Atmospheric Environment (v.45, #13)

Strategic ozone sounding networks: Review of design and accomplishments by Anne M. Thompson; Samuel J. Oltmans; David. W. Tarasick; Peter von der Gathen; Herman G.J. Smit; Jacquelyn C. Witte (2145-2163).
Ozone soundings are used to integrate models, satellite, aircraft and ground-based measurements for better interpretation of ozone variability, including atmospheric losses (predominantly in the stratosphere) and pollution (troposphere). A well-designed network of ozonesonde stations gives information with high vertical and horizontal resolution on a number of dynamical and chemical processes, allowing us to answer questions not possible with aircraft campaigns or current satellite technology. Strategic ozonesonde networks are discussed for high, mid- and low latitude studies. The Match sounding network was designed specifically to follow ozone depletion within the polar vortex; the standard sites are at middle to high northern hemisphere latitudes and typically operate from December through mid-March. Three mid-latitude strategic networks (the IONS series) operated over North America in July–August 2004, March–May and August 2006, and April and June-July-2008. These were designed to address questions about tropospheric ozone budgets and sources, including stratosphere–troposphere transport, and to validate satellite instruments and models. A global network focusing on processes in the equatorial zone, SHADOZ (Southern Hemisphere Additional Ozonesondes), has operated since 1998 in partnership with NOAA, NASA and the Meteorological Services of host countries. Examples of important findings from these networks are described.
Keywords: Ozone; Ozonesondes; TTL; Stratosphere–troposphere exchange; Tropospheric ozone; Tropics; Ozone depletion;

On 10th March 2009 a widespread and severe dust storm event that lasted several hours struck Riyadh, and represented one of the most intense dust storms experienced in Saudi Arabia in the last two decades. This short-lived storm caused widespread and heavy dust deposition, zero visibility and total airport shutdown, as well as extensive damage to buildings, vehicles, power poles and trees across the city of Riyadh.Changes in Meteorological parameters, aerosol optical depth (AOD), Angstrom exponent α, infrared (IR) sky temperature and atmospheric emissivity were investigated before, during, and after the storm. The analysis showed significant changes in all of the above parameters due to this event. Shortly after the storm arrived, air pressure rapidly increased by 4 hPa, temperature decreased by 6 °C, relative humidly increased from 10% to 30%, the wind direction became northerly and the wind speed increased to a maximum of 30 m s−1. AOD at 550 nm increased from 0.396 to 1.71. The Angstrom exponent α rapidly decreased from 0.192 to −0.078. The mean AOD at 550 nm on the day of the storm was 0.953 higher than during the previous clear day, while α was −0.049 in comparison with 0.323 during the previous day. Theoretical simulations using SMART software showed remarkable changes in both spectral and broadband solar radiation components. The global and direct radiation components decreased by 42% and 68%, respectively, and the diffuse components increased by 44% in comparison with the previous clear day. IR sky temperatures and sky emissivity increased by 24 °C and 0.3, respectively, 2 h after the arrival of the storm. The effect of aerosol loading by the storm on IR atmospheric emission was investigated using MODTRAN software. It was found that the effect of aerosols caused an increase of the atmospheric emission in the atmospheric window (8–14 μm) such that the window emissions resembled those of a blackbody and the atmospheric window was almost closed.► Strongest dust storm on the last two decades on Saudi’s history. ► Analysis of Meteorological and AOD data. ► Its impact on the solar radiation components investigated theoretically. ► Its impact on the sky temperature investigated experimentally. ► Its impact on the sky temperature investigated theoretically.
Keywords: Sky temperature; Dust storm; AOD; MODTRAN; Synoptic; Meteorology;

Experiments were carried out on a four-cylinder direct-injection diesel engine operating on Euro V diesel fuel blended with diethyl adipate (DEA). The blended fuels contain 8.1%, 16.4%, 25% and 33.8% by volume fraction of DEA, corresponding to 3%, 6%, 9% and 12% by mass of oxygen in the blends. The engine performance and exhaust gas emissions of the different fuels were investigated at five engine loads at a steady speed of 1800 rev/min. The results indicated an increase of brake specific fuel consumption and brake thermal efficiency when the engine was fueled with the blended fuels. In comparison with diesel fuel, the blended fuels resulted in an increase in hydrocarbon (HC) and carbon monoxide (CO), but a decrease in particulate mass concentrations. The nitrogen oxides (NOx) emission experienced a slight variation among the test fuels. In regard to the unregulated gaseous emissions, formaldehyde and acetaldehyde increased, while 1,3-butadiene, ethene, ethyne, propylene and BTX (benzene, toluene and xylene) in general decreased. A diesel oxidation catalyst (DOC) was found to reduce significantly most of the investigated unregulated pollutants when the exhaust gas temperature was sufficiently high.► DEA leads to a slight increase in the brake specific fuel consumption and in the brake thermal efficiency. ► DEA generates higher CO and HC emissions, while particulate emissions decrease evidently and NOx emissions experience fluctuation with increasing percentage of DEA in the blends. ► The formaldehyde and acetaldehyde increase, whereas ethene, ethyne, propylene, 1,3-butadiene and BTX in general decrease with an increase of DEA in the blends. ► DOC can effectively reduce most of the unregulated emissions.
Keywords: Euro V diesel fuel; Diethyl adipate (DEA); Diesel engine; Regulated emissions; Unregulated emissions;

Aerosol and trace gas vehicle emission factors measured in a tunnel using an Aerosol Mass Spectrometer and other on-line instrumentation by Roberto Chirico; Andre S.H. Prevot; Peter F. DeCarlo; Maarten F. Heringa; Rene Richter; Ernest Weingartner; Urs Baltensperger (2182-2192).
In this study we present measurements of gas and aerosol phase composition for a mixed vehicle fleet in the Gubrist tunnel (Switzerland) in June 2008. PM1 composition measurements were made with a High-Resolution Time-of-Flight Aerosol Mass Spectrometer (AMS) and a Multi Angle Absorption Photometer (MAAP). Gas-phase measurements of CO, CO2, NOx and total hydrocarbons (THC) were performed with standard instrumentation. Weekdays had a characteristic diurnal pattern with 2 peaks in concentrations for all traffic related species corresponding to high vehicle density (∼300 ± 30 vehicles per 5 min) in the morning rush hour between 06:00 and 09:00 and in the afternoon rush hours from approximately 15:30 to 18:30.The emission factors (EF) of OA were heavily influenced by the OA mass loading. To exclude this partitioning effect, only organic aerosol mass concentrations from 60 μg m−3 to 90 μg m−3 were considered and for these conditions the EF(OA) value for HDV was 33.7 ± 2.3 mg km−1 for a temperature inside the tunnel of 20–25 °C. This value is not directly applicable to ambient conditions because it is derived from OA mass concentrations that are roughly a factor of 10 higher than typical ambient concentrations. An even higher EF(OA)HDV value of 47.4 ± 1.6 mg km−1 was obtained when the linear fit was applied to all data points including OA concentrations up to 120 μg m−3.Similar to the increasing EF, the OA/BC ratio in the tunnel was also affected by the organic loading and it increased by a factor of ∼3 over the OA range 10–120 μg m−3. This means that also the OA emission factors at ambient concentrations of around 5–10 μg m−3 would be 2–3 times lower than the emission factor given above. For OA concentrations lower than 40 μg m−3 the OA/BC mass ratio was below 1, while at an OA concentration of 100–120 μg m−3 the OA/BC ratio was ∼1.5. The AMS mass spectra (MS) acquired in the tunnel were highly correlated with the primary organic aerosol (POA) MS from a EURO 3 diesel vehicle with a speed similar to the average tunnel speed.► Measurements of gas and aerosol phase composition in a tunnel are presented. ► PM1 measurements were made with a HR-ToF-AMS and a MAAP. ► Among the species analyzed, OA and BC were the main constituents of PM1. ► The emission factors for OA and the OA/BC ratio were affected by the organic mass loading. ► At higher OA concentration more organics in the gas phase will condense producing more OA mass.
Keywords: Organic aerosol; Black carbon; Aerosol mass spectrometer; Gubrist tunnel; Emission factor;

Road dust contribution to PM levels – Evaluation of the effectiveness of street washing activities by means of Positive Matrix Factorization by Angeliki Karanasiou; Teresa Moreno; Fulvio Amato; Julio Lumbreras; Adolfo Narros; Rafael Borge; Aurelio Tobías; Elena Boldo; Cristina Linares; Jorge Pey; Cristina Reche; Andrés Alastuey; Xavier Querol (2193-2201).
The primary aim of this study was to quantify the contribution of road dust to airborne particulate matter (PM10) and evaluate the effects of street washing on the mitigation of resuspension. With this purpose an intensive campaign was carried out in a heavily trafficked central road of Madrid (Spain) including PM10 sampling and chemical analysis. PM10 daily levels during dry, unwashed conditions were 2–15% higher than those present during the day after nightly street washing. However, this reduction is lower than the standard deviation of the PM10 measurements. The diurnal variation of PM10 revealed that a reduction in PM10 was noticeable only during the morning hours.The emission sources for the urban area of Madrid were resolved by means of a receptor model, Positive Matrix Factorization, PMF. The results showed that the main sources were vehicle emissions, road dust, secondary aerosol including sulphate and nitrate, and soil. Vehicle emissions and road dust were the major contributor to PM10 particle mass with similar average contributions of 31% and 29% respectively. The effect of street washing was also evaluated by examining the daily variation of the road dust source contribution between days with and without street washing. The mass contribution from the road dust source was ∼2 μg m−3 lower during the days that street washing was implemented with this corresponding to a reduction of 15% of its mass contribution during the days that the road surface was left untreated.► We quantify the contribution of road dust to airborne particulate matter (PM10). ► We investigate the effects of street washing on the mitigation of resuspension. ► PM10 chemical components concentrations were slightly reduced during street washing. ► Mass contribution of road dust aerosol source was lower during street washing period. ► There is evidence of a beneficial (short-lived) effect of street washing on PM10.
Keywords: PM10; Road dust; Resuspension; Source apportionment; Madrid; Non-exhaust emissions;

Seasonal variations of isoprene emissions from five oak tree species in East Asia by Yong-Jae Lim; Al Armendariz; Youn-Suk Son; Jo-Chun Kim (2202-2210).
Emissions of biogenic volatile organic compounds (BVOC) from trees can enhance the photochemical production of tropospheric ozone. Isoprene is one of the most environmentally important BVOCs, since its emission rate from certain tree species can be high and its chemical structure gives it high ozone forming potential. Understanding of isoprene emission rates from many tree species is limited, including influences of tree age, season, and other factors. Five oak species were studied which represent approximately 85 percent of the deciduous trees in South Korean forests. In general, there were obvious seasonal variations of isoprene emissions from five oak trees. Especially, Quercus aliena B. and Quercus mongolica F showed substantial seasonal variations of isoprene emissions; However, Quercus serrata T. and Quercus acutissima C. generally did not. It was found that Q. serrata T. showed the highest isoprene emission rates among the species tested (up to 130.5 μgC gdw−1  h−1) and its emission rates were highest during spring followed by summer and fall. The emission rates from two (Q. acutissima C., Quercus variabilis B.) of the other tested oak species were lower by more than 3 orders of magnitude. Besides, two oak species, Q. aliena B. and Q. mongolica F. were chosen to determine the effect of tree age on isoprene emissions. Trees at the age of 21∼30 years had significantly higher isoprene emission rates than those at the age of 41∼50.► There were obvious seasonal variations of isoprene emissions from five oak tree species. ► Three oak species are high isoprene emitters, but the others are low emitters. ► Q. acutissima C. and Q. variabilis B. were extremely low emitters compared to the other species.
Keywords: Isoprene; Biogenic emissions; Deciduous trees; BVOC; Quercus aliena Blume; Quercus mongolica Fischer;

Secondary organic aerosol from biogenic volatile organic compound mixtures by Meagan L. Hatfield; Kara E. Huff Hartz (2211-2219).
The secondary organic aerosol (SOA) yields from the ozonolysis of a Siberian fir needle oil (SFNO), a Canadian fir needle oil (CFNO), and several SOA precursor mixtures containing reactive and non-reactive volatile organic compounds (VOCs) were investigated. The use of precursor mixtures more completely describes the atmosphere where many VOCs exist. The addition of non-reactive VOCs such as bornyl acetate, camphene, and borneol had very little to no effect on SOA yields. The oxidation of VOC mixtures with VOC mass percentages similar to the SFNO produced SOA yields that became more similar to the SOA yield from SFNO as the complexity and concentration of VOCs within the mixture became more similar to overall SFNO composition. The SOA yield produced by the oxidation of CFNO was within the error of the SOA yield produced by the oxidation of SFNO at a similar VOC concentration. The SOA yields from SFNO were modeled using the volatility basis set (VBS), which predicts the SOA yields for a given mass concentration of mixtures containing similar VOCs.► SOA yields from the ozonolysis of fir needle oils and surrogates were measured. ► Non-ozone-reactive VOCs had little effect on SOA yields. ► As the surrogate composition approached the fir needle oil, yields were similar. ► SOA yields from fir needle oils were modeled using the volatility basis set.
Keywords: Secondary organic aerosol; Biogenic volatile organic compounds; Essential oils; Ozonolysis;

Fugitive coal mine methane emissions at five mining areas in China by Shi Su; Jiaye Han; Jinyan Wu; Hongjun Li; Rhys Worrall; Hua Guo; Xin Sun; Wenge Liu (2220-2232).
Large quantities (about 28 billion m3) of methane are released to the atmosphere every year from coal-mining activities around the world. This methane represents not only a significant greenhouse gas that is contributing to global temperature change, but is also a wasted energy resource. China, the largest coal producer in the world, is responsible for over 50% of the total global release of methane-containing ventilation air from coal mines. A mine site investigation methodology was developed for collecting reliable methane emission data from coal mines. Five main coal-mining areas in China were studied and specific data were collected from two mines in each of the five mining groups. Information such as coal and methane reserves, ventilation air released, methane concentration and methane release rates were collected. Future development plans were evaluated and used to estimate potential future emissions. It was determined that most of the methane generated in the five mining areas is currently released to the atmosphere.► Coal mine production and methane data were collected from five mining areas in China. ► More than 15 billion m3 of methane are emitted by Chinese coal mines. ► Over 80% (∼14.7 billion m3) originates from air vented from mines. ► Methane levels in ventilated air are often too low to be used commercially.
Keywords: Coal mining; Coal bed methane; Fugitive methane; Greenhouse gas;

Quantification of diffuse and fugitive PM10 sources by integrated “hot-spot” method by C. Mensink; G. Cosemans; N. Bleux; P. Berghmans; F. Deutsch; L. Janssen; I. Liekens; R. Torfs; H. Van Rompaey (2233-2241).
Between 2002 and 2006, various exceedances of air quality directive 1999/30/EC were reported in a number of PM10 monitoring stations in Flanders. A study was carried out with the objectives: i) to identify and quantify the sources that have caused or have contributed to the exceedances over this period; and ii) to propose suitable emission reduction measures to comply with the current air quality standards (2010).We followed an integrated multi-disciplinary approach consisting of a detailed analysis of the PM10 data series, specific air quality measuring campaigns, air quality modelling and expertise on emission reduction measures (including current BAT and BREF studies). The data analysis was based on 5 steps: 1) The pollution roses of the individual monitoring stations were analyzed. 2) The variation of the PM10 concentration in function of wind speed was assessed to determine whether we were dealing with a fugitive source of primary particles (e.g. mineral dust) or a source of smaller secondary particles taken up and dispersed by the ambient air flow (e.g. industrial combustion sources or traffic sources). 3) The temporal patterns of the potential sources were analyzed. 4) Specific measurement campaigns were organized in the neighbourhood of the potential sources. This included mapping of PM10 concentrations and a detailed analysis of the chemical composition. 5) The (fugitive) PM10 sources were quantified by means of reversed modelling.After deduction of a high background concentration, observed in all monitoring stations in Flanders, results for the individual monitoring stations show that in almost all cases the peak concentrations can be attributed to local fugitive PM10 emissions. Thus for most of the analysed cases it could be concluded that the cause of the exceedances or nearly exceedances is the combination of high background concentrations and local contributions from diffuse or fugitive sources. The total contribution of these non-registered diffuse sources was estimated to be 9–16% of the measured annual averaged PM10 concentrations.► We developed a methodology to identify and quantify fugitive PM10 sources. ► Local fugitive sources contribute significantly to PM10 exceedances in Flanders. ► Storage and handling activities are the main cause of local diffuse PM10 sources. ► Diffuse sources contribute 9–16% to the measured annual PM10 concentrations.
Keywords: Reverse modelling; PM10 measurements; Air quality policy; Abatement strategy; PM10; Fugitive emission sources;

Maritime transport plays a central role in the transport sector’s sustainability debate. Its contribution to air pollution and greenhouse gases is significant.An effective policy strategy to regulate air emissions requires their robust estimation in terms of quantification and location.This paper provides a critical analysis of the ship emission modelling approaches and data sources available, identifying their limits and constraints. It classifies the main methodologies on the basis of the approach followed (bottom-up or top-down) for the evaluation and geographic characterisation of emissions.The analysis highlights the uncertainty of results from the different methods. This is mainly due to the level of uncertainty connected with the sources of information that are used as inputs to the different studies. This paper describes the sources of the information required for these analyses, paying particular attention to AIS data and to the possible problems associated with their use. One way of reducing the overall uncertainty in the results could be the simultaneous use of different sources of information. This paper presents an alternative methodology based on this approach.As a final remark, it can be expected that new approaches to the problem together with more reliable data sources over the coming years could give more impetus to the debate on the global impact of maritime traffic on the environment that, currently, has only reached agreement via the “consensus” estimates provided by .► Estimation of emissions from ships still needs further research. ► Uncertainties and errors in the data are key issues for this topic. ► AIS data are the most promising source of information for emissions calculation. ► Different types of errors in AIS data frequently occur and may undermine their reliability. ► Different data should be jointly used to reduce the uncertainty in estimations of global emissions.
Keywords: Bottom-up approach; Top-down approach; Maritime transport statistics;

The effect of proximity to major roads on indoor air quality in typical Australian dwellings by Sarah J. Lawson; Ian E. Galbally; Jennifer C. Powell; Melita D. Keywood; Suzie B. Molloy; Min Cheng; Paul W. Selleck (2252-2259).
An Indoor Air Quality Study of residential dwellings was carried out in Melbourne, Australia, and a subset of the data was analysed to investigate the effect of proximity to major roads on indoor air quality (IAQ). Seven-day measurements of PM10, NO2, benzene, toluene, ethylbenzene and xylenes, along with continuous CO and PM2.5 measurements were utilised. The measurements were made indoors and outdoors in 27 dwellings; 15 Near Road (<50 m from a major road) and 12 Far Road (>300 m from a major road). Dwellings were sampled for one week each in Winter/Spring 2008 and Summer/Autumn 2009, over an eight month period. Analysis of 7-day measurements showed that NO2 and toluene were elevated at the 5% significance level both indoors and outdoors at Near Road Dwellings compared to Far Road Dwellings. Indoor/Outdoor (I/O) ratios of NO2 and toluene were not significantly different between Near and Far Road dwellings giving no evidence of any anomalous dominant indoor source for NO2 and toluene in Near Road dwellings. Indoor NO2 was significantly correlated to gas stovetop and oven use in both Near and Far Road dwellings. In the absence of gas cooking, indoor NO2 was elevated in Near Road dwellings relative to Far Road dwellings by approximately 4 ppb and this can be attributed to infiltration of outdoor air. I/O ratios for NO2 were <1 for Near and Far Road dwellings, indicating that outdoor NO2, and hence roadway emissions can potentially contribute a significant proportion to the indoor NO2 concentration. Mean toluene I/O ratios were >2 indicating that indoor sources dominate with minor contribution from outdoors. Hence the relative contribution of roadways to indoor NO2 is potentially greater than the relative contribution of roadways to indoor toluene. Findings elsewhere suggest that a similar outdoor enhancement of traffic related NO2 (∼5 ppb) increases risk of lung cancer and childhood asthma (). A simple conceptual model indicated spatial and temporal variance in the concentrations was the biggest limitation in detecting roadway influence outside Near Road dwellings for PM10, PM2.5 and NO2 while measurement uncertainty was also important for CO.► Elevated indoor NO2 and toluene at Near Road dwellings attributed to road emissions. ► Road emissions contribute a significant proportion to indoor NO2 concentrations. ► Road emissions contribute a minor proportion to the indoor toluene concentrations. ► Elevated NO2 in Near Road dwellings likely to result in adverse health effects. ► Conceptual model explores spatial, temporal variance in background concentrations.
Keywords: Indoor air; Traffic; Roads; Nitrogen dioxide; BTEX; PM2.5;

A mechanistic modeling system for estimating large-scale emissions and transport of pollen and co-allergens by Christos Efstathiou; Sastry Isukapalli; Panos Georgopoulos (2260-2276).
Allergic airway diseases represent a complex health problem which can be exacerbated by the synergistic action of pollen particles and air pollutants such as ozone. Understanding human exposures to aeroallergens requires accurate estimates of the spatial distribution of airborne pollen levels as well as of various air pollutants at different times. However, currently there are no established methods for estimating allergenic pollen emissions and concentrations over large geographic areas such as the United States. A mechanistic modeling system for describing pollen emissions and transport over extensive domains has been developed by adapting components of existing regional scale air quality models and vegetation databases. First, components of the Biogenic Emissions Inventory System (BEIS) were adapted to predict pollen emission patterns. Subsequently, the transport module of the Community Multiscale Air Quality (CMAQ) modeling system was modified to incorporate description of pollen transport. The combined model, CMAQ-pollen, allows for simultaneous prediction of multiple air pollutants and pollen levels in a single model simulation, and uses consistent assumptions related to the transport of multiple chemicals and pollen species. Application case studies for evaluating the combined modeling system included the simulation of birch and ragweed pollen levels for the year 2002, during their corresponding peak pollination periods (April for birch and September for ragweed). The model simulations were driven by previously evaluated meteorological model outputs and emissions inventories for the eastern United States for the simulation period. A semi-quantitative evaluation of CMAQ-pollen was performed using tree and ragweed pollen counts in Newark, NJ for the same time periods. The peak birch pollen concentrations were predicted to occur within two days of the peak measurements, while the temporal patterns closely followed the measured profiles of overall tree pollen. For the case of ragweed pollen, the model was able to capture the patterns observed during September 2002, but did not predict an early peak; this can be associated with a wider species pollination window and inadequate spatial information in current land cover databases. An additional sensitivity simulation was performed to comparatively evaluate the dispersion patterns predicted by CMAQ-pollen with those predicted by the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model, which is used extensively in aerobiological studies. The CMAQ estimated concentration plumes matched the equivalent pollen scenario modeled with HYSPLIT. The novel pollen modeling approach presented here allows simultaneous estimation of multiple airborne allergens and other air pollutants, and is being developed as a central component of an integrated population exposure modeling system, the Modeling Environment for Total Risk studies (MENTOR) for multiple, co-occurring contaminants that include aeroallergens and irritants.► New, integrated modeling system for large-scale pollen emissions and transport. ► Adaptation of the regulatory air quality model (CMAQ) to study pollen transport. ► Case studies focus on predicting regional-scale levels of birch and ragweed. ► This system allows calculation of levels of multiple allergens and pollutants. ► Developed as a component of the Modeling Environment for Total Risk studies (MENTOR).
Keywords: Bioaerosols; Pollen emission; Pollen dispersion; Mesoscale model; Birch allergy; Ragweed allergy;

Correlation of fungi and endotoxin with PM2.5 and meteorological parameters in atmosphere of Sao Paulo, Brazil by Cristiane Degobbi; Fernanda D.T.Q.S. Lopes; Regiani Carvalho-Oliveira; Julian Esteban Muñoz; Paulo H.N. Saldiva (2277-2283).
Particulate matter, especially PM2.5, is associated with increased morbidity and mortality from respiratory diseases. Studies that focus on the chemical composition of the material are frequent in the literature, but those that characterize the biological fraction are rare. The objectives of this study were to characterize samples collected in Sao Paulo, Brazil on the quantity of fungi and endotoxins associated with PM2.5, correlating with the mass of particulate matter, chemical composition and meteorological parameters. We did that by Principal Component Analysis (PCA) and multiple linear regressions. The results have shown that fungi and endotoxins represent significant portion of PM2.5, reaching average concentrations of 772.23 spores μg−1 of PM2.5 (SD: 400.37) and 5.52 EU mg−1 of PM2.5 (SD: 4.51 EU mg−1), respectively. Hyaline basidiospores, Cladosporium and total spore counts were correlated to factor Ba/Ca/Fe/Zn/K/Si of PM2.5 (p < 0.05). Genera Pen/Asp were correlated to the total mass of PM2.5 (p < 0.05) and colorless ascospores were correlated to humidity (p < 0.05). Endotoxin was positively correlated with the atmospheric temperature (p < 0.05). This study has shown that bioaerosol is present in considerable amounts in PM2.5 in the atmosphere of Sao Paulo, Brazil. Some fungi were correlated with soil particle resuspension and mass of particulate matter. Therefore, the relative contribution of bioaerosol in PM2.5 should be considered in future studies aimed at evaluating the clinical impact of exposure to air pollution.► Fungi and endotoxin are present in considerable amounts in PM2.5. ► Some fungi genera were correlated to elements of soil resuspension and mass of PM2.5. ► Endotoxin and some fungi were influenced mainly by meteorological parameters. ► Studies regarding atmospheric pollution should include bioaerosol analysis.
Keywords: Fungi; Endotoxin; PM2.5; Chemical composition;

Global crop yield reductions due to surface ozone exposure: 1. Year 2000 crop production losses and economic damage by Shiri Avnery; Denise L. Mauzerall; Junfeng Liu; Larry W. Horowitz (2284-2296).
Exposure to elevated concentrations of surface ozone (O3) causes substantial reductions in the agricultural yields of many crops. As emissions of O3 precursors rise in many parts of the world over the next few decades, yield reductions from O3 exposure appear likely to increase the challenges of feeding a global population projected to grow from 6 to 9 billion between 2000 and 2050. This study estimates year 2000 global yield reductions of three key staple crops (soybean, maize, and wheat) due to surface ozone exposure using hourly O3 concentrations simulated by the Model for Ozone and Related Chemical Tracers version 2.4 (MOZART-2). We calculate crop losses according to two metrics of ozone exposure – seasonal daytime (08:00–19:59) mean O3 (M12) and accumulated O3 above a threshold of 40 ppbv (AOT40) – and predict crop yield losses using crop-specific O3 concentration:response functions established by field studies. Our results indicate that year 2000 O3-induced global yield reductions ranged, depending on the metric used, from 8.5–14% for soybean, 3.9–15% for wheat, and 2.2–5.5% for maize. Global crop production losses totaled 79–121 million metric tons, worth $11–18 billion annually (USD2000). Our calculated yield reductions agree well with previous estimates, providing further evidence that yields of major crops across the globe are already being substantially reduced by exposure to surface ozone – a risk that will grow unless O3-precursor emissions are curbed in the future or crop cultivars are developed and utilized that are resistant to O3.► Surface O3 is having a substantial impact on the yields of key crops. ► Yields of wheat, soybean, and maize were reduced by up to 15% globally in 2000. ► Global year 2000 crop production losses totaled 79–121 million metric tons. ► Agricultural losses are estimated to be worth $11–18 billion USD2000 annually.
Keywords: Ozone; Ozone impacts; Agriculture; Crop loss; Integrated assessment;

We examine the potential global risk of increasing surface ozone (O3) exposure to three key staple crops (soybean, maize, and wheat) in the near future (year 2030) according to two trajectories of O3 pollution: the Intergovernmental Panel on Climate Change Special Report on Emissions Scenarios (IPCC SRES) A2 and B1 storylines, which represent upper- and lower-boundary projections, respectively, of most O3 precursor emissions in 2030. We use simulated hourly O3 concentrations from the Model for Ozone and Related Chemical Tracers version 2.4 (MOZART-2), satellite-derived datasets of agricultural production, and field-based concentration:response relationships to calculate crop yield reductions resulting from O3 exposure. We then calculate the associated crop production losses and their economic value. We compare our results to the estimated impact of O3 on global agriculture in the year 2000, which we assessed in our companion paper [Avnery et al., 2011]. In the A2 scenario we find global year 2030 yield loss of wheat due to O3 exposure ranges from 5.4 to 26% (a further reduction in yield of +1.5–10% from year 2000 values), 15–19% for soybean (reduction of +0.9–11%), and 4.4–8.7% for maize (reduction of +2.1–3.2%) depending on the metric used, with total global agricultural losses worth $17–35 billion USD2000 annually (an increase of +$6–17 billion in losses from 2000). Under the B1 scenario, we project less severe but still substantial reductions in yields in 2030: 4.0–17% for wheat (a further decrease in yield of +0.1–1.8% from 2000), 9.5–15% for soybean (decrease of +0.7–1.0%), and 2.5–6.0% for maize (decrease of + 0.3–0.5%), with total losses worth $12–21 billion annually (an increase of +$1–3 billion in losses from 2000). Because our analysis uses crop data from the year 2000, which likely underestimates agricultural production in 2030 due to the need to feed a population increasing from approximately 6 to 8 billion people between 2000 and 2030, our calculations of crop production and economic losses are highly conservative. Our results suggest that O3 pollution poses a growing threat to global food security even under an optimistic scenario of future ozone precursor emissions. Further efforts to reduce surface O3 concentrations thus provide an excellent opportunity to increase global grain yields without the environmental degradation associated with additional fertilizer application or land cultivation.► Surface O3 will have an increasingly detrimental impact on future crop yields. ► Yields of wheat, soybean, and maize could be reduced by up to 26% globally in 2030. ► Global losses up to 17% are possible even in an optimistic scenario of future O3. ► Agricultural losses worldwide may be worth $17–35 billion annually by 2030.
Keywords: Surface ozone; Ozone impacts; Agriculture; Crop loss; Integrated assessment;

Distribution of heavy metals in road dust along an urban-rural gradient in Massachusetts by Eric Apeagyei; Michael S. Bank; John D. Spengler (2310-2323).
Human exposures to particulate matter emitted from on-road motor vehicles include complex mixtures of metals from tires, brakes, parts wear and resuspended road dust. The aim of this study was to assess road dust for metals associated with motor vehicle traffic, particularly those metals coming from brake and tire wears. We hypothesized that the road dust would show significant difference in both composition and concentration by traffic type, road class and by location. X-ray fluorescence (XRF) analyses of 115 parked car tires showed Zn and Ca were likely associated with tire wear dust. XRF results of three used brake pads indicated high concentrations of Fe, Ti, Cu, Ba, Mo and Zr. To assess heavy metal exposures associated with tires and brake wear adjacent to roads of varying traffic and functional classes, 85 samples of road dust were collected from road surfaces adjacent to the curb and analyzed by XRF. Median concentrations for Fe, Ca and K were greater than Ti (1619 ppm), with concentration ratios of Fe: Ca: K: Ti [16:5:3:1]. Cumulative frequency distribution graphs showed distribution of Fe, Ba, Cu, and Mo were similar regardless of road traffic rating. However, Zn, Ti, and Zr varied significantly (p < 0.05) with traffic ratings of roadways (heavy > moderate > low traffic). Fe, Ba, Cu, and Mo also had similar distributions regardless of road class while composition of Zn, Ti, and Zr varied significantly across road class (p < 0.05) (Major roads > Minor roads > highway). In comparing urban road dust to rural road dust, we observed Fe, Ca, K, and Ti were significantly greater in urban road dust (p < 0.05). In urban road dust the Fe: Ca: K: Ti relationship with median Ti of 2216 ppm was 12: 6: 3.5: 1. These results indicate that roadway dust may be important sources of metals for runoff water and localized resuspended particulate matter.► Concentrations of metals found in brake pads and tires were elevated in road dust. ► Metals were associated with higher road traffic in both urban and rural areas. ► Spatiotemporal variation in roadway emissions was important to metal concentrations. ► Future studies are needed to assess human and environmental exposures to road dust.
Keywords: Heavy metal; Road dust; Tire wear; Brake wear; Traffic-related emissions;

Secondary organic aerosol formation from toluene in an atmospheric hydrocarbon mixture: Water and particle seed effects by Richard M. Kamens; Haofei Zhang; Eric H. Chen; Yang Zhou; Harshal M. Parikh; Rebecca L. Wilson; Katherine E. Galloway; Elias P. Rosen (2324-2334).
Atmospherically relevant secondary organic aerosol (SOA) concentrations from toluene, in an urban hydrocarbon environment, with oxides of nitrogen in natural sunlight, were studied in a large outdoor chamber with different initial humidity and types of initial seed aerosols. Ammonium sulfate particles (38 μg m−3) in the presence of an atmospheric hydrocarbon mixture and NOx in sunlight under a dry atmosphere (%RH = 6 to 10%) show reduced SOA formation when compared to similar gas phase conditions with lower ammonium sulfate (7 μg m−3) and higher relative humidities (%RH 40 to 90%). No post particle nucleation (particles in the 6 to 10 nm range) was observed in either seeded system. When initial background particles levels were below 0.5 μg m−3 particle nucleation was observed. A new condensed aromatic kinetic chemical mechanism was developed to simulate experimental data. A particle water phase was highly related to SOA formation. Reasonable fits to the gas and total SOA concentrations emphasize the important impact of different initial particle seed levels and particle phase water when simulating SOA formation from aromatic compounds like toluene.► Illustrates the extraordinary impact of particle phase water and initial particle seed concentrations on aromatic SOA. ► Changing RH between 90 and 10% can vary SOA yields by a factor of 2–7. ► Uses outdoor chamber data to test a newly developed aromatic gas-particle kinetics model. ► First study to investigate aromatic SOA within the context of an atmospheric urban hydrocarbon mixture.
Keywords: Toluene SOA; Secondary organic aerosol modeling; SOA yields; Glyoxal; Water phase;

Measurements of particulate sugars at urban and forested suburban sites by Sae Tominaga; Kiyoshi Matsumoto; Naoki Kaneyasu; Ado Shigihara; Koichi Katono; Manabu Igawa (2335-2339).
Neutral sugars (arabinose, fucose, galactose, glucose, mannose, rhamnose, and xylose) in fine and coarse aerosols were measured at urban and forested suburban sites in Japan. The most dominant compound in the sugar group was glucose at both sites. Size partitioning of the sugars generally showed dominance in the fine mode range but shifted toward the coarse mode range in summer. Seasonal trends in the sugar concentrations in the fine and coarse mode ranges were opposite: higher concentrations of fine mode sugars were found in winter, although coarse mode sugars increased in summer. Fine mode glucose consisted dominantly of the combined form, whereas free glucose increased in the coarse mode range. Although the sources of the sugars in the aerosols remain largely uncertain, primary biogenic particles can be considered as candidates of main sources of the sugars in both coarse and fine mode ranges.
Keywords: Glucose; Sugars; Water-soluble organic carbon; Primary biogenic particles; Organic carbon;