Atmospheric Environment (v.81, #C)

Downscaling is a technique that is used to extract high-resolution information from regional scale variables produced by coarse resolution models such as Chemical Transport Models (CTMs). Statistical downscaling methods in geophysics often rely on Empirical Orthogonal Functions (EOFs). EOFs are spatial Principal Components (PCs) that display space-time modes of variability of a quantity over a region. Here we present a novel statistical downscaling method that employs Fitted Empirical Orthogonal Functions (F-EOFs) to provide local forecasts. F-EOFs differ from EOFs in that they represent space-time variations associated with a particular location through the use of inverse regression. We illustrate our downscaling method, for ozone levels over the US, with the Regional chEmical trAnsport Model (REAM) whose outputs are over 70 by 70 km grid cells. We use ground level ozone observations from monitoring stations within the south-eastern US region to downscale REAM. We select the first leading F-EOFs and regress our observations on the corresponding F-EOF loadings. We also compare our results to linear regression and PC regression. The regression on F-EOFs shows the best predictive ability. To examine the consistency of our results we repeat the analysis for different fitting and validation periods. Furthermore, in our application, PFC regression also outperforms PC regression as a dimension reduction technique.
Keywords: Principal Fitted Components; Principal Components; Dimension reduction; Empirical Orthogonal Functions; Downscaling;

Ozone removal by occupants in a classroom by Andreas Fischer; Evert Ljungström; Sarka Langer (11-17).
Ozone concentrations were measured in a classroom with and without occupants, with the purpose to quantify effects on indoor O3 concentrations. The teacher and 24 11-year old pupils each removed O3 at a rate, first order in O3, corresponding to a rate constant of (2.5 ± 0.6) × 10−5 s−1 in the present locality and to a deposition velocity of 0.45 cm s−1. The O3-removal caused by the occupants was approximately 2.6 times larger than that of the available surfaces belonging to the classroom and its furniture. Observation of 6-methyl-5-hepten-2-one and 4-oxopentanal at maximum concentrations of 0.2 ppb and 0.7 ppb, respectively, suggested squalene from human skin oil as a reactive, ozone-consuming substance. There are indications of a source of 4-oxopentanal in the classroom, even some time after the pupils left for the day. The work presented is important for a proper description of indoor exposure, both to ozone itself and some of its reaction products when trying to quantify relations between exposure and health effects.
Keywords: Squalene; 4-Oxopentanal; Ozone; Deposition velocity; Indoor environment; School;

The present work describes the determination of Sb and Mo in dust deposited on tree leaves using direct solid sample analysis. Nineteen air particulate samples were collected from different districts of Cairo and surrounding cities. Since some samples have been taken from places less exposed to the pollution factors, the present study allows the comparison of air quality between high and low polluted areas. High-resolution continuum source graphite furnace atomic absorption spectrometry has been investigated, using direct solid sample analysis. The optimum pyrolysis and atomization temperatures for Sb were found to be 800 °C and 1900 °C, and 1200 °C and 2650 °C, respectively for Mo. The limits of detection and quantification for both, Sb and Mo, were 15 μg g−1 and 50 ng g−1, respectively. The characteristic mass at was found to be m 0 = 38 pg for Sb (217.582 nm) and m 0 = 28 pg for Mo (313.259 nm). The results obtained for three certified reference materials of urban particulate matter confirmed the validity of the investigated method. The content of Sb varied between 213 ± 1.3 μg g−1 and 1117 ± 230 μg g−1 with an average of 667 ± 339 μg g−1. On the other hand, the Mo content varied from 113 ± 2.3 μg g−1 to 361 ± 51 μg g−1 and its average value equals 190 ± 62 μg g−1.
Keywords: Air pollution; Sb; Mo; Direct solid sample analysis; High-resolution continuum source graphite furnace atomic absorption spectrometry;

Volatile organic compound (VOC) emission from building materials into air has been quantified, characterized and modeled. Internal diffusion of VOC through a material based on Fick's law of diffusion is the basis for mass transfer modeling of diffusive emission used to estimate VOC concentrations in air over time. Current mass transfer models have been shown to appropriately estimate air VOC concentrations at approximate room temperature, while other research has shown that temperature has a profound effect on the diffusion coefficient, D, of VOC in a material. Here, a mass transfer model is operated at 23 °C and 40 °C using input parameters applicable for each temperature. The model estimates are validated against environmental test chamber data for styrene emission from a vinyl ester resin thermoset composite material. The model correlates well with the 23 °C chamber data, but underestimates chamber data by as much as 10−4 at 264 h for the 40 °C modeling. This suggests that the model requires adjustment for predicting VOC air concentrations at temperatures other than 23 °C.
Keywords: Modeling; VOC; Mass transfer; Diffusion coefficient; Styrene; Environmental test chamber;

Particle size distributions of currently used pesticides in a rural atmosphere of France by Clara Coscollà; Abderrazak Yahyaoui; Patrice Colin; Corine Robin; Laurent Martinon; Stéphanie Val; Armelle Baeza-Squiban; Abdelwahid Mellouki; Vicent Yusà (32-38).
This work presents first data on the particle size distributions of current-used pesticides in the atmosphere. Ambient air samples were collected using a cascade impactor distributed into four size fractions in a rural site of Centre Region (France). Most pesticides were accumulated in the fine (0.1–1 μm) particle size fraction such as cyprodinil, pendimethalin, fenpropidin, fenpropimorph and spiroxamine. Other pesticides such as acetochlor and metolachlor presented a bimodal distribution with maximum concentrations in the ultrafine (0.03–0.1 μm)–coarse (1–10 μm) and in the ultrafine–fine size ranges, respectively. No pesticides were detected in the size fraction >10 μm.
Keywords: Pesticide; Size distribution; Atmospheric concentrations;

Impacts of Asian dust events on atmospheric fungal communities by Eun Mi Jeon; Yong Pyo Kim; Kweon Jeong; Ik Soo Kim; Suk Won Eom; Young Zoo Choi; Jong-Ok Ka (39-50).
The composition of atmospheric fungi in Seoul during Asian dust events were assessed by culturing and by molecular methods such as mold specific quantitative PCR (MSQPCR) and internal transcribed spacer cloning (ITS cloning). Culturable fungal concentrations in the air were monitored from May 2008 to July 2011 and 3 pairs of ITS clone libraries, one during Asian dust (AD) day and the other during the adjacent non Asian dust (NAD) day for each pair, were constructed after direct DNA extraction from total suspended particles (TSP) samples. In addition, six aeroallergenic fungi in the atmosphere were also assessed by MSQPCR from October, 2009 to November, 2011. The levels of the airborne culturable fungal concentrations during AD days was significantly higher than that of NAD days (P < 0.005). In addition, the correlation of culturable fungal concentrations with particulate matters equal to or less than 10 μm in aerodynamic diameter (PM10) concentrations was observed to be high (0.775) for the AD days while correlation coefficients of PM10 as well as other particulate parameters with airborne fungal concentrations were significantly negative for the NAD days during intensive monitoring periods (May to June, 2008). It was found that during AD days several airborne allergenic fungal levels measured with MSQPCR increased up to 5–12 times depending on the species. Comparison of AD vs. NAD clones showed significant differences (P < 0.05) in all three cases using libshuff. In addition, high proportions of uncultured soil fungus isolated from semi-arid regions were observed only in AD clone libraries. Thus, it was concluded that AD impacts not only airborne fungal concentrations but also fungal communities.
Keywords: Asian dust events; MSQPCR; Allergenic fungi; Airborne culturable fungal concentration; ITS clone library;

Annual variations of the altitude distribution of aerosols and the effect of long-range transport in modulating the aerosol loading over Thiruvananthapuram (8.5°N, 77°E), a relatively clean tropical station located in the southwest coast of Peninsular India, are investigated using dual polarization Micro Pulse Lidar observations carried out during March 2008–May 2011. Combined analysis of these lidar observations with the spatial distribution of aerosols derived from satellite data shows the occurrence of elevated layers of highly non-spherical aerosols in the 1.5–4 km altitude region, which are associated with the wide-spread aerosol plumes over the Arabian Sea during the pre-monsoon and summer-monsoon seasons. In contrast, ∼90% of the column integrated aerosol backscatter coefficient (β a) (below 5 km altitude) occurs below ∼1.5 km during winter. Seasonal variation of mean β a below ∼1 km altitude is <20%. Altitude profiles of β a above ∼1 km during January – characterised by the smallest values of β a, absence of elevated aerosol layers, and weak atmospheric winds – may be considered as the upper limit of the contribution by locally produced aerosols for quantifying the effect of long-range transport during the other months. Compared to January, a 3–10 fold increase in β a occurs in the 2–4 km altitude region during April–May and July–August. The elevated layers contribute ∼20–30% of the total aerosol loading during the above months.Display Omitted
Keywords: Aerosols; Lidar; Indian region; Elevated aerosol layer; Depolarization ratio;

Validation of the Institute of Atmospheric Physics emergency response model with the meteorological towers measurements and SF6 diffusion and pool fire experiments by Junling An; Weiling Xiang; Zhiwei Han; Kaitao Xiao; Zifa Wang; Xinhua Wang; Jianbin Wu; Pingzhong Yan; Jie Li; Yong Chen; Jian Li; Ying Li (60-67).
The urban canopy layer parameterization (UCP), a successive bias correction method (SBC), an atmospheric dispersion module for denser-than-air releases, and the emission intensity of chemicals monitored by a Fourier-transform-infrared remote sensor (EM27) were incorporated into the Institute of Atmospheric Physics emergency response model (IAPERM). IAPERM's performance was tested in Beijing using the field data collected from a 325-m meteorological tower and sulfur hexafluoride (SF6) diffusion and pool fire experiments. The results show that the IAPERM simulations of the vertical wind speeds in the urban canopy layer (UCL) with the UCP perform much better than those with the Monin–Obukhov similarity parameterization scheme. The IAPERM forecasts for air temperature and relative humidity are more accurate than those for wind speed and direction, which require correction. When the SBC with the local terrain effect is adopted, the wind speed and direction and the maximum concentrations of black carbon near the ground are well forecasted. IAPERM reproduces the spatial distributions of the SF6 observations more accurately near the release source (≤500 m) than at locations far away from the release source with the use of the observed meteorological parameters. These results suggest that IAPERM could be a promising tool for passive and dense gas diffusion simulations or forecasts.
Keywords: Dense gas; Sulfur hexafluoride; Urban canopy layer parameterization; Emergency response; Atmospheric dispersion model;

Black carbon (BC) or soot particles formed by combustion are ubiquitous in the atmosphere and have a significant effect on climate and human health. Oxidation can change the physicochemical characteristics of BC, thereby increasing its toxicity. The physicochemical properties of BC and ozone-oxidized BC are investigated in this study through transmission electron microscopy, X-ray photoelectron spectroscopy, diffuse reflectance infrared Fourier transform spectroscopy, ultraviolet–visible spectrophotometry, and electron paramagnetic resonance. The contents of oxygen-containing functional groups, hydrophilicity, water-soluble organic compounds, and free radicals increased after ozone treatment. The redox capacity and cytotoxicity of BC particles were enhanced by ozone oxidation as detected by dithiothreitol (DTT) and 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide assays. The redox activities of different BC particles are compared. Particle phase contributed significantly to total redox activity as detected by the DTT assay. Results indicate that BC particles that have undergone aging in the atmosphere may be more toxic and harmful to human health.
Keywords: Black carbon; Ozone; Redox capacity; Toxicity; DTT assay;

Effects of collinearity, unknown source and removed factors on the NCPCRCMB receptor model solution by Ying-Ze Tian; Gui-Rong Liu; Cai-Yan Zhang; Jian-Yu Wu; Fang Zeng; Guo-Liang Shi; Yin-Chang Feng (76-83).
Traditional chemical mass balance (CMB) model is sensitive to collinearity problem among source profiles, which may result in unreliable information. A Nonnegative Constrained Principal Component Regression Chemical Mass Balance (NCPCRCMB) model was developed in our previous work to solve the collinearity problem for source apportionment. In this work, the effects of both source collinearity and presence of unknown source on NCPCRCMB model were investigated, through synthetic datasets with different degrees of collinearity among source profiles and different proportions of unknown source (the ratio of unknown source contribution to the total contribution of the known sources). The results suggest that, compared with USEPA CMB8.2, the NCPCRCMB model could obtain more stable outcomes, even if when dealing with the datasets with strong collinearity problem. NCPCRCMB model can tolerate high levels of both source collinearity degrees and unknown source proportions. When collinearity was very high and contributions of two collinear sources were very different, the results of NCPCRCMB might not be satisfactory. In addition, a method to determine the number of removed factors (a pivotal step for NCPCRCMB model), was proposed and validated by synthetic datasets as well as an ambient dataset from Kaifeng, China. The results of both synthetic datasets and ambient dataset indicate that investigating source profiles weighted by Initial Effective Variance could be more reasonable when determining the number of removed factors for NCPCRCMB model.
Keywords: NCPCRCMB model; CMB model; Unknown source; Collinearity problem; PCR;

Diurnal variability of chlorinated polycyclic aromatic hydrocarbons in urban air, Japan by Takeshi Ohura; Yuichi Horii; Mitsuhiro Kojima; Yuta Kamiya (84-91).
Concentrations of 3- to 5-ring chlorinated polycyclic aromatic hydrocarbons (ClPAHs) and corresponding PAHs were quantified in 3-h integrated air samples, taken serially over 3-day periods in December 2009 (winter) and August 2010 (summer) in the urban area of Shizuoka, Japan. Twenty species of targeted ClPAHs were detected in both gas and particle phases throughout each campaign. Mean concentrations of total ClPAHs in the winter and summer campaigns were 133 ± 53 pg m−3 and 32 ± 27 pg m−3, respectively. Throughout the campaigns, diurnal variations of total ClPAHs concentrations did not have periodic fluctuation such as decreasing in daytime and increasing in nighttime, observed in PAHs. However, the mean concentrations of particulate ClPAHs trended to be slightly higher in nighttime than in daytime, but not for gaseous ClPAHs. Significant correlations were observed between the concentrations of total ClPAHs and total PAHs in particulate phase, but not in gaseous phase. In addition, for particulate phase, there were significant correlations between the concentrations of individual ClPAHs and corresponding parent PAHs, nitrate, and chlorine in summer, but not in winter. Considering these behaviors of ClPAHs in the air, the emission sources could have features of as follows: (i) specific emission sources emitted both ClPAHs and PAHs in particulate phase could be present in the area; (ii) particulate ClPAHs could be more strongly influenced by local sources and photochemical reactions rather than by transboundary air pollution; (iii) the possible sources could be combustion processes included biomass and fossil fuels.
Keywords: Chlorinated polycyclic aromatic hydrocarbons; PAHs; Urban air pollution; Diurnal variation; Emission sources;

Although large quantities of air pollutants are released into the atmosphere, they are partially monitored and routinely assessed for their health implications. This paper proposes a statistical model describing the temporal behavior of hazardous air pollutants (HAPs), which can have negative effects on human health. Benzo[a]pyrene (BaP) is selected for statistical modeling. The proposed model incorporates the linkage between BaP and meteorology and is specifically formulated to identify meteorological effects and allow for seasonal trends. The model is used to estimate and forecast temporal fields of BaP conditional on observed (or forecasted) meteorological conditions, including temperature, precipitation, wind speed, and air quality. The effects of BaP on human health are examined by characterizing health indicators, namely the cancer risk and the hazard quotient. The model provides useful information for the optimal monitoring period and projection of future BaP concentrations for both industrial and residential areas in Korea.
Keywords: Benzo[a]pyrene; Cancer risk; Hazardous air pollutants (HAPs); Polycyclic aromatic hydrocarbons(PAHs); Statistical model;

The observed response of Ozone Monitoring Instrument (OMI) NO2 columns to NO x emission controls on power plants in the United States: 2005–2011 by Bryan N. Duncan; Yasuko Yoshida; Benjamin de Foy; Lok N. Lamsal; David G. Streets; Zifeng Lu; Kenneth E. Pickering; Nickolay A. Krotkov (102-111).
We show that Aura Ozone Monitoring Instrument (OMI) nitrogen dioxide (NO2) tropospheric column data may be used to assess changes of the emissions of nitrogen oxides (NO x ) from power plants in the United States, though careful interpretation of the data is necessary. There is a clear response for OMI NO2 data to NO x emission reductions from power plants associated with the implementation of mandated emission control devices (ECDs) over the OMI record (2005–2011). This response is scalar for all intents and purposes, whether the reduction is rapid or incremental over several years. However, it is variable among the power plants, even for those with the greatest absolute decrease in emissions. We document the primary causes of this variability, presenting case examples for specific power plants.
Keywords: Ozone Monitoring Instrument; Nitrogen dioxide; Air quality; Space-based observations; Power plant emissions; Emission control devices;

Southwest Memphis is a residential region surrounded by fossil fuel burning, steel, refining, and food processing industries, and considerable mobile sources whose emissions may pose adverse health risks to local residents. This study characterizes cancer and non-cancer risks resulting from exposure to ambient air toxics in southwest Memphis. Air toxics samples were collected at a central location every 6 days from June 5, 2008 to January 8, 2010. Volatile organic compounds (VOCs) were collected in evacuated stainless-steel canisters and aldehydes by DNPH cartridges, and samples were analyzed for 73 target compounds. A total of 60 compounds were detected and 39 were found in over 86% of the samples. Mean concentrations of many compounds were higher than those measured in many industrial communities throughout the U.S. The cumulative cancer risk associated with exposure to 13 carcinogens found in southwest Memphis air was 2.3 × 10−4, four times higher than the national average of 5.0 × 10−5. Three risk drivers were identified: benzene, formaldehyde, and acrylonitrile, which contributed 43%, 19%, and 14% to the cumulative risk, respectively. This is the first field study to confirm acrylonitrile as a potential risk driver. Mobile, secondary, industrial, and background sources contributed 57%, 24%, 14%, and 5% of the risk, respectively. The results of this study indicate that southwest Memphis, a region of significant income, racial, and social disparities, is also a region under significant environmental stress compared with surrounding areas and communities.
Keywords: Air toxics; Hot spot; Volatile organic compound; Aldehyde; Acrylonitrile; Disparity;

Reduction in (pro-)inflammatory responses of lung cells exposed in vitro to diesel exhaust treated with a non-catalyzed diesel particle filter by Sandro Steiner; Jan Czerwinski; Pierre Comte; Loretta L. Müller; Norbert V. Heeb; Andreas Mayer; Alke Petri-Fink; Barbara Rothen-Rutishauser (117-124).
Increasingly stringent regulation of particulate matter emissions from diesel vehicles has led to the widespread use of diesel particle filters (DPFs), the effect of which on exhaust toxicity is so far poorly understood. We exposed a cellular model of the human respiratory epithelium at the air-liquid interface to non-catalyzed wall-flow DPF-filtered diesel exhaust and compared the resulting biological responses to the ones observed upon exposure to unfiltered exhaust. Filtered diesel exhaust acted highly oxidative, even though to a lesser extent than unfiltered exhaust (quantification of total reduced glutathione), and both exhaust types triggered comparable responses to oxidative stress (measurement of heme-oxygenase 1 (HMOX1) and superoxide-dismutase (SOD1) gene expression). Further, diesel exhaust filtration significantly reduced pro-inflammatory responses (measurement of tumor necrosis factor (TNF) and interleukin-8 (IL-8) gene expression and quantification of the secretion of their gene products TNF-α and IL-8). Because inflammatory processes are central to the onset of adverse respiratory health effects caused by diesel exhaust inhalation, our results imply that DPFs may make a valuable contribution to the detoxification of diesel vehicle emissions. The induction of significant oxidative stress by filtered diesel exhaust however, also implies that the non-particulate exhaust components also need to be considered for lung cell risk assessment.
Keywords: Diesel particle filter; Exhaust toxicity; Inhalation toxicity; Diesel exhaust particles;

Particulate and gas sampling of prescribed fires in South Georgia, USA by Sivaraman Balachandran; Jorge E. Pachon; Sangil Lee; Michelle M. Oakes; Neeraj Rastogi; Wenyan Shi; Efthimios Tagaris; Bo Yan; Aika Davis; Xiaolu Zhang; Rodney J. Weber; James A. Mulholland; Michael H. Bergin; Mei Zheng; Armistead G. Russell (125-135).
Gaseous and particulate species from two prescribed fires were sampled in-situ, to better characterize prescribed burn emissions. Measurements included gaseous and fine particulate matter (PM2.5) species, particle number concentration, particulate organic carbon (POC) speciation, water-soluble organic carbon (WSOC) and water-soluble iron. Major PM2.5 components included OC (∼57%), EC (∼10%), chloride (∼1.6%), potassium (∼0.7%) and nitrate (∼0.9%). Major gaseous species include carbon dioxide, carbon monoxide, methane, ethane, methanol and ethylene. Particulate organic tracers of biomass burning, such as levoglucosan, dehydroabietic acid and retene, increased significantly during the burns. Water-soluble organic carbon (WSOC) also increased significantly during the fire and levels are highly correlated with total potassium (K) (R 2 = 0.93) and levoglucosan (R 2 = 0.98). The average WSOC/OC ratio was 0.51 ± 0.03 and did not change significantly from background levels. Thus, the WSOC/OC ratio may not be a good indicator of secondary organic aerosol (SOA) in regions that are expected to be impacted by biomass burning. Results using a biomass burning source profile derived from this work further indicate that source apportionment is sensitive to levels of potassium in biomass burning source profiles. This underscores the importance of quantifying local biomass burning source profiles.
Keywords: Prescribed fires; Biomass burning; PM2.5; Gas; Emissions; Tracers; Source apportionment;

Remote sensing of surface visibility from space: A look at the United States East Coast by Amy L. Kessner; Jun Wang; Robert C. Levy; Peter R. Colarco (136-147).
Measurement of surface visibility is important for the management of air quality, human health, and transportation. Currently, visibility measurements are only available through ground-based instrumentation, such as the Automated Surface Observing System (ASOS), and therefore lack spatial coverage. In analogy to the recent work of using satellite-based aerosol optical depth (AOD) to derive surface dry aerosol mass concentration at continental-to-global scale for cloud-free conditions, this study evaluates the potential of AOD retrieved from the MODerate Resolution Imaging Spectroradiometer (MODIS) for deriving surface visibility. For this purpose of evaluation the truncated (up to ∼16 km or 10 miles) and discrete (at the interval no less than 0.4 km or 1/4 mile) visibility data from hourly operational weather reports are not suitable, and the ASOS-measured one-minute raw surface extinction coefficient (b ext) values have to be used. Consequently, a method for quality control on the b ext data is first developed to eliminate frequent problems such as extraneous points, poor calibration, and bad formatting, after which reliable b ext data are obtained to estimate the surface visibility. Subsequent analysis of the AOD and b ext relationship on the East Coast of the United States reveals their average linear correlation coefficient (R) of 0.61 for all twelve (2000–2011) years of data at 32 ASOS stations, with the highest R value in summer and the lowest values in fall and winter. Incorporation of the Goddard Earth Observing System, Version 5 (GEOS-5) modeled vertical profile of aerosols into the derivation of visibility from AOD is evaluated for two methods, one scaling the modeled surface b ext with the ratio of MODIS AOD to the modeled AOD, and another scaling the ratio of modeled AOD in the boundary layer to total columnar AOD with the MODIS AOD and assuming well-mixed aerosol extinction in the boundary layer. Analysis with three summers (2003–2004, 2006) of available GEOS-5 data and ASOS data reveals that the second method is superior, and generates a regression model that, after independent evaluation for summer 2005, is found to be statistically robust with R of 0.70 and a mean bias of 0.32 km in derived visibility. This study is among the first to demonstrate the potential of using satellite-based aerosol product over land to operationally derive surface visibility.
Keywords: Visibility; Remote sensing; Aerosol optical depth; MODIS; GEOS-5;

Remote measurement of diesel locomotive emission factors and particle size distributions by G.R. Johnson; E.R. Jayaratne; J. Lau; V. Thomas; A.M. Juwono; B. Kitchen; L. Morawska (148-157).
A technique for analysing exhaust emission plumes from unmodified locomotives under real world conditions is described and applied to the task of characterizing plumes from railway trains servicing an Australian shipping port. The method utilizes the simultaneous measurement, downwind of the railway line, of the following pollutants; particle number, PM2.5 mass fraction, SO2, NO x and CO2, with the last of these being used as an indicator of fuel combustion. Emission factors are then derived, in terms of number of particles and mass of pollutant emitted per unit mass of fuel consumed. Particle number size distributions are also presented.The practical advantages of the method are discussed including the capacity to routinely collect emission factor data for passing trains and to thereby build up a comprehensive real world database for a wide range of pollutants.Samples from 56 train movements were collected, analyzed and presented. The quantitative results for emission factors are: EF(N) = (1.7 ± 1) × 1016 kg−1, EF(PM2.5) = (1.1 ± 0.5) g kg−1, EF(NO x ) = (28 ± 14) g kg−1, and EF(SO2) = (1.4 ± 0.4) g kg−1. The findings are compared with comparable previously published work. Statistically significant (p < α, α = 0.05) correlations within the group of locomotives sampled were found between the emission factors for particle number and both SO2 and NO x .
Keywords: Exhaust emission plumes; Emission factors; Particle size distributions; Unmodified locomotives;

Diagnostic identification of the impact of meteorological conditions on PM2.5 concentrations in Beijing by Jizhi Wang; Yaqiang Wang; Hua Liu; Yuanqin Yang; Xiaoye Zhang; Yi Li; Yangmei Zhang; Guo Deng (158-165).
Using daily PM2.5 concentration data from Beijing, surface observations and upper-air sounding data from regional weather stations in Beijing and North China from 2007 to 2008, 5-min AWS (automatic weather station) observations and hourly AMS (aerosol mass spectrum) data from July 2008, we analysed sensitive meteorological parameters and conditions that affect the concentration of PM2.5. We also diagnosed and identified the impact of meteorological conditions on air quality (AQ). The results show that the condensation function fc is a sensitive and significant parameter for PM2.5 concentration, favourable for generation of secondary aerosol particles. Statistical analysis of a large sample of PM2.5 and meteorological observation data indicates that adaptive weight parameter β is of great value in diagnosing changes in PM2.5 concentrations. When Beijing and North China experience dry, cold winters with a low fc, the parameter β will be large, creating conditions that are conducive to suspended fine particles. In moist, hot summers, the high temperature and humidity increase the fc, but β plays a much weaker role than in winter. β and fc influence and restrict each other, and their impacts on the changes in PM2.5 concentrations are consistent with the observed seasonal changes in meteorological elements and PM2.5 concentrations. In addition, a good correlation exists between the 24-h forecast of the I index and the PM2.5 observations in Beijing, which will prove useful in diagnosing, identifying and predicting the influence of meteorological conditions on AQ based on PM2.5 concentrations.
Keywords: PM2.5; Diagnosis; Condensation function; Adaptive weight parameter; Meteorological condition;

A top-down approach to evaluate high ozone (O3) formation, attributed to different emission sources, is developed for anti-cyclonic conditions in a region of Hong Kong influenced by meso-scale circulations. A near-explicit photochemical model coupled with the Master Chemical Mechanism (MCMv3.2) is used to investigate the chemical characteristics in the region. Important features have been enhanced in this model including the photolysis rates, simulated by the National Center for Atmospheric Research (NCAR) Tropospheric Ultraviolet and Visible (TUV) Radiation Model, as well as hourly variation of Volatile Organic Compound (VOC) concentration input from on-site sampling. In general, the combined model gives a reasonably good representation of high O3 levels in the region. The model successfully captured a multi-day O3 event in the autumn of 2010. Source apportionment via Positive Matrix Factorization (PMF) was carried out on the sampled VOC data, to determine the major sources in the region. Based on the outcomes of the PMF source apportionment, a sensitivity analysis using the developed photochemical model was conducted and used to estimate O3 reduction under different source removal regimes. Results indicate that vehicular emissions are the dominant VOC source contributing to O3 formation. This study has demonstrated a potentially efficient secondary pollutants control methodology, using a combined field measurements and modelling approach.
Keywords: Photochemical model; Master Chemical Mechanism (MCM); Volatile Organic Compounds (VOC); Photochemical Ozone Creation Potential (POCP); Positive Matrix Factorization (PMF);

A laboratory-based closure study was completed to compare measured and modeled optical properties and their dependence on controlled relative humidity (RH) for inorganic salts, dicarboxylic acids, and their mixtures. The closure between measured and modeled values of the light scattering coefficients were evaluated by calculating the average relative difference (ARD) values, which revealed agreement within 8.0% for the total scattering (σ sp ) and 14.8% for the back scattering (σ bsp ) values at dry RH conditions for all test aerosols. These ARD values were less than the total relative uncertainty based on the measurement and modeling approaches, indicating the achievement of closure for σ sp and σ bsp . Optical properties derived from σ sp including: (1) the hygroscopic growth factor, f σ s p , (2) the backscatter ratio, b, and (3) the Ångström exponent, å, were also compared with measured values. The ARD values between corresponding measured and modeled results for these derived optical parameters ranged from 0.1% to 30.8%. The impact of particulate organic matter (POM) on optical and hygroscopic properties of the aerosols tested here was also compared to the aerosol optical and composition measurements that occurred during the New England Air Quality Study-Intercontinental Transport and Chemical Transformation field campaign. Such comparison confirmed that a larger POM mass fraction resulted in less hygroscopicity for both the ambient and the laboratory aerosols. This study evaluated closure between laboratory measurements and model calculations and validated the reliability of the measured and modeled results with the closure analysis. Therefore, Mie-Lorentz model can be used to calculate the optical properties and their dependence on RH for other aerosols with more confidence.
Keywords: Optical property; Dicarboxylic acid; Closure study; Hygroscopic property;

Identification of gas leakage source term is important for atmosphere safety. Optimization is one useful method to determine leakage source parameters. The performances of different optimization methods, including genetic algorithm (GA), simulated annealing (SA), pattern search (PS) method, Nelder–Mead simplex method (N–M simplex) and their hybrid optimization methods, were discussed. It was seen that GA–PS hybrid optimization has the best performance for location and source strength estimation while the hybrid methods with N–M simplex is the best one when time cost and robustness are added into consideration. Moreover, the performances of these optimization methods with different initial values, signal noise ratios (SNR), sensor numbers and sensor distribution forms were discussed. Further, experiment data test showed that the less deviation of forward simulation model from the real condition, the better performance of the source parameters determination method is. When two error correction coefficients were added to the Gaussian dispersion model, the accuracy of source strength and downwind distance estimation is increased. Other different cost functions were also applied to identify the source parameters. Finally, a new forward dispersion model based on radial basis function neural network and Gaussian model (Gaussian–RBF network) was presented and then it was applied to determine the leakage source parameters. The results showed that the performance of optimization method based on Gaussian–RBF network model is significantly improved, especially for location estimation. Therefore, the optimization method with a good selection of forward dispersion model and cost function will obtain a satisfactory estimation result.Display Omitted
Keywords: Gas leakage; Source identification; Optimization methods; Neural network; Atmosphere dispersion;

An ozone prediction model based on a supervised hidden Markov model (HMM) and generalized linear models (GLMs) has been developed and tested on data from Livermore Valley, CA. Hidden states in the supervised HMM are assigned to represent different ozone concentration ranges which make the parameters of the supervised HMM easy to be explained. Using the Viterbi algorithm (VA), not only the most likely state of 8 h-average ozone concentrations but also the relative probabilities of different concentration ranges can be obtained. Then, GLMs corresponding to different ozone concentration ranges are used to quantitatively predict surface ozone levels. Using the relative probabilities and ozone levels predicted by GLMs, an ozone concentration value in the most likely concentration range can be finally determined. In this paper, data from 8 ozone seasons spanning 2000 to 2007 are used to build the prediction model and data from 2008 to 2009 are used for validation. The results show that this model can be used to predict all ozone exceedance days correctly. Compared to the generalized linear mixed effects model (GLMM), which is also used to model grouped data, the true prediction rate (TPR) of the proposed model is higher by 27%. Compared to the prediction results using the supervised HMM alone, the mean absolute error (MAE) of ozone exceedance days predicted by the proposed model is reduced by 72%.
Keywords: Ozone prediction; Data-driven models; Hidden Markov models;

An improved system for modelling Spanish emissions: HERMESv2.0 by Marc Guevara; Francesc Martínez; Gustavo Arévalo; Santiago Gassó; José M. Baldasano (209-221).
Emission models play a key role in the development of high-resolution air quality modelling systems (AQMS). To minimise the uncertainty presented by these models, it is essential to match the high-resolution requirements of chemical transport models (CTMs) and to use up-to-date information and emission methodologies. During 2005 and 2006, the Barcelona Supercomputing Center – Centro Nacional de Supercomputación (BSC-CNS) developed the High-Elective Resolution Modelling Emissions System (HERMES04), which is a model that estimates anthropogenic and biogenic emissions for Spain with a temporal and spatial resolution of 1 h and 1 km2, taking 2004 as the reference period. Due to both the changes in Spanish emissions patterns and the age of the activity data and methodologies used, it has become necessary to update and improve the whole system. Hence, a new high-resolution emission model for Spain (HERMESv2.0) has been developed. This work introduces the improved emission estimation methodologies and data on which the model is based, as well as an analysis of the results obtained. The annual emissions estimated by HERMESv2.0 for Spain in 2009 are: NO x , 924 kt; NMVOCs, 2331 kt; SO2, 278 kt; CO, 2178 kt; NH3, 339 kt; PM10, 139 kt; and PM2.5, 105 kt. Compared with HERMES04, major differences are found in NMVOCs (+1172 kt) and SO2 (−870 kt). Important changes in emission patterns are also observed in terms of spatial and temporal distributions. A numerical comparison of both models with the Spanish National Emission Inventory indicates that previous underestimations have been heavily reduced in HERMESv2.0, especially for NO x (from −669 kt·year−1 to −176 kt·year−1), CO (from −761 kt·year−1 to 271 kt·year−1) and NMVOCs (from −1217 kt·year−1 to 135 kt·year−1). The new model substitutes HERMES04 as the emission core of the operational air quality forecasting system for Spain CALIOPE.
Keywords: High-elective resolution modelling emission system version 2.0; HERMESv2.0; Anthropogenic emissions; Biogenic emissions;

Real-world emissions of inland ships on the Grand Canal, China by Mingliang Fu; Yan Ding; Yunshan Ge; Linxiao Yu; Hang Yin; Wentao Ye; Bin Liang (222-229).
Ship emissions are widely recognized as a relevant source of the total air pollution and have a remarkable impact on air quality of the sea, territorial waters and coastal areas. To assess this impact, various emission models have been developed to calculate the emission inventory of ship based on ship activity data. However, few studies in China have collected the emission factors of local ship which are decisive factors in accurate assessment of ship emission inventory. This study intends to obtain emission data of inland ships on the Grand Canal of China by conducting on-board emission tests. We measured CO, HC NO x and PM emission from 7 inland ships of different engine powers, and derive distance-based and fuel-based emission factors on the basis of the cruise and manoeuvring (including port departure and port arrival) operating modes. The results show that average distance-based emission factors of CO, HC and PM for manoeuvring mode are higher than those for cruise mode. For NO x , average distance-based emission factors for cruise mode are higher than those for port arrival mode but lower than those for port departure mode. Particular number (PN) distribution analysis indicates that larger amounts of small size PM (D p < 0.01 μm) appeared on manoeuvring mode, which can affect regional air quality and human health. The average fuel-based emission factor of NO x in this study is 1.4–4.3 times higher than those in on-board studies. When compared with estimated Tier 1 standard limit (in unit of g kg−1 fuel), NO x in this study is nearly twice of Tier 1. The higher NO x emission indicates that stricter emission strategies and policies should be implemented to control ship emission in China. It is noticeable that distance-based emission factors of four pollutants are higher with the increase of engine loads.
Keywords: Inland ships; Emission factors; PEMS; Operating modes;

A global 3-D chemical transport model (GEOS-Chem) is used with the volatility basis set (VBS) approach to examine the effects of chemical aging on global secondary organic aerosol (SOA) concentrations and budgets. We present full-year simulations and their comparisons with the global aerosol mass spectrometer (AMS) dataset, the Interagency Monitoring of Protected Visual Environments (IMPROVE) dataset from the United States, the European Monitoring and Evaluation Programme (EMEP) dataset from Europe, and water-soluble organic carbon observation data collected over East Asia. Using different chemical aging constants, we find that the model results with 4 × 10−11 cm3 molecule−1 s−1 are in better agreement with all observations relative to the model results with other aging constants, without aging, and with the two-product approach. The model simulations are improved when chemical aging is considered, especially for rural regions. However, the simulations still underestimate observed oxygenated organic aerosol (OOA) in urban areas. Two sensitivity simulations including semi-volatile primary organic aerosol (POA) were conducted. We find that including semi-volatile POA improves the model in terms of the hydrogen-like organic aerosol (HOA) to OOA ratio. However, the total OA concentrations are not improved. The total SOA production is considerably increased by 53%, from 26.0 to 39.9 Tg yr−1, after considering chemical aging, remaining lower than top-down estimates of SOA production. Direct radiative forcing (DRF) increases by −0.07 W m−2 due to the chemical aging of SOA, which is comparable to the mean DRF (−0.13 W m−2) of OA from the AeroCom multi-model study. This result indicates considerable global and, more importantly, regional climate implications. For example, the regional DRF change due to chemical aging of SOA in the eastern US is −0.29 W m−2, which is 4 times greater in magnitude than the global mean value.
Keywords: Secondary organic aerosol; Chemical aging; Volatility distribution; Direct radiative forcing;

Seasonal and vertical variations in aerosol distribution over Shijiazhuang, China by Xia Sun; Yan Yin; Yuwen Sun; Yun Sun; Wei Liu; Yang Han (245-252).
To obtain a representative sampling of aerosol vertical profiles, we performed an extensive airborne characterization of aerosols under different environmental conditions over Shijiazhuang, China. Surface aerosol concentration and aerosol vertical distribution were analyzed using a set of 104 vertical profiles of aerosol number concentration and size distribution ranging from 0.1 to 3 μm observed by PCASP-100X. A four modal lognormal size distribution with 10-based logarithm was applied to fit measured aerosol size distributions at different altitudes of three seasons (spring, summer and autumn). It was found that the surface aerosol number concentration had a negative correlation with wind speed. In addition to wet removal of aerosols owing to precipitation in summer, vertical transport of aerosols from the surface to high levels is strongly influenced by convective instability, which contributes to the seasonality of aerosol vertical profiles. The aerosol vertical profiles under a wide range of synoptic conditions can be categorized as “ED” (exhibiting an exponential declining tendency with altitude), “SAL” (aerosol layers existing near surface), and “BAL” (aerosol layers at the boundary layer height). The multi-lognormal fitting captures the total aerosol number size distribution at 0.1–3 μm reasonably well. The average scale height of aerosols during spring, summer and autumn is 1.0 km, 1.6 km and 1.0 km, respectively.
Keywords: Aerosol; Vertical distribution; Size distribution; Seasonality; Synoptic conditions; Airborne observation;

Time-series analysis of mortality effects from airborne particulate matter size fractions in Beijing by Pei Li; Jinyuan Xin; Yuesi Wang; Shigong Wang; Kezheng Shang; Zirui Liu; Guoxing Li; Xiaochuan Pan; Linbo Wei; Mingzhen Wang (253-262).
Evidence concerning the health risk of fine and coarse particles is limited in developing Asian countries. The modifying effect between particles and temperature and season also remains unclear. Our study is one of the first to investigate the acute effect of particles size fractions, modifying effects and interannual variations of relative risk in a developing megacity where particulate levels are extraordinarily high compared to other Asian cities. After controlling for potential confounding, the results of a time-series analysis during the period 2005–2009 show that a 10 μg m−3 increase in PM2.5 levels is associated with a 0.65% (95% CI: 0.29–0.80%), 0.63% (95% CI: 0.25–0.83%), and 1.38% (95% CI: 0.51–1.71%) increase in non-accidental mortality, respiratory mortality, and circulatory mortality, respectively, while a 10 μg m−3 increase in PM10 is similarly associated with increases of 0.15% (95% CI: 0.04–0.22%), 0.08% (95% CI: 0.01–0.18%), and 0.44% (95% CI: 0.12–0.63%). We did not find a significant effect of PM2.5 10 on daily mortality outcomes. Our analyses conclude that temperature and particulates, exposures to both of which are expected to increase with climate change, might act together to worsen human health in Beijing, especially in the cool seasons. The level of the estimated percentage increase assume an escalating tendency during the study period, in addition to having a low value in 2008, and after the Olympic Games, the values increased significantly as the temporary atmospheric pollution control measures were terminated mostly.
Keywords: Particulate matter; PM2.5; Mortality; Health effect; Weather factors; GAM; Time-series; Beijing;

On-vehicle emission measurement of a light-duty diesel van at various speeds at high altitude by Xin Wang; Hang Yin; Yunshan Ge; Linxiao Yu; Zhenxian Xu; Chenglei Yu; Xuejiao Shi; Hongkun Liu (263-269).
As part of the research on the relationship between the speed of a vehicle operating at high altitude and its contaminant emissions, an on-vehicle emission measurement of a light-duty diesel van at the altitudes of 1000 m, 2400 m and 3200 m was conducted. The test vehicle was a 2.8 L turbocharged diesel Ford Transit. Its settings were consistent in all experiments. Regulated gaseous emissions, including CO, HC and NOx, together with particulate matter was measured at nine speeds ranged from 10 km h−1 to 90 km h−1 with 10 km h−1 intervals settings. At each speed, measurement lasted for at least 120 s to ensure the sufficiency and reliability of the collected data. The results demonstrated that at all altitudes, CO and HC emissions decreased as the vehicle speed increased. However both NOx and PM increased with vehicle speed. In terms of the effects of altitude, an increase in CO, HC and PM was observed with the rising of altitude at each vehicle speed. NOx behaved different: emission of NOx initially increased as the vehicle was raised from 1000 m to 2400 m, but it decreased when the vehicle was further elevated to 3200 m.
Keywords: On-vehicle emission test; Diesel vehicle; High altitude;

The carboxylic acid component of autumn aerosol and wet deposition (fog water and rainwater) in a broad-leaved forest in central Taiwan was investigated. High levels of low molecular weight carboxylic acids (LMWCAs) were noted in all deposition types. Acetic acid, oxalic acid and formic acid were the most prevalent carboxylic acids, together accounting for 72.2% (fog water), 86.7% (rain water), 77.2% (PM2.5) and 88.3% (PM2.5–10) of total carboxylic acid. The forest fog water contained 2453.9 ± 1030.5 ng mL−1 of carboxylic acid, 2.71 times more than was contained in forest rainwater. In PM, most carboxylic acid existed in the fine PM2.5 aerosol (576.6 ± 254.1 ng m−3 or 6.28 times more than was contained in PM2.5–10. Most carboxylic acids in PM had higher concentrations during the day. Pyruvic acid concentration was higher during the night (2.97 times), however, owing to its rapid photodegradation during the day. Citric acid accounted for 9.1% of the total carboxylic acid in fog water compared with just 1.8% in rainwater, confirming its origin from emissions from leaves. Raman spectroscopy was used to observe the photochemical conversion of citric acid into intermediate products and this observation confirmed that the carboxylic acids identified in the forest dry and wet depositions originated directly from biological emissions in the forest environment.
Keywords: Broad-leaved forest; Aerosol; Wet deposition; Organic acids; Raman spectroscopy;

Composite chemical profiles of motor vehicle emissions were extracted from ambient measurements at a near-road site in Baltimore during a windless traffic episode in November, 2002, using four independent approaches, i.e., simple peak analysis, windless model-based linear regression, PMF, and UNMIX. Although the profiles are in general agreement, the windless-model-based profile treatment more effectively removes interference from non-traffic sources and is deemed to be more accurate for many species. In addition to abundances of routine pollutants (e.g., NOx, CO, PM2.5, EC, OC, sulfate, and nitrate), 11 particle-bound metals and 51 individual traffic-related organic compounds (including n-alkanes, PAHs, oxy-PAHs, hopanes, alkylcyclohexanes, and others) were included in the modeling.
Keywords: Chemical mass balance profile; Windless regression model; Motor vehicle emissions; Semi-volatile organic compounds;

Airborne investigation of the aerosols–cloud interactions in the vicinity and within a marine stratocumulus over the North Sea during EUCAARI (2008) by S. Crumeyrolle; R. Weigel; K. Sellegri; G. Roberts; L. Gomes; A. Stohl; P. Laj; G. Momboisse; T. Bourianne; V. Puygrenier; F. Burnet; F. Chosson; J.L. Brenguier; J.M. Etcheberry; P. Villani; J.M. Pichon; A. Schwarzenboeck (288-303).
Within the European Aerosol Cloud Climate and Air Quality Interactions (EUCAARI) project, the Meteo France research aircraft ATR-42 was operated from Rotterdam (Netherlands) airport during May 2008, to perform scientific flights dedicated to the investigation of aerosol–cloud interactions. The objective of this study is to illustrate the impact of cloud processing on the aerosol particle physical and chemical properties. The presented results are retrieved from measurements during flight operation with two consecutive flights, first from Rotterdam to Newcastle (United Kingdom) and subsequently reverse along the same waypoints back to Rotterdam using data measured with compact Time of Flight Aerosol Mass Spectrometer (cToF-AMS) and Scanning Mobility Particle Sizer (SMPS). Cloud-related measurements during these flights were performed over the North Sea within as well as in close vicinity of a marine stratocumulus cloud layer. Particle physical and chemical properties observed in the close vicinity, below and above the stratocumulus cloud, show strong differences: (1) the averaged aerosol size distributions, observed above and below the cloud layer, are of bimodal character with pronounced minima between Aitken and accumulation mode, very likely due to cloud processing. (2) the chemical composition of aerosol particles is strongly dependent on the position relative to the cloud layer (vicinity or below/above cloud). In general, the nitrate and organic relative mass fractions decrease with decreasing distance to the cloud, in the transit from cloud–free conditions towards the cloud boundaries. This relative mass fraction decrease ranges from a factor of three to ten, thus leading to an increase of the sulfate and ammonium relative mass concentrations while approaching the cloud layer. (3), the chemical composition of cloud droplet residuals, analyzed downstream of a Counterflow virtual Impactor (CVI) inlet indicates increased fractions of mainly soluble chemical compounds such as nitrate and organics, compared to non cloud processed particles. Finally, a net overbalance of nitrate aerosol has been revealed by comparing cloud droplet residual and non cloud processed aerosol chemical compositions. Conclusively, this study highlights gaps concerning the sampling strategy that need to be addressed for the future missions.
Keywords: Aerosols; CCN; In-situ measurements; Stratocumulus; Activation;

Variability of particulate matter (PM10) in Santiago, Chile by phase of the Madden–Julian Oscillation (MJO) by Kelsey M. Ragsdale; Bradford S. Barrett; Anthony P. Testino (304-310).
Topographical, economical, and meteorological characteristics of Santiago, Chile regularly lead to dangerously high concentrations of particulate matter (PM10) in the city during winter months. Although the city has suffered from poor air quality for at least the past forty years, variability of PM10 in Santiago on the intraseasonal time scale had not been examined prior to this study. The Madden–Julian Oscillation (MJO), the leading mode of atmospheric intraseasonal variability, modulates precipitation and circulation on a regional and global scale, including in central Chile. In this study, surface PM10 concentrations were found to vary by phase of the MJO. High PM10 concentrations occurred during phases 4, 5 and 7, and low concentrations of PM10 occurred during phases 1 and 2. Precipitation, low-troposphere circulation, and lower-troposphere temperatures supported the observed PM10 variability. For example, during phases 1 and 2 (low PM10), precipitation was above normal, morning and evening temperature inversions were less intense than normal, and 900 hPa winds were anomalously westerly. During phases 4, 5 and 7 (high PM10), precipitation was normal to below normal, morning and evening temperature inversions were stronger than normal, and 900 hPa winds were anomalously easterly.
Keywords: Madden–Julian oscillation; Particulate matter; Santiago; Chile; Air pollution;

A literature overview of micrometeorological CH4 and N2O flux measurements in terrestrial ecosystems by Giacomo Nicolini; Simona Castaldi; Gerardo Fratini; Riccardo Valentini (311-319).
The use of micrometeorological (MM) techniques for methane (CH4) and nitrous oxide (N2O) flux measurements in terrestrial ecosystems is increasing and a general outline which summarizes key results is needed. This work provides an overview of the current status of global flux measurements of CH4 and N2O by MM techniques in terrestrial ecosystems. Published studies were grouped into four main terrestrial land cover categories and the reported flux ranges, the consistency of different MM approaches over the same ecosystem types, the variability of the MM technique performances as regards the flux detection limit and environmental conditions, were analysed. Furthermore, the issue of the comparability between MM and soil chambers measurements was evaluated. The existing dataset, although temporally and spatially limited, shows that CH4 and N2O fluxes are extremely variable in both time and space with mean fluxes spanning within interquartile ranges of 1.33 ÷ 5.45, 11.02 ÷ 68.48, 5.38 ÷ 29.28, 13.87·103 ÷ 47.60·103 nmol CH4 m−2 s−1 in forest, wetlands, croplands and artificial lands respectively, and of 0.09 ÷ 0.42, 0.24 ÷ 1.47, 9.13 ÷ 20.89 nmol N2O m−2 s−1 in forest, croplands and artificial lands (no published works were found for wetlands). When environmental conditions were comparable, a general agreement of flux ranges was found within each ecosystem type, in particular when estimates were based on accurate footprint analysis. Exceptions were mainly related to site-specific aspects or to particular measurement periods. Not all the measurement set-ups were suitable for all ecosystems, environmental conditions, turbulence characteristics and flux intensity, however the latest technological improvements make the detection of fluxes feasible virtually in all ecosystems. MM studies of CH4 and N2O fluxes were unevenly distributed around the globe and, in particular, were lacking in sensitive areas like Africa, South America and Central Asia.
Keywords: Methane; Nitrous oxide; Trace gases; Eddy covariance; Flux detection limit;

The application of inverse-dispersion and gradient methods to estimate ammonia emissions from a penguin colony by Mark R. Theobald; Peter D. Crittenden; Y. Sim Tang; Mark A. Sutton (320-329).
Penguin colonies represent some of the most concentrated sources of ammonia emissions to the atmosphere in the world. The ammonia emitted into the atmosphere can have a large influence on the nitrogen cycling of ecosystems near the colonies. However, despite the ecological importance of the emissions, no measurements of ammonia emissions from penguin colonies have been made. The objective of this work was to determine the ammonia emission rate of a penguin colony using inverse-dispersion modelling and gradient methods. We measured meteorological variables and mean atmospheric concentrations of ammonia at seven locations near a colony of Adélie penguins in Antarctica to provide input data for inverse-dispersion modelling. Three different atmospheric dispersion models (ADMS, LADD and a Lagrangian stochastic model) were used to provide a robust emission estimate. The Lagrangian stochastic model was applied both in ‘forwards’ and ‘backwards’ mode to compare the difference between the two approaches. In addition, the aerodynamic gradient method was applied using vertical profiles of mean ammonia concentrations measured near the centre of the colony. The emission estimates derived from the simulations of the three dispersion models and the aerodynamic gradient method agreed quite well, giving a mean emission of 1.1 g ammonia per breeding pair per day (95% confidence interval: 0.4–2.5 g ammonia per breeding pair per day). This emission rate represents a volatilisation of 1.9% of the estimated nitrogen excretion of the penguins, which agrees well with that estimated from a temperature-dependent bioenergetics model. We found that, in this study, the Lagrangian stochastic model seemed to give more reliable emission estimates in ‘forwards’ mode than in ‘backwards’ mode due to the assumptions made.Display Omitted
Keywords: Ammonia emissions; Penguins; Seabirds; Inverse-dispersion modelling; Nitrogen;

Gas chromatographic vapor pressure determination of atmospherically relevant oxidation products of β-caryophyllene and α-pinene by Kari Hartonen; Jevgeni Parshintsev; Vesa-Pekka Vilja; Heidi Tiala; Sinivuokko Knuuti; Ching Kwan Lai; Marja-Liisa Riekkola (330-338).
Vapor pressures (subcooled liquid, p liquid) of atmospherically relevant oxidation products of β-caryophyllene (β-caryophyllene aldehyde 0.18 ± 0.03 Pa and β-nocaryophyllene aldehyde 0.17 ± 0.03 Pa), and α-pinene (pinonaldehyde 16.8 ± 0.20 Pa, cis-pinic acid 0.12 ± 0.06 Pa, and cis-pinonic acid 0.99 ± 0.19 Pa) at 298 K were obtained by gas chromatography with flame ionization detection (FID) and mass spectrometric (MS) detection. The effects of stationary phase polarity and column film thickness on the vapor pressure values were investigated. Increase in stationary phase polarity provided smaller values, while increase in film thickness gave slightly higher values. Values for vapor pressure were at least two orders of magnitude lower when obtained by a method utilizing vaporization enthalpy (determined by gas chromatography–mass spectrometry) than by retention index method. Finally, the results were compared with values calculated by group contribution theory. For the β-caryophyllene oxidation products, the values measured by gas chromatography were slightly lower than those obtained by theoretical calculations. The opposite trend was observed for the α-pinene oxidation products. The methods based on gas chromatography are concluded to be highly useful for the determination of vapor pressures of semi-volatile compounds. Except for the most polar pinic and pinonic acids, differences between vapor pressure values obtained by GC–FID and GC–MS were small. Since GC–MS provides structural information simultaneously, the use of GC–MS is recommended.Display Omitted
Keywords: Vapor pressure; Gas chromatography; β-Caryophyllene aldehydes; Pinonaldehyde; Pinic acid; cis-pinonic acid;

In this paper we report the first direct measurements of nitrogen dioxide (NO2) in the UK using a vehicle emission remote sensing technique. Measurements of NO, NO2 and ammonia (NH3) from almost 70,000 vehicles were made spanning vehicle model years from 1985 to 2012. These measurements were carefully matched with detailed vehicle information data to understand the emission characteristics of a wide range of vehicles in a detailed way. Overall it is found that only petrol fuelled vehicles have shown an appreciable reduction in total NO x emissions over the past 15–20 years. Emissions of NO x from diesel vehicles, including those with after-treatment systems designed to reduce emissions of NO x , have not reduced over the same period of time. It is also evident that the vehicle manufacturer has a strong influence on emissions of NO2 for Euro 4/5 diesel cars and urban buses. Smaller-engined Euro 4/5 diesel cars are also shown to emit less NO2 than larger-engined vehicles. It is shown that NO x emissions from urban buses fitted with Selective Catalytic Reduction (SCR) are comparable to those using Exhaust Gas Recirculation for Euro V vehicles, while reductions in NO x of about 30% are observed for Euro IV and EEV vehicles. However, the emissions of NO2 vary widely dependent on the bus technology used. Almost all the NO x emission from Euro IV buses with SCR is in the form of NO, whereas EEV vehicles (Enhanced Environmentally friendly Vehicle) emit about 30% of the NO x as NO2. We find similarly low amounts of NO2 from trucks (3.5–12t and >12t). Finally, we show that NH3 emissions are most important for older generation catalyst-equipped petrol vehicles and SCR-equipped buses. The NH3 emissions from petrol cars have decreased by over a factor of three from the vehicles manufactured in the late 1990s compared with those manufactured in 2012. Tables of emission factors are presented for NO x , NO2 and NH3 together with uncertainties to assist the development of new emission inventories.
Keywords: Vehicle emissions; Remote sensing; Primary NO2; Emissions inventory; Selective catalytic reduction; Hybrid vehicle;

Greenhouse gas emission from the total process of swine manure composting and land application of compost by Jia Zhong; Yuansong Wei; Hefeng Wan; Yulong Wu; Jiaxi Zheng; Shenghui Han; Bofu Zheng (348-355).
Greenhouse gas (GHG) emissions from animal manure management are of great concern in China. However, there are still great uncertainties about China's GHG inventory due to the GHG emission factors partly used default values from the Intergovernmental Panel of Climate Change (IPCC) guidelines. The purpose of this study was to use a case study in Beijing to determine the regional GHG emission factors based on the combination of swine manure composting and land application of the compost with both on-site examination and a life cycle assessment (LCA). The results showed that the total GHG emission factor was 240 kgCO2eq tDS 1 (dry solids), including the direct GHG emission factor of 115 kgCO2eq tDS 1 for swine manure composting and 48 kgCO2eq tDS 1 for land application of the compost. Among the total GHG emissions of 5.06 kgCH4 tDS 1 and 0.13 kgN2O tDS 1, the swine manure composting contributed approximately 89% to CH4 emissions while land application accounted for 92% of N2O emission. Meanwhile, the GHG emission profile from the full process in Beijing in 2015 and 2020 was predicted by the scenario analysis. The composting and land application is a cost-effective way for animal manure management in China considering GHG emissions.
Keywords: Greenhouse gas emission; Compost; Land application; Pig manure; Life cycle assessment;

Temporal and spatial variability of methane emissions in a northern temperate marsh by Li Sun; Changchun Song; Yuqing Miao; Tianhua Qiao; Chao Gong (356-363).
Although methane (CH4) fluxes from northern wetlands in Asia have been described in previous research at different temporal and spatial scales, integrated studies at the ecosystem scale were scarce. In this study, CH4 fluxes were measured using eddy covariance (EC) technique and the chamber method in a cool temperate marsh in northeast China during the growing season (May–September) of 2011. CH4 emissions were highly variable, both temporally and spatially during the measurement period. According to the EC observation data, CH4 fluxes showed a significant diurnal cycle during the mid-growing season with nighttime average flux about 67% of the average daytime values. Daily cumulative CH4 fluxes varied from 54 to 250 mg CH4 m−2 d−1 with an average flux of 136.2 mg CH4 m−2 d−1. The observations of chamber method showed that CH4 emissions differed markedly among the three main plant communities. Average flux at the Carex lasiocarpa site was about 4 times and 13.5 times of that at the Glyceria spiculosa site and Deyeuxia angustifolia site, respectively. The spatial variability of CH4 flux was mainly controlled by the varying water table level as well as the spatial distribution of different vascular plants, while the seasonal dynamic of CH4 emission could be best explained by the change of surface soil temperature and air pressure. A comparison was made between EC measurements and the upscaled chamber based model. The results from the model overestimated CH4 emission by 28% compared to the EC data. Considering the large variability of methane emission, it is necessary to conduct continuous observations on CH4 emission from northern wetlands at different temporal and spatial scales to comprehend the variability and also to predict responses to climate change.
Keywords: Methane flux variability; Marsh; Eddy covariance; Chamber method;

Examination of total mercury inputs by precipitation and litterfall in a remote upland forest of Southwestern China by Jun Zhou; Xinbin Feng; Hongyan Liu; Hui Zhang; Xuewu Fu; Zhengduo Bao; Xun Wang; Yiping Zhang (364-372).
China is regarded as one of the largest anthropogenic mercury (Hg) emission source regions over the world. However, wet and dry deposition of atmospheric Hg in China has not been well investigated. In the present study, wet and litterfall depositions of total mercury (THg) were continuously measured from June 2011 to May 2012 at a high-altitude site in Mt. Ailao area, Southwestern China. The annual volume-weighted mean concentration of THg and reactive mercury (RHg) in precipitation was 2.98 and 0.92 ng L−1, respectively. The mean THg concentration in litterfall was 52 ng g−1 (dry weight). Atmospheric deposition was highly elevated in forest in the study area, with the annual mean THg deposition fluxes of 76.7 μg m−2 yr−1. Litterfall Hg depositions were the major pathway for Hg loading to the forest catchment, which were 71.2 μg m−2 yr−1 (about 92.8% of total input for THg). Forest ecosystem in the study area was a large pool of atmospheric Hg, and the average storage of Hg in forest soil (0–80 cm depth) was 191.3 mg m−2.
Keywords: Atmospheric mercury deposition; High-altitude forest; Atmospheric Hg pool; China;

Methane emissions in two small shallow neotropical lakes: The role of temperature and trophic level by Cleber Palma-Silva; Cláudio Cardoso Marinho; Edélti Faria Albertoni; Iara Bueno Giacomini; Marcos Paulo Figueiredo Barros; Leonardo Marques Furlanetto; Claudio Rossano Trindade Trindade; Francisco de Assis Esteves (373-379).
It is estimated that lakes are responsible for up to 16% of global methane (CH4) emissions. Studying the CH4 concentrations and emissions in these environments is important to estimate the total regional production of CH4 and to understand the main factors related to these emissions. The aim of this study was to measure the CH4 emissions from two shallow polymictic lakes in southern Brazil and to evaluate the roles of temperature and trophic level in increasing these emissions. Temperature was positively correlated with CH4 concentration in the water column, bubble emissions and diffusion. Both lakes exhibited significant seasonal differences in water-column and sediment methane concentrations and diffusion. The eutrophic lake produced more bubble emissions [6868.95 (±7645.97) μmol m−2 d−1 in winter and 11,251.10 (±10,160.92) μmol m−2 d−1 in summer]. Water-column and sediment concentrations [19.92 (±11.74) μmol L−1 and 1727.85 (±1581.19) μmol g−1, respectively)] and diffusion [27,549.94 (±18,258.15) μmol m−2 d−1] were also higher in summer than in winter in both lakes. All measured parameters were higher in the eutrophic lake, highlighting the maintenance of aquatic ecosystems in a low trophic state. Based on bubble emissions, the oligo-mesotrophic lake released an estimated 3142.8 g ha−1 yr−1 of CH4, while the eutrophic lake contributed 287,868.6 g ha−1 yr−1. Estimates of diffusive flux were higher: 41,832 g ha−1 yr−1 in summer for the oligo-mesotrophic lake and 1388.52 kg ha−1 yr−1 for the eutrophic lake. Our results show that shallow aquatic subtropical ecosystems are potential sources of atmospheric methane, and their contribution to global warming must be taken into account.
Keywords: Methane concentration; Eutrophication; Greenhouse gases; Global warming;

Comparison of the toxicity of diesel exhaust produced by bio- and fossil diesel combustion in human lung cells in vitro by Sandro Steiner; Jan Czerwinski; Pierre Comte; Olga Popovicheva; Elena Kireeva; Loretta Müller; Norbert Heeb; Andreas Mayer; Alke Fink; Barbara Rothen-Rutishauser (380-388).
Alternative fuels are increasingly combusted in diesel- and gasoline engines and the contribution of such exhausts to the overall air pollution is on the rise. Recent findings on the possible adverse effects of biodiesel exhaust are contradictive, at least partly resulting from the various fuel qualities, engine types and different operation conditions that were tested. However, most of the studies are biased by undesired interactions between the exhaust samples and biological culture media. We here report how complete, freshly produced exhausts from fossil diesel (B0), from a blend of 20% rapeseed-methyl ester (RME) and 80% fossil diesel (B20) and from pure rapeseed methyl ester (B100) affect a complex 3D cellular model of the human airway epithelium in vitro by exposing the cells at the air–liquid interface. The induction of pro-apoptotic and necrotic cell death, cellular morphology, oxidative stress, and pro-inflammatory responses were assessed. Compared to B0 exhaust, B20 exhaust decreased oxidative stress and pro-inflammatory responses, whereas B100 exhaust, depending on exposure duration, decreased oxidative stress but increased pro-inflammatory responses. The effects are only very weak and given the compared to fossil diesel higher ecological sustainability of biodiesel, it appears that – at least RME – can be considered a valuable alternative to pure fossil diesel.
Keywords: Rapeseed methyl-ester; Biodiesel; Diesel exhaust; Inhalation toxicity; Lung cell cultures;

Measurements of C1–C4 alkyl nitrates and their relationships with carbonyl compounds and O3 in Chinese cities by Ming Wang; Min Shao; Wentai Chen; Sihua Lu; Chen Wang; Daikuan Huang; Bin Yuan; Limin Zeng; Yue Zhao (389-398).
Ambient alkyl nitrates (RONO2) are important byproducts of O3 formation. Although concern about O3 pollution has increased recently, few studies have investigated RONO2 chemistry and distributions in China. In this study, ambient levels of C1–C4 RONO2 were measured in Chinese cities, and their relationships with parent hydrocarbons (RH), carbonyls, and total oxidant (Ox = O3 + NO2) were investigated. Our measurements showed that 2-butyl nitrate (2-BuONO2) was the most abundant RONO2 species, with mixing ratios of 48–88 pptv, followed by 2-propyl nitrate (2-PrONO2), ethyl nitrate (EtONO2), methyl nitrate (MeONO2), and 1-propyl nitrate (1-PrONO2). The measured RONO2 species exhibited maximum levels in the early afternoon (13:00–14:00) of summer, suggesting the importance of RONO2 photochemical production. Relative to 2-BuONO2/n-butane, the measured 1-PrONO2/propane agreed well with the modeled ratio based on laboratory kinetic data, suggesting that propane was the dominant precursor of ambient 1-PrONO2. However, the measured ratios for MeONO2/methane, EtONO2/ethane, and summertime 2-PrONO2/propane showed significant positive deviations from the predicted values, indicating the existence of additional sources other than OH oxidation of the parent hydrocarbons. Initial mixing ratios of C1–C3 carbonyls during 08:00–12:00 in summer at the PKU site exhibited significant correlations with RONO2 levels, suggesting the importance of secondary sources for ambient carbonyls. The measured ratios of formaldehyde/MeONO2 were close to the theoretical ratio, whereas the derived ratios for acetaldehyde/EtONO2, propanal/1-PrONO2, and acetone/2-PrONO2 were higher than the kinetic ratios, indicating that these carbonyls might be produced from sources other than the reaction of alkoxy radicals with O2. Carbonyls are important precursors of Ox, but their photochemical reactions do not result in RONO2 production. Therefore, Ox/RONO2 could indicate the relative importance of carbonyls to Ox formation. On the basis of the measured ratios of Ox/2-BuONO2, we estimated the maximum contributions of secondary carbonyls to Ox at the PKU site to be 25–32% during 12:00–16:00 in summer.
Keywords: Alkyl nitrates; Carbonyls; Ozone; Photochemistry;

Naturally occurring radioactive noble gas, radon (222Rn) is a valuable tracer to study atmospheric processes and to validate global chemical transport models. However, the use of radon as a proxy in atmospheric and climate research is limited by the uncertainties in the magnitude and distribution of the radon flux density over the Earth's surface. Terrestrial gamma radiation is a useful proxy for generating radon flux maps. A previously reported radon flux map of Europe used terrestrial gamma radiation extracted from automated radiation monitoring networks. This approach failed to account for the influence of local artificial radiation sources around the detector, leading to under/over estimation of the reported radon flux values at different locations. We present an alternative approach based on soil radionuclides which enables us to generate accurate radon flux maps with good confidence. Firstly, we present a detailed comparison between the terrestrial gamma radiation obtained from the National Radiation Monitoring network of the Netherlands and the terrestrial gamma radiation calculated from soil radionuclides. Extending further, we generated radon flux maps of the Netherlands and Europe using our proposed approach. The modelled flux values for the Netherlands agree reasonably well with the two observed direct radon flux measurements (within 2σ level). On the European scale, we find that the observed radon flux values are higher than our modelled values and we introduce a correction factor to account for this difference. Our approach discussed in this paper enables us to develop reliable and accurate radon flux maps in countries with little or no information on radon flux values.
Keywords: Radon flux; Radionuclides; Terrestrial gamma radiation; Local influence; Soil moisture; Ambient dose rate;

The emission of radon from building materials and soil depends upon the radium content, porosity, moisture content and radon diffusion length of materials. Several techniques have been used to reduce the radon emission from the soil using different flooring materials. But the effectiveness of radon shielding depends upon the diffusion of radon through these materials. The present study proposes a method for producing a radon resistant material for decreasing radon diffusion through it. The method involves rice husk ash (RHA) in addition to cement for the preparation of concrete used for flooring and walls. The radon diffusion, exhalation and mechanical property of concrete prepared by rice husk ash blended cement were studied. The addition of RHA caused the reduction in radon diffusion coefficient, exhalation rates, porosity and enhanced the compressive strength of concrete. The bulk radon diffusion coefficient of cementitious concrete was reduced upto 69% by addition of rice husk ash as compare to that of control concrete.
Keywords: Radon diffusion coefficient; Rice husk ash; Exhalation rate; Compressive strength;

WRF-Chem simulation of NO x and O3 in the L.A. basin during CalNex-2010 by Dan Chen; Qinbin Li; Jochen Stutz; Yuhao Mao; Li Zhang; Olga Pikelnaya; Jui Yi Tsai; Christine Haman; Barry Lefer; Bernhard Rappenglück; Sergio L. Alvarez; J. Andrew Neuman; James Flynn; James M. Roberts; John B. Nowak; Joost de Gouw; John Holloway; Nicholas L. Wagner; Patrick Veres; Steven S. Brown; Thomas B. Ryerson; Carsten Warneke; Ilana B. Pollack (421-432).
NO x emissions and O3 chemistry in the Los Angeles (L.A.) Basin during the CalNex-2010 field campaign (May–June 2010) have been evaluated by analyzing O3 and NO y (NO, NO2, HNO3, PAN) observations using a regional air quality model (WRF-Chem). Model simulations were conducted at 4-km spatial resolution over the basin using the Carbon-Bond Mechanism version Z (CBM-Z) and NO x emissions reduced by 24% relative to 2005 National Emissions Inventory (NEI’05), according to recent state emission statistics (BASE_NO x scenario). In addition, a 22–26% NO x emission reduction from weekday to weekend was applied. WRF-Chem reproduced the observed diurnal cycle and day-to-day variations in surface O3, O x , HNO3 and HCHO (correlation r 2  = 0.57 − 0.63; pairs of data n > 400; confidence value p < 0.01) at the CalNex supersite at Caltech but consistently overestimated surface NO and NO2. A 45% reduction of NO x emissions relative to NEI’05 (LOW_NO x scenario), as suggested by the OMI-NO2 column trend in California over the same period, improved the agreement of modeled NO2, NO x , and O3 with observations on weekdays. Three-dimensional distributions of daytime O3 and NO y were compared with five daytime NOAA WP-3D flights (three on weekdays and two on weekends) to study the Weekend-to-Weekday (WE-to-WD) effects by using the LOW_NO x scenario. Aircraft data showed a 17.3 ppb O3 increase and a 54% NO y reduction in the boundary layer on weekends relative to weekdays, while modeled WE-to-WD differences were much smaller, with a 2.9 ppb O3 increase and 16% NO y reduction only. Model results on weekends underestimated O3 by 23% and overestimated NO y and HNO3 by 40% and 27%, respectively, which may indicate that weekend NO x emissions (45% reduction relative to NEI’05 with a 22–26% reduction on weekends compared to weekdays) were still overestimated in the model. Comparisons of PAN to HNO3 ratios also indicated that the enhanced photochemistry on weekends was not well represented in the model. Although modeled weekday O3 was close to the observations in the boundary layer, modeled PAN and HNO3 were overestimated by 30% and 22%, respectively, and modeled NO y was underestimated by 24% on weekdays. Interpreted as emission ratios, the slopes of volatile organic compound (VOC) species versus CO concentrations indicated that speciated VOC emissions in the model were not accurately represented, impacting the photochemistry in the model. These findings argue for the need to improve our understanding of VOC emissions and their photochemical processing in the model.
Keywords: CalNex; WRF-Chem evaluation; Ozone; NO x ; L.A. basin;

CO2 emissions on roads in urban centers substantially affect global warming. It is important to quantify CO2 emissions in terms of the link unit in order to reduce these emissions on the roads. Therefore, in this study, we utilized real-time traffic data and attempted to develop a methodology for estimating CO2 emissions per link unit. Because of the recent development of the vehicle-to-infrastructure (V2I) communication technology, data from probe vehicles (PVs) can be collected and speed per link unit can be calculated. Among the existing emission calculation methodologies, mesoscale modeling, which is a representative modeling measurement technique, requires speed and traffic data per link unit. As it is not feasible to install fixed detectors at every link for traffic data collection, in this study, we developed a model for traffic volume estimation by utilizing the number of PVs that can be additionally collected when the PV data are collected. Multiple linear regression and an artificial neural network (ANN) were used for estimating the traffic volume. The independent variables and input data for each model are the number of PVs, travel time index (TTI), the number of lanes, and time slots. The result from the traffic volume estimate model shows that the mean absolute percentage error (MAPE) of the ANN is 18.67%, thus proving that it is more effective. The ANN-based traffic volume estimation served as the basis for the calculation of emissions per link unit. The daily average emissions for Daejeon, where this study was based, were 2210.19 ton/day. By vehicle type, passenger cars accounted for 71.28% of the total emissions. By road, Gyeryongro emitted 125.48 ton/day, accounting for 5.68% of the total emission, the highest percentage of all roads. In terms of emissions per kilometer, Hanbatdaero had the highest emission volume, with 7.26 ton/day/km on average. This study proves that real-time traffic data allow an emissions estimate in terms of the link unit. Furthermore, an analysis of CO2 emissions can support traffic management to make decisions related to the reduction of carbon emissions.
Keywords: Advanced Traffic Information System; Traffic volume estimation; Carbon dioxide; Multiple linear regression; Artificial neural network; Urban traffic;

Comparison of dicarboxylic acids and related compounds in aerosol samples collected in Xi'an, China during haze and clean periods by Chunlei Cheng; Gehui Wang; Bianhong Zhou; Jingjing Meng; Jianjun Li; Junji Cao; Shun Xiao (443-449).
PM10 aerosols from Xi'an, a mega city of China in winter and summer, 2009 were measured for secondary organic aerosols (SOA) (i.e., dicarboxylic acids (DCA), keto-carboxylic acids, and α-dicarbonyls), water-soluble organic (WSOC) and inorganic carbon (WSIC), elemental carbon (EC) and organic carbon (OC). Molecular compositions of SOA on haze and clean days in both seasons were compared to investigate their sources and formation mechanisms. DCA in the samples were 1843 ± 810 ng m−3 in winter and 1259 ± 781 ng m−3 in summer, respectively, which is similar and even higher than those measured in 2003. Oxalic acid (C2, 1162 ± 570 ng m−3 in winter and 1907 ± 707 ng m−3 in summer) is the predominant species of DCA, followed by t-phthalic (tPh) in winter and phthalic (Ph) in summer. Such a molecular composition is different from those in other Asian cities where succinic acid (C4) or malonic acid (C3) is the second highest species, which is mostly due to significant emissions from household combustion of coal and open burning of waste material in Xi'an. Mass ratios of C2/diacids, diacids/WSOC, WSOC/OC and individual diacid-C/WSOC are higher on the haze days than on the clean days in both seasons, suggesting an enhanced SOA production under the haze condition. We also found that the haze samples are acidic while the clean samples are almost neutral. Such a difference in particle acidity is consistent with the enhanced SOA production, because acid-catalysis is an important aqueous-phase formation pathway of SOA. Gly/mGly mass ratio showed higher values on haze days than on clean day in both seasons. We comprehensively investigated the ratio in literature and found a consistent pattern. Based on our observation results and those documented data we proposed for the first time that concentration ratio of Gly/mGly can be taken as an indicator of aerosol ageing.
Keywords: PM10; Dicarboxylic acids; Secondary organic aerosols; Haze; Formation mechanism;

In this study, in-vehicle and out-vehicle concentrations of fine particulate matter (PM2.5) and carbon monoxide (CO) are measured to assess commuter's exposure in a commercial residential area and on a highway, under three popular ventilation modes namely, one window half opened, air conditioning on fresh air intake, and air conditioning on recirculation and examine its relationship to scarcely studied parameters including self pollution, out-vehicle sample intake location and meteorological gradients. Self pollution is the intrusion of a vehicle's own engine fumes into the passenger's compartment. For this purpose, six car makes with different ages were instrumented to concomitantly monitor in- and out-vehicle PM2.5 and CO concentrations as well as meteorological parameters. Air pollution levels were unexpectedly higher in new cars compared to old cars, with in-cabin air quality most correlated to that of out-vehicle air near the front windshield. Self-pollution was observed at variable rates in three of the six tested cars. Significant correlations were identified between indoor to outdoor pressure difference and PM2.5 and CO In/Out (IO) ratios under air recirculation and window half opened ventilation modes whereas temperature and humidity difference affected CO IO ratios only under the air recirculation ventilation mode.
Keywords: In-vehicle exposure; Automotive emissions; Self-pollution; Meteorological gradient;

Summer methane fluxes from a boreal bog in northern Quebec, Canada, using eddy covariance measurements by Daniel F. Nadeau; Alain N. Rousseau; Carole Coursolle; Hank A. Margolis; Marc B. Parlange (464-474).
A boreal bog located in the James Bay lowlands, Canada, was instrumented with an open-path gas analyzer to monitor the turbulent fluxes of methane throughout the summer of 2012. The mostly continuous eddy covariance measurements permitted the study of methane dynamics at the hourly, daily and seasonal scales. To exclude data segments for which the biological methane fluxes were underestimated due to inefficient atmospheric transport under stable stratification, we applied a novel approach based on both the atmospheric stability parameter ζ = z/L and the friction velocity u , where z is the measurement height and L the Obukhov length. The field measurements revealed the existence of at least one sustained ebullition event, triggered by low barometric pressures, a declining water table and increasing mechanical turbulence – suggesting that large-scale release of methane bubbles can be an important transport mechanism of methane in boreal bogs. The validity of similarity scaling for atmospheric methane under convective conditions was also assessed and the normalized standard deviations of methane concentrations did not scale well with ζ, highlighting the heterogeneity in natural methane production and release across the bog. Overall the hourly emissions ranged between −2.0 and 32.1 mg CH4 m−2 h−1, with a summertime mean of 2.4 mg CH4 m−2 h−1. At the daily scale, the two main controls on methane emissions were found to be the water table position and the peat temperature at 0.3 m under the surface. Contrary to other studies, seasonal methane emissions peaked when the water table was at its maximum distance from the surface, around mid-August. No clear diurnal pattern could be found in methane emissions, indicating that methane was produced quite deep within the peat. The seasonal emissions were estimated at 4.4 g CH4 m−2, and compared well with other observations over similar landscapes using different measurement techniques. Given that methane releases and transport are greatly affected by local characteristics such as climate and vegetative cover, this study emphasizes the need for further in situ continuous measurements of methane fluxes across northern peatlands.
Keywords: Atmospheric stability; Diurnal cycle; Ebullition; Eddy covariance; Flux-variance relationship; Ombrotrophic peatland; Open-path gas analyzer; Regression tree analysis;

Aerosol optical properties during firework, biomass burning and dust episodes in Beijing by Xingna Yu; Chanzhen Shi; Jia Ma; Bin Zhu; Mei Li; Jing Wang; Suying Yang; Na Kang (475-484).
In order to characterize the aerosol optical properties during different pollution episodes that occurred in Beijing, the aerosol loading, scattering, and size distributions are presented using solar and sky radiance measurements from 2001 to 2010 in this paper. A much higher aerosol loading than the background level was observed during the pollution episodes. The average aerosol optical depth (AOD) is largest during dust episodes coupled with the lowest Ångström exponent (α), while higher AOD and lower α were more correlated with firework and biomass burning days. The total mean AOD at 440, 675, 870 and 1020 nm were 0.24, 0.49, 0.64 and 1.38 in the clean, firework display, biomass burning and dust days, respectively. The mean α for dust days was 0.51 and exceeded 1.1 for the remaining episodes. The size distribution of the dusty periods was dominated by the coarse mode, but the coarse mode was similar magnitude to the fine mode during the firework and biomass burning days. The volume concentration of the coarse mode during the dust days increased by a magnitude of more than 2–8 times that derived in the other three aerosol conditions, suggesting that dust is the major contributor of coarse mode particles in Beijing. The single scattering albedo (SSA) values also increased during the pollution episodes. The overall mean SSA at the four wavelengths were 0.865, 0.911, 0.922 and 0.931 in clean, firework display, biomass burning, and dust days in Beijing, respectively. However, in the blue spectral range, the dust aerosols exhibited pronounced absorption.
Keywords: Aerosol; Dust; Biomass burning; Firework display; Optical property;

A coupled road dust and surface moisture model to predict non-exhaust road traffic induced particle emissions (NORTRIP). Part 2: Surface moisture and salt impact modelling by B.R. Denby; I. Sundvor; C. Johansson; L. Pirjola; M. Ketzel; M. Norman; K. Kupiainen; M. Gustafsson; G. Blomqvist; M. Kauhaniemi; G. Omstedt (485-503).
Non-exhaust traffic induced emissions are a major source of airborne particulate matter in most European countries. This is particularly important in Nordic and Alpine countries where winter time road traction maintenance occurs, e.g. salting and sanding, and where studded tyres are used. Though the total mass generated by wear sources is a key factor in non-exhaust emissions, these emissions are also strongly controlled by surface moisture conditions. In this paper, Part 2, the road surface moisture sub-model of a coupled road dust and surface moisture model (NORTRIP) is described. We present a description of the road surface moisture part of the model and apply the coupled model to seven sites in Stockholm, Oslo, Helsinki and Copenhagen over 18 separate periods, ranging from 3.5 to 24 months. At two sites surface moisture measurements are available and the moisture sub-model is compared directly to these observations. The model predicts the frequency of wet roads well at both sites, with an average fractional bias of −2.6%. The model is found to correctly predict the hourly surface state, wet or dry, 85% of the time. From the 18 periods modelled using the coupled model an average absolute fractional bias of 15% for PM10 concentrations was found. Similarly the model predicts the 90'th daily mean percentiles of PM10 with an average absolute bias of 19% and an average correlation (R 2) of 0.49. When surface moisture is not included in the modelling then this average correlation is reduced to 0.16, demonstrating the importance of the surface moisture conditions. Tests have been carried out to assess the sensitivity of the model to model parameters and input data. The model provides a useful tool for air quality management and for improving our understanding of non-exhaust traffic emissions.
Keywords: Air quality; Non-exhaust emissions; Road dust; Suspension; Road surface moisture;

Source apportionment of volatile organic compounds measured in Edmonton, Alberta by Michael C. McCarthy; Yayne-Abeba Aklilu; Steven G. Brown; David A. Lyder (504-516).
From 2003 to 2009, whole air samples were collected at two sites in Edmonton and analyzed for over 77 volatile organic compounds (VOCs). VOCs were sampled in the downtown area (Central site) and an industrial area on the eastern side of the city (East site). Concentrations of most VOCs were highest at the East site, with an average total VOC mass concentration of 221 μg m−3. The average total VOC mass concentration at the Central site was 65 μg m−3. The United States Environmental Protection Agency's positive matrix factorization receptor model (EPA PMF) was used to apportion ambient concentrations of VOCs into eleven factors, which were associated with emissions sources. On average, 94 and 99% of the measured mass were apportioned by PMF at the East and Central site, respectively. Factors include transportation combustion (gasoline and diesel), industrial sources (industrial evaporative, industrial feedstock, gasoline production/storage, industrial chemical use), mixed mobile and industrial (gasoline evaporative, fugitive butane), a biogenic source, a natural gas related source, and a factor that was associated with global background pollutants transported into the area. Transportation sources accounted for more than half of the reconstructed VOC mass concentration at the Central site, but less than 10% of the reconstructed mass concentration at the East site. By contrast, industrial sources accounted for ten times more of the reconstructed VOC mass concentration at the East site than at the Central site and were responsible for approximately 75% of the reconstructed VOC mass concentration observed at the East site. Of the six industrial factors identified at the East site, four were linked to petrochemical industry production and storage. The two largest contributors to the reconstructed VOC mass concentration at the East site were associated with fugitive emissions of volatile species (butanes, pentanes, hexane, and cyclohexane); together, these two factors accounted for more than 50% of the reconstructed VOC mass concentration at the East site in contrast to less than 2% of the reconstructed mass concentration at the Central site. Natural gas related emissions accounted for 10%–20% of the reconstructed mass concentration at both sites. Biogenic emissions and VOCs associated with well-mixed global background were less than 10% of the reconstructed VOC mass concentration at the Central site and less than 3% of the reconstructed mass concentration at the East site.
Keywords: Source apportionment; Positive matrix factorization; Volatile organic compounds; National air pollution surveillance;

An ensemble statistical post-processor (ESP) is developed for the National Air Quality Forecast Capability (NAQFC) to address the unique challenges of forecasting surface ozone in Baltimore, MD. Air quality and meteorological data were collected from the eight monitors that constitute the Baltimore forecast region. These data were used to build the ESP using a moving-block bootstrap, regression tree models, and extreme-value theory. The ESP was evaluated using a 10-fold cross-validation to avoid evaluation with the same data used in the development process. Results indicate that the ESP is conditionally biased, likely due to slight overfitting while training the regression tree models. When viewed from the perspective of a decision-maker, the ESP provides a wealth of additional information previously not available through the NAQFC alone. The user is provided the freedom to tailor the forecast to the decision at hand by using decision-specific probability thresholds that define a forecast for an ozone exceedance. Taking advantage of the ESP, the user not only receives an increase in value over the NAQFC, but also receives value for costly decisions that the NAQFC couldn't provide alone.
Keywords: Ensemble forecast; Air quality; Baltimore; Regression tree; Extreme value; Bootstrap;

Characterization of nitromethane emission from automotive exhaust by Kanako Sekimoto; Satoshi Inomata; Hiroshi Tanimoto; Akihiro Fushimi; Yuji Fujitani; Kei Sato; Hiroyuki Yamada (523-531).
We carried out time-resolved experiments using a proton-transfer-reaction mass spectrometer and a chassis dynamometer to characterize nitromethane emission from automotive exhaust. We performed experiments under both cold-start and hot-start conditions, and determined the dependence of nitromethane emission on vehicle velocity and acceleration/deceleration as well as the effect of various types of exhaust-gas treatment system. We found that nitromethane emission was much lower from a gasoline car than from diesel trucks, probably due to the reduction function of the three-way catalyst of the gasoline car. Diesel trucks without a NO x reduction catalyst using hydrocarbons produced high emissions of nitromethane, with emission factors generally increasing with increasing acceleration at low vehicle velocities.
Keywords: Nitromethane; Oxidation catalyst; Proton-transfer-reaction mass spectrometry; Reduction catalyst; Three-way catalyst;

This paper focuses on analyzing the shortwave (SW; 280–3000 nm) radiative forcing associated with changes in total ozone column (TOC) under cloud- and aerosol-free conditions over the Iberian Peninsula during the last three decades (1979–2012). For this goal, net solar irradiances at the tropopause are simulated by the LibRadtran radiative transfer code using as input TOC data from the ERA-Interim reanalysis. The results showed large inter-annual variability of the SW ozone RF values, e.g., the largest difference between two consecutive years is about 0.26 W m−2 between 1990 and 1991. The linear relationship between SW ozone RF and TOC changes allowed to determinate SW ozone efficiency (ozone forcing per unit of TOC) from the slope of the regression line (−0.011 W m−2 per Dobson Unit). From this efficiency and long-term projections of future TOC recovery, the estimation of the SW ozone RF for the period 2000–2100 was −0.34 W m−2 over the Iberian Peninsula. On the other hand, average conditions during three consecutive years (2010–2011–2012) were chosen to represent the present-day state. Hence, for the entire study region, the SW ozone RF from 1979 to 1981 to present-day period was +0.14 W m−2 on annual average, showing higher values for the Northerner than for the Southerner latitudes. The marked seasonal pattern of long-term ozone trends over northern midlatitudes observed by previous studies produces notable differences in the seasonal ozone RF, with the largest forcing values occurring in spring (+0.26 W m−2). Summer months present an ozone RF of +0.11 W m−2, while autumn and winter values are below 0.1 W m−2. Finally, a detailed spectral analysis showed that the visible range (400–700 nm) represents about 79% of the SW ozone RF, followed by far by the ultraviolet range (280–400) with a relative contribution of 18%, and the infra-red interval with a low percentage of 3%.
Keywords: Radiative forcing; Total ozone; Shortwave radiation; Iberian Peninsula;

Premature mortality in Japan due to ozone by Amin Nawahda; Ken Yamashita; Toshimasa Ohara; Junichi Kurokawa; Tsuyoshi Ohizumi; Fang Chen; Hajime Akimoto (538-545).
In Japan, all 47 prefectures conduct routine air quality monitoring at 1145 stations throughout the country to assess environmental effects. This study aims to provide a better understanding of possible estimations of premature mortality in Japan caused by exposure to monitored and modeled concentrations of tropospheric ozone during the period from January to December, 2005. The spatial distribution and temporal variation of ozone concentrations were modeled using the Models-3 Community Multiscale Air Quality modeling system coupled with the Regional Emission Inventory in Asia (CMAQ/REAS). Premature mortality caused by exposure to ozone was calculated assuming a relative risk (RR) value of 1.003 [95% Confidence Interval (CI): 1.001–1.004] for concentrations above 35 ppb according to the SOMO35 index (annual Sum of daily maximum 8-h Ozone Means Over 35 ppb) recommended by WHO (2008). Based on CMAQ/REAS simulations, the estimated all-cause premature mortality in 2005 is about 13,000 (95% CI: 4320–17,300) cases. This value is 2.5 times greater than the estimated premature mortality based on monitored ozone concentrations, which is 5220 (95% CI: 1740–6960) cases.
Keywords: Premature mortality; Ozone; Exposure; CMAQ/REAS; Japan;

This study of indoor air quality reports VOC concentrations in 386 suburban homes located in Perth Western Australia, a city of low ambient pollution and temperate climate. Details of indoor VOC concentrations, temperature, relative humidity, and information on house characteristics and occupant activities were collected during the sampling periods. The concentration of VOCs observed in typical homes was low and individual compounds rarely exceeded 5 μg m−3. Median individual VOC concentrations ranged from 0.06 μg m−3 for 1,1,1 trichloroethane and butyl ether to 26.6 μg m−3 for cis/trans 2-butene. Recently renovated homes had higher concentrations of VOCs than non renovated homes, including ∑VOCs (p = 0.026), ∑BTEX (p = 0.03), ∑xylene (p = 0.013), toluene (p = 0.05), cyclohexane (p = 0.039), and propyl benzene (p = 0.039). Statistical analyses showed house age and attached garages were not significant factors for any of the VOCs tested. The concentrations of indoor VOCs in Perth were lower than overseas observations and those reported in recent Australian studies, with inferences made to differences in the climate and the occupant behaviour. The results are a baseline profile of indoor VOCs over the period 2006–2011, in an Australian city of low population density and of generally low ambient pollution.
Keywords: Indoor VOC; Indoor air pollution; Passive VOC sampling; Active VOC sampling;

Bifunctional carbonyls are ubiquitous in the atmosphere and are important contributors to atmospheric aerosols through heterogenous reactions. However, the actual contributions of bifunctional carbonyls to atmospheric aerosols have been little measured because of their capacity to coexist in both the gaseous phase and the particulate phase, making it difficult to sample them in both phases simultaneously. Using a short time resolution (2 h), we measured the atmospheric partitioning of semivolatile species to understand their contributions to atmospheric aerosols. Our results indicate that equilibrium between the gaseous phase and the particulate phase was due not only to thermodynamic partitioning but also to an aging process. Fresh emissions from motor vehicles affected the partitioning, and partitioning coefficients stabilized when the aerosols aged. The contribution of bifunctional carbonyl compounds to atmospheric aerosols was 3–8 orders of magnitude higher than that estimated by thermodynamic predictions, corroborating previous findings.
Keywords: Bifunctional carbonyls; Atmospheric secondary aerosol; Semivolatile species partitioning; Roadside sampling;

One-year study of nitro-organic compounds and their relation to wood burning in PM10 aerosol from a rural site in Belgium by Ariane Kahnt; Shabnam Behrouzi; Reinhilde Vermeylen; Mohammad Safi Shalamzari; Jordy Vercauteren; Edward Roekens; Magda Claeys; Willy Maenhaut (561-568).
Nitro-organic compounds were determined in a one-year set of atmospheric PM10 filter samples that were collected at a rural background site in Hamme, Belgium. In an earlier study, it was found that the site was substantially impacted by wood burning, making the filter samples appropriate for further investigations on wood burning indicators. In total, four groups of nitro-aromatic compounds (with molecular weights (MWs) of 139, 155, 169, and 183), α-pinene-related nitrooxy-organosulfates (MW 295), and the resin acid dehydroabietic acid (DHAA, MW 300) were quantified using liquid chromatography combined with negative ion electrospray ionization mass spectrometry. The annual mean concentrations were 0.94, 6.0, 7.7, 4.8, 7.8, and 1.76 ng m−3 for the sum of the nitrophenols (MW 139), 4-nitrocatechol (MW 155), the sums of the methyl-nitrocatechols (MW 169), of the dimethyl-nitrocatechols (MW 183), and of the α-pinene-related nitrooxy-organosulfates (MW 295), and DHAA (MW 300), respectively. 4-nitrocatechol, the sum of the methyl-nitrocatechols, and the sum of the dimethyl-nitrocatechols were substantially correlated with levoglucosan (r-values of 0.71, 0.66, and 0.65, respectively), consistent with their proposed origin from biomass burning. The nitro-aromatic compounds were also observed during the summer months, indicating a non-negligible usage of wood burning for domestic purposes at the site. The α-pinene-related nitrooxy-organosulfates (MW 295) were detected in high concentrations during the winter period, but they were poorly correlated with the biomass burning tracers. All of the targeted species showed a clear seasonal variation with highest concentrations in winter, followed by autumn, spring, and summer. Based on the DHAA measurements, it is suggested that burning of softwood is likely an important source for the formation of all the nitro-organic compounds measured.Display Omitted
Keywords: Wood burning; Nitrocatechols; Nitrophenols; Nitrooxy-organosulfates; Atmospheric aerosol; HPLC/(–)ESI-ITMS; Resin acid;

Phototransformation of 4-phenoxyphenol sensitised by 4-carboxybenzophenone: Evidence of new photochemical pathways in the bulk aqueous phase and on the surface of aerosol deliquescent particles by Elisa De Laurentiis; Joanna Socorro; Davide Vione; Etienne Quivet; Marcello Brigante; Gilles Mailhot; Henri Wortham; Sasho Gligorovski (569-578).
In addition to direct photolysis, degradation of organic compounds by solar light can also occur by indirect photolysis or photo-sensitised processes. These reactions are important because they are involved in, among others, direct and indirect climate changes, adverse health effects from inhaled particles, effects on cloud chemistry and ozone production. In this work, the importance of atmospheric photo-sensitisation is evaluated in bulk aqueous solution and on the surface of aerosol deliquescent particles. Irradiation experiments in aqueous solution indicate that 4-carboxybenzophenone (CBP) is able to photosensitise the degradation of 4-phenoxyphenol (4 PP). The process takes place via the CBP triplet state (3CBP*), which has an oxidising nature. 4 PP is fluorescent, unlike the photosensitiser CBP, with two emission bands at ∼320 and ∼380 nm. However, addition of CBP to a 4 PP solution considerably decreases the intensity of 4 PP fluorescence bands and causes a very intense new band to appear at ∼420 nm. This behaviour suggests a possible interaction between CBP and 4 PP in solution, which could favour further light-induced processes. Moreover, the new band overlaps with the fluorescence spectrum of atmospheric HULIS (HUmic-LIke Substances), suggesting that supramolecular photosensitiser–substrate interactions may have a role in HULIS fluorescence properties. The interaction between CBP and 4 PP coated on silica particles (gas–solid system) was also investigated under simulated sunlight, and in the presence of variable relative humidity. The water molecules inhibit the degradation of 4 PP, induced by 3CBP* on the surface of aerosol particles, indicating that the process could be even faster on particles than in solution. We demonstrate that phenol substances adsorbed on aerosol surfaces and in bulk solution are substantially altered upon photosensitised processes.Display Omitted
Keywords: Atmospheric photosensitisers; Triplet-sensitised photochemical reactions; Humic-like substances; Atmospheric aqueous phase; Atmospheric aerosol; Gas–solid reactivity;

Analysis of the vehicle fleet in the Kathmandu Valley for estimation of environment and climate co-benefits of technology intrusions by Shreejan Ram Shrestha; Nguyen Thi Kim Oanh; Quishi Xu; Maheswar Rupakheti; Mark G. Lawrence (579-590).
Technologies and activities of the on-road traffic fleets, including bus, van, 3-wheeler, taxi and motorcycle (MC) in the Kathmandu Valley, Nepal, during 2010, were investigated with the aim to produce emission estimates, using the International Vehicle Emission (IVE) model, for the base year and for an optimistic technology scenario. The parking lot survey, GPS monitoring and video camera monitoring were conducted over four typical road types (arterial, highway, residential and outskirt roads). The average age of vehicles in the bus, van, 3-wheeler, taxi and MC fleet was 9, 8.7, 11, 9.5 and 4 years, respectively. There were some extremely old buses (over 40 years old) which had extremely high emission factors. Except for MCs that had a large share of Euro III technology (75%), other types of surveyed vehicles were at most Euro II or lower. The average vehicle kilometers traveled (VKT) for each vehicle type was estimated based on odometer readings which showed comparable results with the GPS survey. The emission factors (EFs) produced by the IVE model for the driving and meteorological conditions in Kathmandu were used to estimate emissions for the base case of 2010. EFs in Kathmandu were higher than other developing cities, especially for PM and NO x from the bus fleet. Diurnal variations of the emissions were consistent with the diurnal vehicle density. From the fleet in 2010, total emissions of the major pollutants, i.e., CO, VOC, NO x , PM, BC, and CO2, were 31, 7.7, 16, 4.7, 2.1, and 1554 Gg, respectively. If the entire fleet in the Kathmandu Valley would comply with Euro III then the emission would decrease, as compared to the base case, by 44% for toxic air pollutants (excluding CO2) and 31% for climate-forcers in terms of the 20-year horizon CO2-equivalent. Future surveys should include other vehicle types such as trucks, personal cars, and non-road vehicles. The EFs obtained for the Euro III scenario in Kathmandu were well above those in other parts of the World, hence strongly suggesting influences of the driving conditions, especially the low vehicle speeds, on the vehicle emission in the valley.
Keywords: Emission inventory; Traffic; High emitter; BC; Climate co-benefit; Kathmandu;

Multiple oxygen and sulfur isotope compositions of secondary atmospheric sulfate in a mega-city in central China by Xiaoqian Li; Huiming Bao; Yiqun Gan; Aiguo Zhou; Yunde Liu (591-599).
Sulfate aerosol is an important atmosphere constituent that can be formed secondarily through the oxidation of sulfur gases. Atmospheric sulfur oxidation can take different pathways depending on meteorological conditions, which affects sulfate aerosol size and composition and therefore local or global climate. The magnitude of 17O enrichment (Δ17O) in secondary atmospheric sulfate (SAS) is a tracer for the apportionment of different sulfur oxidation pathways. Atmospheric chemistry-transport models predict a low 17O enrichment (Δ17O < 1‰) for SAS in mid-latitude continental sites. However, there are few long-term site observations to test the prediction, and data from interior metropolitan sites are entirely absent. We report here multiple oxygen and sulfur isotope compositions (Δ17O, δ18O, and δ34S) of SAS collected over a 950-day period in the city of Wuhan, central China, and to compare to data from a similar sampling campaign in the city of Baton Rouge, LA, U.S.A. The isotope compositions of bulk atmospheric sulfate closely reflect those of SAS in Wuhan, with the Δ17O ranging from 0.14‰ to 1.02‰, the δ18O from 8.0‰ to 16.1‰, and the δ34S from 2.1‰ to 7.3‰. The average Δ17O value at 0.53‰–0.59‰ is consistent with model prediction for continental interior, mid-latitude sites. The Asian monsoon-influenced meteorological condition in Wuhan appears to produce a weak but discernible seasonal pattern for Δ17O and δ18O of the SAS. The average rainwater pH value is higher in Wuhan than in Baton Rouge (5.47 versus 4.78) while the two cities have a statistically identical average SAS Δ17O value. We suggest that the higher pH does result in a higher fraction of SAS generated by aqueous O3 oxidation, but the resulted higher Δ17O value for SAS is diluted by the 17O-normal SAS generated from an enhanced transition-metal-catalyzed O2 oxidation pathway. The enhancement is corroborated with the much higher content of atmospheric particulate matter especially mineral dusts in Wuhan, a point to be considered by future effort to quantify the climate impact of SO2.
Keywords: Oxygen-17 anomaly; Atmospheric sulfate; Metal-catalyzed O2 oxidation; Rainwater; Mega-city;

The size-fractionated dry deposition fluxes of aerosol particles and nitrogen species were estimated in coastal region of the Yellow Sea from July 2005 to March 2006 using size-dependent particle dry deposition velocities and measurements for size-segregated aerosol samples. During the study period, the estimated dry deposition fluxes of aerosol particles, total dissolved nitrogen (TDN), total inorganic nitrogen (TIN), dissolved organic nitrogen (DON), ammonium and nitrate were 1067.5 ± 903.3 mg m−2 month−1, 15.9 ± 7.2 mg N m−2 month−1, 12.6 ± 6.6 mg N m−2 month−1, 3.3 ± 1.5 mg N m−2 month−1, 6.5 ± 4.2 mg N m−2 month−1 and 7.2 ± 4.5 mg N m−2 month−1, respectively. The dry deposition flux for the coarse mode of aerosol particles and nitrogen species consisted more than 66% of the total deposition flux. This result suggests that nitrogen species in coarse particles are important in the estimation of atmospheric deposition input. The estimated wet deposition fluxes of TDN, DON, TIN, ammonium and nitrate were 154.5 ± 178.9 mg N m−2 month−1, 126.9 ± 152.2 mg N m−2 month−1, 24.2 ± 34.1 mg N m−2 month−1, 85.4 ± 98.6 mg N m−2 month−1, and 40.8 ± 56.1 mg N m−2 month−1, respectively. The wet deposition contributed 65%, 72%, 55%, and 56% to the sum of the dry and wet flux of TDN, ammonium, nitrate, and DON, respectively. Inorganic nitrogen contributed much more than DON to the TDN, with a percentage of 75% and 86% in the dry and wet deposition, respectively. The dry and wet nitrogen deposition can be converted to a new primary biological productivity of 1.5–30.0 gC m−2 yr−1 in the Yellow Sea, and the nitrogen input accounts for 0.3–6.7% of the new productivity in the Yellow Sea. As an important nutrient source, the atmospheric deposition of nitrogen could have a significant influence on biogeochemical cycles.
Keywords: Dry deposition flux; Wet deposition flux; Nitrogen; Aerosols; Primary productivity;

Bioaerosols, including aerosolized bacteria, viruses, and fungi, are associated with public health and environmental problems. One promising control method to reduce the harmful effects of bioaerosols is thermal inactivation via a continuous-flow high-temperature short-time (HTST) system. However, variations in bioaerosol physical characteristics – for example, the particle size and shape – during the continuous-flow inactivation process can change the transport properties in the air, which can affect particle deposition in the human respiratory system or the filtration efficiency of ventilation systems. Real-time particle monitoring techniques are a desirable alternative to the time-consuming process of microscopic analysis that is conventionally used in sampling and particle characterization. Here, we report in situ real-time optical scattering measurements of the physical characteristics of airborne bacteria particles following an HTST process in a continuous-flow system. Our results demonstrate that the aerodynamic diameter of bacterial aerosols decreases when exposed to a high-temperature environment, and that the shape of the bacterial cells is significantly altered. These variations in physical characteristics using optical scattering measurements were found to be in agreement with the results of scanning electron microscopy analysis.Display Omitted
Keywords: Bioaerosols; Thermal inactivation; Real-time measurement; Particle shape;

Simulation and validation of greenhouse gas emissions and SOC stock changes in arable land using the ECOSSE model by M.I. Khalil; M. Richards; B. Osborne; M. Williams; C. Müller (616-624).
Model simulations of C and N dynamics, based on country-specific agricultural and environmental conditions, can provide information for compiling national greenhouse gas (GHG) inventories, as well as insights into potential mitigation options. A multi-pool dynamic model, ‘ECOSSE’ (v5 modified), was used to simulate coupled GHGs and soil organic carbon (SOC) stock changes. It was run for an equivalent time frame of 8 years with inputs from conventionally-tilled arable land cropped with spring barley receiving N fertilizer as calcium ammonium nitrate at 135–159 kg N ha−1 and crop residues (3 t ha−1 yr−1). The simulated daily N2O fluxes were consistent with the measured values, with R 2 of 0.33 (p < 0.05) and the total error and bias differences were within 95% confidence levels. The measured seasonal N2O losses were 0.39–0.60% of the N applied, with a modelled estimate of 0.23–0.41%. In contrast, the measured annual N2O loss (integrated) was 0.35% and the corresponding simulated value of 0.45% increased to 0.59% when the sum of the daily fluxes was taken into account. This indicates intermittent gas samplings may miss the peak fluxes. On an 8-year average the modelled N2O emission factor (EF) was 0.53 ± 0.03%. The model successfully predicted the daily heterotrophic respiration (R H ), with an R 2 of 0.45 (p < 0.05) and the total error and bias differences were within the 95% confidence intervals. The simulated and measured total R H (3149 versus 3072 kg C ha−1 yr−1) was within the cropland average values previously reported. The total measured CH4 fluxes indicated that the unfertilized treatments were a small source (−2.29 g C ha−1 yr−1), whilst the fertilized treatments were a sink (+3.64). In contrast, the simulated values suggested a sink (26.61–31.37 g C ha−1 yr−1), demonstrating fertilizer-induced decreases in CH4 oxidation. On average, based on the simulated SOC content a loss of 516 kg C ha−1 yr−1 was indicated, which is within the uncertainty range for temperate regions. Results suggest that the model is suitable for estimating the GHG balance of arable fields. However, further refinements and analyses to fully determine and narrow down the uncertainty ranges for GHG estimates are required.
Keywords: Greenhouse gases; Carbon balance; Spring barley; Tillage; ECOSSE model;

Atmospheric nutrient deposition to the west coast of South Africa by Justine M. Nyaga; Michael D. Cramer; Jason C. Neff (625-632).
Atmospheric deposition is an important source of nutrients to many ecosystems, but is of particular importance to plant nutrition in areas where nutrients are scarce. Nutrient containing aerosols enter the atmosphere through industrial and agricultural activities, wildfires, and the production of terrigenous and marine aerosols. In this study, we collected bulk rain precipitation along the Atlantic coast of South Africa in a coastal “strandveld” vegetation region. This region is relatively remote from significant anthropogenic influences and is downwind of a highly productive and stormy portion of the Atlantic. Samples were collected over 12 months at sites along a 17 km downwind transect from the shoreline and analyzed for N, P, Na, Ca, Mg and K. Annual total N and total P fluxes of 4.8 kg ha−1 yr−1 and 0.16 kg ha−1 yr−1 are low compared to global averages. In contrast, fluxes of Na were 88.7 kg ha−1 yr−1, 16.2 kg ha−1 yr−1 for Ca, 12.1 kg ha−1 yr−1 for Mg and 5.2 kg ha−1 yr−1 for K; rates that are higher than most other measurements elsewhere in the world. Dissolved organic N represented ca. 71% of the N flux while 43% of the P flux was in the form of soluble reactive P (SRP). These results combined with the high fluxes of Na and Mg strongly suggest that marine aerosols are important contributors to nutrient deposition at this site.
Keywords: Atmospheric deposition; Cape Floristic Region; Coastal ecosystem; Marine aerosols;

Estimating multi-annual PM2.5 air pollution levels using sVOC soil tests: Ashkelon South, Israel as a case study by Marina Zusman; Josefa Ben Asher; Itai Kloog; Boris A. Portnov (633-641).
In most developed countries, air pollution is monitored by stationary networks of air quality monitoring stations (AQMS). Due to high installation and maintenance costs, the number of such stations (especially those measuring particulate matter (PM) is often insufficient, placing limitations on the geographic coverage of air pollution monitoring and the accuracy of exposure assessment studies based on AQMS data. Semi-volatile organic compounds (sVOCs) often spread with PM and contribute to the PM composition when emitted into the atmosphere. As a result, sVOC concentrations in soil can help, as we hypothesize, to estimate average levels of PM air pollution in geographic areas in which PM monitoring by AQMS is sparse or unavailable.Soil samples taken around the Ashkelon-South industrial area in Israel were tested for the presence of sVOCs compounds using a standard EPA 8270C protocol. PM pollution data obtained from local AQMSs were then mutually compared with sVOC soil contamination levels observed in the same locations, using spatial interpolation methods and multivariate statistical analysis tools.PM levels in the atmosphere, estimated using sVOC soil concentrations, and adjusted for several locational attributes and average levels of other commonly monitored air pollutants, revealed a reasonably strong association with PM2.5 averages actually recorded by AQMS, helping to explain 86–88% of the observed PM variation (R 2-Adj. = 0.859–0.879), depending on the model type.The study confirms feasibility of obtaining reasonably accurate PM air pollution estimates using sVOC soil testing. While the costs of establishment and maintenance of a dense network of AQMS may be prohibitive, the proposed approach may help to obtain reasonably accurate PM air pollution estimates for geographic areas in which PM monitoring by AQMS is sparse or unavailable.
Keywords: Particulate matter (PM); Semi-volatile organic compound (sVOC); Air quality monitoring station (AQMS); Geographic information systems (GIS); Soil contamination;

Intensive nitrogen (N) fertilizer application in the vegetable fields of China has commonly occurred during recent decades and may substantially increase both nitrous oxide (N2O) and nitric oxide (NO) emissions. However, the quantification of N2O and NO emissions from vegetable fields has been rare due to both the lack of long-term field measurements and reliable methods for extrapolating these measurements. Using a unique dataset from a four-year measurement study of an intensively managed conventional vegetable field in southeastern China, we tested a process-based biogeochemical model, denitrification-decomposition (DNDC), for its applicability for quantifying the impact of fertilizer management practices on emissions of N trace gases from vegetable production. The results from the model validation indicate that the simulations of vegetable yields and seasonal cumulative N2O and NO emissions are consistent with the observations. In addition, DNDC can generally capture the measured temporal pattern of daily N2O and NO fluxes. The modeled impacts of fertilization alternatives can be summarized as follows: (a) both the type and application rate of N fertilizers play important roles in regulating N2O and NO emissions as well as vegetable growth; (b) reducing the N application rate to 75% of the conventional amount decreased N2O and NO emissions by 31% and showed little impact on vegetable biomasses, suggesting that reducing the N dose to a reasonable level would be advisable for both the mitigation of N gases emissions and the maintenance of vegetable production; and (c) replacing synthetic fertilizer under the conventional management practices with organic manure may significantly stimulate N2O emission by 62% while decreasing vegetable yields. The results from this modeling study may provide useful information for the ongoing debate regarding the optimization of fertilizer use strategies in China. This study also demonstrates the potential of utilizing process-based models, such as DNDC, to quantify and mitigate N2O and NO emissions from intensive vegetable production through interpreting, integrating, and extrapolating field observations.
Keywords: DNDC; Fertilization practices; Nitrous oxide; Nitric oxide; Vegetable;

Case studies of new particle formation (NPF), subsequent growth and possible particle shrinkage occurring in the western Mediterranean regional background are presented in this work. Owing to the mid-altitude height of the station (720 m.a.s.l.), aerosol processes were highly influenced by mixing layer height and development, and mountain breezes. Nucleation processes were observed to occur both under cold and warm conditions, when solar radiation and sulphuric acid concentrations were sufficiently high. Intense bursts of NPF were recorded when the station resided above the polluted mixing layer with little influence of upslope transport of pollution. NPF and growth was also observed to occur within polluted air masses residing over the site, owing to the probable abundance of anthropogenic and natural organic vapours promoting rapid particle growth after nucleation. Measurable growth rates for the NPF episodes ranged from 1.3 to 6.9 nm h−1. Reductions in modal diameters, indicating particle shrinkage, were also observed and were attributed to the evaporation of semi-volatile species from the particulate phase to the gas phase. Particle shrinkage was observed both for pre-existing particles and for freshly formed particles. In the latter case, an “arch” formation was observed in the size distribution contour plot, as the nucleating particles grew and subsequently evaporated until the mode disappeared completely. In agreement with the few articles on particle shrinkage published to date, evaporation appears to be favoured under warm temperatures, high solar radiation, low relative humidity and atmospheric dilution, causing particle-to-gas transformations.
Keywords: Ultrafine particles; Nucleation processes; Atmospheric aerosols; Particle shrinkage;

Atmospheric deposition of nitrogen and sulfur over southern Europe with focus on the Mediterranean and the Black Sea by U. Im; S. Christodoulaki; K. Violaki; P. Zarmpas; M. Kocak; N. Daskalakis; N. Mihalopoulos; M. Kanakidou (660-670).
Atmospheric deposition provides significant amounts of nutrients to the continental and marine ecosystems. Using the mesoscale WRF/CMAQ modeling system, the nitrogen (N) and sulfur (S) atmospheric deposition fluxes over the Mediterranean and the Black seas and continental Europe are evaluated for the year 2008. The annual N and S deposition fluxes are calculated to be 4.89 Tg(N) yr−1 and 2.07 Tg(S) yr−1 over continental Europe, 0.92 Tg(N) yr−1 and 0.52 Tg(S) yr−1 over West Mediterranean, 1.10 Tg(N) yr−1 and 0.84 Tg(S) yr−1 over East Mediterranean and 0.36 Tg(N) yr−1 and 0.17 Tg(S) yr−1 over the Black Sea. Inorganic N deposition fluxes are calculated to be about 3 times higher than gaseous organic N deposition fluxes. Comparison to available observations associates the annual mean model estimates with about 40 ± 30% of uncertainty depending on location. Dry deposition dominates over wet deposition for both N and S in agreement with the observations. Results suggest that an important fraction of the N deposited over the Mediterranean basin can be attributed to transported N species while S deposition is dependent more on the local emissions. In Black Sea and West Mediterranean Sea waters the calculated atmospheric N inputs are comparable to the N export measured by sediment traps whereas in the East Mediterranean N input exceeds by a factor of about 5 the N export. Our simulations show that the critical N load of 1 g(N) m−2 yr−1 is exceeded over 84% of the European forested areas.
Keywords: Atmospheric deposition; Nitrogen; Sulfur; Mediterranean Sea; Black Sea; WRF; CMAQ; Atmospheric chemistry and transport modeling;

Ambient monitoring of airborne asbestos in non-occupational environments in Tehran, Iran by Hossein Kakooei; Mohsen Meshkani; Kamal Azam (671-675).
Airborne asbestos fiber concentrations were monitored in the urban areas of Tehran, Iran during the period of 23 August to 21 September 2012. The airborne fiber concentrations of 110 air samples collected from 15 different sites in five regions of Tehran. The monitoring sites were located 2.5 m above ground nearby the main street and heavy traffic jam. The ambient air samples were analyzed using scanning electron microscopy (SEM), with energy-dispersive X-ray analysis and phase-contrast optical microscopy (PCM). The geometric means of the airborne asbestos fiber concentrations in the outdoor living areas was 1.6 × 10−2 SEM f ml−1 (1.18 × 10−3 PCM f ml−1). This criteria is considerably higher than those reported for the levels of asbestos in outdoor living areas in the Europe and the non-occupational environment of the Korea. No clear correlation was found between asbestos fiber concentration and the relative humidity and temperature. The SEM and PLM analysis revealed that all samples examined contained only chrysotile asbestos. It can be concluded that several factor such as heavy traffic, cement sheet and pipe consumption of asbestos, and geographical conditions play an important role for the high airborne asbestos levels in the non-occupational environments.
Keywords: Asbestos; Ambient monitoring; SEM; PCM; PLM; Iran;

Inversion of CO emissions over Beijing and its surrounding areas with ensemble Kalman filter by X. Tang; J. Zhu; Z.F. Wang; M. Wang; A. Gbaguidi; J. Li; M. Shao; G.Q. Tang; D.S. Ji (676-686).
Inversion of the carbon monoxide (CO) emissions over Beijing and surrounding areas in the summer of 2010 is carried on the Nested Air Quality Prediction Modeling System (NAQPMS) in coupling with an ensemble Kalman filter. CO emission is estimated through integration of observations data obtained from 25 sites in Beijing and surrounding areas of which 13 sites selected as assimilation sites are used to perform a joint adjustment of both CO concentrations and emissions with hourly surface CO observations, and 12 other sites selected to validate the inversion emission inventory. As a result, estimated CO emissions (Tg year−1) for Beijing, Tianjin, Tangshan and Baoding are 4.11, 3.75, 3.17 and 4.08, respectively; higher than the a priori estimates in the Regional Emission inventory in Asia Version 1.1 (REAS V1.1) by 50%, 80%, 120% and 150% respectively. Obviously, the regional CO emissions are underestimated in REAS1.1, especially over Beijing and surrounding areas. Use of the inverse emission inventory reduces the bias of CO simulation by 64% at assimilation sites and 48% at validation sites.
Keywords: Ensemble Kalman filter; CO emissions; Inversion estimation; Beijing;

Aerosol radiative forcing controls: Results from an Indian table-top mining region by R. Latha; B.S. Murthy; Manoj Kumar; K. Lipi; S. Jyotsna (687-694).
Aerosol radiative forcing (ARF) over intense mining area in Indian monsoon trough region, computed based on the aerosol optical properties obtained through Prede (POM-1L) sky radiometer and radiative transfer model, are analysed for the year 2011 based on 21 clear sky days spread through seasons. Due to active mining and varied minerals ARF is expected to be significantly modulated by single scattering albedo (SSA). Our studies show that radiative forcing normalized by aerosol optical depth (AOD) is highly correlated with SSA (0.96) while ARF at the surface with AOD by 0.92. Our results indicate that for a given AOD, limits or range of ARF are determined by SSA, hence endorses the need to obtain SSA accurately, preferably derived through observations concurrent with AOD. Noticeably, ARF at the top-of the atmosphere is well connected to SSA (r = 0.77) than AOD (r = 0.6). Relation between observed black carbon and SSA are investigated. A possible over estimation of SSA by the inversion algorithm, SKYRAD.pack 4.2, used in the current study is also discussed. Choice of atmospheric profiles deviating from tropical to mid altitude summer or winter does not appear to be sensitive in ARF calculation by SBDART. Based on the 21 clear sky days, a multiple linear regression equation is obtained for ARFbot as a function of AOD and SSA with a bias of ±2.7 Wm−2. This equation is verified with an independent data set of seasonal mean AOD and SSA to calculate seasonal ARF that compares well with the modeled ARF within ±4 Wm−2.
Keywords: Solar radiation extinction; Sun-sky radiometer; Radiative transfer model; Black carbon; Regression equations;

Elemental characterization of urban particulates at receptor locations in Abuja, north-central Nigeria by Olawale Emmanuel Abiye; Imoh B. Obioh; Godwin C. Ezeh (695-701).
The rising population and increasing urban infrastructures of Abuja have led to increased pressure on the urban environment. Two decades after putting the city of Abuja to use, there is yet no information on the air quality status of the city. Hence, this study was conducted in order to assess the mass concentration and elemental characterization of airborne particulate matter in Abuja, north-central Nigeria. Sampling of PM2.5: aerodynamic diameter ≤2.5 μm and PM10: aerodynamic diameter ≤10 μm were carried out in five urban sites within the city from April, 2009 to May, 2010. "Gent" stacked filter unit sampler equipped with a double stage filters in series was employed for sample collection. Charged helium (4He+) Particle Induced X-ray Emission technique of 2500 keV particle energy and Genie 2000 software were used for spectra acquisition while elemental characterization was achieved using Gupixwin software in order to determine the concentration of eighteen elements (Si, S, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Sn, Ba, Ta and Pb). Mass concentrations range between 7–86 μg m−3 and 22–343 μg m−3 for PM2.5 and PM10 respectively. Crustal elements (Si, Ca, and Fe) were found to be predominant in PM10 than in PM2.5 fraction with very high values. Positive correlation r > 0.90 and r > 0.53 to 0.90 exist between metals (V, Co, Ni, Cd, Zn and Pb). PM2.5/PM10 mass ratios were well within the range specified by WHO for developing urban scenario.
Keywords: PM10; PM2.5; PIXE; FCT;

Air quality in the Industrial Heartland of Alberta, Canada and potential impacts on human health by Isobel J. Simpson; Josette E. Marrero; Stuart Batterman; Simone Meinardi; Barbara Barletta; Donald R. Blake (702-709).
The “Industrial Heartland” of Alberta is Canada's largest hydrocarbon processing center, with more than 40 major chemical, petrochemical, and oil and gas facilities. Emissions from these industries affect local air quality and human health. This paper characterizes ambient levels of 77 volatile organic compounds (VOCs) in the region using high-precision measurements collected in summer 2010. Remarkably strong enhancements of 43 VOCs were detected, and concentrations in the industrial plumes were often similar to or even higher than levels measured in some of the world's largest cities and industrial regions. For example maximum levels of propene and i-pentane exceeded 100 ppbv, and 1,3-butadiene, a known carcinogen, reached 27 ppbv. Major VOC sources included propene fractionation, diluent separation and bitumen processing. Emissions of the measured VOCs increased the hydroxyl radical reactivity (k OH), a measure of the potential to form downwind ozone, from 3.4 s−1 in background air to 62 s−1 in the most concentrated plumes. The plume value was comparable to polluted megacity values, and acetaldehyde, propene and 1,3-butadiene contributed over half of the plume k OH. Based on a 13-year record (1994–2006) at the county level, the incidence of male hematopoietic cancers (leukemia and non-Hodgkin lymphoma) was higher in communities closest to the Industrial Heartland compared to neighboring counties. While a causal association between these cancers and exposure to industrial emissions cannot be confirmed, this pattern and the elevated VOC levels warrant actions to reduce emissions of known carcinogens, including benzene and 1,3-butadiene.
Keywords: Volatile organic compounds; Emissions; Industrial Heartland; Alberta; Hematopoietic cancer;

New Directions: GEIA's 2020 vision for better air emissions information by Gregory J. Frost; Paulette Middleton; Leonor Tarrasón; Claire Granier; Alex Guenther; Beatriz Cardenas; Hugo Denier van der Gon; Greet Janssens-Maenhout; Johannes W. Kaiser; Terry Keating; Zbigniew Klimont; Jean-Francois Lamarque; Catherine Liousse; Slobodan Nickovic; Toshimasa Ohara; Martin G. Schultz; Ute Skiba; John van Aardenne; Yuxuan Wang (710-712).

New Directions: Light absorbing aerosols and their atmospheric impacts by Yuan Wang; Alexei Khalizov; Misti Levy; Renyi Zhang (713-715).

Corrigendum to “Modelling air quality impact of a biomass energy power plant in a mountain valley in Central Italy” [Atmos. Environ. 62 (2012) 248–255] by Gabriele Curci; Giovanni Cinque; Paolo Tuccella; Guido Visconti; Marco Verdecchia; Marco Iarlori; Vincenzo Rizi (716-717).