fell from 0.044 mm a−1 to 0.026 mm a−1 over the same period. The rates of surface change and erosion were significantly higher in the 1980–1990 measurement period compared to the 1990–2000 measurement period, whilst the average rates for the 1990–2000 measurement period were approximately the same as those for the 2000–2010 measurement period. There is no clear evidence for a memory effect, and rates of erosion and surface change now approach those found on natural karst surfaces.► 30 years of limestone erosion data are available for St Paul's Cathedral, London (1980–2010). ► Rates of erosion have declined from 0.049 mm a−1 to 0.035 mm a−1 over this period. ► Sulphur dioxide levels have declined from 80 ppb to less than 3 ppb over the same period. ► Erosion rates are declining less steeply than levels of sulphur dioxide. ► Analysis of the data does not suggest any impact of the ‘memory’ effect.
Keywords: Limestone erosion; Sulphur dioxide; London; Erosion rates; Atmospheric pollution;

Comparison of models for estimation of long-term exposure to air pollution in cohort studies by I.J. Beverland; C. Robertson; C. Yap; M.R. Heal; G.R. Cohen; D.E.J. Henderson; C.L. Hart; R.M. Agius (530-539).
This study compared three spatio-temporal models for estimation of exposure to air pollution throughout the central part of Scotland during 1970–79 for approximately 21,600 individuals in 2 closely-related prospective cohort studies. Although 181 black smoke (BS) monitoring sites operated in this region at some point during 1970–79, a substantial amount of BS exposure data was missing at many sites. The three exposure estimation methods were: (i) area-based regression models to impute missing data followed by assignment of exposure by inverse distance weighting of observed BS at nearby monitoring sites (IDWBS); (ii) area-based regression models to impute missing data followed by a spatial regression additive model using four local air quality predictors (LAQP): altitude; distance to the nearest major road; household density within a 250 m buffer zone; and distance to the edge of urban boundary (AMBS); (iii) a multilevel spatio-temporal model using LAQP (MultiBS). The three methods were evaluated using maps of predicted BS, and cross validation using monitored and imputed BS at sites with ≥80% data. The use of LAQP in the AMBS and MultiBS exposure models provided spatial patterns in BS consistent with known sources of BS associated with major roads and the centre of urban areas. Cross-validation analyses demonstrated that the MultiBS model provided more precise predictions (R 2 = 60%) of decadal geometric mean BS concentrations at monitoring sites compared with the IDWBS and AMBS models (R 2 of 19% and 20%, respectively).► Three approaches for modelling long-term exposure to black smoke were evaluated. ► Missing data require development of imputation procedures. ► Cross validation & GIS-based visualisation were used for model evaluation. ► Marked differences in performance were noted in evaluation of different models. ► Improved black smoke exposure estimates were observed using a multi-level model.
Keywords: Black smoke; Cohort; Exposure estimation; Multi-level model;

Wet deposition of mercury at a remote site in the Tibetan Plateau: Concentrations, speciation, and fluxes by Jie Huang; Shichang Kang; Qianggong Zhang; Haiyu Yan; Junming Guo; Matt G. Jenkins; Guoshuai Zhang; Kang Wang (540-550).
Precipitation samples collected at a remote high elevation site (i.e., Nam Co Station, 4730 m a.s.l.) in the southern Tibetan Plateau were analyzed for total mercury (HgT) between July 2009 and 2011, particulate-bound mercury (HgP) between July 2010 and 2011 and methylmercury (MeHg) from July through August of 2009. The volume-weighted mean (VWM) concentrations and wet deposition fluxes of HgT and MeHg in precipitation were 4.8 ng L−1 and 1.75 μg m−2 yr−1, 0.031 ng L−1 and 0.01 μg m−2 yr−1, respectively. VWM HgT concentration was approximately two times higher during the non-monsoon season than during the monsoon season, while 83% of the HgT wet deposition fluxes occurred during the monsoon season. The HgT and MeHg concentrations are comparable to the reported data for some of the most remote alpine and polar regions worldwide (e.g., Churchill), but the wet deposition fluxes of HgT and MeHg were among the lowest in the world. Analysis of Hg speciation has presented that HgP and MeHg concentrations are high, making up 71.2% and 1.82% of the HgT on average (VWM), respectively. The high HgP%, as well as a significantly positive between HgT and HgP (R 2 = 0.91; n = 44; p < 0.001), confirmed that atmospheric deposition of Hg in the Tibetan Plateau was occurring in the form of HgP. A decreasing trend in HgT concentrations with increasing amount of precipitation (R 2 = 0.08; N = 101; p < 0.005) was found at Nam Co Station, indicative that scavenging of HgP from the atmosphere was an important mechanism contributing Hg to precipitation. The precipitation amount, rather than HgT concentration, was found to be the governing factor affecting HgT wet deposition flux. Moreover, a comparison between measured wet deposition flux of Hg at Nam Co Station and the estimates from environmental records indicated that both snowpits and lake sediments appear to be reliable archives for estimating historical Hg accumulation rates over the Tibetan Plateau.► We present a 2-year measured data of wet Hg deposition at a remote site in Tibet. ► HgP dominated the concentration and flux of HgT in the wet-deposition samples. ► The precipitation amount was the governing factor affecting HgT wet deposition flux. ► Measured annual HgT flux was comparable to the estimates from environmental records.
Keywords: Mercury; Concentration; Speciation; Wet deposition flux; Nam Co Station; Tibetan Plateau;

Application of SIM-air modeling tools to assess air quality in Indian cities by Sarath K. Guttikunda; Puja Jawahar (551-561).
A prerequisite to an air quality management plan for a city is some idea of the main sources of pollution and their contributions for a city. This paper presents the results of an application of the SIM-air modeling tool in six Indian cities – Pune, Chennai, Indore, Ahmedabad, Surat, and Rajkot. Using existing and publicly available data, we put together a baseline of multi-pollutant emissions for each of the cities and then calculate concentrations, health impacts, and model alternative scenarios for 2020. The measured annual PM10 (particulate matter with aerodynamic diameter less than 10 micron meter) concentrations in μg m−3 averaged 94.7 ± 45.4 in Pune, 73.1 ± 33.7 in Chennai, 118.8 ± 44.3 in Indore, 94.0 ± 20.4 in Ahmedabad, 89.4 ± 12.1 in Surat, and 105.0 ± 25.6 in Rajkot, all exceeding the annual standard of 60 μg m−3. The PM10 inventory in tons/year for the year 2010 of 38,400 in Pune, 50,200 in Chennai, 18,600 in Indore, 31,900 in Ahmedabad, 20,000 in Surat, and 14,000 in Rajkot, is further spatially segregated into 1 km grids and includes all known sources such as transport, road dust, residential, power plants, industries (including the brick kilns), waste burning, and diesel generator sets. We use the ATMoS chemical transport model to validate the emissions inventory and estimate an annual premature mortality due to particulate pollution of 15,200 for the year 2010 for the six cities. Of the estimated 21,400 premature deaths in the six cities in 2020, we estimate that implementation of the six interventions in the transport and brick kiln sectors, can potentially save 5870 lives (27%) annually and result in an annual reduction of 16.8 million tons of carbon dioxide emissions in the six cities.Display Omitted► An overview of the SIM-air modeling system to assess urban air quality. ► A multi-pollutant emissions inventory for six cities in India. ► An analysis of sectoral contributions and health impacts of particulate pollution. ► A review of pollution control strategies and their implications.
Keywords: Particulate pollution; Pune; Chennai; Indore; Ahmedabad; Surat; Rajkot; India; Emissions inventory; Dispersion modeling; Air quality management;

This study evaluates the relative recovery (RR) of five different carbonyls (CCs) (i.e., acetaldehyde, propionaldehyde, butyraldehyde, isovaleraldehyde, and valeraldehyde) following their reaction as 2, 4-dinitrophenylhydrazine (DNPH) derivatives when using gas phase and liquid phase standards. To this end, relative efficiency of CC-DNPH derivatization is compared between two liquid-phase standards (commercially available vs. lab made mixture) and between liquid and gas-phase standard. If the results are compared in terms of response factors (RF) derived for five carbonyls from all different standard phases, the recovery of gaseous CC standard was distinguished from that of liquid counterparts. The RR of the heavier carbonyls (propionaldehyde, butyraldehyde, isovaleraldehyde, and valeraldehyde) was approximately 60% low relative to their liquid counterparts; however, it was not the case for the lighter carbonyls (acetaldehyde) with the RR of ∼92%. This study thus suggests that the quantification of heavy carbonyls in ambient air, unless made by standards of the same matrix (i.e., gas phase) or compensated by the proper correction factor, may be subject to a large bias due to difference in derivatization reaction efficiency between matrix types. Hence, consideration of the matrix effect at the calibration stage is of particular importance to measure CC quantitatively.
Keywords: Carbonyl compound; DNPH cartridge; HPLC; Standard-phase; Recovery;

Ozone and short-term mortality in nine French cities: Influence of temperature and season by Mathilde Pascal; Vérène Wagner; Edouard Chatignoux; Grégoire Falq; Magali Corso; Myriam Blanchard; Sabine Host; Sophie Larrieu; Laurence Pascal; Christophe Declercq (566-572).
Several epidemiological studies have observed significant short-term associations between ozone and daily mortality. In a context of climate change, it is important to understand how this association is influenced by the meteorological conditions.We investigated how season and temperature modified the short-term effect of ozone on mortality by cause in nine French urban areas during the 1998–2006 period.The relationship between daily max-8 h ozone and daily mortality was analysed in each city using a time-stratified case-crossover model for the whole year, by season, and by temperature strata. Sensitivity of the results to the statistical modelling strategy, to the choice of the temperature terms, and to the introduction of PM2.5 was examined.A 10 μg m 3 increase in daily ozone level was significantly associated with an increase in non-accidental (+0.3% [95% CI 0.1; 0.5]), cardiac (+0.7% [0.2; 1.1]) and cardiovascular mortality (+0.4% [0.0; 0.7]). The estimates were larger during summer (+0.8% [0.5; 1.2], +1.3% [0.6; 1.9] and +1.1% [0.3; 1.9] respectively) and for the warmest temperature strata (+0.9% [0.4; 1.3], +1.3% [0.6; 2.1] and +1.2% [0.3; 2.1] respectively). A significant interaction was found between ozone and warm days for non-accidental mortality. Results were robust to the sensitivity analyses.This study provides evidences of a larger impact of ozone when the temperatures are warmer for non-accidental mortality and cardiovascular mortality.► The study investigated if temperature modifies the mortality impacts of ozone. ► Nine cities and six causes of mortality were investigated per seasons and temperature. ► A significant interaction was found between ozone, warm days and mortality. ► The non-accidental and cardiovascular causes were the most impacted.
Keywords: Ozone; Temperature; Mortality;

The effect of rain characteristics on scavenging rate of tritium-oxide from the atmosphere by V.N. Piskunov; A.V. Golubev; Yu.S. Balashov; S.V. Mavrin; V.N. Golubeva; A.Yu. Aleinikov; V.P. Kovalenko; I.I. Solomatin (573-583).
The results of field experiments, involving HTO scavenging from the atmosphere by precipitation in the vicinity of HT and HTO emission sources, are presented. The experiments were aimed at obtaining direct experimental data on atmospheric HTO scavenging for a variety of rain characteristics (rain intensity and drop spectra).The most reliable are the calculations of the rate of wash-out with precipitation with the use of the method of integration of the constant exchange for a spectrum of drops. The results of such calculations are in good agreement with the experimental data and can serve as a basis for the generalized parameterization dependences. It is shown that the exact calculation can be replaced by a simpler formula using the mean-value theorem.For the known approximations of the spectra of the rain drops, formulas were obtained to give parameterization dependence of the rate of wash-out Λ on the intensity of precipitation p. This approach can be used for rapid assessment, as well as to determine parameters of wash-out of gases with precipitation in the numerical complexes, which are used for the calculation of the transfer and removal of impurities from the atmosphere.► The results of field experiments in HTO scavenging with precipitations from the atmosphere are presented. ► The precipitation parameters were experimentally measured, the drop spectra were processed. ► The comparison of the calculations with the results has shown a good agreement. ► The model was developed to calculate scavenging rates for arbitrary drop spectra. ► The parameterized dependence for the Λ scavenging rate on precipitation intensity p was proposed.
Keywords: Tritium; Tritium oxide (HTO); Wash-out; Field experiments; Scavenging rate; Parameterization;

Stable hydrogen-isotope analysis of methyl chloride emitted from heated halophytic plants by Markus Greule; Stefan G. Huber; Frank Keppler (584-592).
Stable isotope techniques are increasingly applied to study atmospheric budgets of methyl halides. Here we use compound specific thermal conversion isotope ratio mass spectrometry to measure the stable hydrogen isotope values of methyl chloride ( δ 2 H CH 3 Cl ) released thermally from dried leaves of halophyte plants collected from different geographical locations. We developed an automated purification and pre-concentration unit to enable measurement of δ 2 H CH 3 Cl from samples (100 ml) when mixing ratios were as low as 1 ppmv. Even though this is considerably higher than normal atmospheric mixing ratios this unit enabled measurement of the δ2H values of CH3Cl released during heating of samples at temperatures ranging from 30 to 300 °C. No substantial changes of δ 2 H CH 3 Cl values were observed over this temperature range. However, the δ 2 H CH 3 Cl values of all plants examined were strongly depleted (−178 ± 34‰) relative to the δ2H values of their modelled meteoric water, but differ only by 1–50‰ from those observed for their methoxyl groups. Our results indicate that plant methoxyl groups are an important precursor of the methyl group for CH3Cl thermally emitted from lyophilised and homogenized dry halophyte leaves. Furthermore, the thermal reaction producing CH3Cl did not show a substantial kinetic hydrogen isotope fractionation between CH3Cl and precursor methoxyl groups over the temperature range investigated. Moreover, we found a moderate linear correlation (R 2 = 0.37) for the relationship between δ 2 H CH 3 Cl values released from halophytes and the δ2H values of modelled precipitation at their geographical locations. As CH3Cl emissions from terrestrial vegetation, including senescent and dry plants and biomass burning, are considered to provide a substantial fraction of the global emissions our findings are important when establishing a global hydrogen isotope model for atmospheric CH3Cl.► We have developed a method to measure D/H ratios of chloromethane (CH3Cl). ► We measure D/H ratios of CH3Cl released from halophytes. ► D/H ratiosCH3 Cl released from halophytes are similar over large temperature range. ► Good correlation between D/H ratios of CH3Cl and modelled meteoric water. ► Implication for global hydrogen model for atmospheric CH3Cl.
Keywords: Deuterium; Chloromethane; Atmospheric budget; Isotope ratio mass spectrometry; Vegetation;

In the event of an accidental or intentional contaminant release, it is imperative to locate the source of the contaminant for use in hazard prediction models. In some situations more than a single contaminant release will be present, which becomes a complicating factor when contaminants from these releases significantly overlap. Here we present a Lagrangian approach to determine the source locations of multiple contaminant releases. For this approach, we assume that the concentration field is approximated by a superposition of contaminant entities, where an entity is a discrete object; namely a puff for an instantaneous release and a plume for a continuous release. The state of each entity is inferred from surface observations of the contaminant, and extrapolation of each entity's state provides an estimate of the contaminant source locations. We call this method a Multi-Entity Field Approximation (MEFA) because together the entities' concentration fields sum to approximate the observed concentration field. In this work, we outline the MEFA process for both instantaneous and continuous contaminant releases using data from two FUSION Field Trial 2007 (FFT07) Trials where contaminant fields from multiple contaminant releases overlap close to the source location.► We adopt a state estimation approach to locate the source of multiple contaminant releases. ► This technique is called a Multi-Entity Field Approximation (MEFA). ► We determine and analyze each entity's state to infer the contaminant source information. ► We demonstrate the method for instantaneous and continuous release scenarios using FFT07 Trial data.
Keywords: Source term estimation; Multi-Entity Field Approximation; Entity; Atmospheric transport and dispersion; FUSION Field Trial 2007; Genetic Algorithm optimization;

A study on the trends of vehicular emissions in the Beijing–Tianjin–Hebei (BTH) region, China by Jianlei Lang; Shuiyuan Cheng; Wei Wei; Ying Zhou; Xiao Wei; Dongsheng Chen (605-614).
This paper aims to study the vehicular emissions trends in the Beijing–Tianjin–Hebei (BTH) region, located in northern China. The multiyear emission inventories of NO X , CO, VOC and PM10 from road vehicles in the period 1999–2010 were developed by the COPERT IV model. Results show that vehicular emissions of CO and VOC have decreased by annual average change rates (AACR) of −3.1% to −5.2% and −4.4% to −6.9% in the study area, respectively. However, due to the rapid development of freight traffic, emissions of NO X and PM10 have kept increasing in Tianjin and Hebei. Based on the vehicular emission inventories, trends of emission levels for vehicles with different standards, as well as the overall effects of implementing vehicular emission mitigation strategies were assessed. It is suggested that passenger cars (PC) with Euro 0 and Euro I standards, which were at higher emission level in the PC fleet, should be gradually eliminated. Although the increasing rates (IR) of emissions from PC were lower than those of the PC population, the sharp growth of PC population in recent years contributed to a remarkable increase of emissions, weakening the overall mitigation effect. Total vehicle population capacity and other mitigation measures should be studied in China in order to develop new and more effective vehicular emission control strategies.► Vehicular emissions from 1999 to 2010 were estimated in BTH. ► CO and VOC emissions have decreased, while NO X and PM10 emissions kept increasing. ► Overall effects of implementing emission control strategies were assessed. ► High-pollution vehicles should be eliminated. ► Sharp growth of vehicle numbers and freight traffic lead to increasing emissions.
Keywords: Emission inventory; Vehicular pollutants; Control policy assessment; COPERT;

An assessment of the significance of sulphate sources over the Atlantic Ocean based on sulphur isotope data by C.T. Lin; A.R. Baker; T.D. Jickells; S. Kelly; T. Lesworth (615-621).
The results of fine mode (<1 μm) aerosol sulphate, MSA and major ion composition and isotopic analyses are presented for aerosol samples collected over the Atlantic Ocean. The results are used to apportion the measured sulphate into sea-salt sulphate, anthropogenic sulphate and marine biogenic (dimethyl sulphide DMS) sulphate sources. The contribution of volcanic sulphur is argued to be very small within this data set. The results confirm other studies showing that DMS makes a major contribution to the sulphate burden over the remote ocean. DMS can be oxidised to form SO2 or methane sulphonic acid (MSA). Using our estimates of marine biogenic sulphate and measurements of MSA concentrations we confirm that the ratio of MSA/sulphate from DMS oxidation increases systematically from low to high latitudes, consistent with the laboratory measurements, inferences from field studies and modelling predictions of others.► Apportionment of aerosol sulphate into biogenic, anthropogenic and sea-salt sources. ► Biogenic sulphate is a very important sulphate source over the remote Atlantic. ► Ratio of MSA/Sulphate from DMS oxidation increases systematically with latitude.
Keywords: Sulphate aerosol; Sulphate isotopes; MSA; Atlantic;

To better understand time-resolved variations of water-soluble organic aerosols in the atmosphere, we collected atmospheric particles (TSP) every 3 h during summertime (8–10 August, 2005) in Sapporo, northern Japan. We measured inorganic ions, carbonaceous components, dicarboxylic acids, ketoacids and α-dicarbonyls in TSP. SO4 2− was found as the most abundant ionic species (57 ± 9% of total ions determined) followed by NH4 + and NO3 . However, none of the ionic species showed any diurnal trend throughout the campaign. Organic carbon (OC) ranged from 2.1 to 12.1 μg m−3 whereas elemental carbon (EC) was negligible in most of the samples (0.31 ± 0.56 μg m−3). Oxalic (C2) acid was the most abundant diacid species, followed by malonic (C3) and succinic (C4) acids. Water-soluble OC (WSOC), water-insoluble OC (WIOC) and OC as well as dominant diacids (C2–C4), total diacids, ketoacids and α-dicarbonyls did not show diurnal trend on 8 August, but they showed clear diurnal distributions during 9–10 August following the changes in ambient temperature (and radiation). Detailed analyses of time-resolved aerosols demonstrate that diurnal variations of organic aerosol compositions are caused by local in situ photochemical production, but are significantly superimposed by long-range atmospheric transport of aerosols, particularly when the air masses are enriched with emissions from higher plants and/or biomass burning, and their photochemical processing during the transport.► We studied time-resolved variations of chemical species of aerosols from Sapporo. ► Inorganic/organic aerosols showed different trends during the 3-day campaign. ► WSOC and diacid diurnal variations were caused by in situ photochemical production. ► Long-range transported aerosols of biogenic origin were superimposed on diurnal trend.
Keywords: Inorganic ions; Organic carbon; WSOC; Dicarboxylic acids; Ketoacids; α-Dicarbonyls; Time-resolved variation; Long-range transport;

Passive air samplers have been installed in industrial, urban, rural and remote forested environments in order to collect coarse airborne particles for subsequent chemical characterization. To identify principal polluting sources, isotopic tracers, such as Sr, Nd and Pb isotopic ratios, have been used. The mass deposition rates (MDRs) of trace metals, determined for each of the studied environments, clearly indicate that industrial and traffic sites are especially affected by air pollution. Elements such as V, Pb, Fe, Cr, Co, Mo, Cd, Ni, As, Sb and Zn are notably enriched in samples from industrial zones, whereas V, Mn, Ba, Sr, Al, U, Th, rare earth elements (REE), Zr, Y, Cs, Rb, Sb, Sn and Cu are principal components of the airborne particles collected close to areas influenced by heavy traffic. The chemical/isotopic baseline composition derived from the airborne particles is the result of mixing of particles from different industrial sources, traffic and fertilizers. The monthly analysis of trace-metal MDRs of the collected airborne particle samples from different stations around the industrial zone allows for the detection of distinct atmospheric dust-deposition events during the year, characterized by high MDRs. “Natural” dusts from regional soil re-suspension, including from more distant regions like the Sahara desert, might overprint the regional atmospheric baseline composition, as suggested by trace metal trajectories in ternary diagrams and by Sr, Nd and Pb isotope data.► Trace element data of coarse airborne particles collected with passive air samplers. ► Industrial and traffic sites are similarly affected by high atmospheric dust deposition rates. ► Isotopic tracers (Sr, Nd, Pb) and element triangle plots allow to identify polluting sources. ► Distinct atmospheric dust deposition events occur during the year.
Keywords: Atmospheric particles; Passive sampler; Sr–Nd–Pb isotopes; Trace elements; Air pollution; Industrial sources; Traffic; Saharan dusts;

In this study, we quantify the frequency of stratosphere-troposphere exchange (STE) events that result in ozone (O3) concentration enhancements (i.e., hourly average concentrations ≥50 ppb) observed at 39 high- and low-elevation monitoring sites in the US during the years 2007–2009. We employ a refined forward trajectory-based approach to address the relationship between stratospheric intrusions and enhancements in hourly average O3 concentrations. The model is applied to high-resolution European Center for Medium-Range Weather Forecasting (ECMWF) analyses to identify specific days when the potential for stratosphere-to-troposphere transport (STT) exists to affect surface O3 levels. Our results indicate that STT down to the surface (STT-S) frequently contributes to enhanced surface O3 hourly averaged concentrations at sites across the US, with substantial year-to-year variability. The O3 concentrations associated with the STT-S events appear to be large enough to enhance the measured O3 concentrations during specific months of the year. Months with a statistically significant coincidence between enhanced O3 concentrations and STT-S occur most frequently at the high-elevation sites in the Intermountain West, as well as at the high-elevation sites in the West and East. These sites exhibit a preference for coincidences during the springtime and in some cases, the summer, fall, and late winter. Besides the high-elevation monitoring sites, low-elevation monitoring sites across the entire US experience enhanced O3 concentrations coincident with STT-S events.► The study quantifies the frequency of STT with enhanced surface O3. ► Trajectories were used to identify coincidences between enhanced surface O3 and STT. ► Many US sites exhibit frequent coincidences between enhanced surface O3 and STT. ► STT plays an important role in affecting background O3 concentrations across the US.
Keywords: Background ozone; Stratosphere–troposphere exchange; Stratosphere-to-troposphere transport; Surface ozone;

Will Euro 6 reduce the NO x emissions of new diesel cars? – Insights from on-road tests with Portable Emissions Measurement Systems (PEMS) by Martin Weiss; Pierre Bonnel; Jörg Kühlwein; Alessio Provenza; Udo Lambrecht; Stefano Alessandrini; Massimo Carriero; Rinaldo Colombo; Fausto Forni; Gaston Lanappe; Philippe Le Lijour; Urbano Manfredi; Francois Montigny; Mirco Sculati (657-665).
The nitrogen dioxide (NO2) pollution in urban areas of Europe can be partially attributed to the increasing market penetration of diesel cars that show higher distance-specific nitrogen oxides (NO x ) emissions than gasoline cars. The on-road NO x emissions of diesel cars, furthermore, appear to exceed substantially applicable emissions standards. This observation raises concerns that the introduction of more stringent Euro 6 emissions standards in 2014 may not adequately reduce the distance-specific on-road NO x emissions of new diesel cars. We address the existing concerns by analyzing the gaseous emissions of one novel Euro 6 diesel car and six Euro 4–5 diesel cars with Portable Emissions Measurement Systems (PEMS). We find that the average on-road NO x emissions of the Euro 6 car (0.21 ± 0.09 g per kilometer [g km 1]) are considerably lower than those of the Euro 4 cars (0.76 ± 0.12 g km 1) and the Euro 5 cars (0.71 ± 0.30 g km 1). The selective catalytic reduction (SCR) system of the Euro 6 diesel car is suitable to limit NO x emissions during real-world on-road driving. Still, all tested cars, including the Euro 6 diesel car, exceed their NO x emissions standards on the road by 260 ± 130%. This finding suggests that the current type-approval procedure does not adequately capture the on-road NO x emissions of diesel cars. By introducing a complementary emissions test procedure that covers a wide range of normal operating conditions, the European legislative authorities can address this problem and ensure that Euro 6 will indeed deliver an adequate reduction in the NO x emissions of new diesel cars.► First on-road emissions test of a Euro 6 diesel car with PEMS. ► Nitrogen oxides emissions exceed type-approval levels. ► Complementary test procedure could limit the on-road emissions of diesel cars.
Keywords: On-road emissions; Euro 6 emissions standards; Nitrogen oxides (NO x ); Passenger cars; Portable Emissions Measurement System (PEMS);