Atmospheric Environment (v.41, #36)

Roadside BTEX and other gaseous air pollutants in relation to emission sources by Vo Thi Quynh Truc; Nguyen Thi Kim Oanh (7685-7697).
Hourly concentrations of benzene, toluene, ethylbenzene, m,p-xylenes, and o-xylene (BTEX) plus CO, NO x , SO2 were monitored at roadsides simultaneously with the traffic volume during the dry season of 2004, in Hanoi, Vietnam. The selected three streets included Truong Chinh (TC) with high traffic volume, Dien Bien Phu (DBP) with low traffic volume, and Nguyen Trai (NT) with high traffic volume running through an industrial estate. BTEX were sampled by SKC charcoal tubes and analyzed by GC–FID. Geometric means of hourly benzene, toluene, ethylbenzene, m,p-xylenes and o-xylene are, respectively, 65, 62, 15, 43, and 22 μg m−3 in TC street; 30, 38, 9, 26, and 13 μg m−3 in DBP street; and 123, 87, 24, 56, and 30 μg m−3 in NT street. Levels of other gaseous pollutants including CO, NO x , and SO2, measured by automatic instruments, were low and not exceeding the Vietnam national ambient air quality standards. BTEX levels were comparatively analyzed for different downwind distances (3–50 m) from the street, between peak hours and off-peak hours, as well as between weekdays and weekend. Results of principal component analysis suggest that the gaseous pollutants are associated with different vehicle types.
Keywords: BTEX; Hanoi; Traffic pattern; Roadside; Gaseous pollutants; Principal component analysis;

Optical properties of Asian dusts in the free atmosphere measured by Raman lidar at Taipei, Taiwan by Wei-Nai Chen; Fu-Jung Tsai; Charles C.-K. Chou; Shih-Yu Chang; Yi-Wei Chen; Jen-Ping Chen (7698-7714).
The optical properties (extinction-to-backscatter ratio, backscattering, depolarization, and backscatter-related Angstrom exponent) and height distribution of Asian dusts were measured using a two-wavelength Raman/depolarization lidar at Taipei, Taiwan, during the Asian dust seasons in 2004 and 2005. Dust layers were frequently observed in the free atmosphere (1–6 km). Dust optical thickness ranged from 0.01 to 0.55; backscatter-related Angstrom exponents ranged from 0.42 to 1.47; and lidar ratios (extinction-to-backscatter ratio) for 355 nm ranged from 32 to 72 sr (steradian). The mean values of dust particle depolarization and extinction coefficient are 14 ± 6 % and 0.16 km - 1 , respectively, which are close to the moderate dust depolarizations and extinctions observed in free atmosphere in China and Japan. Backscatter-related Angstrom exponents were found correlated positively with lidar ratio and negatively with particle depolarization, indicating that the dust optical characteristics are predominated by size distribution. Dusts were found to tend to exhibit unusual low depolarization properties under moist conditions (relative humidity RH > 70 % ), and the possible explanations are discussed.
Keywords: Lidar; Depolarization ratio; Lidar ratio; Angstrom exponent; Asian dust;

Urban air pollution in many cities of the developing world in Asia, particularly in Vietnam, is increasing significantly. Atmospheric particulate matter pollution is dangerous to the health of millions of people and is a particular concern. In this study, two nitro-polycyclic aromatic hydrocarbons (nitro-PAHs), 1-nitropyrene (1-NP) and 2-nitrofluoranthene (2-NF) and several polycyclic aromatic hydrocarbons (PAHs)—highly carcinogenic and mutagenic compounds—were quantified in particulate matter (PM) collected at three ambient air sites (VNU, ITTE and DOSTE) in an urban area of Ho Chi Minh City, Vietnam, between January 2005 and March 2006. The DOSTE site was close to ground level on a street with a high traffic density. 2-NF was more abundant than 1-NP at all sampling sites. Concentrations of 1-NP and PAHs at the traffic site (DOSTE) were higher than those at the other sites (VNU and ITTE). The daytime/nighttime distribution of 2-NF and the 2-NF/1-NP ratios were used to evaluate the gas-phase formation of 2-NF and its formation route. The average ratios of 2-NF/1-NP at the VNU and ITTE sites were much higher than those at the DOSTE site, suggesting that the gas-phase reactions are an important source of 2-NF in the ambient air. The higher nighttime concentration of 2-NF observed at the VNU and ITTE sites and the converse result observed for the traffic site indicates that an NO3 radical-initiated reaction is the dominant route for 2-NF formation in ambient air, while the majority of 2-NF at the traffic site may be attributed to OH radical-initiated reactions.
Keywords: Particulate matter; Nitro-polycyclic aromatic hydrocarbons (nitro-PAHs); PAHs; Urban air; Ho Chi Minh City;

Long-term assessment of particulate matter using CHIMERE model by A. Monteiro; A.I. Miranda; C. Borrego; R. Vautard; J. Ferreira; A.T. Perez (7726-7738).
Particulate matter (PM) and aerosols have became a critical pollutant and object of several research applications, due to their increasing levels, especially in urban areas, causing air pollution problems and thus effects on human health. The main purpose of this study is to perform a first long-term air quality assessment for Portugal, regarding aerosols and PM pollution. The CHIMERE chemistry-transport model, forced by the MM5 meteorological fields, was applied over Portugal for 2001 year, with 10 km horizontal resolution, using an emission inventory obtained from a spatial top-down disaggregation of the 2001 national inventory database. The evaluation model exercise shows a model trend to overestimate particulate pollution episodes (peaks) at urban sites, especially in winter season. This could be due to an underprediction of the winter model vertical mixing and also to an overestimation of PM emissions. Simulated inorganic components (ammonium and sulfate) and secondary organic aerosols (SOA) were compared to measurements taken at Aveiro (northwest coast of Portugal). An underestimation of the three components was verified. However, the model is able to predict their seasonal variation. Nevertheless, as a first approach, and despite the complex topography and coastal location of Portugal affected by sea salt natural aerosols emissions, the results obtained show that the model reproduces the PM levels, temporal evolution, and spatial patterns. The concentration maps reveal that the areas with high PM values are covered by the air quality monitoring network.
Keywords: Aerosol; Long-term simulation; Model validation; CHIMERE model;

Daily 500 m above sea level (ASL) 3-day back-trajectories ending in Beijing over 5 years (2001–2005) were computed using hybrid single particle Lagrangian integrated trajectory model (HYSPLIT_4). The dependence of daily aerosol data on long-range transport of air masses was analyzed using back-trajectory analysis. The results showed that the technique was successful at separating aerosol data into physically distinct groups. About 47% of variance in aerosol optical depth (AOD) was explained, except in spring when the value was about 25%. The cleaner nature of northerly and northwesterly transport patterns in comparison to southerly ones, as well as the effect of near-stagnant air masses on air pollution in Beijing was identified. Elevated AODs were generally associated with slowly moving back trajectories, especially for air masses slowly moving from south and east of the site. The AOD differences associated with slowly and fast moving air masses were statistically significant. The higher AOD associated with slowly moving air masses was generally accompanied by higher precipitable water vapor, and aerosols generally had higher single-scattering albedo in comparison with fast moving air masses.
Keywords: Aerosol; Back trajectories;

Chemical characteristics of atmospheric aerosols over southwest coast of India by P. Hegde; A.K. Sudheer; M.M. Sarin; B.R. Manjunatha (7751-7766).
Ambient aerosol samples, collected from Mangalore region in the southwest coast of India during the period of late winter (February and March) to early summer (April and May), have been analysed for water-soluble ionic species. Their abundance pattern is dominated by HCO3 , SO4 2−, Na+, Cl, with minor contribution from NO3 , Ca2+, NH4 +, K+ and Mg2+ indicating the contribution from not only sea salt, but also from anthropogenic and dust sources; with pronounced seasonal variability. The suspended particulate matter concentration varied from 35 to 160 μg m−3, with consistently higher values during the late winter. Back trajectory analysis suggests the origin of the air masses shifting from Indo-Gangetic Plains (during late winter) to those from the Arabian Sea and the area around Persian Gulf during April–May. Air masses passing over Northern India (Indo-Gangetic Plains) impart characteristic contribution of ionic species from fossil fuel combustion, biomass burning and eolian dust as asserted by the factor analysis. A detailed study on characterisation of aerosols from south Asian region is rather sparse but essential for modelling the effect of tropospheric aerosols on climate.
Keywords: Air pollution; Seasonal variation; Sources;

Assessing the importance of ab- and adsorption to the gas-particle partitioning of PCDD/Fs by Rainer Lohmann; Rosalinda Gioia; Steven J. Eisenreich; Kevin C. Jones (7767-7777).
The gas-particle partitioning of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) was examined (i) by re-interpreting results from controlled field experiments and (ii) in diurnal samples taken in the New Jersey (NJ), New York (NY) City region. In the controlled field experiments, aerosol-laden filters were exposed to elevated concentrations of PCDD/Fs. Gas-particle partitioning coefficients, K p's, were significantly correlated with octanol–air partitioning coefficients, K oa's. The regression of all individual datapoints resulted in the following best fit (r 2=0.74, n=87): log  K p,meas=1.00(±0.13) log(10−12 f om K oa/ρ oct)−0.15(±0.48). We interpret this as showing that the ability of organic matter (OM) to absorb PCDD/Fs is generally well described by the octanol–air partitioning model (f om K oa). At the NJ land-based sites, samples were taken and analyzed for organic carbon (OC) and elemental carbon (EC), gaseous and particulate PCDD/Fs. K p's were significantly correlated with the f om K oa approach. Adsorption to the filter and possibly to black carbon (BC), which was estimated based on EC measurements, could have contributed to the observed K p values. Gas-particle predictions based on BC adsorption and OM absorption, with K p=f om K oa/(1012 ρ oct)+f BC K BC–air/(1012 ρ BC) resulted in K p predictions that were close to measured values. Adsorption to the filter might have been the major reason for elevated K p's: The one NJ site with highest K p's was most prone to the filter adsorption sampling artefact because of relatively low sampling volumes and concentrations of total suspended particulates. In addition, while adsorption to BC would result in better prediction of K p values, no influence of f BC or f BC/f om ratios was seen, suggesting that it was of lesser importance in our sample set.
Keywords: Gas-particle partitioning; Dioxins; Organic matter; Absorption; Black carbon; Adsorption; Sampling artifact;

Determinants of airborne benzene concentrations in rural areas of western Canada by Igor Burstyn; Xiaoqing (Isabelle) You; Nicola Cherry; Ambikaipakan Senthilselvan (7778-7787).
This study estimated the level and determinants of airborne benzene concentrations in rural western Canada. A multi-site, multi-month unbalanced two-factorial design was used to collect air samples at 1206 fixed sites across a geographic area associated with primary oil and gas industry in Canadian provinces of Alberta, north-eastern British Columbia, and central and southern Saskatchewan from April 2001 to December 2002. Benzene concentrations integrated over 1 calendar month were determined using passive organic vapour monitors. Linear mixed effects models were applied to identify the determinants of airborne benzene concentrations, in particular the proximity to oil and gas facilities. The observed geometric mean of benzene concentrations was 158 ng m−3, with large geometric standard deviation: 4.9. Benzene concentrations showed a seasonal variation with maxima in winter and minima in summer. Emissions from oil well (within 2 km) and compressor influenced monthly airborne benzene concentrations. However, in our study, being located in the general area of a gas plant seems to be the most important in determining monthly airborne benzene concentrations. These findings support the need for investigation of the impact of oil and gas industry on quality of rural air.
Keywords: Air pollution; Oil and gas industry; Source identification; Statistical modelling;

Modeling the space/time distribution of particulate matter in Thailand and optimizing its monitoring network by Sitthichok Puangthongthub; Supat Wangwongwatana; Richard M. Kamens; Marc L. Serre (7788-7805).
The space/time distribution of PM10 in Thailand is modeled using the Bayesian maximum entropy (BME) method of modern spatiotemporal geostatistics. Three kinds of BME spatiotemporal maps over Thailand are sought on the most polluted day for each year of a 6-year period from 1998 to 2003. These three maps are (1) the map of the BME estimate of daily PM10, (2) the map of the associated BME prediction error, and (3) the BME non-attainment map showing areas where the BME estimate does not attain a 68% probability of meeting the ambient standard for PM10. These detailed space/time PM10 maps provide invaluable information for decision-makers in air quality management. Knowing accurately the spatiotemporal distribution of PM10 is necessary to develop and evaluate strategies used to abate PM10 levels. The space/time BME estimate of PM10 on the worst day of the year offers a general picture as to where daily PM10 levels are not in compliance with the air-quality standard. Delineating these areas leads to the BME non-attainment maps, which are useful in identifying unhealthy zones, where sensitive population such as asthmatic children, seniors, or those with cardiopulmonary disease should be advised to avoid outdoor activities. The results of the space/time BME analysis of PM10 are further extended to assess whether the current monitoring network is adequate. The current distribution of monitoring stations can be evaluated by combining the available demographic information with the BME estimation error maps. Administrative districts with large population size and high BME normalized estimation error are suggested as the target for adding new monitoring stations.
Keywords: PM10; Particulate matter; Bayesian maximum entropy; Space–time analysis; Monitoring network; Thailand;

An assessment of the polar HO x photochemical budget based on 2003 Summit Greenland field observations by G. Chen; L.G. Huey; J.H. Crawford; J.R. Olson; M.A. Hutterli; S. Sjostedt; D. Tanner; J. Dibb; B. Lefer; N. Blake; Douglas Davis; A. Stohl (7806-7820).
An interpretative modeling analysis is conducted to simulate the diurnal variations in OH and HO2+RO2 observed at Summit, Greenland in 2003. The main goal is to assess the HO x budget and to quantify the impact of snow emissions on ambient HO x as well as on CH2O and H2O2. This analysis is based on composite diurnal profiles of HO x precursors recorded during a 3-day period (July 7–9), which were generally compatible with values reported in earlier studies. The model simulations can reproduce the observed diurnal variation in HO2+RO2 when they are constrained by observations of H2O2 and CH2O. By contrast, model predictions of OH were about factor of 2 higher than the observed values. Modeling analysis of H2O2 suggests that its distinct diurnal variation is likely controlled by snow emissions and loss by deposition and/or scavenging. Similarly, deposition and/or scavenging sinks are needed to reproduce the observed diel profile in CH2O. This study suggests that for the Summit 2003 period snow emissions contribute ∼25% of the total CH2O production, while photochemical oxidation of hydrocarbon appears to be the dominant source. A budget assessment of HO x radicals shows that primary production from O(1D)+H2O and photolysis of snow emitted precursors (i.e., H2O2 and CH2O) are the largest primary HO x sources at Summit, contributing 41% and 40%, respectively. The snow contribution to the HO x budget is mostly in the form of emissions of H2O2. The dominant HO x sink involves the HO2+HO2 reaction forming H2O2, followed by its deposition to snow. These results differ from those previously reported for the South Pole (SP), in that primary production of HO x was shown to be largely driven by both the photolysis of CH2O and H2O2 emissions (46%) with smaller contributions coming from the oxidation of CH4 and the O(1D)+H2O reaction (i.e., 27% each). In sharp contrast to the findings at Summit in 2003, due to the much higher levels of NO x , the SP HO x sinks are dominated by HO x –NO x reactions, leading to the formation and deposition of HNO3 and HO2NO2. Thus, a comparison between SP and Summit studies suggests that snow emissions appear to play a prominent role in controlling primary HO x production in both environments. However, as regards to maintaining highly elevated levels of OH, the two environments differ substantially. At Summit the elevated rate for primary production of HO x is most important; whereas, at SP it is the rapid recycling of the more prevalent HO2 radical, through reaction with NO, back to OH that is primarily responsible.
Keywords: Polar HO x ; Snow emission; HO x budget; Formaldehyde; Hydrogen peroxide;

Characterization of aerosol over the Northern South China Sea during two cruises in 2003 by Xingying Zhang; Guoshun Zhuang; Jinghua Guo; Kedong Yin; Peng Zhang (7821-7836).
Atmospheric transport of trace elements has been found to be an important pathway for their input to the ocean. TSP, PM10, and PM2.5 aerosol samples were collected over the Northern South China Sea in two cruises in 2003 to estimate the input of aerosol from continent to the ocean. About 23 elements and 14 soluble ions in aerosol samples were measured. The average mass concentration of TSP in Cruise I in January (78 μg m−3) was ∼twice of that in Cruise II in April (37 μg m−3). Together with the crustal component, heavy metals from pollution sources over the land (especially from the industry and automobiles in Guangzhou) were transported to and deposited into the ocean. The atmospheric MSA concentrations in PM2.5 (0.048 μg m−3 in Cruise I and 0.043 μg m−3 in Cruise II) over Northern South China Sea were comparable to those over other coastal regions. The ratio of non-sea-salt (NSS)-sulfate to MSA is 103-655 for Cruise I and 15-440 for Cruise II in PM2.5 samples, which were much higher than those over remote oceans. The estimated anthropogenic sulfate accounts for 83–98% in Cruise I and 63–95% in Cruise II of the total NSS-sulfate. Fe (II) concentration in the aerosols collected over the ocean ranged from 0.1 to 0.9 μg m−3, accounting for 16–82% of the total iron in the aerosol, which could affect the marine biogeochemical cycle greatly.
Keywords: Marine aerosol; Northern South China Sea; Air–sea exchange;

Atmospheric concentrations and dry deposition fluxes of particulate trace metals in Salvador, Bahia, Brazil by Pedro A. de P. Pereira; Wilson A. Lopes; Luiz S. Carvalho; Gisele O. da Rocha; Nei de Carvalho Bahia; Josiane Loyola; Simone L. Quiterio; Viviane Escaleira; Graciela Arbilla; Jailson B. de Andrade (7837-7850).
Respiratory system is the major route of entry for airborne particulates, being the effect on the human organism dependent on chemical composition of the particles, exposure time and individual susceptibility. Airborne particulate trace metals are considered to represent a health hazard since they may be absorbed into human lung tissues during breathing. Fossil fuel and wood combustion, as well as waste incineration and industrial processes, are the main anthropic sources of metals to the atmosphere. In urban areas, vehicular emissions—and dust resuspension associated to road traffic—become the most important manmade source.This work investigated the atmospheric concentrations of TSP, PM10 and elements such as iron, manganese, copper and zinc, from three different sites around Salvador Region (Bahia, Brazil), namely: (i) Lapa Bus Station, strongly impacted by heavy-duty diesel vehicles; (ii) Aratu harbor, impacted by an intense movement of goods, including metal ores and concentrates and near industrial centers and; (iii) Bananeira Village located on Maré Island, a non-vehicle-influenced site, with activities such as handcraft work and fishery, although placed near the port. Results have pointed out that TSP concentrations ranged between 16.9 (Bananeira) and 354.0 μg m−3 (Aratu#1), while for PM10 they ranged between 30.9 and 393.0 μg m−3, both in the Lapa Bus Station. Iron was the major element in both Lapa Station and Aratu (#1 and #2), with average concentrations in the PM10 samples of 148.9, 79.6 and 205.0 ng m−3, respectively. Zinc, on the other hand, was predominant in samples from Bananeira, with an average concentration of 145.0 ng m−3 in TSP samples, since no PM10 sample was taken from this site. The main sources of iron in the Lapa Station and Aratu harbor were, respectively, soil resuspension by buses and discharge of solid granaries, as fertilizers and metal ores. On the other hand, zinc and copper in the bus station were mainly from anthropic contributions, probably heavy-duty vehicle ageing and wearing actions releasing off Zn from tires and Cu from brake linings. In the Aratu harbor, the high copper concentrations found were probably due to the port's activities, as discharges of copper concentrate on its terminal, although other sources could be possible, as burning of diesel fuel on ships and heavy oil in heaters. Finally, the Bananeira site has been presented as a different profile, since this remote site has shown zinc as the most abundant element, demonstrating to have an unexpected anthropic contribution. On a mass-to-mass basis, both zinc and manganese were in high levels in the Bananeira site and their presence strongly suggest the impact of other sources, such as the Industrial Center of Aratu and/or a siderurgy plant, not far away from that location.
Keywords: Trace metals; ICP OES; PM10; TSP; Bus station; Harbor and island; Brazil; Salvador;

For quantitative estimate of biogenic volatile organic compound emissions (BVOCs) in South China and their impact on the regional atmospheric chemistry, a 3-day tropical cyclone-related ozone episode was modeled using chemical transport model CMAQ, which was driven by the mesoscale meteorological model MM5. Hourly biogenic emission inventories were constructed using the Sparse Matrix Operator Kernel Emissions (SMOKE) model. The simulation results show good agreement with observation data in air temperature, ozone and NO x levels. The estimated biogenic emissions of isoprene, terpene, and other reactive VOCs (ORVOCs) during this tropical cyclone-related episode are 8500, 3400, and 11 300 ton day−1, respectively. The ratio of isoprene to the total BVOCs was 36.4%. Two test runs were carried out with one incorporated biogenic emissions and the other without. The simulations show that Guangdong province, particularly the Pearl River Delta (PRD) region, was the area most reactive to biogenic emissions in South China. More ozone was produced in all layers under 1500 m when biogenic emissions were included in comparison to that without BVOCs. The net formation of ozone from 9:00 to 15:00 h was the highest near the surface and could reach 38 ppb, which include 4 ppb attributed to biogenic impact. The enhanced ozone due to biogenic emissions first appeared in the PRD region and slowly spread to a greater area in South China. Process analysis indicated that the surface ozone budget was dominated by the vertical transport and dry deposition. The horizontal transport and gas-phase chemical production were relatively small in the surface layer. Presumably, ozone was produced in upper layers within the atmospheric boundary layer and convected down to surface where it is destroyed. When BVOCs was included, apart from the enhancement of gas-phase chemical production of ozone, both the surface deposition and vertical transport were also augmented.
Keywords: Biogenic emissions; Tropical cyclone; The Pearl River Delta region; Ozone episode; Air modeling;

Monitoring of ozone precursors in ambient air using pumped and diffusive sampling on the sorbent Carbopack X by Paul Quincey; David Butterfield; Hansa D’Souza; Malcolm Henderson (7865-7873).
EU legislation for ambient ozone concentrations puts a requirement on Member States to monitor a large set of ozone precursor species, mostly hydrocarbons. We describe an investigation into how much of this information is readily available from manual methods used routinely for benzene monitoring in the United Kingdom, using pumped or diffusive sampling of ambient air onto the sorbent Carbopack X, followed by thermal desorption and gas chromatography with a flame ionisation detector. Identifiable peaks were assessed for reliability by comparison with independent automated measurements and emissions inventories. We conclude that 21 of the 29 specified hydrocarbons can be usefully monitored without any change to the methods used.
Keywords: Ozone precursors; Hydrocarbons; Ambient air monitoring; Air quality; Health;

A new dispersion model for dense gas which is released into the atmosphere on the flat terrain is constructed within the Lagrangian framework. Using the hydrostatic assumption for pressure distribution within cloud due to density variation, slumping motion is successfully incorporated into the Lagrangian model with entrainment effect naturally considered. Turbulence suppression due to stable stratification within cloud is also taken into consideration in the model formulation. Various results including time variant and maximum concentration predictions by the proposed model are compared with the available measured data in the experiment conducted in Thorney Island in 1984 with good agreement.
Keywords: Dense-gas dispersion model; Thorney Island trials; Lagrangian stochastic model; Stratification; Gravity slumping;

The present research proposes the local urban air quality management plan which combines two different modelling approaches (hybrid model) and possesses an improved predictive ability including the ‘probabilistic exceedances over norms’ and their ‘frequency of occurrences’ and so termed, herein, as episodic-urban air quality management plan (e-UAQMP). The e-UAQMP deals with the consequences of ‘extreme’ concentrations of pollutant, mainly occurring at urban ‘hotspots’ e.g. traffic junctions, intersections and signalized roadways and are also influenced by complexities of traffic generated ‘wake’ effects. The e-UAQMP (based on probabilistic approach), also acts as an efficient preventive measure to predict the ‘probability of exceedances’ so as to prepare a successful policy responses in relation to the protection of urban environment as well as disseminating information to its sensitive ‘receptors’. The e-UAQMP may be tailored to the requirements of the local area for the policy implementation programmes. The importance of such policy-making framework in the context of current air pollution ‘episodes’ in urban environments is discussed. The hybrid model that is based on both deterministic and stochastic based approaches predicting the ‘average’ as well as ‘extreme’ concentration distribution of air pollutants together in form of probability has been used at two air quality control regions (AQCRs) in the Delhi city, India, in formulating and executing the e-UAQMP—first, the income tax office (ITO), one of the busiest signalized traffic intersection and second, the Sirifort, one of the busiest signalized roadways.
Keywords: Pollutant extreme concentrations; Episodic events; Probabilistic approach; Traffic intersections; Air quality management plan;

To make progress towards linking the atmosphere and biogeosphere parts of the black carbon (BC) cycle, a chemothermal oxidation method (CTO-375), commonly applied for isolating BC from complex geomatrices such as soils, sediments and aquatic particles, was applied to investigate the BC also in atmospheric particles. Concentrations and 14C-based source apportionment of CTO-375 based BC was established for a reference aerosol (NIST RM-8785) and for wintertime aerosols collected in Stockholm and in a Swedish background area. The results were compared with thermal–optical (OC/EC) measurements. For NIST RM-8785, a good agreement was found between the BCCTO-375 concentration and the reported elemental carbon (EC) concentration measured by the “Speciation Trends Network—National Institute of Occupational Safety and Health” method (ECNIOSH) with BCCTO-375 of 0.054±0.002 g g−1 and ECNIOSH of 0.067±0.008 g g−1. In contrast, there was an average factor of ca. 20 difference between BCCTO-375 and ECNIOSH for the ambient Scandinavian wintertime aerosols, presumably reflecting a combination of BCCTO-375 isolating only the recalcitrant soot-BC portion of the BC continuum and the ECNIOSH metric inadvertently including some intrinsically non-pyrogenic organic matter. Isolation of BCCTO-375 with subsequent off-line radiocarbon analysis yielded fraction modern values (fM) for total organic carbon (TOC) of 0.93 (aerosols from a Swedish background area), and 0.58 (aerosols collected in Stockholm); whereas the fM for BCCTO-375 isolates were 1.08 (aerosols from a Swedish background area), and 0.87 (aerosols collected in Stockholm). This radiocarbon-based source apportionment suggests that contribution from biomass combustion to cold-season atmospheric BCCTO-375 in Stockholm was 70% and in the background area 88%.
Keywords: Black carbon; Elemental carbon; Chemothermal oxidation method; CTO-375; Source apportionment; Radiocarbon; 14C;

To examine the diversity of chemical and physical properties of aerosol particles, in particular dust, over the North Pacific, aerosols were collected along ∼32°N latitude between 140°E and 170°W longitude aboard the NOAA R/V Ronald H. Brown during the Asian Pacific Regional Aerosol Characterization Experiment (ACE-Asia) in the spring 2001. A total of 11,482 aerosol particles were examined through individual-particle analysis. Results indicate that dust particles over this region were dominated primarily by Si-rich particles, including aluminosilicates that contain Fe. Fe is also present as separate Fe-rich particles. Additional common particle types include Ca- and S-rich particles; many of the later appear to represent soil-derived calcium carbonate and its reaction products whereas the former are predominantly reaction products of sea salt and sulfate. Particles are often aggregates of different types including pollution-derived substances and highly heterogeneous, both internally and externally. Dust particles are non-spherical, having circularities from 1.0 up to 4.5, suggesting the high degree of complexity of particle shape. The majority of dust particles were dominated by particles with median diameters from 0.67 to 1.26 μm. However, dust particles with diameters of 5 μm or even larger do exist associated with those events of dust originated from Asian desert areas. The existence of soot and Fe-rich particles over this region indicates the influence of fossil fuel sources in Asia. Aerosol Fe from both Asian desert and fossil fuel combustion may contribute to the nutrient Fe in the surface waters of the North Pacific basin. Therefore, the transport of Asian dust associated with species of fossil fuel burning in the spring may play an important role in altering the natural composition of aerosols over the North Pacific.
Keywords: Dust; Asian aerosols; Shipboard sampling; Soot; Iron;

A source apportionment study was conducted at two rural locations, Potsdam and Stockton, to assess the in-state/out-of-state sources of PM2.5 and Hg in New York State. At both locations, samples were collected between November 2002 and August 2005 and analyzed for fine PM mass and its chemical constituents. The measured chemical constituents included elements, cations, anions, organic and elemental carbon (OC and EC), black carbon (BC), and water-soluble short-chain (WSSC) organic acids. Positive matrix factorization (PMF) was applied to the measured concentrations and eight and seven factors were resolved at Potsdam and Stockton, respectively. Four factors were resolved in common between the two locations including secondary sulfate, secondary nitrate, secondary OC, and a crustal factor. The factor profiles of mixed industrial and motor vehicle factors resolved at Potsdam were different compared with the corresponding profiles for these factors at Stockton. A resuspended road salt factor was identified at Potsdam, while an aged sea salt factor was identified at Stockton. At Potsdam, a wood smoke factor was also resolved. Among the resolved factors, secondary sulfate was the highest contributor to the measured mass at both sites. Potential source contribution function (PSCF) analysis indicated the Ohio River Valley region as a common potential source region for this factor at both locations. For the secondary nitrate factor, at Potsdam PSCF analysis indicated the Midwestern US (NO x emissions), and the US farm belt (ammonia emissions) as potential source regions, while at Stockton, the Midwestern US (power plant NO x emissions) was indicated as a major potential source region.
Keywords: PM2.5; Chemical constituents; Potsdam; Stockton; Positive matrix factorization (PMF); Potential source contribution function (PSCF);

Emissions generated roadside and at intersections are observed to be affected when there is a sudden change in the traffic flow pattern or increase in the vehicular population, particularly, during peak hours and during special events. The vehicles that queue up at traffic intersections spend a longer amount of time in idle driving mode generating more pollutant emissions per unit time. Other driving patterns (i.e., acceleration, deceleration and cruising) are also observed at intersections, affecting the emission pattern and therefore the resulting pollutant concentrations. The emission rate is not only affected by the increase in the vehicular population but also by the constantly changing traffic flow patterns and vehicles’ driving modes. The nature of the vehicle flows also affects the rate and nature of the dispersion of pollutants in the vicinity of the road, influencing the pollutant concentration. It is, therefore, too complex to simulate the effect of such dynamics on the resulting emission rates using conventional deterministic causal models.In view of this, a simple semi-empirical box model based on the ‘traffic flow rate’, is demonstrated in the present study for estimating the hourly average carbon monoxide (CO) concentrations on a 1-week data at one of the busiest traffic intersections in Delhi. The index of agreement for a whole week, was found to be 0.84, suggesting that the semi-empirical model is 84% error free. A value of 0.87 was found for weekdays and 0.75 for weekend days. The correlation coefficient for the whole week was found to be 0.75, with 0.78 for the weekdays and 0.62 for the weekend days. The RMSE and RRMSE were found to be 1.87% and 41% for a whole week, with 1.81% and 39.93% for the weekdays and 2.0% and 43.47% for the weekend days, respectively. Specific vehicle emission rates are optimized in this study for individual vehicle category, which may be useful in assessing their impacts on the air quality when there is a significant change in a specific vehicular population and the traffic pattern.
Keywords: Traffic flow rate; Vehicle emission rate; Vehicle density; Semi-empirical box air quality model; Carbon monoxide concentration;

Multiple 24-h average outdoor, indoor and personal respirable particulate matter (RPM) measurements were made in different urban residential colonies to determine major routes of personal exposure. The study area was Bhilai-Durg, District Durg, Chhattisgarh, India. About 100 residentials from each of two selected colonies have been surveyed for consent to participate in the study and for preparation of time–activity diary. On the basis of their time–activity diary, residentials have been categorized into three types: type-A, purely residential; type-B, residents who go out, and type-C, residence who go into work, specially in industrial area. A total of 28 adult participants (14 males and 14 females; mean age 40±15, range 21–61 years) were selected and monitored longitudinally during the summer (15 March–15 June) of 2004. Participants’ residential indoor RPM level and also local ambient outdoor RPM levels were measured,and these are done simultaneous with personal monitoring. Residential indoor and ambient outdoors RPM monitoring sessions were throughout the year to obtain infiltration factor more precisely. To compare RPM levels with Indian National Ambient Air Quality Standards (NAAQS) of PM10, simultaneous measurements of PM10 were also done with the course of ambient outdoor RPM monitoring. RPM levels in indoors were higher compared to ambient outdoors. The annual average ratio RPM/PM10 was found to vary significantly among residential sites due to variation in surroundings. Source contribution estimates (SCE) of personal exposure to RPM in selected 12 residences (six from each colony) have been investigated using chemical mass balance model CMB8. Ambient outdoors, residential indoors, soils and road-traffic borne RPM were identified as main routes and principal sources of personal RPM. Results of model output have shown that residential indoors and soil-borne RPM are the major routes of personal exposure.
Keywords: Respirable particulate matter; Microenvironments; Residential indoors; Source apportionment; Personal exposure;

The physical principles of the Black Smoke method for measuring airborne particulate matter are very similar to those of the optical transmission method for Black Carbon, known as aethalometry. A simple quadratic relationship between the two methods can be derived, which could be useful in the interpretation of historical Black Smoke data for human health and climate change studies. Data supporting the relationship from a London kerbside site are presented.
Keywords: Black Smoke; Black Carbon; Soot; Air quality; Human health; Climate change;

Characterization and contribution to PM2.5 of semi-volatile aerosols in Paris (France) by Olivier Favez; Hélène Cachier; Jean Sciare; Yvon Le Moullec (7969-7976).
Collocated PM2.5 measurements using a conventional R&P TEOM (model 1400a) and a TEOM-FDMS were performed at a Paris urban background site during winter/summer field experiments. Results showed that conventional TEOM underestimates PM2.5 mass concentrations by about 50% in winter and 35% in summer. They also confirmed that this negative sampling artifact, due to the volatilization of semi-volatile material (SVM) inside the instrument, cannot be accurately accommodated by a single correction factor because of SVM routine fluctuations. A basic filter-based investigation of the SVM chemical composition also indicated that SVM, measured by the TEOM–FDMS, is mainly formed by ammonium nitrate in winter while significant contributions of semi-volatile organic matter were observed in summer. The latter species was found to possibly account for more than 50% of secondary organic aerosol formed during summer afternoons. These findings call for more investigation of the SVM chemical composition, particularly during the summer season, in Paris and in Europe.
Keywords: Semi-volatile material; Ammonium nitrate; Organic aerosol; TEOM(–FDMS); PM2.5;

Mass levels, crustal component and trace elements in PM10 in Palermo, Italy by G. Dongarrà; E. Manno; D. Varrica; M. Vultaggio (7977-7986).
Results concerning the levels and elemental compositions of daily PM10 samples collected at four air quality monitoring sites in Palermo (Italy) are presented. The highest mean value of PM10 concentrations (46 μg m−3, with a peak value of 158 μg m−3) was recorded at the Di Blasi urban station, and the lowest at Boccadifalco station (25 μg m−3), considered as a sub-urban background station. Seventeen elements (Al, As, Ba, Co, Cr, Cu, Fe, Li, Mn, Mo, Ni, Pb, Sb, Sr, U, V, Zn) were measured by ICP-MS. Al and Fe showed the highest concentrations, indicating the significant contribution of soil and resuspended mineral particles to atmospheric PM10. Ba, Cr, Cu, Mn, Mo, Ni, Pb, Sb, V and Zn had higher concentrations at the three urban sampling sites than at the sub-urban background station. Besides soil-derived particles, an R-mode cluster analysis revealed a group of elements, Mo, Cu, Cr, Sb and Zn, probably related to non-exhaust vehicle emission, and another group, consisting of Ba, As and Ni, which seemed to be associated both with exhaust emissions from road traffic, and other combustion processes such as incinerators or domestic heating plants. The results also suggest that Sb, or the association Sb–Cu–Mo, offers a way of tracing road traffic emissions.
Keywords: PM10; Heavy metals; Environmental geochemistry; Enrichment factors; Chemical tracers;

An algorithm and a device for counting airborne pollen automatically using laser optics by Shigeto Kawashima; Bernard Clot; Toshio Fujita; Yuichi Takahashi; Kimihito Nakamura (7987-7993).
Airborne pollen is important in relation to the social issues of pollinosis and of the environmental effects of genetically modified plants. Existing methods for pollen counting involve counting and classifying the grains that adhere to a sampling surface, requiring much time and skilled labor. We therefore have developed a method of automatically monitoring pollen, using a laser-optics instrument. In this instrument, the sideways and forward scattering of laser light by each particle is recorded in real time for computer processing. A field experiment was conducted in 2005, comparing our method with that of the older Hirst method. A scatter plot was made of the forward scattering vs. the sideways scattering for each particle. An algorithm was developed to find the optimum rectangular region of the plot for each type of pollen, and a count of points inside this region was taken as the count for that type of pollen. For the three most common types of pollen found in the field test (Urticaceae, Poaceae, and Ambrosia), the daily counts from this algorithm were compared with the daily counts from the Hirst-type (Burkard) sampler. There was a very high correlation (determination coefficient approximately 0.8) between the results of the two methods.
Keywords: Airborne pollen; Concentration; Automatic pollen monitoring; Semiconductor laser;