Atmospheric Environment (v.61, #C)

Elemental carbon as an indicator for evaluating the impact of traffic measures on air quality and health by M.P. Keuken; S. Jonkers; P. Zandveld; M. Voogt; S. Elshout van den (1-8).
From 2005 to 2009 there was a 40% decrease in the number of days on which the European daily limit value of PM10 was exceeded at traffic locations in European cities. Yet, in many of these cities, air quality is still not in compliance with the European Air Quality Directive and additional traffic measures are planned. Our study shows that elemental carbon (EC) is a more appropriate indicator than PM2.5 and PM10 for evaluating the impact of traffic measures on air quality and health. The modelled improvement in EC concentration was translated in life years gained as a result of a traffic measure. This was investigated for a speed management zone on a motorway in the city of Rotterdam. Eighty-five per cent of those living within 400 m of the motorway gained 0–1 months of life expectancy and another 15% gained 1–3 months, depending on their distance from the motorway. In addition, EC was used to evaluate a low emission zone in Amsterdam, specifically for those living along inner-urban roads with intense traffic levels. The zone only restricts heavy duty vehicles with Euro emission class 0 to 2, Euro 3 older than eight years or more recent Euro 3 without diesel particulate filter. The results indicate a population-weighted, average gain of 0.2 months in life expectancy as compared with a maximum potential gain of 2.9 months. It is concluded that on motorways speed management is an effective measure, while a low emission zone as implemented in our case study, is less effective to reduce health effects of road traffic emissions. For inner-urban roads reduction of traffic volume seems the most effective traffic measure for improving air quality and health.► EC more appropriate indicator to evaluate traffic measures than PM2.5 and PM10. ► Speed management effective measure to improve air quality and health near a motorway. ► Low emission zone for heavy duty trucks is hardly effective at inner-urban roads.
Keywords: Air quality; Traffic measures; Health impact; Elemental carbon;

Evolution of atmospheric carbon dioxide concentration at different temporal scales recorded in a tall forest by Jiabing Wu; Dexin Guan; Fenhui Yuan; Hong Yang; Anzhi Wang; Changjie Jin (9-14).
Understanding the temporal evolution of CO2 over specific ecosystems can provide additional insight into atmospheric CO2 variability. From 2003 to 2010, CO2 ambient concentrations in an old-growth temperate forest were measured continuously by using an infrared analyzer. The results show that daily cycle and seasonal variation of CO2 were mostly dominated by vegetation activity, whereas the weak turbulent mixing at night contributed frequently to CO2 build-up below the canopy. As a result, CO2 concentrations changed considerably during daytime and nighttime in the forest stand. The monthly means exhibited a seasonal variation characterized by a primary peak in December and a minimum during July to August, with an average seasonal amplitude (the difference of minimum and maximum monthly means) of 60.5 ppmv. By fitting a harmonic model to the monthly means, linear increase trends of 1.7 ppmv yr−1 in the annual mean CO2 concentrations and 0.58 ppmv yr−1 in the amplitude of the seasonal cycle were estimated. The upward trend of annual mean CO2 concentration may be attributed to the dramatic global increase in CO2 emissions during the study period. This study also found that the stratification of CO2 concentrations below the canopy during nighttime was easily disrupted after sunrise, which suggests that forest floor plants are not, as previous assumed, exposed to significantly greater CO2 concentrations than the normal atmospheric concentrations.► We report a long-term CO2 evolution recorded in a CO2 observation station. ► CO2 present linear increase trend in annual mean and in the seasonal amplitude. ► CO2 trapped below canopy is not greatly significant to the shade flora.
Keywords: Carbon dioxide; Greenhouse gas; CO2 concentration; Temperate forest;

Reactivity of polycyclic aromatic compounds (PAHs, NPAHs and OPAHs) adsorbed on natural aerosol particles exposed to atmospheric oxidants by Johany Ringuet; Alexandre Albinet; Eva Leoz-Garziandia; Hélène Budzinski; Eric Villenave (15-22).
Reactivity of polycyclic aromatic compounds (PACs) adsorbed on natural aerosol particles exposed to different atmospheric oxidants (O3, OH and NO2/O3 mixture) was studied. Decay of polycyclic aromatic hydrocarbons (PAHs) and formation/decay of oxygenated PAHs (OPAHs) and nitrated PAHs (NPAHs) were monitored. Overall, benzo[a]pyrene appeared to be the most reactive PAH (degradation of 50%). Only its nitrated derivative, 6-nitrobenzo[a]pyrene, was significantly formed explaining just 0.4% of reacted benzo[a]pyrene. No other nitrated or oxygenated benzo[a]pyrene derivatives were detected. Interestingly, B[e]P and In[1,2,3,c,d]P, which are usually considered as quite stable PAHs, also underwent decay in all experiments. In presence of O3, ketones were significantly formed but their amount was not totally explained by decay of parent PAH. These results suggest that PAH derivatives could be formed from the reaction of other compounds than their direct parent PAHs and raise the question to know if the oxidation of methyl-PAHs, identified in vehicle-exhausts, could constitute this missing source of OPAHs. NPAHs were significantly formed in presence of O3/NO2 and OH. Surprisingly, NPAH formation was clearly observed during O3 experiments. Nitrated species, already associated with aerosol particles (NO3 , NO2 ) or formed by ozonation of particulate nitrogen organic matter, could react with PAHs to form NPAHs. Heterogeneous formation of 2-nitropyrene from pyrene oxidation was for the first time observed, questioning its use as an indicator of NPAH formation in gaseous phase. Equally, formation of 2-nitrofluoranthene by heterogeneous reaction of fluoranthene with O3/NO2 was clearly shown, while only its formation by homogeneous processes (gaseous phase) is reported in the literature. Finally, results obtained highlighted the dependence of heterogeneous PAH reactivity with the substrate nature and the importance to focus reactivity studies on natural particles, whatever the quality of the models previously studied.► We performed reactivity studies of PAC adsorbed on natural aerosol with OH, O3 or NO2. ► PAH degradations led to the formation of oxygenated and nitrated derivatives. ► Benzo[a]pyrene appeared as the most reactive PAH with all oxidants. ► Dependence of heterogeneous PAH reactivity with the substrate nature was highlighted. ► We showed the strong interest to work on natural aerosol particles from ambient air.
Keywords: Polycyclic aromatic hydrocarbons; Nitrated PAH; Oxygenated PAH; Benzo[a]pyrene; Reactivity; Aerosol;

Biodiesel derived from waste cooking oil (WCO) is gaining increased attention as an alternative fuel due to lower particulate emissions and other beneficial factors such as low cost and utilization of waste oil. However, very little information is available on toxicity of airborne particulate matter (PM) emitted from biodiesel combustion. In this study, PM emitted from WCO-derived biodiesel (B100) was analyzed for its toxic potential together with ultra low sulphur diesel (ULSD) as a reference fuel and their blend (B50). Human lung epithelial carcinoma cells (A549) were used for this comparative toxicity study. Results indicate that cytotoxicity and oxidative stress were higher for B100 relative to ULSD. Furthermore, caspase 3/7 activity indicates that cell death induced by B100 was due to either caspase independent apoptotic process or other programmed cell death pathways. The toxicity was also evaluated for different engine load conditions. It was observed that at lower loads there was no significant difference in the toxicological response of B100 and ULSD. However, with increase in the engine load, B100 and B50 showed significantly higher toxicity and oxidative stress compared to ULSD.► In vitro cytotoxicity of diesel and biodiesel exhaust were evaluated using A549 cells. ► Waste cooling oil-derived biodiesel showed higher toxicity and oxidative stress compared to diesel. ► Particulate-bound metals appear to play a key role in cytotoxic effects of particulate emissions.
Keywords: Ultra low sulphur diesel; Waste cooking oil biodiesel; Cytotoxicity; Oxidative stress; A549 cells;

Daily average air concentrations of ammonia plus particulate ammonium, nitric acid plus particulate nitrate, sulphur dioxide and particulate sulphate have been measured at four EMEP (European Monitoring and Evaluation Programme) sites in Sweden since 1986. From 1993 sampling was made with a filter pack that separates the gaseous and particulate forms. The separation is not perfect, but fairly good when compared to a denuder. The same filter pack was used for monthly measurements at four high altitude sites in the Swedish mountain areas. The concentration of particulate ammonium decreases more rapidly than the ammonia emissions in Sweden and neighbouring countries while the ammonia concentration increases. Particulate ammonium is mainly long-range transported from the continent to the southern parts of Sweden, while gaseous ammonia comes from all directions. The particulate ammonium concentrations are charged balanced with particulate sulphate and nitrate concentrations and the long-range transport is therefore limited by the availability of these anions.► Ammonia cannot be long-range transported in gas phase. ► Long-range atmospheric transport of reduced nitrogen is limited by particulate acids. ► Particulate ammonium is charged balanced by non-marine sulphate and nitrate. ► Ammonia concentrations increase when particulate ammonium concentrations go down.
Keywords: Long-range transport; Time trend; Ammonia; Ammonium sulphate;

Ozonation of isoproturon adsorbed on silica particles under atmospheric conditions by Maryline Pflieger; Irena Grgić; Zoran Kitanovski (40-47).
The results on heterogeneous ozonation of a phenylurea pesticide, isoproturon, under atmospheric conditions are presented for the first time in the present study. The study was carried out using an experimental device previously adopted and validated for the heterogeneous reactivity of organics toward ozone (Pflieger et al., 2011). Isoproturon was adsorbed on silica particles via a liquid-to-solid equilibrium with a load far below a monolayer (0.02% by weight/surface coverage of 0.5%). The rate constants were estimated by measuring the consumption of the organic (dark, T = 26 °C, RH < 1%). The experimental data were fitted by both the modified Langmuir–Hinshelwood and the Eley–Rideal patterns, resulting in atmospheric lifetimes of heterogeneous ozonation of 4 and 6 days, respectively (for 40 ppb of O3). Parameters, such as the number and the quantity of pesticides adsorbed on the solid support, which can significantly influence the heterogeneous kinetics, were investigated as well. The results obtained suggest that the organic compound is adsorbed in multilayer aggregates on the aerosol even though submonolayer coverage is assumed. The presence of a second herbicide, trifluralin, together with isoproturon on the aerosol surface does not affect the kinetics of ozonation, indicating that both compounds are adsorbed on different surface sites of silica particles.► Little is known about the atmospheric heterogeneous processes of pesticides. ► Heterogeneous ozonation kinetics is faster for lower surface coverage. ► Isoproturon very likely adsorbs on the solid support in isolated aggregates. ► Trifluralin is about 20–25-times less reactive to ozone than isoproturon. ► The lifetime of isoproturon in particulate phase is ca. one week regarding ozone.
Keywords: Heterogeneous reactivity; Ozone; Pesticides; Semi-volatile organic compounds; Trifluralin; Isoproturon;

Effects of building roof greening on air quality in street canyons by Jong-Jin Baik; Kyung-Hwan Kwak; Seung-Bu Park; Young-Hee Ryu (48-55).
Building roof greening is a successful strategy for improving urban thermal environment. It is of theoretical interest and practical importance to study the effects of building roof greening on urban air quality in a systematic and quantitative way. In this study, we examine the effects of building roof greening on air quality in street canyons using a computational fluid dynamics (CFD) model that includes the thermodynamic energy equation and the transport equation of passive, non-reactive pollutants. For simplicity, building roof greening is represented by specified cooling. Results for a simple building configuration with a street canyon aspect ratio of one show that the cool air produced due to building roof greening flows into the street canyon, giving rise to strengthened street canyon flow. The strengthened street canyon flow enhances pollutant dispersion near the road, which decreases pollutant concentration there. Thus, building roof greening improves air quality near the road. The degree of air quality improvement near the road increases as the cooling intensity increases. In the middle region of the street canyon, the air quality can worsen when the cooling intensity is not too strong. Results for a real urban morphology also show that building roof greening improves air quality near roads. The degree of air quality improvement near roads due to building roof greening depends on the ambient wind direction. These findings provide a theoretical foundation for constructing green roofs for the purpose of improving air quality near roads or at a pedestrian level as well as urban thermal environment. Further studies using a CFD model coupled with a photochemistry model and a surface energy balance model are required to evaluate the effects of building roof greening on air quality in street canyons in a more realistic framework.► Building roof greening effects on air quality in street canyons are examined. ► Building roof greening is represented by specified cooling. ► Building roof greening improves near-road air quality. ► The degree of near-road air quality improvement increases as the cooling is strong. ► The degree of near-road air quality improvement depends on ambient wind direction.
Keywords: Building roof greening; Cooling; Air quality; Street canyon; CFD model;

Hourly mean dust concentration observations and meteorological measurements obtained from a sandstorm monitoring station in Horqin Sandy Land area in China from December 2010 to November 2011 were used to investigate the seasonal variations in dust concentration and dust emission flux as well as their relationship with meteorological parameters and soil condition. Based on 14 local dust emission events in spring 2011, the friction velocity (u *) and free convective velocity (w *) were calculated, and their correlation with dust emission flux was used to evaluate the dynamic and thermal impact on dust emission by turbulence. Results indicated that dust events occur in every season with peak dust activity in spring. The maximum dust concentration is 1654.1 μg m−3 and dust emission flux is 98.4 μg m−2 s−1. Freezing of soil in winter effectively decreases soil erodibility and suppresses dust emission. However, soil moisture does not show a significant impact on dust emission in this semi-arid Horqin Sandy Land area. Both friction velocity and free convective velocity could reflect the trend in dust emission flux, but both with obvious underestimation. The thermal impact on dust emission by turbulence is found to be far less than its dynamic impact.► Seasonal variations in dust concentration and dust emission flux. ► Effects of meteorological and soil conditions on dust emission. ► Evaluation on dynamic and thermal impact of turbulence on dust emission flux.
Keywords: Horqin Sandy Land area; Dust concentration; Dust emission flux; Friction velocity; Free convective velocity;

Regional scale atmospheric dispersion simulation of accidental releases of radionuclides from Fukushima Dai-ichi reactor by C.V. Srinivas; R. Venkatesan; R. Baskaran; V. Rajagopal; B. Venkatraman (66-84).
This paper presents the results of regional scale atmospheric dispersion simulation of accidental emission of radionuclides from the Fukushima Daiichi Reactor, Japan following the Tohoku earthquake and tsunami event on 11 March 2011. The objective was to study the temporal behaviour of plume trajectory, concentration, deposition and radiation dose pattern over an 80 km range around the reactor. The time-varying meteorological parameters during the release period were simulated with a multi-scale nested atmospheric model WRF ARW and the trajectory, plume dispersion were computed with Lagrangian Particle Dispersion models HYSPLIT, FLEXPART using the available information on accidental source term. The simulations indicated that the wind flow over Japan during the release period was driven by the large scale extra-tropical westerly waves and associated low pressure systems. In the lower levels, the flow was influenced by the local topography/sea breeze causing occasional landward wind shift on the east coast of Japan. Simulated airflow trajectories revealed that the plume stayed over the ocean by westerly winds on most days and the radioactivity dispersed over sea surface. Landward trajectories were found on a few days due to southeasterly, easterly and northeasterly flow (15–17, 19–21 March 2011) during which much of the radionuclides deposited over the land region. The hotspot of depositions occurred over east Pacific Ocean near to Japan. Over the land relatively high depositions were simulated in a narrow zone of 20 km width and 80 km length in the northwest sector in agreement with monitor data. Simulations showed wet depositions over the land to be higher than the dry depositions during 12–30 March due to occurrence of rainfall on some days. Comparison of activity deposition and air dose values with available observations confirmed that the plume pattern in a finer length scale around the site could be simulated realistically and agree with the measurements within the limitations of the uncertainty in source term.► Regional scale dispersion of accidental releases from Fukushima Reactor simulated. ► Flow trajectories were mainly westerly with radioactivity dispersed over sea. ► Mesoscale easterly/southeastery flow was simulated on 15–17, 19–21 March'11. ► Plume shift on 15–21 Mach caused deposition of radionuclides over the land region. ► A narrow 80 km high deposition zone simulated in northwest in agreement with data.
Keywords: Atmospheric dispersion; Regional scale; Fukushima accident;

Comparison between atmospheric chemistry model and observations utilizing the RAQMS–CMAQ linkage by Daegyun Lee; Jingqian Wang; Xun Jiang; Yongmi Lee; Keewon Jang (85-93).
EPA's Community Multiscale Air Quality (CMAQ) model was used to investigate the influence of lateral boundary conditions (LBCs) on ozone simulation. Meteorological fields used to drive the model were from the fifth generation Mesoscale Model (MM5). Emission files were prepared from the Sparse Matrix Operating Kernel for Emissions (SMOKE) model. Realtime Air Quality Modeling System (RAQMS) model with assimilated satellite observations were used as the LBCs for the CMAQ. CMAQ simulations with RAQMS LBCs and predefined LBCs were compared with INTEX Ozonesonde Network Study (IONS) ozonesonde data and Ozone Monitoring Instrument (OMI) satellite measurements. CMAQ forced with RAQMS LBCs could reasonably reproduce the vertical profiles of ozone mixing ratio. It was revealed that the influence of LBCs on ozone simulations is significant in the upper troposphere, moderate in the middle troposphere, and small in the lower troposphere. CMAQ model outputs provided a unique opportunity to evaluate the quality of the current air quality model and would help mission designers to better design future mission.► Updated RAQMS–CMAQ linking tool by adding the CMAQ aerosol modules (AERO3 & AERO4). ► Included additional gas phase species from RAQMS to RAQMS–CMAQ. ► Investigated the impacts of the lateral boundary condition on CMAQ simulations. ► Characterized the model results by comparing with in-situ measurements at Moody Tower. ► Used the improved dynamic boundary conditions to discuss the improvement of ozone simulation.
Keywords: CMAQ; Ozone simulation; Lateral boundary conditions;

Atmospheric particulate mercury: Concentrations and size distributions by Pyung-Rae Kim; Young-Ji Han; Thomas M. Holsen; Seung-Muk Yi (94-102).
In this study, the size distributions of atmospheric particulate mercury (PHg) were measured in both urban and rural areas during the summer, fall, and winter. Both PHg concentrations and the contribution of PHg to total PM aerosol were higher at the urban (PHg = 6.8 ± 6.5 pg m−3, PHg/total PM = 0.18 pg μg−1) than at the rural site (PHg = 4.6 ± 2.7 pg m−3, PHg/total PM = 0.06 pg μg−1). Based on size-distribution measurements, the fine mode was the dominant size at both sites in winter while the coarse mode became more important during summer. In winter PHg concentrations in the fine mode increased because of the effective adsorption of gaseous Hg onto the fine particles at the low temperature and increased Hg oxidation reactions in the presence of high particles concentrations. During winter elevated concentrations of total PHg were measured when the prevailing winds were northwesterly originating in China.► Size distributions of atmospheric particulate Hg (PHg) were measured in urban and rural areas. ► The size distribution of PHg was frequently observed to be uni-modal. ► The fine mode was dominant in winter while the coarse mode became important in summer. ► PHg in fine mode increased due to the partitioning of gaseous Hg onto the fine particles in winter.
Keywords: Particulate mercury; Size distribution; Urban; Rural; Oxidation;

Analysis of the spatial correlation of ozone mixing ratio in the vertical provides information useful for several purposes: (a) it aids description of the degree of regionality of the ozone transport-transformation processes, (b) the information provided in the form of a priori covariance matrices for remote retrieval algorithms can simplify and sharpen accuracy of the resulting estimates, and most importantly, (c) it allows a first evaluation of the improvement that remote retrievals can give over boundary-layer climatology. Vertical profiles of mean, variance, and vertical autocovariance, and vertical autocorrelation of ozone mixing ratios were estimated and given parameterizations. The WOUDC ozonesonde network database was used. During the years 2004–2006, these were considerably augmented by sondes taken by NASA, NOAA, and Canadian agencies during recent summertime intensive periods in North America. There are large differences across the North American continent in the patterns and magnitudes of correlation, especially in the lowest 2–3 km of the troposphere. This is especially significant for the near-surface layers (100's of meters deep) which determine actual surface O3 smog exposure and phytotoxicity, since satellite retrievals typically characterize at best a thick layer extending 3 km or more from the surface. The relative variation of O3 decreases in the vertical, particularly for the somewhat polluted launch stations, and this affects inference of surface O3 significantly. We outline a simple synthesis of mixed-layer and ozone-chemistry behavior to aid discussion of this and similar phenomena. Regional differences suggest broad if qualitative explanations in terms of larger-scale (interstate-transport) and local-scale phenomena (lake and sea breezes, degree/frequency of subsidence), inviting future study. The character of near-surface-to-full-layer covariance suggests that remote retrieval can describe surface ozone surprisingly well using 0–3 km partial-column ozone… for many situations. This indicates that there is substantial utility for new remote-retrieval methods that exploit ozone absorption in multiple wavelength regions, e.g., UV + Vis, UV + IR, or UV + Vis + IR. In summary, we find considerable value in interpreting retrievable O3 columns to estimate O3 quantities that are closely relevant to air pollution mitigation.► We parametrize vertical autocorrelations and covariances structure of N American O3. ► Covariances define a mapping from the remotely retrievable to the pollution-relevant. ► Sources and mixing processes explain lower-troposphere O3 variability. ► Near-surface ozone mapscan be inferred from 0 to 3 km averages. ► New satellite remote-retrieval instruments can map near-surface ozone.
Keywords: Remote retrieval; Smog ozone; Surface ozone; Statistical structure of atmosphere; Ozonesonde; Boundary layer structure; Pollution layering;

The growth of commercial aviation has fueled concerns over air quality around airports and the surrounding communities. Airports must expand their operations to meet the increase in air traffic, but expansion plans have been delayed or canceled due to concerns over local air quality. This paper presents the methodology for real-time measurements of aircraft engine specific Particulate Matter (PM) emissions and analysis of the associated high resolution data acquired during normal Landing and Take-Off (LTO) operations 100–300 m downwind of an active taxi-/runway at the Oakland International Airport. The airframe–engine combinations studied included B737-300 with CFM56-3B engines, B737-700/800 with CFM56-7B engines, A320 with V2500-A5 engines, MD-80 with JT-8D engines, A300 with CF6-80 engines, DC-10 with CF6-50 engines, and CRJ-100/200 with CF34-3B engines. For all engine types studied, the size distributions were typically bimodal in nature with a nucleation mode comprised of freshly nucleated PM and an accumulation mode comprised mostly of PM soot with some condensed volatile material. The PM number-based emission index observed ranged between 7 × 1015–3 × 1017 particles kg−1 fuel burned at idle/taxi and between 4 × 1015–2 × 1017 particles kg−1 fuel burned at take-off, and the associated PM mass-based emission index (EIm) ranged between 0.1 and 0.7 g kg−1 fuel burned at both the idle/taxi and take-off conditions. Older technology engines such as the CFM56-3B and JT8D engines were observed to have as much as 3× higher PM EIm values at take-off compared to newer engine technology such as the CFM56-7B engine. The results from this study provide information for better characterizing evolving PM emissions from in-service commercial aircraft under normal LTO operations and assessing their impact on local and regional air quality and health related impacts.► Real-time measurements of aircraft engine specific Particulate Matter emissions. ► At idle, number-based emission index was 7 × 1015–3 × 1017 particles kg−1 fuel burned. ► At takeoff, number-based emission index was 4 × 1015–2 × 1017 particles kg−1 fuel burned. ► Mass-based emission index was between 0.1 and 0.7 g kg−1 fuel burned at idle and takeoff. ► Mass-based emissions for older technology engines were 3× higher at takeoff.
Keywords: Aircraft engine PM emissions; Oakland International Airport; Advected plumes; LTO cycle; Emission index;

Regulatory and scientific applications of photochemical models are typically evaluated by comparing model estimates to measured values. It is important to compare quantitative model performance metrics to a benchmark or other studies to provide confidence in the modeling results. Since strict model performance guidelines may not be appropriate for many applications, model evaluations presented in recent literature have been compiled to provide a general assessment of model performance over a broad range of modeling systems, modeling periods, intended use, and spatial scales. Operational model performance is compiled for ozone, total PM2.5, speciated PM2.5, and wet deposition of sulfate, nitrate, ammonium, and mercury. The common features of the model performance compiled from literature are photochemical models that have been applied over the United States or Canada and use modeling platforms intended to generally support research, regulatory or forecasting applications. A total of 69 peer-reviewed articles which include operational model evaluations and were published between 2006 and March 2012 are compiled to summarize typical model performance. The range of reported performance is presented in graphical and tabular form to provide context for operational performance evaluation of future photochemical model applications. In addition, recommendations are provided regarding which performance metrics are most useful for comparing model applications and the best approaches to match model estimates and observations in time and space for the purposes of metric aggregations.► Compilation of operational air-quality model evaluations published from 2006 to 2012. ► Model performance summarized for ozone and PM2.5. ► Model performance also shown for wet deposition of sulfate, nitrate, ammonium, and Hg. ► Benefits of common performance metrics are discussed and evaluated. ► Recommendations given on how to perform evaluations for regulatory applications.
Keywords: Model performance evaluation; CMAQ; CAMx; Particulate matter; Ozone; Wet deposition; Operational evaluation; PM2.5; Mercury;

► XRF is used to analyze Si and Al concentrations in ambient PM2.5 filter samples. ► Pure ammonium sulfate fine particles are added to the ambient filters. ► Si masses from XRF re-analysis are systematically higher. Al has large changes. ► Implication: IMPROVE Si and Al values have large uncertainties when S/Fe is high. ► Impacts 50% of IMPROVE data from 2002 to 2010.
Keywords: X-ray fluorescence; Spectral interference; S; Si; Al; Interagency Monitoring of PROtected Visual Environments;

The emissions of greenhouse gases (GHGs) and air pollutants from aircraft in the boundary layer at four major international airports in Korea over a two-year period (2009–2010) were estimated using the Emissions and Dispersion Modeling System (EDMS) (i.e. activity-based (Landing/Take-Off (LTO) cycle) methodology). Both domestic and international LTOs and ground support equipment at the airports were considered. The average annual emissions of GHGs (CO2, N2O, CH4 and H2O) at all four airports during the study period were 1.11 × 103, 1.76 × 10−2, −1.85 × 10−3 and 3.84 × 108 kt yr−1, respectively. The emissions of air pollutants (NO x , CO, VOCs and particulate matter) were 5.20, 4.12, 7.46 × 10−1 and 3.37 × 10−2 kt yr−1, respectively. The negative CH4 emission indicates the consumption of atmospheric CH4 in the engine. The monthly and daily emissions of GHGs and air pollutants showed no significant variations at all airports examined. The emissions of GHGs and air pollutants for each aircraft operational mode differed considerably, with the largest emission observed in taxi-out mode.► We calculated the emissions of GHGs and air pollutants at 4 international airports. ► The aircraft emissions in the boundary layer were estimated by a LTO based method. ► The largest emission mode of GHGs was estimated to be taxi-out mode. ► The monthly and daily emissions of GHGs and air pollutants showed no significant variations.
Keywords: Aircraft; Airport; Greenhouse gas; Air pollutants; Emission; EDMS;

Assessing spatial and temporal variability of VOCs and PM-components in outdoor air during the Detroit Exposure and Aerosol Research Study (DEARS) by Sarah D. Bereznicki; Jon R. Sobus; Alan F. Vette; Matthew A. Stiegel; Ron W. Williams (159-168).
Exposure models for air pollutants often adjust for effects of the physical environment (e.g., season, urban vs. rural populations) in order to improve exposure and risk predictions. Yet attempts are seldom made to attribute variability in observed outdoor air measurements to specific environmental variables. This research presents a statistical strategy to identify and explain the spatial and temporal components of air pollutant measurement variance using regional predictors and large-scale (with impacts over multiple kilometers of distance) emission source effects. The emission sources considered in this investigation include major highways and industries, and were chosen based on their proximity to monitoring areas designated in the Detroit Exposure and Aerosol Research Study (DEARS). Linear mixed effects models were used to investigate 24-h averaged outdoor residential air measurements of several pollutants, including PM2.5 mass, PM components (elemental carbon, organic carbon, metals, elements), nitrogen dioxide, and volatile organic compounds (VOCs). Three hierarchal statistical models were utilized to calculate and examine variance component estimates for each analyte before and after adjustment for fixed effects, which included sampling season, day of the week, air concentrations at an ambient (centralized) monitoring site, and the frequency of time a receptor was downwind of specific large-emissions sources. Results indicate that temporal variability accounted for the majority of total measurement variance (90% on average). Adjustments for ambient concentration and sampling season significantly reduced temporal variance estimates for most VOCs and for about half of the PM components (generally with reductions of 24–97%). Major exceptions to this trend were found with metals (Fe, Mn, and Zn), ethyltoluene, and p-dichlorobenzene, where only 4–30% of the temporal variance was explained after the same adjustments. Additional reductions in temporal variance (up to 37%) were observed after adjusting for the large-emission sources and day of the week effects, with the strongest effects observed for PM components, including select metals. Thus, for the Detroit airshed, VOCs appear to have been largely affected by regional factors, whereas PM components were explained by both regional factors and localized large-emissions sources. Examination of the radial directions associated with suspected emission sources generally supported a priori expectations of source–analyte associations (e.g., NO2 increases from areas of high vehicle traffic). Overall, this investigation presents a statistical multi-pollutant analysis strategy that is useful for simultaneously (1) estimating spatial and temporal variance components of outdoor air pollutant measurements, (2) estimating the effects of regional variables on pollutant levels, and (3) identifying likely emissions sources that may affect outdoor air levels of individual or co-occurring pollutants.► Linear mixed models can be used to identify influences to measurement variance. ► Variance observed for VOCs is largely explained by seasonal and regional effects. ► Effects on variance from large-emission sources are limited to some PM components. ► Central sites do not show the spatial/temporal trends of PM components in Detroit.
Keywords: DEARS; Elements; VOCs; Spatial variability; Temporal variability; Mixed models;

Climatic isotope signals in tree rings masked by air pollution: A case study conducted along the Mont Blanc Tunnel access road (Western Alps, Italy) by Giovanni Leonelli; Giovanna Battipaglia; Rolf T.W. Siegwolf; Matthias Saurer; Umberto Morra di Cella; Paolo Cherubini; Manuela Pelfini (169-179).
Three sites at about 1400 m a.s.l., were chosen for this study along the Mt. Blanc Motorway in Italy. Chronologies of stable isotope ratios (δ13C, δ18O, δ15N), total N concentration and ring width of Larix decidua Mill. were analyzed to observe changes in growth and climatic signals in tree rings after significant changes in air pollution emissions occurred locally over time. The tunnel opened in 1968 and was closed for three years from March 1999 to March 2002. The obtained series from the three sites (Close = C, High = H and Far = F from the highway) for the analyzed periods, 1950–1970 (only sites H and F) and 1985–2008 (all sites), did not show any particular long-term change except site H that showed significant changes in δ18O (enrichment), δ15N (depletion) and total N (increase). δ13C values at site C were enriched in the first year of the tunnel closure (1999), showing an opposite trend in δ13C at site C, in comparison to the two control sites H and F, which cannot be explained by climatic factors. Since no great differences in δ18O were recorded in 1999, this enrichment in δ13C could be related to an enhancement in photosynthetic rate during periods of low air pollution loads. Opposite to δ15N, total N concentration shows a generally good correlation between sites, and site F was measured as the most N enriched. In a correlation analysis performed on the two study periods between the climatic parameters and ring width, we did not find any clear relationships, whereas for the series of stable isotopes and total N, we found the strongest and most significant relationships only between δ13C and summer (June to August) temperature (positive correlations) and precipitation (negative correlations) at sites H and F. These same relationships at site C were, instead, mostly insignificant, indicating an alteration of the climatic signal recorded in the δ13C chronology, caused by direct exposure to the high level of air pollution at this site. Given that site C is more affected by pollution with respect to the other two sites (whereas the same climatic conditions influence tree growth at all sites), the lack of a climatic signal in the δ13C chronology at this site can be ascribed to air pollution. Few other long-term changes were recorded by tree rings (e.g. at site H), indicating that trees probably record better the pollution events or the worsening of the environmental conditions rather than a lack of pollution for a relatively short time period in a polluted environment.► Influence of air pollution on the climatic signal recorded in the δ13C chronologies. ► Air pollution loads strongly influence the photosynthetic process. ► Significant long-term changes in δ18O, δ15N and total N concentration. ► Trees respond to pollution events but less to the lack of pollution for short times.
Keywords: Tree rings; Climate signal; Air pollution; Stable isotopes; 13Carbon; 18Oxygen; 15Nitrogen; Mont Blanc Tunnel; Western Italian Alps;

Between 2000 and 2008, columnar optical and radiative properties were measured at the Plymouth Marine Laboratory (PML), UK (50° 21.95′N, 4° 8.85′W) using an automatic Prede POM01L sun–sky photometer. The database was analyzed for aerosol optical properties using the SKYRAD radiative inversion algorithm and calibrated using the in situ SKYIL calibration method. Retrievals include aerosol optical depth, Ångström wavelength exponent, aerosol volume distribution, refractive index and single scattering albedo. The results show that the Plymouth site is characterized by low values of aerosol optical depth with low variability (0.18 ± 0.08 at 500 nm) and a mean annual Ångström exponent of 1.03 ± 0.21. The annual mean of the single scattering albedo is 0.97, indicative of non-absorbing aerosols. The aerosol properties were classified in terms of air mass back trajectories: the area is mainly affected by Atlantic air masses and the dominant aerosol type is a mixture of maritime particles, present in low burdens with variable size. The maritime air masses were defined by annual mean values for the AOD (at 500 nm) of 0.13–0.14 and a wavelength exponent of 0.96–1.03. Episodic anthropogenic and mineral dust intrusions occasionally occur, but they are sporadic and dilute (AOD at 500 nm about 0.20). Tropical continental air masses were characterized by the highest AOD at 500 nm (0.34) and the lowest wavelength exponent (0.83), although they were the least represented in the analysis.► An 8 year aerosol climatology is presented for a northeastern Atlantic site. ► A new calibration and processing software has been used. ► The region is characterized by low aerosol optical depth and low variability. ► The aerosol properties have been classified in terms of the air mass types. ► The main aerosol is a mixture dominated by maritime particles with low concentration.
Keywords: Marine aerosols; AOD; Prede POM; ESR; SKYNET; Skyradiometer;

Field experimental study of traffic-induced turbulence on highways by A. Alonso-Estébanez; P. Pascual-Muñoz; C. Yagüe; R. Laina; D. Castro-Fresno (189-196).
This paper is focused on traffic-induced turbulence (TIT) analysis from a field campaign performed in 2011, using ultrasonic anemometers deployed in the M-12 Highways, Madrid (Spain). The study attempts to improve knowledge about the influence of traffic-related parameters on turbulence. Linear relationships between vehicle speed and turbulent kinetic energy (TKE) values are found with coefficients of determination (R 2) of 0.75 and 0.55 for the lorry and van respectively. The vehicle-induced fluctuations in the wind components (u′, v′ and w′) showed the highest values for the longitudinal component (v) because of the wake-passing effect. In the analysis of wake produced by moving vehicles it is indicated how the turbulence dissipates in relation to a distance d and height h. The TKE values were found to be higher at the measuring points closer to the surface during the wake analysis.► Linear models between vehicle speed and TKE values are found for the lorry and van. ► The lorry induces higher TKE values than the van or the car. ► The longitudinal component exhibits the highest values of turbulence intensity. ► An increase of distance, d will diminish the TKE values. ► An increase of height, h will diminish the TKE values.
Keywords: Vehicle-induced turbulence; Parameterization; Highway turbulence; Turbulence intensity;

Inhaled particle counts on bicycle commute routes of low and high proximity to motorised traffic by Tom Cole-Hunter; Lidia Morawska; Ian Stewart; Rohan Jayaratne; Colin Solomon (197-203).
Frequent exposure to ultrafine particles (UFP) is associated with detrimental effects on cardiopulmonary function and health. UFP dose and therefore the associated health risk are a factor of exposure frequency, duration, and magnitude of (therefore also proximity to) a UFP emission source. Bicycle commuters using on-road routes during peak traffic times are sharing a microenvironment with high levels of motorised traffic, a major UFP emission source. Inhaled particle counts were measured on popular pre-identified bicycle commute route alterations of low (LOW) and high (HIGH) proximity to motorised traffic to the same inner-city destination at peak commute traffic times. During commute, real-time particle number concentration (PNC; mostly in the UFP range) and particle diameter (PD), heart rate, geographical location, and meteorological variables were measured. To determine inhaled particle counts, ventilation rate was calculated from heart-rate-ventilation associations, produced from periodic exercise testing. Total mean PNC of LOW, compared to HIGH, was reduced (1.56 × e4 ± 0.38 × e4 versus 3.06 × e4 ± 0.53 × e4 ppcc; p = 0.012). Total estimated ventilation rate did not differ significantly between LOW and HIGH (43 ± 5 versus 46 ± 9 L min−1; p = 0.136); however, due to total mean PNC, minute inhaled particle counts were 48% lower in LOW, compared to HIGH (6.71 × e8 ± 1.30 × e8 versus 14.08 × e8 ± 1.77 × e8 particles total; p = 0.003). For bicycle commuting at peak morning commute times, inhaled particle counts and therefore cardiopulmonary health risk may be substantially reduced by decreasing proximity to motorised traffic, which should be considered by both bicycle commuters and urban planners.► We identify popular bicycle commute routes of Brisbane, Australia. ► We assess particle number concentrations for popular bicycle commute routes. ► We calculate and compare inhaled particle count of routes from real-time data. ► Inhaled particle count is positively-associated with proximity to motorised traffic.
Keywords: Bicycle commuting; Motorised traffic; Ultrafine particles; Exposure concentration; Inhaled particle count;

Over 900 fine particle Teflon filters were collected within the Sydney Basin between 1 January 2001 and 31 December 2011 and analyzed using simultaneous PIXE, PIGE, RBS and PESA techniques to determine 21 different elements between hydrogen and lead. These elements were used in positive matrix factorization (PMF) and multi-linear engine (ME) techniques together with HYSPLIT wind back trajectory techniques to quantitatively determine source fingerprints and their contributions from coal-fired power stations. The power stations were many kilometers outside the greater Sydney metropolitan area but still had a significant impact on the fine particle mass loadings measured at the sampling site within this metropolitan area. The PM2.5 eleven year average mass at the sampling site was 6.48 μg m−3. The corresponding ammonium sulfate estimate was 1.65 μg m−3 or 26% of the PM2.5 mass. By applying back trajectory data and (ME) analysis methods, two power related fingerprints, secondary sulfate (2ndrySPower) and aged industrial sulfur (IndSagedPower) were determined. These two power related fingerprints were responsible for between 14 and 18% of the total PM2.5 mass and 34–47% of the total sulfate measured at the sampling site. That is on average somewhere between a third and a half of all the sulfate measured in the greater Sydney region could be attributed to coal-fired power station emissions.► IBA methods have characterized an 11 year fine particle pollution dataset. ► PMF, ME methods combined with back trajectory data identified coal-fired fingerprints. ► Quantitative fingerprints and their contributions have been determined. ► Coal-fired power stations contribute between 30 and 50% to the total fine sulfate mass.
Keywords: Ion beam analysis; Fine particles; PIXE; Factor analysis; HYSPLIT;

Emission estimates of organic and elemental carbon from household biomass fuel used over the Indo-Gangetic Plain (IGP), India by T. Saud; R. Gautam; T.K. Mandal; Ranu Gadi; D.P. Singh; S.K. Sharma; Manisha Dahiya; M. Saxena (212-220).
Biomass burning emits large amount of aerosols and trace gases into the atmosphere, which have significant impact on atmospheric chemistry and climate. In the present study, we have selected seven Indian states (Delhi, Punjab, Haryana, Uttar Pradesh, Uttarakhand, Bihar and West Bengal) over the IGP, India. Samples of biomass fuel (Fuel Wood, Crop Residue and Dung Cake) from rural household have been collected (Saud et al., 2011a). The burning process has been simulated using a dilution sampler following the methodology developed by Venkatraman et al. (2005). In the present study, emission factor represents the total period of burning including pyrolysis, flaming and smoldering. We have determined the emission factors of organic carbon (OC) and elemental carbon (EC) from different types of biomass fuels collected over the study area. Average emission factors of OC from dung cake, fuel wood and crop residue over IGP, India are estimated as 3.87 ± 1.09 g kg−1, 0.95 ± 0.27 g kg−1, 1.46 ± 0.73 g kg−1, respectively. Similarly, average emission factors of EC from dung cake, fuel wood and crop residue over IGP, India are found to be 0.49 ± 0.25 g kg−1, 0.35 ± 0.07 g kg−1 and 0.37 ± 0.14 g kg−1, respectively. Dung cake and crop residue are normally not used in Uttarakhand. Annual budget of OC and EC from biomass fuels used as energy in rural households of IGP, India is estimated as 361.96 ± 170.18 Gg and 56.44 ± 29.06 Gg respectively. This study shows the regional emission inventory from Indian scenario with spatial variability.► Determination of EF of OC and EC of residential fuels in the Laboratory. ► State wise EF of carbonaceous aerosol from residential fuels over IGP, India. ► Estimation of emission budget of OC and EC over seven states in IGP, India. ► Refinement of estimation of emission budget of OC and EC over India.
Keywords: Biomass; Indo-Gangetic Plain; Organic and elemental carbon; Emission factors; Budget estimation;

Estimation of radiative forcing by the dust and non-dust content in mixed East Asian pollution plumes on the basis of depolarization ratios measured with lidar by Young M. Noh; Detlef Müller; Hanlim Lee; KwonHo Lee; Kwanchul Kim; Sungkyun Shin; Young J. Kim (221-231).
The contribution of dust and non-dust aerosols to the lidar observed total backscattering was estimated from the linear particle depolarization ratios (δ p) under the assumption of externally mixed aerosols. During intensive observation period, the contribution rate of the non-dust aerosol optical depth (AOD, τ) to total AOD increased from 30% on 22 October to 82% on 30 October, which implies that large amount of non-dust particles was transported along with Asian dust storm. Using independent aerosol optics and profiles for dust and non-dust, for the first time, instantaneous aerosol direct radiative forcing (ADRF) of the Asian dust plumes on atmosphere-surface system was quantified. The average ADRF by the dust particles was −31.5 ± 16.1 (−66.3 ± 20.2) W m−2 at the surface, −16.5 ± 8.8 (−11.2 ± 9.2) W m−2 at the TOA, respectively. The forcing efficiency, defined as the aerosol forcing per unit τ (532 nm), for dust (non-dust) particles was −124.6 ± 12.2 (−209.4 ± 59.1) W m−2/τ 532 at the surface and −64.9 ± 7.8 (−35.1 ± 28.0) W m−2/τ 532 at the TOA, respectively. Though the contribution of non-dust optical depth to total τ was smaller than the contribution of optical depth from dust to total optical depth, the non-dust particles contributed larger to the radiative forcing at the surface than the dust radiative forcing. This result demonstrates that increased Asian dust radiative forcing can be largely attributed to the presence of non-dust particles mixed into Asian dust layers rather than the radiative forcing by pure dust particles. We also found that non-dust particles play a significant role in stabilizing the dust layer by increasing the radiative heating rates within dust layers.► We calculated the respective radiative forcing of dust and non-dust part of the Asian dust plumes. ► Vertically resolved optical properties of the aerosols derived by Lidar were used as inputs for RTM. ► The non-dust particles contributed larger to the radiative forcing at the surface than the dusts. ► Asian dust radiative forcing can be enhanced largely due to non-dust particles mixed into dust layer. ► Pollution particles play a key role in stabilizing the dust layer by increasing the heating rates.
Keywords: Radiative forcing; Depolarization ratios; Heating rate; Asian dust; Raman lidar;

Based on the requirement of the international conventions, there is a pressing need for inventory of NH3, CH4, CO2 and N2O emissions from livestock buildings. The main aim of this study was to quantify the gas emissions and investigate the influence of the climatic factors on ammonia emissions. The measurements were carried out in two naturally ventilated dairy cattle buildings with different layouts, floor types and manure management systems during three periods covering winter and summer time. Air temperature and the three dimensional air velocities inside and outside the buildings were recorded over the course of summer period. Emission rates were determined by CO2 production model.The results showed that the internal concentrations of NH3, CH4 and CO2 were increased or decreased simultaneously. Low concentration of N2O was measured outside and inside the buildings; the difference of the concentrations were also very low. The variation of CH4 and CO2 concentrations showed a strong correlation. The NH3 emission rates varied from 32 to 77 g HPU−1 d−1 in building 1 and varied from 18 to 30 g HPU−1 d−1 in building 2. The average emission of CH4 was 290 and 230 g HPU−1 d−1 from building 1 and 2, respectively. Diurnal pattern was found for NH3 and CH4 emission rates. From multiple linear regression models, there was a significant linear relationship between NH3 emission rates and climatic factors including the external wind speed as well as the air temperature (P < 0.001), but not with the external wind directions (P > 0.05).► Variation of internal concentrations of NH3, CH4 and CO2 followed the same trend. ► NH3 emission rates varied from 18 to 77 g HPU−1 d−1 for the two buildings. ► Diurnal pattern was found for NH3 and CH4 emission rates. ► A linear relationship existed between NH3 emission and wind speed (P < 0.001). ► A linear relationship was found between NH3 emission and air temperature (P < 0.001).
Keywords: Ammonia emission; Air exchange rate; Climatic factors; Dairy housing; CO2 production model;

Multi-pollutant exposures in an asthmatic cohort by Ron Williams; Ana G. Rappold; Martin Case; Mike Schmitt; Susan Stone; Paul Jones; Jonathan Thornburg; Robert B. Devlin (244-252).
An investigation of personal fine and coarse particulate matter (PM2.5, PM10–2.5), nitrogen dioxide (NO2), and ozone (O3) exposures was conducted with an adult asthmatic cohort as part of the U.S. Environmental Protection Agency's Moderate and Severe Asthmatics and their Environment Study (MASAES). The overall goal of the MASAES was to determine the association of particulate matter on the degree of resulting lung inflammation, with those having severe asthma hypothesized to be more highly susceptible to such outcomes. The primary exposure objective was to determine the spatial (personal versus ambient) and temporal relationships associated with the aforementioned air pollutants and establish the precision of a new dual PM2.5, PM10–2.5 monitor (CPEM) for personal exposure monitoring. A total of 16 non-smoking adults of various asthma severities were monitored over the course of a 14 month period during 2008–2009. Participants were monitored for 24 continuous hours each monitoring day with a maximum of five events per participant. Median personal PM2.5 and PM10–2.5 exposures were 16.5 and 10.1 μg m−3, respectively. Daily ambient mass concentrations accounted for less than 1% of the observed variability in personal PM2.5 or PM10–2.5 exposures. Duplicate personal measures yielded R 2 values of 0.92 PM2.5 and 0.77 PM10–2.5, respectively. Maximum daily personal exposures of 17.0 ppb NO2 and 21.7 ppb O3 occurred with respective mean exposures of 5.8 and 3.4 ppb. Ambient NO2 and O3 measures were observed to be poorly associated with personal exposures (R 2 < 0.08) when viewed independent of the participant. The poor correlation between personal and ambient concentrations of PM as well as the various gaseous copollutants indicates the complexity of the multi-pollutant environment and the impact of non-ambient sources on these pollutants relative to total personal exposures.► Exposure monitoring was conducted for a total of 16 non-smoking adults. ► Simultaneous collection of PM2.5 and PM10–2.5 size fractions was performed. ► Passive diffusion badges provided for ozone and nitrogen dioxide collections. ► Median respective personal PM2.5 and PM10–2.5 exposures were 16.5 and 10.1 μg m−3.
Keywords: Personal exposure; MASAES; Coarse particulate matter; Nitrogen dioxide; Ozone;

Mobile monitoring of particle number concentration and other traffic-related air pollutants in a near-highway neighborhood over the course of a year by Luz T. Padró-Martínez; Allison P. Patton; Jeffrey B. Trull; Wig Zamore; Doug Brugge; John L. Durant (253-264).
Accurate quantification of exposures to traffic-related air pollution in near-highway neighborhoods is challenging due to the high degree of spatial and temporal variation of pollutant levels. The objective of this study was to measure air pollutant levels in a near-highway urban area over a wide range of traffic and meteorological conditions using a mobile monitoring platform. The study was performed in a 2.3-km2 area in Somerville, Massachusetts (USA), near Interstate 93 (I-93), a highway that carries 150,000 vehicles per day. The mobile platform was equipped with rapid-response instruments and was driven repeatedly along a 15.4-km route on 55 days between September 2009 and August 2010. Monitoring was performed in 4–6-h shifts in the morning, afternoon, and evening on both weekdays and weekends in winter, spring, summer, and fall. Measurements were made of particle number concentration (PNC; 4–3000 nm), particle size distribution, fine particle mass (PM2.5), particle-bound polycyclic aromatic hydrocarbons (pPAH), black carbon (BC), carbon monoxide (CO), and nitrogen oxides (NO and NO x ). The highest pollutant concentrations were measured within 0–50 m of I-93 with distance-decay gradients varying depending on traffic and meteorology. The most pronounced variations were observed for PNC. Annual median PNC 0–50 m from I-93 was two-fold higher compared to the background area (>1 km from I-93). In general, PNC levels were highest in winter and lowest in summer and fall, higher on weekdays and Saturdays compared to Sundays, and higher during morning rush hour compared to later in the day. Similar spatial and temporal trends were observed for NO, CO and BC, but not for PM2.5. Spatial variations in PNC distance-decay gradients were non-uniform largely due to contributions from local street traffic. Hour-to-hour, day-to-day and season-to-season variations in PNC were of the same magnitude as spatial variations. Datasets containing fine-scale temporal and spatial variation of air pollution levels near highways may help to inform exposure assessment efforts.► Mobile monitoring was performed on 55 days throughout one year. ► Hourly, daily, and seasonal variations were observed. ► Distance-decay gradients were highly dependent on traffic and meteorology. ► Annual median PNC 0–50 m from the highway was two-fold higher than background. ► Temporal variations in PNC were similar to spatial variations.
Keywords: Traffic-related air pollution; Highway; Urban; Temporal variation; Spatial variation; Mobile monitoring;

Vehicular emissions are the major sources of air pollution in urban areas. For metropolitan cities with large population working and living in environments with direct traffic impact, emission control is of great significance to protect public health. Implementation of more stringent emission standards, retrofitting fleet with emission control devices and switching to clearer fuel has been commonly practiced in different cities including Hong Kong. The present study employed a new plume chasing method for effective and quick evaluation of on-road fleet emission factors of particulate matter (PM), nitrogen oxides (NO x ), and butane from heavy duty diesel trucks, diesel buses and liquefied petroleum gas (LPG) vehicles. The results showed distinct profiles of the emissions from different fleets with excessive butane emissions from LPG fleet and contrasting PM and NO x emissions from diesel trucks and buses fleets. A cross comparison was also made with emission data from other cities and from historic local studies. The implications of the observed difference on the effectiveness of emission control measures and policy are discussed with recommendations of direction for future research and policy making.► On-road vehicles fleet emission factors of PM, NO x and butane in Hong Kong. ► Emissions under real world driving conditions using plume chasing approach. ► Ion-Molecule Reaction-Mass Spectrometer measurement of butane emissions. ► Fleets variation of pollutants emissions and their control policies.
Keywords: On-road vehicle emissions; Plume chasing; Particulate matter (PM); Nitrogen oxides (NO x ); Butane;

Power-dependent speciation of volatile organic compounds in aircraft exhaust by Andreas J. Beyersdorf; K. Lee Thornhill; Edward L. Winstead; Luke D. Ziemba; Donald R. Blake; Michael T. Timko; Bruce E. Anderson (275-282).
As part of the third NASA Aircraft Particle Emissions Experiment (APEX-3, November 2005), whole air samples were collected to determine the emission rates of volatile organic compounds (VOCs) from aircraft equipped with three different gas-turbine engines (an Allison Engine 3007-A1E, a Pratt–Whitney 4158, and a Rolls–Royce RB211-535E4B). Samples were collected 1 m behind the engine exhaust plane of the engines while they were operated at powers ranging from idle up to 30% of maximum rated thrust.Exhaust emission indices (mass emitted per kilogram of fuel used) for CO and non-methane hydrocarbons (NMHCs) were calculated based on enhancements over background relative to CO2. Emissions of all NMHCs were greatest at low power with values decreasing by an order of magnitude with increasing power. Previous studies have shown that scaling idle hydrocarbon emissions to formaldehyde or ethene (which are typically emitted at a ratio of 1-to-1 at idle) reduces variability amongst engine types. NMHC emissions were found to scale at low power, with alkenes contributing over 50% of measured NMHCs. However, as the power increases hydrocarbon emissions no longer scale to ethene, as the aromatics become the dominant species emitted. This may be due in part to a shift in combustion processes from thermal cracking (producing predominantly alkenes) to production of new molecules (producing proportionally more aromatics) as power increases. The formation of these aromatics is an intermediate step in the production of soot, which also increases with increasing power. The increase in aromatics relative to alkenes additionally results in a decrease in the hydroxyl radical reactivity and ozone formation potential of aircraft exhaust.Samples collected 30 m downwind of the engine were also analyzed for NMHCs and carbonyl compounds (acetone, 2-butanone and C1–C9 aldehydes). Formaldehyde was the predominant carbonyl emitted; however, the ratio of ethene-to-formaldehyde varied between the aircraft, possibly due to the sampling of transient emissions such as engine start-up and power changes. A large portion of the measured emissions (27–42% by mass) in the plume samples was made up of hazardous air pollutants (HAPs) with oxygenated compounds being most significant.► At low power, scaling hydrocarbons to ethene reduces variability amongst engines. ► At high power, there is a difference in composition with aromatics dominating. ► At low power, thermal cracking dominates. ► At high power, aromatic species are formed via the HACA process in the exhaust. ► In downwind samples, HAPs make up a large portion of measured emissions (27–42%).
Keywords: Aircraft emissions; Turbine engine; Hydrocarbon emission indices; Oxygenated hydrocarbons;

Urban particulate pollution reduction by four species of green roof vegetation in a UK city by A.F. Speak; J.J. Rothwell; S.J. Lindley; C.L. Smith (283-293).
Urban particulate pollution in the UK remains at levels which have the potential to cause negative impacts on human health. There is a need, therefore, for mitigation strategies within cities, especially with regards to vehicular sources. The use of vegetation as a passive filter of urban air has been previously investigated, however green roof vegetation has not been specifically considered. The present study aims to quantify the effectiveness of four green roof species – creeping bentgrass (Agrostis stolonifera), red fescue (Festuca rubra), ribwort plantain (Plantago lanceolata) and sedum (Sedum album) – at capturing particulate matter smaller than 10 μm (PM10). Plants were grown in a location away from major road sources of PM10 and transplanted onto two roofs in Manchester city centre. One roof is adjacent to a major traffic source and one roof is characterised more by urban background inputs. Significant differences in metal containing PM10 capture were found between sites and between species. Site differences were explained by proximity to major sources. Species differences arise from differences in macro and micro morphology of the above surface biomass. The study finds that the grasses, A. stolonifera and F. rubra, are more effective than P. lanceolata and S. album at PM10 capture. Quantification of the annual PM10 removal potential was calculated under a maximum sedum green roof installation scenario for an area of the city centre, which totals 325 ha. Remediation of 2.3% (±0.1%) of 9.18 tonnes PM10 inputs for this area could be achieved under this scenario.► Green roofs act as passive filters of airbourne particulate matter. ► Species differences in particle capture efficiency were observed. ► Morphological reasons for differences in particle capture efficiency were posited. ► Spatial differences in leaf SIRM were observed in relation to PM10 sources. ► 0.24 tonnes of PM10 a year could be removed from Manchester city centre.
Keywords: PM10; Green roof; Sedum; Magnetic biomonitoring;

Inclusion of direct radiative forcing by mineral dust is important for accurate simulation of meteorological conditions, and planetary boundary-layer (PBL) parameterization plays a critical role in proper representation of such forcing. The direct radiative forcing of mineral dust and its feedback effects on boundary-layer dynamics are investigated using the Weather Research and Forecasting with Chemistry (WRF/Chem) model. Furthermore, this study examines the sensitivity of dust radiative effects associated with two different PBL schemes: the Yonsei University (YSU) scheme with both Noah and RUC (Rapid Update Cycle) land-surface models (LSMs), and the Mellor–Yamada–Janjic (MYJ) scheme. By reflecting and absorbing solar radiation, dust aerosols are predicted to cool the atmosphere from the surface to near the boundary-layer top, while warm the boundary-layer top and lower free atmosphere by absorbing both solar and infrared radiation. The simulated surface cooling and heating at the boundary-layer top stabilizes the lower atmosphere, causing a reduction of boundary-layer depth. The stabilized atmosphere restricts vertical exchange of momentum, resulting in an overall decrease of wind speeds in the lower boundary layer and an increase within the upper boundary layer and lower free atmosphere. Use of the YSU-RUC scheme resulted in larger dust feedback effects on atmospheric characteristics, while the MYJ scheme produced lower radiative feedback effects because of lower dust concentrations and reduced vertical mixing of dust. The differences in radiative forcing by dust in model runs are found to be mainly due to differences in PBL scheme, rather than the LSM used in the model.► Shortwave direct radiative forcing by dust aerosols is successfully modelled. ► Radiative forcing shown to be sensitive to boundary-layer and land surface schemes. ► Mineral dust cools and warms the lower and upper boundary layer, respectively. ► Suspended dust modifies boundary-layer profiles, stabilizing the lower atmosphere. ► Aerosols cause near-surface reduction of wind speed with increase aloft.
Keywords: Radiative forcing by dust; Boundary layer; PBL parameterization; Land-surface model (LSM); WRF/Chem;

Multi-season, multi-year concentrations and correlations amongst the BTEX group of VOCs in an urbanized industrial city by Lindsay Miller; Xiaohong Xu; Alice Grgicak-Mannion; Jeffrey Brook; Amanda Wheeler (305-315).
An air quality monitoring study focusing on spatial patterns was carried out in the urban industrial city of Windsor, Ontario, Canada (42.267°N, 82.95°W). This study took place over a three-year period (2004–2006), during all four seasons for a total of 12 two-week sampling periods (each with approximately 50 sites) at 162 sites across the city. Benzene, toluene, ethylbenzene, (m + p)-xylene, and o-xylene (BTEX) were measured using 3M #3500 Organic Vapor Samples (Guillevan, Montreal). Results from this investigation indicate that significant variability is present temporally (seasonally and annually) and spatially. The three-year mean concentrations in μg m−3 were: benzene (0.76), toluene (2.75), ethylbenzene (0.45), o-xylene (0.47), (m + p)-xylene (1.36), and total BTEX (5.64), with greater variability within each year compared with variability between the three years. Concentrations were highly correlated between most BTEX species, consistent with previous studies in urban areas. Toluene to benzene ratios were consistent between years, with the highest observed ratios occurring in summer, the lowest in winter, and fall and spring values falling in between. The range of ratios suggests that the majority of these two compounds originate from mobile emissions. (m + p)-Xylene to ethylbenzene ratios, used as indicators of photochemical age, showed a three-year mean of 3.0 with little spatial and temporal variability suggesting that relatively fresh and homogenous sources of these species are present in this area. The seasonal trends across the spatial network were representative of the seasonal patterns obtained at a long term monitoring station, with both methods indicating that fall and spring concentrations were preferred proxies of annual means. However, significant spatial variability of concentrations was observed. The upper range of concentrations compared with the values obtained at the central monitoring station differed by up to a factor of six, highlighting the importance of multiple sampling sites to reduce exposure misclassification. Significant correlations between seasons were observed in all three years, revealing a consistent rank order of high to low concentrations among the monitoring sites within a given year. Consideration of all analyses suggests that when resources are limited to a single sampling season, fall and spring mean values for concentrations and ratios seem to best represent the annual average in this city. Other study design consideration suggestions are also provided for future air quality research.► High density, multi-year, multi-season network to monitor VOC concentrations. ► Determination of annual variability of concentrations and correlations. ► Seasonal trends and identification of proxy seasons for annual exposure. ► Investigation of key ratios indicative of source origin and photochemical age. ► Spatial variability and misclassification associated with central monitoring.
Keywords: BTEX; VOCs; Air quality; Temporal variability; Spatial variability;

Comparison of three techniques for analysis of data from an Aerosol Time-of-Flight Mass Spectrometer by Chiara Giorio; Andrea Tapparo; Manuel Dall'Osto; Roy M. Harrison; David C.S. Beddows; Chiara Di Marco; Eiko Nemitz (316-326).
The Aerosol Time-of-Flight Mass Spectrometer (ATOFMS) is one of few instruments able to measure the size and mass spectra of individual airborne particles with high temporal resolution. Data analysis is challenging and in the present study, we apply three different techniques (PMF, ART-2a and K-means) to a regional ATOFMS dataset collected at Harwell, UK. For the first time, Positive Matrix Factorization (PMF) was directly applied to single particle mass spectra as opposed to clusters already generated by the other methods. The analysis was performed on a total of 56,898 single particle mass spectra allowing the extraction of 10 factors, their temporal trends and size distributions, named CNO–COOH (cyanide, oxidized organic nitrogen and carboxylic acids), SUL (sulphate), NH4-OOA (ammonium and oxidized organic aerosol), NaCl, EC+ (elemental carbon positive fragments), OC-Arom (aromatic organic carbon), EC− (elemental carbon negative fragments), K (potassium), NIT (nitrate) and OC–CHNO (organic nitrogen). The 10 factor solution from single particle PMF analysis explained 45% of variance of the total dataset, but the factors are well defined from a chemical point of view. Different EC and OC components were separated: fresh EC (factor EC−) from aged EC (factor EC+) and different organic families (factors NH4-OOA, OC-Arom, OC–CHNO and CNO–COOH). A comparison was conducted between PMF, K-means cluster analysis and the ART-2a artificial neural network. K-means and ART-2a give broadly overlapping results (with 9 clusters, each describing the full composition of a particle type), while PMF, by effecting spectral deconvolution, was able to extract and separate the different chemical species contributing to particles, but loses some information on internal mixing. Relationships were also examined between the estimated volumes of ATOFMS PMF factors and species concentrations measured independently by GRAEGOR and AMS instruments, showing generally moderate to strong correlations.► Comparison of three techniques for ATOFMS data analysis: PMF, K-means and Art-2a. ► PMF is applied, for the first time, to individual particle mass spectra. ► Efficient mass spectra deconvolution by single particle PMF analysis. ► Extraction of different organic families and two EC contributions. ► Results have been compared with independent measurements.
Keywords: Aerosol; ATOFMS; PMF; Single particle analysis; K-means; ART-2a;

► Distribution of air and particles is modelled by a two-phase flow Euler–Euler method. ► A new flow-oriented discretization scheme is employed. ► The convection terms in three directions (3D) are reformulated. ► The performance of the numerical scheme is tested in case of inclined flow. ► The new discretization scheme leads to a significant reduction of false diffusion.
Keywords: Computational fluid dynamics; Numerical scheme; Euler–Euler method; Air-particles flow; Indoor environment;

Particle pollution – An environmental magnetism study using biocollectors located in northern Portugal by Helena Sant'Ovaia; Maria João Lacerda; Celeste Gomes (340-349).
In this study the magnetic properties of tree leaves were measured in order to compare their capability to accumulate particles, to establish the relationship between magnetic properties and chemical data and to assess the particle pollution in selected locations in the cities of Braga, Porto, Valongo and Trancoso-Reboleiro, northern Portugal. In Porto, Braga and Valongo, leaves from the evergreen Nerium oleander were sampled each month during a year. N. oleander and deciduous Quercus spp. and Platanus spp. samples were collected in the same site in Porto, in order to determine the ability of these different leaves to accumulate particles. The leaves of deciduous Tilia spp. were collected in Porto and in a rural area (Trancoso-Reboleiro) so that a comparison could be established between them. The results indicated a contrast between the urban and the rural areas. The highest concentration of magnetic particles was found in the sampling site of Valongo and the lowest concentration in the sampling site of Trancoso-Reboleiro. In Porto, the results have shown that the Quercus leaves possessed the highest capability to accumulate particles even though it is a deciduous species. The IRM acquisition curves and the S-300 ratios found in the samples of the urban areas indicated the presence of magnetite-like structures. SIRM/χ ratio revealed particles whose dimensions ranged between 5 μm and 8 μm in urban areas. The chemical elements copper and iron have a significant positive correlation with χ and SIRM, which highlights the use of magnetic properties as a proxy for the concentration of these metals in atmospheric dust. The magnetic properties were interpreted taking into consideration the rainfall peaks and then compared with the PM10 concentration levels monitored in an air quality station in Porto. Our data corroborated that magnetic properties provide a fast and inexpensive tool to evaluate long-term urban pollution from anthropogenic origin, especially heavy traffic.► Magnetic properties were compared in leaves collected in rural and urban areas. ► In urban areas magnetite-like particles dimensions range between 1 and 9 μm. ► The magnetic particles are adsorbed by the leaf and deposited on its surface. ► Magnetic particles are due to heavy traffic. ► Leaves magnetic properties provide a tool to determine particle pollution.
Keywords: Environmental magnetism; Leaves; Magnetic parameters; Particulate matter;

Properties of aerosol signature size distributions in the urban environment as derived by cluster analysis by Tobias Wegner; Tareq Hussein; Kaarle Hämeri; Timo Vesala; Markku Kulmala; Stephan Weber (350-360).
A cluster analysis algorithm was applied to reduce the amount and complexity of 30 min aerosol number size distributions in a three year data set (2006–2008) at a urban background station in Helsinki, Finland. Only after objective validity tests to determine the appropriate number of clusters, a k-means cluster algorithm was applied to extract seven characteristic size distributions from the data set. The average total number concentrations of the clustered size distributions range from 6067 cm−3 to 12,818 cm−3 with modal diameters between 5 and 193 nm. The clustered size distributions were analyzed in terms of their physical properties (shape, log-normal modes, mode diameter), temporal occurrence (e.g. time of day, season) and their relation to local meteorology.Three different types of cluster distributions being represented by either three or two log-normal modes (in only one case) were characterized at the site: four clusters that were indicative for urban-type size distributions with different influence of anthropogenic and traffic activities occurring 69% of the study time, two maritime-type distributions (29% occurrence) and one nucleation-type size distribution (2% occurrence). We were able to relate the clusters to characteristic modal diameters, different temporal occurrence on the daily and annual cycle, e.g. urban clusters that occurred year round and those that were attributed to winter daytime situations specifically. Analysis of the daily patterns clearly reveals the influence of local traffic activity on three of the four urban-type cluster size distributions. The method offers the chance for a simple kind of source apportionment by establishing signature size distributions based on the physical properties of the aerosol size spectra.► Characteristic (signature) aerosol number size distributions have been extracted from a large data set. ► K-means cluster analysis was applied. ► The size distributions retain the main information of the large data set. ► Signature size distribution offer a simple way of source apportionment. ► The method can also be applied at other study sites.
Keywords: Particle; Meteorology; Cluster analysis; Signature size distribution; Source apportionment; Helsinki;

A semi-empirical, receptor-oriented Lagrangian model for simulating fine particulate carbon at rural sites by B.A. Schichtel; M.A. Rodriguez; M.G. Barna; K.A. Gebhart; M.L. Pitchford; W.C. Malm (361-370).
Total fine particulate carbon (TC) is an important contributor to fine particulate matter and is measured in routine national monitoring programs. TC contributes to adverse health effects, regional haze, and climate effects. To resolve these adverse effects, there is a need for tools capable of routine and climatological assessments and exploration of the sources contributing to the measured TC. To address this need, a receptor-oriented, Lagrangian particle dispersion model was developed to simulate TC in rural areas, using readily available meteorological and emission inputs. This model was based on the CAPITA (Center for Air Pollution Impact and Trend Analysis) Monte Carlo model (CMC) and simulated the contributions from eight source categories, including biomass burning and secondary organic carbon (SOC) from vegetation. TC removal and formation mechanisms are simulated using a simplified parameterization of atmospheric processes based on pseudo-first-order rate equations. The rate coefficients are empirical functions of meteorological parameters derived from measured, modeled, and literature data. These functions were optimized such that the simulated TC concentrations reproduce the average spatial and seasonal patterns in measured 2008 U.S. TC concentrations, as well as measured SOC fractions at two eastern U.S. sites. The optimized model was used to simulate 2006–2008 rural TC that was evaluated against measured TC. In addition, the model output was compared to TC from a 2006 Eulerian Community Multiscale Air Quality (CMAQ) simulation. It is shown that the CMC model has similar performance metrics as the CMAQ model.► We present a new semi-empirical Lagrangian particle dispersion model. ► The model is used to apportion PM2.5 carbon at rural locations to major source types. ► The results are evaluated against measured data and compared to CMAQ model results. ► The model is best used in the analysis of measured carbonaceous aerosols.
Keywords: Lagrangian particle dispersion model; Carbonaceous aerosols; Source apportionment; Biomass burning;

Daily samples of size-fractionated (18, 10, 2.5 and 1.0 μm) particulate-bound mercury Hg(p) were collected using Micro-Orifice Uniform Deposition Impactors (MOUDI), on randomly selected days each month between November 2010 and July 2011, at a traffic site (Hungkuang), a wetland site (Gaomei), and an industrial site (Quanxing) in central Taiwan. Bulk dry deposition was also collected simultaneously using a surrogate surface. The nine-month average (±standard deviation) Hg(p) concentrations were 0.57 (±0.90), 0.17 (±0.27), and 0.94 (±0.92) ng m−3 at Hungkuang, Gaomei, and Quanxing, respectively. Concentrations in November and December were much higher than in the other months due to a combination of high local emissions and meteorological conditions. PM1.0 contributed more than 50% to the bulk concentration at the traffic and the industrial sites, but only contributed 25% at the wetland site. PM1.0–2.5 contributed 25%–50%, depending on location, to the bulk mass. Coarse fraction (PM2.5–18) contributed 7% at Hungkuang, 25% at Gaomei, and 19% at Quanxing. Samples with very high bulk concentrations had large fine fractions. Annual dry deposition estimated from the surrogate surface measurements was in the range of 30–85 μg m−2 yr−1 at the three sites. Coarse particulate Hg(p) were estimated to contribute 50–85% of the total Hg(p) dry deposition. Daily dry deposition velocities (V d) ranged from 0.01 to 7.7 cm s−1. The annual V d generated from the total measured fluxes was 0.34, 0.60 and 0.29 cm s−1 at Hungkuang, Gaomei, and Quanxing, respectively. These values can be reasonably reproduced using a size-resolved model and measured size fractions.► Highest concentrations for ambient particulate mercury (Hg(p)) were observed in early winter. ► PM1.0 and PM1.0–2.5 dominated the bulk Hg(p) concentration. ► Coarse Hg(p) contributed 7–25% of the bulk Hg(p) concentration. ► Coarse Hg(p) contributed 50–85% of the total Hg(p) dry deposition. ► Dry deposition velocity of Hg(p) was mostly in the range of 0.1–0.8 cm s−1.
Keywords: Atmospheric mercury; Particle size distribution; Fine/coarse fraction; Surrogate surface measurements; Dry deposition; Deposition velocity; Central Taiwan;

On-road emission factors of PM pollutants for light-duty vehicles (LDVs) based on urban street driving conditions by Winnie Kam; James W. Liacos; James J. Schauer; Ralph J. Delfino; Constantinos Sioutas (378-386).
An on-road sampling campaign was conducted on two major surface streets (Wilshire and Sunset Boulevards) in Los Angeles, CA, to characterize PM components including metals, trace elements, and organic species for three PM size fractions (PM10 2.5, PM2.5 0.25, and PM0.25). Fuel-based emission factors (mass of pollutant per kg of fuel) were calculated to assess the emissions profile of a light-duty vehicle (LDV) traffic fleet characterized by stop-and-go driving conditions that are reflective of urban street driving. Emission factors for metals and trace elements were highest in PM10 2.5 while emission factors for PAHs and hopanes and steranes were highest in PM0.25. PM2.5 emission factors were also compared to previous freeway, roadway tunnel, and dynamometer studies based on an LDV fleet to determine how various environments and driving conditions may influence concentrations of PM components. The on-road sampling methodology deployed in the current study captured substantially higher levels of metals and trace elements associated with vehicular abrasion (Fe, Ca, Cu, and Ba) and crustal origins (Mg and Al) than previous LDV studies. The semi-volatile nature of PAHs resulted in higher levels of PAHs in the particulate phase for LDV tunnel studies (Phuleria et al., 2006) and lower levels of PAHs in the particulate phase for freeway studies (Ning et al., 2008). With the exception of a few high molecular weight PAHs, the current study's emission factors were in between the LDV tunnel and LDV freeway studies. In contrast, hopane and sterane emission factors were generally comparable between the current study, the LDV tunnel, and LDV freeway, as expected given the greater atmospheric stability of these organic compounds. Overall, the emission factors from the dynamometer studies for metals, trace elements, and organic species are lower than the current study. Lastly, n-alkanes (C19–C40) were quantified and alkane carbon preference indices (CPIs) were determined to be in the range of 1–2, indicating substantial anthropogenic source contribution for surface streets in Los Angeles.► An on-road PM sampling campaign was conducted on two major streets in Los Angeles. ► Emission factors for metals and trace elements were highest in PM10 2.5. ► Emission factors for organic species were highest in PM0.25. ► The on-road method captured higher PM levels from resuspension and abrasion than earlier roadway studies.
Keywords: On-road emissions; Particulate matter; Surface streets; Los Angeles; Metals; Trace elements; Organic species; Emission factors;

Ensemble-trained source apportionment of fine particulate matter and method uncertainty analysis by Sivaraman Balachandran; Jorge E. Pachon; Yongtao Hu; Dongho Lee; James A. Mulholland; Armistead G. Russell (387-394).
An ensemble-based approach is applied to better estimate source impacts on fine particulate matter (PM2.5) and quantify uncertainties in various source apportionment (SA) methods. The approach combines source impacts from applications of four individual SA methods: three receptor-based models and one chemical transport model (CTM). Receptor models used are the chemical mass balance methods CMB-LGO (Chemical Mass Balance-Lipschitz global optimizer) and CMB-MM (molecular markers) as well as a factor analytic method, Positive Matrix Factorization (PMF). The CTM used is the Community Multiscale Air Quality (CMAQ) model. New source impact estimates and uncertainties in these estimates are calculated in a two-step process. First, an ensemble average is calculated for each source category using results from applying the four individual SA methods. The root mean square error (RMSE) between each method with respect to the average is calculated for each source category; the RMSE is then taken to be the updated uncertainty for each individual SA method. Second, these new uncertainties are used to re-estimate ensemble source impacts and uncertainties. The approach is applied to data from daily PM2.5 measurements at the Atlanta, GA, Jefferson Street (JST) site in July 2001 and January 2002. The procedure provides updated uncertainties for the individual SA methods that are calculated in a consistent way across methods. Overall, the ensemble has lower relative uncertainties as compared to the individual SA methods. Calculated CMB-LGO uncertainties tend to decrease from initial estimates, while PMF and CMB-MM uncertainties increase. Estimated CMAQ source impact uncertainties are comparable to other SA methods for gasoline vehicles and SOC but are larger than other methods for other sources. In addition to providing improved estimates of source impact uncertainties, the ensemble estimates do not have unrealistic extremes as compared to individual SA methods and avoids zero impact days.► We ensemble averaged three receptor models and one chemical transport model. ► We develop a method to calculate new estimates of source impact uncertainties. ► The ensemble average had better performance measures than the individual methods. ► The ensemble has lower relative uncertainties as compared to the individual methods.
Keywords: PM2.5; Source apportionment; Ensemble; Health; Air quality;

Ammonia emissions from urea application to permanent pasture on a volcanic soil by F. Salazar; J. Martínez-Lagos; M. Alfaro; T. Misselbrook (395-399).
Agriculture is the largest source of ammonia (NH3) emission to the atmosphere, deriving mainly from livestock urine and manures, but fertilizer applications to pastures and crops also represent an important source. In Chile, where agriculture and cattle production are important activities (accounting for 4.5% of GDP along with the forestry sector), there are very few published data regarding NH3 emissions from pasture and crop fertilization. This study aimed to provide the first empirical field data for Chile on N losses due to NH3 volatilization following urea application to permanent pasture on a volcanic soil and to assess the influence of environmental conditions on emissions. Four field experiments were carried out on a volcanic acid soil using the micrometeorological integrated horizontal flux (IHF) mass balance method. Measurements were made in winter 2005 and 2007, and spring 2007 and 2008 following urea N fertilization to a permanent pasture at a rate equivalent to 100 kg N ha−1. Cumulative NH3 emissions over the measurement period were 1.4 and 7.7 kg N ha−1 for winter applications, and 12.2 and 26.7 kg N ha−1 for spring dressings. These N losses due to NH3 volatilization are within the range of emissions reported elsewhere. Consideration of urea application timing in Chile, with regards to weather and soil conditions, could have important consequences on minimising potential N losses via volatilization with associated financial benefits to farmers.
Keywords: Ammonia volatilization; Urea; Integrated horizontal flux;

The aim of this study is to interpret the variation of precipitation chemistry during the last 25 years in Montseny (NE Spain) by taking into account the main air mass transport routes and emission sources. To this end, trajectory cluster analysis and source–receptor models were applied to an early monitoring period (1984–1993) and compared to a more recent one (1998–2009). A decrease of Atlantic advections and increase of African and European air flows was found. Cluster analysis and source–receptor approaches showed that this region is under the influence of natural and anthropogenic sources from the local and long-range scale. Sulphate and H+ source areas extended over a vast stretch of central Europe in the early period, but were drastically reduced in the recent period, showing the effectiveness of pollution abatement measures for S. On the other hand, NO3 sources areas from central Europe strikingly increased. Ship emissions and industrialisation in Eastern Europe and North Africa seem to be acquiring a greater role in the recent period.► Precipitation SO4 2− and H+ decreased but NO3 increased (p < 0,05) at a NE Spain site. ► In 1984–1993 these pollutants were mostly originated in central and eastern Europe. ► Recently this shifted to marine traffic and eastern Europe and North Africa emissions.
Keywords: Mediterranean; Long-range transport; Precipitation; Back-trajectories; Cluster analysis; Source–receptor model;

Robustness of the aerosol weekly cycle over Southeastern China by Wenshan Wang; Daoyi Gong; Zhiyang Zhou; Yuanxi Guo (409-418).
A 7-day cycle is a special time-scale that corresponds with the weekly working schedule. However, there is no consensus on the existence of the weekly cycle of aerosol loading, which is closely related to human activities. In the present study, we analyzed the surface concentration of PM10 (Particulate Matter with a diameter of less than 10 μm) and other physically linked variables over Southeastern China under calm weather conditions to detect signs of the aerosol loading weekly cycle. Results show that the weekly cycle of PM10 is distinct; the maximum occurs on Thursday and the minimum occurs on Saturday and Sunday. The range of this cycle is over 8 μg m−3, approximately 8% of the daily average. The existence of the PM10 weekly cycle was supported by the pronounced amplitude of the 7-day cycle compared with those of 6-day and 8-day cycles and by significant results from the Monte–Carlo test. There are also distinct weekly cycles in the directly linked variables of adjusted horizontal visibility, sulfur dioxide (SO2) and nitrogen dioxide (NO2); the patterns of these cycles are corresponding with that of PM10. The changes of total cloud cover and relative humidity on the weekly time-scale were analyzed, and the relationship with PM10 was discussed. It is likely that the cloud cover weekly cycle is conducted by the change of PM10 through the semi-direct aerosol effect. We also found that precipitation and wind might weaken the PM10 weekly cycle by scavenging the heavy aerosol loading.► PM10 weekly cycle is distinct, with maximum on Thu. and minimum on Sat. and Sun. ► Applied Kruskal–Wallis test, Monte–Carlo test and comparison with 6 & 8-day cycles. ► Weekly cycles of NO2, SO2 and meteorological factors correspond with that of PM10. ► The semi-direct aerosol effect may play a leading role on weekly time-scale.
Keywords: Weekly cycle; PM10; Aerosol climate effect;

Plutonium isotopes and 241Am in the atmosphere of Lithuania: A comparison of different source terms by G. Lujanienė; D. Valiulis; S. Byčenkienė; J. Šakalys; P.P. Povinec (419-427).
137Cs, 241Am and Pu isotopes collected in aerosol samples during 1994–2011 were analyzed with special emphasis on better understanding of Pu and Am behavior in the atmosphere. The results from long-term measurements of 240Pu/239Pu atom ratios showed a bimodal frequency distribution with median values of 0.195 and 0.253, indicating two main sources contributing to the Pu activities at the Vilnius sampling station. The low Pu atom ratio of 0.141 could be attributed to the weapon-grade plutonium derived from the nuclear weapon test sites. The frequency of air masses arriving from the North-West and North-East correlated with the Pu atom ratio indicating the input from the sources located in these regions (the Novaya Zemlya test site, Siberian nuclear plants), while no correlation with the Chernobyl region was observed. Measurements carried out during the Fukushima accident showed a negligible impact of this source with Pu activities by four orders of magnitude lower as compared to the Chernobyl accident. The activity concentration of actinides measured in the integrated sample collected in March–April, 2011 showed a small contribution of Pu with unusual activity and atom ratios indicating the presence of the spent fuel of different origin than that of the Chernobyl accident.► Sources of artificial airborne radioactivity were examined. ► The main Pu source originated from the global fallout. ► Fukushima accident had no significant impact on the area. ► Pu atom ratio frequency distribution showed a new source. ► Among analyzed sources are Sellafield, Chernobyl, Novaya Zemlya and Semipalatinsk.
Keywords: Atmospheric radioactivity; Aerosols; Pu isotopes; Global fallout; Chernobyl accident; Fukushima accident;

A new combination of microbial indicators for monitoring composting bioaerosols by Olivier Le Goff; Jean-Jacques Godon; Kim Milferstedt; Hélène Bacheley; Jean-Philippe Steyer; Nathalie Wéry (428-433).
Bioaerosols emitted from composting plants are a cause of concern because of their potential impact on occupational health and neighboring residential areas. The aim of this study was to identify microbial indicators that are most useful for monitoring bioaerosol emittance and dispersal by industrial composting plants. Seven microbial indicators were measured in air collected outdoors in natural environments and at eleven composting plants. The indicators were: cultivable bacteria and fungi, total bacteria (epifluorescent microscopy), viable bacteria (solid-phase cytometry) and quantification by qPCR of three microbial indicators which had been previously shown as strongly associated with composting. For each indicator, the increase in concentrations due to the turning of composting piles as compared to the background concentration obtained in natural environments and upwind of composting plants was determined. Based on these results, the most effective combination of three indicators was selected for monitoring composting bioaerosol emissions: viable bacteria as one general indicator of bioaerosol emission and two bacterial phylotypes specific to composting bioaerosol: NA07, affiliated to Saccharopolyspora sp. and NC38, affiliated to the Thermoactinomycetaceae. This set of indicator was then quantified on-site and at increasing distances downwind during the turning of compost windrows in thermophilic phase. Composting activity was considered to affect bioaerosol emission when the concentrations of the three indicators were higher than their respective background levels. For all the composting sites studied, an impact was measureable up to distances of 100 m. Further away, the impact was not systematically observed as it depended on meteorological conditions (wind speed) and on levels of bioaerosol emissions.► Bioaerosols emitted during the turning of composting piles were quantified. ► Seven microbial measurements based on different techniques including qPCR were compared. ► The best combination of 3 indicators for monitoring composting bioaerosols was determined. ► The dispersal of composting bioaerosols emitted during turning was then analyzed.
Keywords: Bioaerosol; Compost; Dispersal; Indicator; qPCR;

Variations of surface ozone concentration across the Klang Valley, Malaysia by Mohd Talib Latif; Lim Shun Huey; Liew Juneng (434-445).
Hourly air quality data covering the period 2004–2008 was obtained from the Air Quality Division, the Department of Environment (DOE) through long-term monitoring by Alam Sekitar Sdn. Bhd. (ASMA) were analysed to investigate the variations of surface ozone (O3) in the Klang Valley, Malaysia. A total of nine monitoring stations were selected for analysis in this study and the results show that there are distinct seasonal patterns in the surface O3 across the Klang Valley. A high surface O3 concentration is usually observed between January and April, while a low surface O3 concentration is found between June and August. Analysis of daily variations in surface O3 and the precursors – NO, NO2, CO, NMHC and UVb, indicate that the surface O3 photochemistry in this study area exhibits a positive response to the intensity and wavelength in UVb while being influenced by the concentration of NO x , particularly through tritration processes. Although results from our study suggested that NMHCs may influence the maximum O3 concentration, further investigation is required. Wind direction during different monsoons was found to influence the concentration of O3 around the Klang Valley. HYSPLIT back trajectories (−72 h) were used to indicate the air-mass transport patterns on days with high concentrations of surface O3 in the study area. Results show that 47% of the high O3 days was associated with the localized circulation. The remaining 32% and 22% were associated with mid-range and long-range transport across the South China Sea from the northeast.► We analyse ozone data from nine stations in Klang Valley, Malaysia. ► Surface O3 photochemistry exhibits a positive response to an increase in UVb. ► Surface O3 influences by NO x and wind directions. ► 47% of the high O3 days was associated with the localized circulation. ► Surface O3 also associated with mid-range and long-range transport.
Keywords: Ozone temporal variation; Spatial variation; Precursors; HYSPLIT trajectory analysis;

Road transport is a major contributor to pollutant emissions in the Middle East region (MEA). Emissions originating from this sector have a significant impact on the atmosphere, health and the climate change. Identification and quantification of these emissions in this region is of great importance in order to develop emissions reductions strategies. For this purpose and because a detailed emission inventory for road transport is nonexistent for Lebanon (a small developing country in the MEA region) and for its capital city Beirut, a spatially-resolved and temporally-allocated emission inventory for road transport was developed for Lebanon and for the city of Beirut using a bottom-up approach where possible. In order to compare emissions between developed and non-developed cities on the Mediterranean basin, road transport emissions originating in normal (February–June and September–November) and touristic periods (July–August and December–January) were compared between Beirut, Barcelona and Athens, respectively. The comparison obtained between Beirut, Barcelona and Athens showed that emissions per capita for CO and SO2 are highest in Beirut while emissions of particulate matter were highest in Barcelona. The different patterns between these cities showed that emissions increases in winter in Beirut and Barcelona (11 and 9% respectively) and decreases in the city of Athens by 9%. In summer, an increase of 15% in traffic intensities is observed in Athens while in Beirut and Barcelona, traffic intensities decrease by 10 and 40% respectively.At a national level, emissions were calculated for 14 countries in the MEA in order to inter compare them with those of Lebanon. The results show that in the MEA, the highest contributors to total carbon monoxide (CO) and nitrogen oxides (NO x ) emissions (78 and 79% respectively), are countries having a population that exceeds 20 million inhabitants such as Iran, Saudi Arabia, Iraq, Turkey and Egypt. For Lebanon, emissions per capita are important because they are higher than those for many countries in the region.► Transport sector in Lebanon (modeled as tier 3) is the major source of emissions. ► Different discrepancies in seasonal emission between Beirut, Barcelona and Athens. ► Major emissions are dominated by populated countries. ► Good correlation between road transport emissions per capita and GDP.
Keywords: Emission inventory; Road transport; Monthly variation; Lebanon; Beirut;

Intercomparison of thermal-optical method with different temperature protocols: Implications from source samples and solvent extraction by Yuan Cheng; Feng-kui Duan; Ke-bin He; Zhen-yu Du; Mei Zheng; Yong-liang Ma (453-462).
Three temperature protocols with different peak inert mode temperature (T peak-inert) were compared based on source and ambient samples (both untreated and extracted using a mixture of hexane, methylene chloride, and acetone) collected in Beijing, China. The ratio of EC580 (elemental carbon measured by the protocol with a T peak-inert of 580 °C; similar hereinafter) to EC850 could be as high as 4.8 for biomass smoke samples whereas the ratio was about 1.0 for diesel and gasoline exhaust samples. The EC580 to EC850 ratio averaged 1.95 ± 0.89 and 1.13 ± 0.20 for the untreated and extracted ambient samples, whereas the EC580 to EC650 ratio of ambient samples was 1.22 ± 0.10 and 1.20 ± 0.12 before and after extraction. It was suggested that there are two competing mechanisms for the effects of T peak-inert on the EC results such that when T peak-inert is increased, one mechanism tends to decrease EC by increasing the amount of charring whereas the other tends to increase EC through promoting more charring to evolve before native EC. Results from this study showed that EC does not always decrease when increasing the peak inert mode temperature. Moreover, reducing the charring amount could improve the protocols agreement on EC measurements, whereas temperature protocol would not influence the EC results if no charring is formed. This study also demonstrated the benefits of allowing for the OC and EC split occurring in the inert mode when a high T peak-inert is used (e.g., 850 °C).► Extraction significantly reduced the discrepancy between EC580 and EC850. ► Discrepancy between EC580 and EC650 was not significantly influenced by extraction. ► There are two competing mechanisms for the effects of T peak-inert on EC results. ► EC results does not always decrease with T peak-inert. ► Temperature protocol would not influence the EC results if no charring is formed.
Keywords: OC; EC; Thermal-optical; Temperature protocol; Charring;

Temporal variations and sources of Eastern Mediterranean aerosols based on a 9-year observation by F. Öztürk; A. Zararsız; V.A. Dutkiewicz; L. Husain; P.K. Hopke; G. Tuncel (463-475).
Concentrations of 48 elements, NO3 , SO4 2−, Cl, NH4 +, and black carbon (BC) were determined in PM10 aerosols collected daily at a rural Eastern Mediterranean (EM) site (Antalya, 30.34°E, 36.47°N) from 1993 to 2001. Temporal variations (daily, seasonal and long term), sources and source regions of EM aerosols were delineated. Concentrations of elements with marine and crustal origin were more episodic as compared to anthropogenic ones. Most of the variables showed well defined seasonal cycles. Concentrations of crustal elements increased in summer while winter concentrations of marine elements were considerably higher than in summer. Trends in concentrations were analyzed using the Kendall test. Essentially, all elements showed decreasing trends. Sen's slope was applied to find the magnitude of the trends. The annual rate of decrease was found to change from 0.001 to 209 ng m−3. A receptor-based model, Positive Matrix Factorization (PMF), resolved five factors influencing the chemical composition of EM aerosols as airborne dust, oil combustion, coal combustion, motor vehicle emissions and sea salt. Potential Source Contribution Function (PSCF) analysis was performed to identify the likely areas influencing the chemical composition of aerosol samples. Local and remote sources were detected for the factors resolved by PMF. PSCF maps including backward trajectories at starting height of 900 hPa have indicated that North Africa is the major source contributing to the concentrations of variables associated with dust factor.► Aerosols analyzed in terms of 48 elements, 4 ions and BC between 1993 and 2001. ► Decreasing trend was detected for crustal and rare earth elements. ► Decreasing trend was detected for some pollution derived elements (e.g., Pb, Se, As). ► PMF identified five factors affecting the chemical composition of the aerosols. ► North Africa is the major source contributing to dust factor resolved by PMF.
Keywords: Eastern Mediterranean (EM); Aerosol; Trend analysis; PMF; PSCF;

Decadal limestone erosion rates from a 30-year study of St Pauls Cathedral, London are compared with recession rates derived from applying Lipfert's and Tidblad's dose-response functions to the available rainfall and sulphur dioxide data from central London. Comparison of the measured erosion rates and the dose-response function derived recession rates shows consistently higher loss for the measured erosion rates, between 49 and 35 microns per year for measured rates as opposed to 15–12 microns per year for derived rates. Measured erosion rates were 3.33 times as high as derived recession rates towards the start of the 30 year measurement period, falling to almost 2.75 times by the 2000s. Analysis of the disparity suggests that, despite the magnitude of the differences between the two methods, they both record the same patterns of decline in erosion rates as sulphur dioxide levels decline. The disparity may result from using a common index of erosion, loss of height, to express the outcomes of two different measurement systems quantifying surface loss in different ways.► MEM erosion rates are consistently higher than damage function derived rates. ► The ratio between rates is between 3.33 and 2.75. ► The ratio between LPI and damage function derived rates is 2.5. ► Sulphur dioxide has a declining influence on erosion rates.
Keywords: Erosion rates; Stone decay; Atmospheric pollution; Portland limestone; Decadal erosion rates;

Molecular marker characterization of the organic composition of submicron aerosols from Mediterranean urban and rural environments under contrasting meteorological conditions by Barend L. van Drooge; Michael Crusack; Cristina Reche; Claudia Mohr; Andres Alastuey; Xavier Querol; Andre Prevot; Douglas A. Day; Jose L. Jimenez; Joan O. Grimalt (482-489).
In Winter 2009 an intensive experimental campaign (DAURE) was conducted in an urban site (Barcelona) and in an elevated rural background station (Montseny) in the western Mediterranean basin. During this period three main scenarios were identified based on distinct meteorological conditions: A) temperature inversion, B) cloudy days in normal conditions, and C) intense sea breeze. Filter samples of the submicron fraction (PM1) collected during these scenarios were analysed for organic tracer compounds to gain insight into the composition, sources, formation and processing of aerosol organic matter in the region under contrasting conditions. The results were compared to on-line Aerosol Mass Spectrometry (AMS) measurements. Scenario A conditions had the highest pollution concentrations in Barcelona (traffic and secondary aerosol formation) and lowest in Montseny whose sampling station remained above the mixing layer. Under scenario B the biomass burning contribution was highest in Montseny, reflecting nearby biomass burning sources. Under scenario C, the traffic-related contributions were highest in Montseny and lowest in Barcelona in comparison to the other samples, reflecting the enhanced pollution transport to Montseny and greater dilution in Barcelona. In this scenario, secondary organic aerosol was highest in Montseny. Molecular marker data and AMS source apportionment showed strong to moderate correlation for a) dicarboxylic acids and oxygenated organic aerosol, b) levoglucosan and biomass burning organic aerosol and c) Σn-alkanes and hydrocarbon-like organic aerosol.► Larger contributions of primary sources in urban site, leading to higher hydrocarbon levels. ► OA in the urban site is influenced by similar extent to biomass burning as the rural background site. ► Air pollution leads to formation of SOA, resulting in high OOA concentrations in BCN and MSY. ► Good correlations were observed between the off-line and the on-line data for the OA fractions.
Keywords: PM1; Hydrocarbons; Anhydro-saccharides; Dicarboxylic acid; Organic aerosol;

Spatial and temporal variability of ammonia and other inorganic aerosol species by D.E. Day; X. Chen; K.A. Gebhart; C.M. Carrico; F.M. Schwandner; K.B. Benedict; B.A. Schichtel; J.L. Collett (490-498).
Nitrogen deposition to the sensitive ecosystems in Rocky Mountain National Park (RMNP) has been increasing. Ammonia has been shown to be a large fraction of this nitrogen deposition, and sources in northeastern Colorado were found to be a significant contributor. In this work we report on the results from a small network of Radiello passive samplers to investigate the temporal and spatial variability of ammonia gas concentrations in northeastern Colorado. A URG denuder/filter-pack sampler was collocated with a Radiello passive sampler to provide a check on the accuracy of passive ammonia measurements and to provide information about complementary aerosol and trace gas species. These measurements showed seasonal variations in the concentrations of both particulate- and gas-phase aerosol components. The highest concentrations of ammonia occurred during summer months. These were almost twice the lowest concentrations, which occurred during spring and fall months. Ammonia also exhibited higher than expected concentrations during winter. There was considerable spatial variability in average ammonia concentrations, with May–August averages ranging from 3 μg m−3 in rural grasslands to 4–11 μg m−3 at suburban-urban sites to almost 30 μg m−3 in an area of intensive livestock feeding and farming operations. The large ammonia gradients near sources are expected for this primary pollutant with high deposition rates. The overall concentrations in this region are significantly larger than those measured in RMNP, which were around 0.5 μg m−3, and represent a large reservoir of ammonia that can be transported to RMNP with easterly winds.► Ammonia from the plains of Colorado contributes to N deposition in RMNP. ► Ammonia and other inorganic aerosol species show seasonal variability. ► Ammonia concentrations exhibit large spatial variability.
Keywords: Ammonia; Passive sampling; Temporal concentrations; Spatial variability; Front range; Eastern plains of Colorado;

Volatile organic compounds from the exhaust of light-duty diesel vehicles by Jiun-Horng Tsai; Sheng-You Chang; Hung-Lung Chiang (499-506).
The exhaust gas constituents of light-duty diesel vehicles (LDDVs), including total hydrocarbon (THC), non-methane hydrocarbon (NMHC), carbon monoxide (CO), nitrogen oxide (NO x ), and volatile organic compounds (VOCs) were measured by a dynamometer study following federal test procedure-75 (FTP-75) and highway fuel economy cycle. The average fuel consumption of these LDDVs was 0.126 L km−1 for FTP-75, with about 10% fuel consumption savings for highway driving. The average emission factors of NMHC, CO and NO x for light-duty vehicles were 0.158/0.132 (90% of THC), 1.395/1.138, and 1.735/1.907 g km−1 for FTP-75/Highway, respectively. Styrene, n-propylbenzene, n-undecane, o-ethyltoluene, 1,2,4-trimethylbenzene, toluene, o-xylene, isopropylbenzene, m,p-xylene, and ethylbenzene were the dominant VOCs of LDDV exhaust, and the emission factors were about 10–60 mg kg−1. In addition, formaldehyde, acetaldehyde, acetone, butyraldehyde, and m-tolualdehyde were the major carbonyl species from LDDV exhaust, and the emission factors ranged from 1 to 10 mg km−1. The ozone formation potentials of m,p-xylene, o-ethyltoluene, 1,2,4-trimethylbenzene, o-xylene, n-propylbenzene, styrene, and isoprene were >50 mg-O3 km−1. In addition, formaldehyde, acetaldehyde, and butyraldehyde revealed high ozone formation potential of carbonyl species, with values ranging from 10 to 95 mg-O3 km−1. Based on the exhaust constituents and ozone formation potential observed, diesel vehicles could be an important air pollution source for urban and industrial areas.► Diesel vehicle pollution is an important issue for air pollution control. ► FTP-75 and highway fuel economy driving cycles are conducted by dynamometer. ► NMHC, CO, NO x emission factors are conducted for light-duty diesel vehicles (LDDVs). ► VOCs including alkanes, alkenes, aromatics, and carbonyls are determined for LDDVs.
Keywords: Diesel exhaust; Carbonyls; Emission factor; Ozone formation potential;

Ultrafine particle and fine trace metal (As, Cd, Cu, Pb and Zn) pollution episodes induced by industrial emissions in Huelva, SW Spain by R. Fernández-Camacho; S. Rodríguez; J. de la Rosa; A.M. Sánchez de la Campa; A. Alastuey; X. Querol; Y. González-Castanedo; I. Garcia-Orellana; S. Nava (507-517).
Urban air quality impairment by ultrafine particles has become a matter of concern due to the adverse effects on human health. Most of the studies of ultrafine particles in urban air quality have focused on vehicle exhaust emissions. We studied how industrial emissions contribute to ultrafine particle concentrations in downwind urban ambient air. This research is based on experimental data collected in the ambient air of the industrial city of Huelva (SW Spain) over April 2008–December 2009 period (particle number, gaseous pollutants and black carbon concentrations and levels and chemical composition of PM10 and PM2.5 with daily and hourly resolution). This city is affected by emissions from the second largest Cu-smelter in Europe, phosphoric acid and fertilizer production plants and an oil refinery and petrochemical plant. Industrial emissions are the main cause of ultrafine particle episodes. When vehicle exhaust emissions are the main source, ultrafine particles typically show (24-h mean) concentrations within the range 14,700–5000 cm−3 (50th–1st), with 60% of these linked to this source and 30% to industrial emissions. In contrast, when daily mean levels of N are within the range 50,000–25,500 cm−3 (100th–70th), industrial and vehicle exhaust emissions accounted for 49 and 30%, respectively. High concentrations of toxic trace metals (As, Cu, Cd, Zn and Pb) were recorded when the study city suffered fumigations of the Cu-smelter plumes (e.g. 10–25 ng m−3 As, 1–2 ng m−3 Cd and >105 cm−3 of ultrafine particles). Because of these industrial emissions, ultrafine particle concentrations during daylight are about two times higher than those observed in other European cities. Recently, ultrafine particle emissions in vehicle exhausts have been subject to limit values in a recent stage of the EURO standards. Industrial emissions should also be considered.► We studied how industrial emissions contribute to ultrafine particles (UP). ► Traffic and industrial UP episodes are identified from the relation of UP and PM2.5. ► Road traffic emissions, in the morning rush hours, are associated with OM and BC. ► Industrial plumes, during daylight, are related with heavy metals. ► Industrial emissions are the first cause of high UP in Huelva city.
Keywords: Ultrafine particles; Arsenic; Cadmium; Industrial emissions; Vehicle exhausts;

Factors influencing variability in the infiltration of PM2.5 mass and its components by M. MacNeill; L. Wallace; J. Kearney; R.W. Allen; K. Van Ryswyk; S. Judek; X. Xu; A. Wheeler (518-532).
The infiltration of particles into homes can vary seasonally, between homes in a community and between communities. However, few studies have examined the day to day variability across multiple homes. We used continuous data collected from a 2-year (2005–2006) personal exposure study conducted in Windsor, ON to estimate daily infiltration factors (F inf) for fine particulate matter (PM2.5), Black Carbon (BC), and ultrafine particles (UFP) as well as the ambient personal exposure factor (F pex) for PM2.5. In addition, the daily ambient and non-ambient generated components of indoor and personal concentrations were estimated.Median daily F inf estimates ranged from 0.26 to 0.36 across seasons for PM2.5; from 0.28 to 0.59 for BC; and from 0.15 to 0.26 for UFP. Median daily F pex estimates ranged from 0.24 to 0.31 across seasons. Daily PM2.5 and UFP F inf and F pex estimates were higher in summer than winter, although BC showed the opposite trend. Predictors of daily infiltration were typically related to window-opening behaviours, air conditioning, meteorological variables, and home age. In addition, use of electrostatic precipitators and stand alone air cleaners was associated with significantly reduced infiltration factors, indicating that these devices may provide a cost effective mechanism of reducing human exposures to particles of ambient origin.The majority of indoor PM2.5 (median 57–73%) and indoor BC (median 90–100%) was of ambient origin across seasons, while both personal PM2.5 and indoor UFPs had significant non-ambient contributions (median 60–65%). Factors that were found to increase non-ambient particle concentrations were typically related to cooking, candle use, supplemental heating, cleaning, and number of people in the home. Factors that were found to decrease non-ambient particle concentrations were open windows, and air cleaner use.This work has several implications to both epidemiologic studies and risk management. A better understanding of the factors influencing F inf and F pex can improve exposure assessment and contribute to reduced exposure misclassification in epidemiologic studies. Furthermore, by increasing our knowledge of non-ambient and ambient exposures, risk associated with PM exposure can be managed more effectively.► This is one of the few papers to describe and model F inf and F pex on a daily basis. ► F inf and F pex can be lower and less seasonally variable where heating and cooling systems are used. ► Air cleaners and electrostatic precipitators may provide a mechanism of reducing exposures. ► Ambient and Non-ambient contributions can be quantified using F inf and F pex.
Keywords: Infiltration factor (F inf); Ambient personal exposure factor (F pex); PM2.5; Ultrafine particles (UFPs); Black carbon (BC); Ambient; Non-ambient; Indoor air pollution; Windsor, Ontario;

Variations of regional background peroxyacetyl nitrate in marine boundary layer over Baengyeong Island, South Korea by Gangwoong Lee; Hee-Soon Choi; Taehyoung Lee; Jinsu Choi; Jin Su Park; Joon Young Ahn (533-541).
Concurrent two-week measurements of peroxyacetyl nitrate (PAN), other photochemically reactive species (including O3, CO, NO2, and volatile organic compounds), and aerosols (water-soluble ionic species, organic and elemental carbon, and trace metals) were made at an atmospheric monitoring station on Baengyeong Island in the summer and autumn of 2010 and winter and spring of 2011. PAN mixing ratios ranged from the below the detection limit of 0.01–2.47 ppbv, with a median of 0.04, 0.58, 0.32, 0.17 ppbv during the summer, autumn, winter; and spring, respectively. Although the photochemical ages determined from the PAN/NO x ratios indicated that the measurement site was situated under a relatively clean marine boundary layer, significant and abrupt increases in PAN were frequently observed due to transport from nearby land masses, mainly China and South Korea. The vertical trend of PAN with a mid-altitude maximum observed in this study is consistent with previous aircraft campaigns near the site. However, the PAN concentration recorded in this study was about two times higher than those of previous studies at remote marine surface sites in the southern Yellow Sea. In most cases, the marine boundary layer acted as an overall sink for PAN. However, we found that in-situ photochemical production of insoluble PAN also contributes to maintaining high-PAN mixing ratios in the boundary layer over the Yellow Sea and plays a role in the regional transport of reactive nitrogen species.► PAN in autumn was the highest due to frequent transports from source regions. ► The maximum levels of PAN were observed at airs originated from mid-altitudes. ► The marine boundary layer acted as an overall sink for PAN. ► In-situ PAN production within boundary airs was apparent under some conditions. ► PAN in this study was two times higher than previous studies in the Yellow Sea.
Keywords: PAN; Baengyeong Island; Long-range transport; Ozone; Photochemistry; Boundary layer;

The influence of emission sources and meteorological conditions on SO2 pollution in Mongolia by Munkh-Erdene Luvsan; Ruei-Hao Shie; Tseden Purevdorj; Lkhagvasuren Badarch; Barkhasragchaa Baldorj; Chang-Chuan Chan (542-549).
Major urbanization and industrialization began in Mongolia in the mid-1990, and air pollution has since become a challenging environmental problem. This study used air pollution data and meteorological parameters from fourteen monitoring sites to determine spatial and temporal patterns of SO2 in Mongolia from 1996 to 2009 and to estimate the influence of meteorological parameters such as wind speed and direction, temperature and relative humidity on SO2 levels in Ulaanbaatar city from 2005 to 2009. SO2 pollution in urban areas and at the steel industry site was above the National Ambient Air Quality Standard and more serious than at other locations in Mongolia. SO2 pollution in winter was more serious than the other three seasons in Mongolia. SO2 pollution has worsened since 2000 because of rapid urbanization and industrialization. Multiple regression models showed that SO2 concentrations in Ulaanbaatar increased with the decrease of wind speed and temperature, and with the increase of relative humidity. The increase in SO2 pollution in Ulaanbaatar was associated with flow of SO x emitted from industrial sources and gers to the north of the city. This study concludes that SO2 pollution in Mongolia was worsened by the increase in emissions caused by rapid urbanization and industrialization over the last decade and the dispersion of SO2 concentrations in Ulaanbaatar was influenced by the meteorological parameters wind speed and direction, temperature and relative humidity.► SO2 pollution in Mongolia was worsened by rapid urbanization. ► SO2 pollution was more serious in winter due to basic needs for heating. ► SO2 concentrations increased with the decrease of wind speed and temperature. ► SO2 concentrations increased with the increase of relative humidity.
Keywords: Mongolia; SO2; Spatial and temporal pattern; Temperature; Wind speed;

Effects of environmental alerts and pre-emergencies on pollutant concentrations in Santiago, Chile by Rodrigo Troncoso; Louis de Grange; Luis A. Cifuentes (550-557).
To reduce air pollution levels in Santiago, Chile on days when the weather is expected to create poor ventilation conditions and increased air pollutant concentrations, the responsible authorities impose temporary restrictions on motor vehicles and certain industrial activities. We estimate the impact of these restrictions on the city's air quality using data collected by a network of monitoring stations. The estimates show that the restrictions do reduce the average concentrations of coarse and fine particulate matter, carbon monoxide and nitrogen oxide (both gases are emitted mainly by vehicles). However, no significant changes were found in the sulfur dioxide concentrations, which are primarily the result of industrial processes.► Santiago's air quality policy significantly reduced pollutant's concentrations. ► Reductions in PM10 and PM2.5 were 5%–7% in alerts and 12% in pre-emergencies. ► The average decline in CO and NO x was 10% in alerts and 20% in pre-emergencies. ► Restrictions led to significant reductions in CO, NO x , PM10 and PM25 in weekdays.
Keywords: Outdoor air pollution; Environmental policy; Air quality; Traffic; Industries;

Spatial variability of indoor air pollutants in schools. A multilevel approach by Soutrik Banerjee; Isabella Annesi-Maesano (558-561).
The measurement of indoor air pollutants and their health effects are less often studied due to the costs of collection of such data. We have analysed the variability in the measurement of five indoor school air pollutants: fine particulate matter of size ≤2.5 μm (PM2.5), nitrogen dioxide (NO2), and three Volatile Organic Compounds (VOC), namely formaldehyde, acetaldehyde and acrolein, objectively measured over five days of a week at representative points in more than 400 classrooms of 109 schools and courtyards in six French cities spread out over the year. Separate 3-stage multilevel models were fitted to partition the different nested variance components (i.e., classroom, school and city levels), and intra-class correlation (ICC) coefficients were computed to bring out the similarities of pollutants' concentrations among these spatial units. The indoor PM2.5 and NO2 concentrations showed a high degree of similarity (ICC coefficients equal to 76% and 81%, respectively) between the classrooms of a school (and city), whereas the formaldehyde, acetaldehyde and acrolein concentrations showed low to moderate degree of similarity (ICC coefficients equal to 25%, 36% and 57%, respectively) between the classrooms. We conclude that to investigate the impact of indoor air pollutants, a multilevel approach taking into account the full design of the study would be the most appropriate.
Keywords: Indoor air pollutants; Exposure assessment; Variance components; Intra-class correlation;

Use of levoglucosan, potassium, and water-soluble organic carbon to characterize the origins of biomass-burning aerosols by Roberta Cerasi Urban; Michele Lima-Souza; Letícia Caetano-Silva; Maria Eugênia C. Queiroz; Raquel F.P. Nogueira; Andrew G. Allen; Arnaldo A. Cardoso; Gerhard Held; Maria Lucia A.M. Campos (562-569).
Three chemical species related to biomass burning, levoglucosan, potassium and water-soluble organic carbon (WSOC), were measured in aerosol samples collected in a rural area on the outskirts of the municipality of Ourinhos (São Paulo State, Brazil). This region is representative of the rural interior of the State, where the economy is based on agro-industrial production, and the most important crop is sugar cane. The manual harvesting process requires that the cane be first burned to remove excess foliage, leading to large emissions of particulate materials to the atmosphere. Most of the levoglucosan (68–89%) was present in small particles (<1.5 μm), and its concentration in total aerosol ranged from 25 to 1186 ng m−3. The highest values were found at night, when most of the biomass burning occurs. In contrast, WSOC showed no diurnal pattern, with an average concentration of 5.38 ± 2.97 μg m−3 (n = 27). A significant linear correlation between levoglucosan and WSOC (r = 0.54; n = 26; p < 0.0001) confirmed that biomass burning was in fact an important source of WSOC in the study region. A moderate (but significant) linear correlation between levoglucosan and potassium concentrations (r = 0.62; n = 40; p < 0.0001) was indicative of the influence of other sources of potassium in the study region, such as soil resuspension and fertilizers. When only the fine particles (<1.5 μm; typical of biomass burning) were considered, the linear coefficient increased to 0.91 (n = 9). In this case, the average levoglucosan/K+ ratio was 0.24, which may be typical of biomass burning in the study region. This ratio is about 5 times lower than that previously found for Amazon aerosol collected during the day, when flaming combustion prevails. This suggests that the levoglucosan/K+ ratio may be especially helpful for characterization of the type of vegetation burned (such as crops or forest), when biomass-burning is the dominant source of potassium. The relatively high concentrations of WSOC (and inorganic ions) suggest an important influence on the formation of cloud condensation nuclei, which is likely to affect cloud formation and precipitation patterns.► The aerosol chemical composition was highly affected by biomass burning. ► Most of the levoglucosan (up to 89%) was present in small particles (<1.5 μm). ► Biomass burning was an important source of WSOC. ► The levoglucosan:K+ ratio in fine particles (sugar-cane burning) was 0.24.
Keywords: Brazil; São Paulo State; Sugar cane; Cloud condensation nuclei; Organic carbon;

A comparison of methods for the assessment of odor impacts on air quality: Field inspection (VDI 3940) and the air dispersion model CALPUFF by Laura Ranzato; Alberto Barausse; Alice Mantovani; Alberto Pittarello; Maurizio Benzo; Luca Palmeri (570-579).
Unpleasant odors are a major cause of public complaints concerning air quality and represent a growing social problem in industrialized countries. However, the assessment of odor pollution is still regarded as a difficult task, because olfactory nuisance can be caused by many different chemical compounds, often found in hard-to-detect concentrations, and the perception of odors is influenced by subjective thresholds; moreover, the impact of odor sources on air quality is mediated by complex atmospheric dispersion processes. The development of standardized assessment approaches to odor pollution and proper international regulatory tools are urgently needed. In particular, comparisons of the methodologies commonly used nowadays to assess odor impacts on air quality are required. Here, we assess the olfactory nuisance caused by an anaerobic treatment plant for municipal solid waste by means of two alternative techniques: the field inspection procedure and the atmospheric dispersion model CALPUFF. Our goal was to compare rigorously their estimates of odor nuisance, both qualitatively (spatial extent of odor impact) and quantitatively (intensity of odor nuisance). To define the impact of odors, we referred to the German standards, based on the frequency of odor episodes in terms of odor hours. We report a satisfying, although not perfect agreement between the estimates provided by the two techniques. For example, they assessed similar spatial extents of odor pollution, but different frequencies of odor episodes in locations where the odor nuisance was highest. The comparison highlights strengths and weaknesses for both approaches. CALPUFF is a cheaper methodology which can be used predictively, but fugitive emissions are difficult to model reliably, because of uncertainty regarding timing, location and emission rate. Field inspection takes into account the role of human perception, but unlike the model it does not always characterize precisely the extent of the odor nuisance caused by a single source when other odors are present, because only the most unpleasant odor is reported. We conclude that these two assessment methods provide reasonable estimates of odor nuisance.► We compare methods to assess odor pollution from an anaerobic digestion plant for MSW. ► We applied the atmospheric dispersion model CALPUFF and the Odor Field Inspection. ► They were compared quantitatively and qualitatively over the same area for 6 months. ► The methods assessed similar spatial extents of nuisance in terms of odor frequency. ► The two methods provide complementary information about odor nuisance.
Keywords: Air quality; Odor pollution; Atmospheric dispersion modeling; Field inspection (VDI 3940); Anaerobic digestion plant; Municipal solid waste;

Emission factors from road dust resuspension in a Mediterranean freeway by F. Amato; A. Karanasiou; T. Moreno; A. Alastuey; J.A.G. Orza; J. Lumbreras; R. Borge; E. Boldo; C. Linares; X. Querol (580-587).
Particulate matter emissions from paved roads are currently one of the main challenges for a sustainable transport in Europe. Emissions are scarcely estimated due to the lack of knowledge about the resuspension process severely hampering a reliable simulation of PM and heavy metals concentrations in large cities and evaluation of population exposure. In this study the Emission Factors from road dust resuspension on a Mediterranean freeway were estimated per single vehicle category and PM component (OC, EC, mineral dust and metals) by means of the deployment of vertical profiles of passive samplers and terminal concentration estimate. The estimated PM10 emission factors varied from 12 to 47 mg VKT−1 (VKT: Vehicle Kilometer Traveled) with an average value of 22.7 ± 14.2 mg VKT−1. Emission Factors for heavy and light duty vehicles, passenger cars and motorbikes were estimated, based on average fleet composition and EPA ratios, in 187–733 mg VKT−1, 33–131 VKT−1, 9.4–36.9 VKT−1 and 0.8–3.3 VKT−1, respectively. These range of values are lower than previous estimates in Mediterranean urban roads, probably due to the lower dust reservoir on freeways. PM emitted material was dominated by mineral dust (9–10 mg VKT−1), but also OC and EC were found to be major components and approximately 14–25% and 2–9% of average PM exhaust emissions from diesel passenger cars on highways respectively.► Emission factors were estimated for vehicle categories and PM components. ► Values were lower than previous estimate at typical urban roads. ► Mineral dust dominates the emitted mass, but important OC and EC emissions were found. ► An alternative activity approach to the VKT is discussed.
Keywords: PM10; Brake metals; Organic carbon; Elemental carbon; Mineral dust; Deposition flux; Traffic;

Interpretation of the concentrations of aldehydes in rainwater over a wide area and local areas of Japan by some dominant factors by Shigeru Taguchi; Keita Murai; Mizuho Takamatsu; Yukari Hayakawa; Shinya Tamizu; Makoto Kuwata; Yuuki Katayama; Hideki Kuramitz; Noriko Hata (588-596).
Rainwater pollution with formaldehyde, acetaldehyde and other aliphatic aldehydes was investigated from May 2008 to June 2011 at 19 locations over a wide area in Japan to survey the pollution level. The pollution level was remarkably controlled by the amount of precipitation. The concentrations of total aliphatic aldehydes and formaldehyde sometimes exceeded 0.6 mg L−1 and 0.2 mg L−1 when the rainfall was small, and decreased rapidly with increasing the amount of rainfall. And in larger rainfall, the concentrations were converged to ca. 0.09 mg L−1 and 0.06 mg L−1 respectively. It was found that the concentration of the pollutants collected in a bottle for a single rainfall event is expressed by an equation based on a dilution model where heavy deposition occurred only at early rainfall followed by continuous dilution of the water with less polluted rainwater. These results were interpreted that the aldehydes in air were washed out very quickly due to their high solubility in water. As progressing of rainfall, the pollution level attained to an equilibrium state between influx and outflux of the pollutants. Precise investigation through a sequential sampling of rainwater by 1 mm during a rainfall event was also performed at several sites. It was found that a break of rainfall is another dominant factor to control the pollution level. A break of rainfall quickly enhanced the pollution level of the resumed rain. Regional difference on rainwater pollution level was observed only at the early stage throughout a rainfall event. The air-pollution levels were high just before beginning rainfall, and they decreased quickly with increasing the amount of rainfall, but never converged to zero. These results suggest that continuous influx of the pollutants occurs in a wide area in Japan besides regional influx.► Rainwater pollution with aldehydes in Japan was investigated. ► Heavy pollution was observed at any locations, in any seasons in Japan. ► The pollution levels were essentially controlled by the amount of precipitation. ► Other dominant factors were also discussed to interpret the pollution levels.
Keywords: Formaldehyde; Acetaldehyde; Rainwater pollution; Aldehydes; Japan;

Gas-phase reactivity study of (E)-3-pentenenitrile and 4-pentenenitrile towards OH radicals and Cl atoms at atmospheric pressure by Juan P. Colomer; María B. Blanco; Alicia B. Peñéñory; Ian Barnes; Peter Wiesen; Mariano A. Teruel (597-604).
The relative-rate technique has been used to obtain rates coefficients for the reactions of (E)-3-pentenenitrile (CH3CH=CHCHCN) and 4-pentenenitrile (CH2 =CHCH2CH2CN) with OH radicals and Cl atoms at 298 K and (760 ± 10) Torr total pressure of synthetic air using different reference compounds. The experiments were performed in an environmental chamber with “in situ” FTIR spectroscopy to monitor the reactants concentrations. The following room temperature rate coefficients (in cm3 molecule−1 s−1) were obtained: k 1 (OH + CH3CH=CHCHCN) = (5.05 ± 1.10) × 10−11, k 2 (Cl + CH3CH=CHCHCN) = (2.60 ± 0.26) × 10−10, k 3 (OH + CH2 =CHCH2CH2CN) = (2.90 ± 0.64) × 10−11 and k 4 (Cl + CH2 =CHCH2CH2CN) = (2.56 ± 0.26) × 10−10. This is the first kinetic study for all of these reactions. The effect of atom or group substituent on the overall rate coefficients is analyzed and the reactivity of nitriles is compared with those of other unsaturated compounds in the literature. In addition, a comparison between the experimentally determined rate coefficients from this work and the k OH and k Cl predicted from k vs E HOMO correlations is presented.The atmospheric lifetimes at room temperature of these compounds has been estimated using the rate coefficients determined in this work.Display Omitted► First kinetic study of OH and Cl-initiated oxidation of two unsaturated nitriles. ► Experiments in large volume photoreactors using “in situ” FTIR. ► Experimental rate constants were compared by SAR method. ► Free energy relationships were used to estimate rate constants. ► Atmospheric lifetimes of nitriles were discussed.
Keywords: (E)-3-pentenenitrile; 4-Pentenenitrile; Rate coefficients; E HOMO; Tropospheric chemistry;

Carbonaceous aerosol and its characteristics observed in Tokyo and south Kanto region by Hiroaki Minoura; Tazuko Morikawa; Akira Mizohata; Kazuhiko Sakamoto (605-613).
Due to enforcing vehicle emission reduction requirements in Japan, particulate matter (PM) concentration, especially elemental carbon (EC) concentration in roadside atmosphere, obviously decreased in the last decade. In spite of the previous vehicle emission reduction, EC concentration was not shown a clear decrease, recently. To achieve the PM2.5 environmental standard, measurements based on emission source contribution are desirable. However, source apportionment of carbonaceous aerosol was ambiguous because chemical components are complicated, and the components change through photochemical reaction.The goal of this study is to determine source apportionment for carbonaceous aerosols. Examination of PM2.5 was performed in south Kanto including Tokyo in the summer of 2008 and the winter of 2009. Emissions from the industrial area around Tokyo Bay and the agricultural northern area showed transportation and accumulation due to the seasonal prevailing wind. The emissions formed a geographical distribution due to photochemical reactions. The characteristics of carbonaceous aerosol were obtained using carbon profile analysis and carbon isotope analysis, including the source information such as fossil fuel emission origin, vegetation origin, and combustion product, photochemical reaction product, etc.Soot-EC was found as a substance with fossil fuel origin which did not contain biomass combustion matter, and since it is stable, there was no observed difference by site and a uniform concentration was observed in winter. It became apparent from the carbon isotope analysis using 14C that the carbon from the biomass origin involved 29% in total carbon in the summer, and 48% in winter even at Kudan of central Tokyo.► Regional and seasonal comparison of carbon profile measured using IMPROVE method. ► Spatial distribution of percent modern carbon (pMC) obtained carbon isotope analysis. ► Regional and seasonal comparison of pMC included in total carbon and elemental carbon. ► Feature of the emission source presumed from carbon profile and pMC.
Keywords: Elemental carbon; Organic carbon; Carbon profile; Isotropic carbon analysis; Source contribution; Fossil fuels; Biomass combustion;

Temporal variations of organochlorine pesticides in precipitation in Beijing, China by Guosheng Yang; Lingling Ma; Diandou Xu; Liyan Liu; Hongliang Jia; Yang Chen; Yongbao Zhang; Zhifang Chai (614-619).
Temporal variations of organochlorine pesticides (OCPs) were determined in precipitation and monthly depositional fluxes were calculated in Beijing from February 2009 to March 2011. Compounds which were detected most often included α-HCH and β-HCH, and the volume-weighted mean (VWM) concentration of hexachlorocyclohexanes (HCHs) was 33.0 ng L−1, accounting for 72.3% of the ∑OCPs in precipitation. The total concentrations of OCPs ranged from 3.73 to 152 ng L−1 (mean: 29.7 ± 3.5 ng L−1) for dissolved phase and from 1.61 to 114 ng L−1 (mean: 15.9 ± 2.0 ng L−1) for particulate phase, respectively. OCPs in dissolved phase dominated sampled concentrations in precipitation (HCHs: 71.8%, Chlordane: 77.7%, dichlorodiphenyltrichloroethanes-DDTs: 50.1%) with an exception of hexachlorobenzene–HCB (26.3%). Furthermore, the distribution coefficient, K pd, was generally large in low temperature, especially in spring. The abundance of ∑OCPs in the precipitation fluctuated monthly, with high value in late winter and spring. The past farmland near the sampling site was under construction during sampling, which may be an important local re-emission source in this study. The elevated wet deposition flux of 11 selected OCPs was 14.9 μg m−2 yr−1 in Beijing.► We determined the temporal variations of OCPs in precipitation in Beijing from February 2009 to March 2011. ► The concentrations of ∑OCPs were higher in late winter and spring. ► OCPs in dissolved phase dominated sampled concentrations. ► The wet deposition flux of ∑OCPs was 14.9 μg m−2 yr−1.
Keywords: Organochlorine pesticides; Precipitation; Deposition flux; Beijing;

Seasonal and diurnal variation in concentrations of gaseous and particulate phase endosulfan by Qingbo Li; Xianyu Wang; Jing Song; Hongqi Sui; Lei Huang; Lu Li (620-626).
Successive 52-week air monitoring of α-endosulfan (α-E), β-endosulfan (β-E) and endosulfan sulfate (E.S) in the gaseous and particulate phases was conducted in Dalian city, northeast China by using an active high-volume sampler. Significant seasonal and diurnal variations in endosulfan concentrations were observed. It was found that the concentration of gaseous-phase α-E peaked in the summer and the concentration of particulate phase α-E peaked in the winter. For E.S, both gaseous and particulate phase concentrations peaked in the summer. α-E was distributed predominantly in the gas phase in the summer but was distributed mainly in the particulate phase in the winter. β-E was distributed mainly in the gas phase in the summer and in the particulate phase at other times of the year. E.S was distributed mainly in the particulate phase throughout the year. Elevated temperatures facilitated the volatilization of α-E from particle surfaces but exerted little effect on β-E and had almost no effect on E.S. Trajectory-based analysis indicates that the seasonal variation in atmospheric concentrations of endosulfan in Dalian city was influenced strongly by the land and sea air masses. In addition, differences in endosulfan concentrations in the particulate phase between day and night were likely due to the circulation of sea/land breezes. The ‘cold-condensation’ effect occurring during the night may result in the attachment of endosulfan to the particulate phase.Monthly variation of concentration levels of α-endosulfan in gas-phase (a) and particle-phase (b).Display Omitted► Atmospheric concentrations of endosulfan were significantly influenced by the air masses from sea and land. ► Sand-dust weather made a significant impact on particulate-phase endosulfan in the atmosphere. ► The endosulfan concentration in the particulate phase was significantly higher at night than during the day.
Keywords: Endosulfan; Seasonal–diurnal variation; Gaseous-particulate phase distribution; Dalian;

Ozone sounding in the Metropolitan Area of São Paulo, Brazil: Wet and dry season campaigns of 2006 by Andrade Maria de Fátima; Adalgiza Fornaro; Freitas Edmilson Dias de; Caroline R. Mazzoli; Leila Droprinchinski Martins; Claudia Boian; Marcio Gledson Lopes Oliveira; Jean Peres; Samara Carbone; Plínio Alvalá; Neusa Paes Leme (627-640).
In the Metropolitan Area of São Paulo (MASP), located in southeastern Brazil, surface ozone concentrations are often well above the national air quality standards. In this experimental study, we attempted to characterize the vertical profile of atmospheric ozone and transport of the ozone plume in the boundary layer, using data from the first ozone soundings ever taken in the MASP. In 2006, we launched fifteen ozonesondes: eight from 15 to 18 May (dry season); and seven from 30 October to 1 November (wet season). Vertical ozone mixing ratios in the troposphere were approximately 40 ppb, reaching maximum values of approximately 60 ppb during the dry-season campaign and approximately 100 ppb during the wet-season campaign. In the first and second campaigns, the mean tropospheric ozone column abundance was 28.2 and 41.3 DU, respectively, which can be attributed to the considerable variation in the annual temperature cycle over the region. To determine the effect that biomass burning has on ozone concentrations over the MASP, we analyzed wind trajectories and satellite-derived fire counts. We cannot state unequivocally that biomass burning contributed to higher ozone concentrations above the boundary layer during the experimental campaigns. In the boundary layer, ozone concentrations increase with altitude, peaking at the base of the inversion layer, suggesting that local emissions of volatile organic compounds and nitrogen oxides play a significant role in the lower troposphere over MASP, influencing ozone formation not only at the surface but also vertically in the atmosphere and in distant regions.► We analyzed the biomass burning impact on Urban Ozone production. ► We have performed ozone soundings over Metropolitan Area of Sao Paulo. ► We calculated the air mass back-trajectories to analyze the vertical ozone profile over the Metropolitan Area of Sao Paulo. ► We analyzed the local production versus long-range transport of Urban Ozone over the Metropolitan Area of Sao Paulo.
Keywords: Vertical ozone profile; Sao Paulo megacity; Air mass trajectory analysis; Urban air quality;

Emission factors for heavy metals from diesel and petrol used in European vehicles by Tinus Pulles; Hugo Denier van der Gon; Wilfred Appelman; Marc Verheul (641-651).
Heavy metals constitute an important group of persistent toxic pollutants occurring in ambient air and other media. One of the suspected sources of these metals in the atmosphere is combustion of transport fuels in road vehicles. However, estimates of the emissions of these metals from road vehicles as reported in national emission inventories show a very high variability in emission factors used. This paper provides high quality data on concentrations of heavy metals in fuels and derives default emission factors from these. The paper discusses these values against the emission estimates presently reported by the Parties to the LRTAP Convention.The measured concentrations of heavy metals in petrol and diesel fuel show a high variability between different samples taken at gas stations throughout Europe. Metal concentrations in road transport fuels vary over two orders of magnitude, but all remain in the ppb region (a few tenths of a ppb to a few hundred ppb for all metals). The frequency distributions of the measurements could be approximated by lognormal distributions. The emission factors, including 95 percent confidence intervals were derived from a statistical analysis of the survey data. We could not detect a significant difference between samples from different countries.The fuel based emission factors as derived in this study are complemented with those related to unintentional lubricant oil combustion. This allowed an estimation of total exhaust heavy metal emissions for UNECE Europe, indicating that As, Hg and Se exhaust emissions were dominated by fuel combustion while Cd, Cr, Cu, Ni, Pb, and Zn exhaust emissions were dominated by lubricant oil combustion.The proposed emission factors were generally lower than previously published emission factors. National emissions of heavy metals from vehicle exhaust, estimated in this study are in many cases considerably lower than those reported by the countries for this source.► Heavy metal (HM) concentrations in European road transport fuels were measured. ► They all vary over more than two orders of magnitude between different samples. ► Fuel based HM tailpipe emission factors and uncertainty ranges are derived. ► Our data are compared with official national HM emission inventories. ► Significant differences show incomparable reporting by countries.
Keywords: Emission factors; Heavy metals; Air pollution; Road transport; Vehicle exhaust;

The impact of thermodynamic module in the CTM performances by C. Carnevale; G. Finzi; E. Pisoni; P. Thunis; M. Volta (652-660).
This work investigates the impact of the inorganic thermodynamic module on Chemical Transport Model simulations. The study has been focused on Northern Italy, one of the most polluted area in Europe, where high PM10 levels are reached despite the Regional and National Authority efforts to limit emission in the atmosphere.Two different configurations of the Chemical Transport Model TCAM have been tested performing yearly simulation over the selected domain for 2005. In the first configuration, the SCAPE2 thermodynamic module has been implemented, while in the second one, ISORROPIA-II has been integrated into the system.An exhaustive evaluation of the performances is presented for total PM10 with respect to its daily values, and the analysis of the impact of the two modules on PM2.5 and on aerosol chemical components has been performed.The ISORROPIA-II module configuration shows better overall performances both in terms of correlation and Normalized Mean Absolute Error for PM10 and PM2.5. The evaluation of the inorganic ions performances shows a quite different behavior for the two configurations, with ISORROPIA-II providing better results for both Normalized Mean Absolute Error and Normalized Mean Error.► The impact of the thermodynamic module in a Chemical Transport Model has been evaluated. ► The role of secondary inorganic fraction on PM10 levels has been assessed. ► The impact of the different chemical species in aerosol performances has been shown.
Keywords: Chemical Transport Model; Thermodynamic module; PM10; Northern Italy; Aerosol speciation;

Impact of a European directive on ship emissions on air quality in Mediterranean harbours by Clara Schembari; Fabrizia Cavalli; Eleonora Cuccia; Jens Hjorth; Giulia Calzolai; Noemi Pérez; Jorge Pey; Paolo Prati; Frank Raes (661-669).
Ships have been found to be major sources of air pollution in harbours. However, from January 1, 2010, a European Union directive requires that all ships at berth or anchorage in European harbours use fuels with a sulphur content of less than 0.1% by weight while previously, outside of Sulphur Emission Control Areas, up to 4.5% were allowed. The impact of this directive on air quality in some Mediterranean harbours was investigated based on observations made from August to October 2009 and 2010 at a monitoring station placed on a cruise ship, Costa Pacifica, following a fixed weekly route in the Western Mediterranean. The concentrations of SO2 were found to decrease significantly from 2009 to 2010 in three out of the four EU harbours; the average decrease of the daily mean concentrations in the different harbours was 66%. The decrease of SO2 was not statistically significant in the harbour of Barcelona because of large day-to-day variations, however measurements from monitoring stations in the harbour zone of Barcelona as well as downwind of the harbour of Palma de Mallorca confirm a strong decrease in the SO2 concentrations from 2009 to 2010. No decrease was observed in the non-EU harbour of Tunis. Neither NO x nor BC concentrations showed significant changes in any of the harbours.► Observations in Mediterranean harbours show impact of EU directive 2005/33/EC on SO2. ► Statistically significant lower SO2 levels were found in 3 out of the 4 EU harbours. ► SO2 did not change in non-EU harbour. ► The average decrease of the daily means was 66%. ► Neither NO x nor BC changed significantly.
Keywords: Air quality; Sulphur dioxide; Ship emissions; Harbours; Mediterranean; Vanadium; Nickel;