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Atmospheric Environment (v.41, #39)

Editorial board (pp. i).

Haagen-Smit Prize 2007 (pp. 8831-8833).

Characterization and source presumption of wintertime submicron organic aerosols at Saitama, Japan, using the Aerodyne aerosol mass spectrometer by Hiroyuki Hagino; Tomonori Takada; Hitoshi Kunimi; Kazuhiko Sakamoto (pp. 8834-8845).

The chemical composition and size distribution of submicron aerosols were analyzed at a suburban site at Saitama, Japan, in the winter of 2004/2005, using an Aerodyne aerosol mass spectrometer. Although organics and nitrate were the dominant species during the sampling period, a large fraction of sulfate was observed at the accumulation mode when mass loading was low and wind speed was high. The size distributions of m/z 44 (mostly CO₂⁺) and sulfate aerosols during periods of high wind speed showed remarkable similarities in the accumulation mode, indicating that oxygenated organics were aged aerosols and internally mixed with sulfate. Ozone concentrations were also increased during these high wind speed periods although nighttime (e.g., 12/17 2004), indicating that the oxygenated compounds were strongly influenced by transported and aged air masses. The diurnal profiles of ultrafine-mode organics and hydrocarbon-like organic aerosols (HOA) were similar to NO _X derived from traffic and other combustion sources. The temporal variation of oxygenated organic aerosols (OOA) agreed well with that of nitrate as a secondary aerosol tracer, and the diurnal profile of the OOA fraction of organics increased during the day associated with higher UV light intensity. The result of time and size-resolved chemical composition of submicron particles indicated that the OOA is associated with both photochemical activity and transboundary pollution, and ultrafine-mode organic and HOA aerosols are mainly associated with combustion sources.

Keywords: Aerodyne aerosol mass spectrometry; Aerosol chemistry; Urban pollution; Organic aerosol

Validation of trajectory statistical methods by Helfried Scheifinger; August Kaiser (pp. 8846-8856).

A number of works have been trying to validate various trajectory statistical methods (TSMs), mostly through subjective comparison with known sources. Here in a more comprehensive and quantitative approach three trajectory statistical methods (potential source contribution function (PSCF), concentration field method (CF), and redistributed concentration field method (RCF)) were subjected to two validation approaches: validation with virtual and real sources under idealised conditions, where the effects of dispersion and removal of the trace substance are excluded, and comparisons with the EMEP SO₂ emission inventory under realistic conditions.The best performance was achieved in an idealised situation with about 78% common spatial variance between the EMEP emission inventory and the trajectory statistical reconstruction of the EMEP emission inventory with the RCF method, whereas the real world experiments for SO₂ on an European scale resulted in a much lower performance with 33% common spatial variance between the EMEP SO₂ emission inventory and the trajectory statistical reconstruction with the PSCF method.The experiments suggest that the limitation of the accuracy and spatial range of TSMs are rooted in the simplified transport process described just by trajectory paths. If one links these limitations with the concept of the mean residence time of the considered trace substance, a temporal and spatial scope can be deduced, within which the effect of the simplification of the transport process is restricted and useful information can be expected from TSMs. The lower values of the mean residence time for SO₂ range from 9 to 17h, which were deduced from the decay approach, where an exponential decay, respectively, removal of SO₂ was built into the trajectory statistical procedure. The values derived from the optimum real world validation experiment place the upper range of the mean residence time to about 60h or 2.5 days. Both figures are within the range of mean residence times for SO₂ cited in literature. Through the validation experiments of this work the rule of thumb, not to trust TSMs beyond the mean residence time of the substance, has become palpable. Nevertheless TSMs and related methods are computationally fast procedures, which deliver first hints on potential source areas, if applied within the frame of the mean residence time of the considered substance.

Keywords: Potential source contribution function; Concentration field method; Redistributed concentration field method; Validation; Source–receptor relationship

Measurement of organic mass to organic carbon ratio in ambient aerosol samples using a gravimetric technique in combination with chemical analysis by Xi Chen; Jian Zhen Yu (pp. 8857-8864).

Organic materials make up a significant fraction of ambient particulate mass. It is important to quantify their contributions to the total aerosol mass for the identification of aerosol sources and subsequently formulating effective control measures. The organic carbon (OC) mass can be determined by an aerosol carbon analyzer; however, there is no direct method for the determination of the mass of organic compounds, which also contain N, H, and O atoms in addition to C. The often-adopted approach is to estimate the organic mass (OM) from OC multiplying by a factor. However, this OC-to-OM multiplier was rarely measured for a lack of appropriate methods for OM. We report here a top-down approach to determine OM by coupling thermal gravimetric and chemical analyses. OM is taken to be the mass difference of a filter before and after heating at 550°C in air for 4h minus mass losses due to elemental carbon (EC), volatile inorganic compounds (e.g., NH₄NO₃), and loss of aerosol-associated water that arise from the heating treatment. The losses of EC and inorganic compounds are determined through chemical analysis of the filter before and after the heating treatment. We analyzed 37 ambient aerosol samples collected in Hong Kong during the winter of 2003, spring of 2004, and summer of 2005. A value of 2.1±0.3 was found to be the appropriate factor to convert OC to OM in these Hong Kong aerosol samples. If the dominant air mass is classified into two categories, then an OM-to-OC ratio of 2.2 was applicable to aerosols dominated by continent-originated air mass, and 1.9 was applicable to aerosols dominated by marine air mass.

Keywords: Aerosol mass reconciliation; Source apportioning; Organic aerosols; Organic carbon

Transformation of diesel engine exhaust in an environmental chamber by Ari P. Leskinen; Jorma K. Jokiniemi; Kari E.J. Lehtinen (pp. 8865-8873).

Overnight aging experiments with diesel engine exhaust from a diesel power aggregate, with no or 9kW load, and from a diesel-fueled vehicle were conducted in an environmental chamber. During a 24h aging period the volatilities of monodisperse particles at 140, 250 and 360°C heater temperatures were analyzed with volatility tandem differential mobility analysis (VTDMA). The particulate organic to total carbon ratio and organic carbon subfractions at 120, 250, 450 and 550°C were analyzed with thermal-optical carbon analysis for samples from fresh, 8 or 18h aged and 24h aged aerosol. During the experiment also the particle size distribution, ozone and nitrogen oxide concentration, and temperature, relative humidity and total solar and total ultraviolet radiation in the chamber were monitored.After injection, the geometric mean diameter and number concentration of the particles in the chamber were 66–85nm and 0.9–4.6×10⁵cm⁻³, respectively. The particles were seen to grow fast, at a growth rate of 18–47nmh⁻¹ during the first hour. The fresh particles from the diesel power aggregate contained 37–45% of apparent volume semi-volatile compounds with no load and 10–24% with 9kW load. The semi-volatile apparent volume fraction at 360°C for 50nm particles produced by the diesel power aggregate was 57%. After 24h of aging, the semi-volatile apparent volume fraction at 360°C for 100nm particles was 99%. This suggests that the particles in the 24h aged aerosol at this size class are no more primary particles but particles that are formed in the chamber through nucleation and subsequent growth.

Keywords: Aerosol; Diesel engine exhaust; Aging; Environmental chamber; Tandem differential mobility analyzer

Estimating changes in urban ozone concentrations due to life cycle emissions from hydrogen transportation systems by Guihua Wang; Joan M. Ogden; Daniel P.Y. Chang (pp. 8874-8890).

Hydrogen has been proposed as a low polluting alternative transportation fuel that could help improve urban air quality. This paper examines the potential impact of introducing a hydrogen-based transportation system on urban ambient ozone concentrations. This paper considers two scenarios, where significant numbers of new hydrogen vehicles are added to a constant number of gasoline vehicles. In our scenarios hydrogen fuel cell vehicles (HFCVs) are introduced in Sacramento, California at market penetrations of 9% and 20%. From a life cycle analysis (LCA) perspective, considering all the emissions involved in producing, transporting, and using hydrogen, this research compares three hypothetical natural gas to hydrogen pathways: (1) on-site hydrogen production; (2) central hydrogen production with pipeline delivery; and (3) central hydrogen production with liquid hydrogen truck delivery. Using a regression model, this research shows that the daily maximum temperature correlates well with atmospheric ozone formation. However, increases in initial VOC and NO _x concentrations do not necessarily increase the peak ozone concentration, and may even cause it to decrease. It is found that ozone formation is generally limited by NO _x in the summer and is mostly limited by VOC in the fall in Sacramento. Of the three hydrogen pathways, the truck delivery pathway contributes the most to ozone precursor emissions. Ozone precursor emissions from the truck pathway at 9% market penetration can cause additional 3-h average VOC (or NO _x) concentrations up to approximately 0.05% (or 1%) of current pollution levels, and at 20% market penetration up to approximately 0.1% (or 2%) of current pollution levels. However, all of the hydrogen pathways would result in very small (either negative or positive) changes in ozone air quality. In some cases they will result in worse ozone air quality (mostly in July, August, and September), and in some cases they will result in better ozone air quality (mostly in October). The truck pathway tends to cause a much wider fluctuation in degradation or improvement of ozone air quality: percentage changes in peak ozone concentrations are approximately −0.01% to 0.04% for the assumed 9% market penetration, and approximately −0.03% to 0.1% for the 20% market penetration. Moreover, the 20% on-site pathway occasionally results in a decrease of about −0.1% of baseline ozone pollution. Compared to the current ambient pollution level, all three hydrogen pathways are unlikely to cause a serious ozone problem for market penetration levels of HFCVs in the 9–20% range.

Keywords: Life cycle analysis (LCA); Hydrogen; Natural gas (NG); Hydrogen pathways; Ozone formation; Ozone air quality

Atmospheric heavy metal pollution in Aqaba city, Jordan, using Phoenix dactylifera L. leaves by Abdelaziz L. Al-Khlaifat; Omar A. Al-Khashman (pp. 8891-8897).

The leaves of date palms ( Phoenix dactylifera L.) were evaluated as biomonitors of heavy metal contamination in the city of Aqaba, Jordan. The concentrations of iron (Fe), lead (Pb), zinc (Zn), copper (Cu), nickel (Ni), and chromium (Cr) were determined using a flame atomic absorption spectrophotometer. Samples of unwashed leaves for testing were collected from different locations with different degrees of metal pollution (urban, suburban, industrial, highway, and rural sites). Separate leaves were taken from outside the city to be used as a control sample. Samples collected from industrial areas were found to have high contents of all metals except for nickel, copper, and lead, which were found at high concentrations in the samples collected from highway sites. Significant correlations between the heavy metal concentrations in date palm trees in unwashed leave samples were obtained. The principle component analysis (PCA) along with correlation analysis provide significant information about the origin of heavy metals in palm tree samples.

Keywords: Date palm; Phoenix dactylifera; Heavy metals; Biomonitor; Air pollution; Aqaba

Source contributions to carbonaceous aerosols in the Tennessee Valley Region by Lin Ke; Xiang Ding; Roger L. Tanner; James J. Schauer; Mei Zheng (pp. 8898-8923).

Sources of carbonaceous aerosols collected from three sites of Chattanooga, TN (CH), Muscle Shoals, AL (MS), and Look Rock, TN (LR) in the Tennessee Valley Region (TVR) were apportioned using both organic tracer-based chemical mass balance (CMB) modeling and radiocarbon (¹⁴C) measurement and the results were compared. Eight sources were resolved by CMB, among which wood combustion (averaging 0.92μgm⁻³) was the largest contributor to primary organic carbon (OC) concentrations, followed by gasoline exhaust (0.35μgm⁻³), and diesel exhaust (0.18μgm⁻³). The identified primary sources accounted for 43%, 71%, and 14% of measured OC at CH, MS, and LR, respectively. Contributions from the eight primary sources resolved by CMB could explain 107±10% of ambient elemental carbon (EC) concentrations, with diesel exhaust (66±32%) and wood combustion (37±33%) as the most important contributors. The fossil fractions in total carbon determined by¹⁴C measurements were in reasonably good agreement with that in primary (OC+EC) carbon apportioned by CMB in the MS winter samples. The comparison between the¹⁴C and CMB results revealed that contemporary sources dominated other OC in the TVR, especially in summertime (84% contemporary).

Keywords: Source apportionment; CMB; Organic tracer; Radiocarbon; Carbonaceous aerosols

Dissolved organic carbon in rainwater: Glassware decontamination and sample preservation and volatile organic carbon by M.L.A.M. Campos; R.F.P. Nogueira; P.R. Dametto; J.G. Francisco; C.H. Coelho (pp. 8924-8931).

The efficiency of different methods for the decontamination of glassware used for the analysis of dissolved organic carbon (DOC) was tested using reported procedures as well as new ones proposed in this work. A Fenton solution bath (1.0mmolL⁻¹ Fe²⁺ and 100mmolL⁻¹ H₂O₂) for 1h or for 30min employing UV irradiation showed to combine simplicity, low cost and high efficiency. Using the optimized cleaning procedure, the DOC for stored UV-irradiated ultra-pure water reached concentrations below the limit of detection (0.19μmolCL⁻¹). Filtered (0.7μm) rain samples maintained the DOC integrity for at least 7 days when stored at 4°C. The volatile organic carbon (VOC) fraction in the rain samples collected at two sites in São Paulo state (Brazil) ranged from 0% to 56% of their total DOC content. Although these high-VOC concentrations may be derived from the large use of ethanol fuel in Brazil, our results showed that when using the high-temperature catalytic oxidation technique, it is essential to measure DOC rather than non-purgeble organic carbon to estimate organic carbon, since rainwater composition can be quite variable, both geographically and temporally.

Keywords: Glassware decontamination for DOC; Rainwater DOC storage; Wet deposition; Carbon flux; Non-purgeble organic carbon

A Lagrangian model investigation of chemico-microphysical evolution of northeast Asian pollution plumes within the MBL during TRACE-P by C.H. Song; K.M. Han; H.J. Cho; J. Kim; G.R. Carmichael; G. Kurata; N. Thongboonchoo; Z. He; H.S. Kim (pp. 8932-8951).

In this work, we determine the major channels through which air pollutants, mainly originating in Northeast Asian mega-cities, flow out into the Northwestern Pacific atmosphere. For this purpose, comprehensive backward/forward trajectory analyses are conducted. Two important channels along which pollutants from the Northeast Asian mega-cities flow out are defined, and are labeled as “DC8 transport path” and “P3B transport path”. We then comprehensively examine the chemico-microphysical transformations of the anthropogenic pollutants from the Northeast Asian mega-cities along the two major transport paths, using a new Lagrangian forward-trajectory photochemical model. In the newly developed model, state-of-the-science parameterizations for considering chemico-microphysical aging processes and atmospheric aerosol processes are incorporated. As air masses travel toward low latitudes through the marine boundary layer (MBL), the temperature increases along the trajectories and large amounts of PAN experience thermal decomposition. By this process, PAN can be an important supplier of NO₂ in the remote MBL. The O₃ productions in the remote Northwestern Pacific MBL are fueled and maintained by NO _x provided from the PAN decomposition. High O₃ levels (>50ppb) are observed within the remote MBL of the Northwestern Pacific Oceans from several TRACE-P DC8 and P3B measurements under the continental outflow situations. Gas-phase SO₂ is continuously converted into nss-sulfate via heterogeneous oxidation reaction with H₂O₂ at a particle pH of 2–5. The Lagrangian-trajectory modeling studies also indicate that in the remote MBL of Northwestern Pacific Ocean under continental outflow situations, conditions are unfavorable for nucleation events, because of the depletion of SO₂, the large aerosol surface areas available for H₂SO₄ sink, and high temperatures.

Keywords: Lagrangian photochemical model; Trajectory analysis; Chemico-microphysical transformation; O; ₃; formation; Nucleation

Ozone sensitivity of the Mediterranean terophyte Trifolium striatum is modulated by soil nitrogen content by Javier Sanz; Victoria Bermejo; B. Benjamín S. Gimeno; Susana Elvira; R. Rocío Alonso (pp. 8952-8962).

The influence of nitrogen (N) fertilization on the sensitivity to ozone (O₃) has been studied using the O₃ sensitive species Trifolium striatum, an annual species frequently found in therophitic grasslands of the dehesas in the central Iberian Peninsula. The experiment was carried out in open-top chambers using three different O₃ exposure treatments: charcoal-filtered air (CFA), non-filtered air (NFA) and non-filtered air plus 40nll⁻¹ added over ambient concentrations (NFA+). After 30 days of exposure to the different treatments, plants were placed under ambient conditions until seed ripeness was completed. Three N fertilization treatments were established receiving final doses of 10 (low), 30 (medium) or 60 (high)kgNha⁻¹ throughout the growing period divided into four proportional doses at every 15 days. Ozone affected phenology and reduced total aerial and flower biomass and seed production in NFA and NFA+ treatments. Carry-over effects of O₃ on the reproductive ability of this species were found resulting in reductions in flower biomass and seed production detected 1 month after O₃ exposure. By contrast, N fertilization increased aerial and flower biomass. Significant O₃×N interactive effects were detected since N fertilization counterbalanced O₃-induced effects only when plants were exposed to moderate O₃ levels (NFA) but not under high O₃ concentrations (NFA+). The observed O₃ effects on reproductive ability of T. striatum might determine changes in species viability and future diversity of the ecosystem.

Keywords: Grassland; Dehesa; Mediterranean pastures; Ozone critical levels; Clover; Biomass production; Seed production

Estimation of vehicular emission inventories in China from 1980 to 2005 by Hao Cai; S.D. Shaodong Xie (pp. 8963-8979).

Multi-year inventories of vehicular emissions at a high spatial resolution of 40km×40km were established in China using the GIS methodology for the period 1980–2005, based on provincial statistical data from yearbooks regarding vehicles and roads, and on the emission factors for each vehicle category in each province calculated by COPERT III program. Results showed that the emissions of CH₄, CO, CO₂, NMVOC, NO _x, PM₁₀, and SO₂ increased from 5, 1066, 19893, 169, 174, 26, and 16 thousand tons in 1980 to 377, 36197, 674629, 5911, 4539, 983, and 484 thousand tons in 2005 at an annual average rate of 19%, 15%, 15%, 15%, 14%, 16%, and 15%, respectively. Statistical analysis of vehicular emissions and GDP showed that they were well positively correlated, which revealed that increase of pollutant emissions has been accompanying the growth of GDP. Spatial distribution of pollutant emissions was rather unbalanced: over three-quarters of the total emissions concentrated in developed regions of China's southeastern, northern and central areas covering only 35.2% of China's territory, while the remaining emissions were distributed over the southwestern, northwestern and northeastern regions covering as much as 64.8% of the territory. In 2005, the Beijing–Tianjin–Hebei region, the Yangtze River Delta, and the Pearl River Delta covering only 2.3%, 2.2%, and 1.9%, respectively, of the territory, generated about 10%, 19%, and 12%, respectively, of the total emissions. Since 1990, motorcycles have been the major contributors to the CH₄, CO, NMVOC, and PM₁₀ emissions, due to the large population. Heavy-duty vans were the major contributors to the NO _x and SO₂ emissions because of high emission factors. Passenger cars contributed about one third of the emissions of each pollutant. Contributions of vehicle categories to emissions varied from province to province, due to the diversity of vehicle compositions among provinces.

Keywords: Emission inventory; Vehicular pollutant; Air pollution; COPERT III; China

Concentration-dependent NH₃ deposition processes for moorland plant species with and without stomata by M.R. Jones; I.D. Leith; J.A. Raven; D. Fowler; M.A. Sutton; E. Nemitz; J.N. Cape; L.J. Sheppard; R.I. Smith (pp. 8980-8994).

Currently, in operational modelling of NH₃ deposition a fixed value of canopy resistance ( R_c) is generally applied, irrespective of the plant species and NH₃ concentration. This study determined the effect of NH₃ concentration on deposition processes to individual moorland species. An innovative flux chamber system was used to provide accurate continuous measurements of NH₃ deposition to Deschampsia cespitosa (L.) Beauv., Calluna vulgaris (L.) Hull, Eriophorum vaginatum L., Cladonia spp., Sphagnum spp., and Pleurozium schreberi (Brid.) Mitt. Measurements were conducted across a wide range of NH₃ concentrations (1–140μgm⁻³).NH₃ concentration directly affects the deposition processes to the vegetation canopy, with R_c, and cuticular resistance ( R_w) increasing with increasing NH₃ concentration, for all the species and vegetation communities tested. For example, the R_c for C. vulgaris increased from 14sm⁻¹ at 2μgm⁻³ to 112sm⁻¹ at 80μgm⁻³. Diurnal variations in NH₃ uptake were observed for higher plants, due to stomatal uptake; however, no diurnal variations were shown for non-stomatal plants. R_c for C. vulgaris at 80μgm⁻³ was 66 and 112sm⁻¹ during day and night, respectively. Differences were found in NH₃ deposition between plant species and vegetation communities: Sphagnum had the lowest R_c (3sm⁻¹ at 2μgm⁻³ to 23 at 80μgm⁻³), and D. cespitosa had the highest nighttime value (18sm⁻¹ at 2μgm⁻³ to 197sm⁻¹ at 80μgm⁻³).

Keywords: Canopy resistance; Compensation point; Cuticular resistance; Stomatal uptake; Flux chamber; Ammonia

Manometric study of CO₂ and H₂S emission from aqueous solutions and wastewater by Aare Selberg; Diana Enkeli; Maria Matakova; Toomas Tenno (pp. 8995-9001).

The emissions of CO₂ and H₂S from the aqueous solutions and wastewater were studied to determine and compare the times required to reach the equilibrium of H₂S and CO₂ between water and gas phases. The solutions of NaHCO₃ and NaHS were acidified and the change in the pressure of emitted gases was measured with a manometric OxiTop^® system. The average time required to achieve the equilibrium state of distribution of CO₂ between two phases was 16.7±1.5min, and it did not depend on the initial amount of NaHCO₃ in the solution. The average time required to achieve the equilibrium of H₂S (sulfide) was 19.5±5.5min, having the same value for solutions with different initial contents of sulfide ions. The average time required to achieve the equilibrium of H₂S in the wastewater was 16.2±3.6min, and it showed the faster emission of gaseous H₂S to decrease the oversaturation of the solution. The ratio of measured values of pressure to the calculated values did not depend on the concentration of NaHS in the initial solution, and its average value was 0.86±0.14. The results showed that measured values of pressure of H₂S emitted from the wastewater were twice lower than the calculated values and it is necessary to take into account the catalyzed formation of polysulfide in the solution of sulfides.

Keywords: Hydrogen sulfide; Carbon dioxide; OxiTop; ^®; system; Equilibrium; Gas exchange

The flow across a street canyon of variable width—Part 1: Kinematic description by S. Serge Simoëns; Michel Ayrault; J.M. James M. Wallace (pp. 9002-9017).

Measurements have been made of the scalar dispersion of smoke released from a two-dimensional slot in the wall perpendicular to a boundary layer flow and located parallel to and midway between two square obstacles placed on the wall. The Reynolds number of the boundary layer at the slot location without the obstacles in place isRθ≈980. Two optical systems with CCD cameras facing each other have been used to measure simultaneously the velocity and scalar concentration fields, respectively, with PIV and Mie scattering diffusion. In Part B of this paper the data will ultimately provide detailed information about the scalar fluxes for this environmentally relevant geometry. Here in Part A the results of the velocity field measurements in the streamwise plane will be reported for spacings between the obstacles of 1–10 obstacle heights.The mean flow measurements reveal the increasing complexity of the canyon flow with increasing obstacle spacing. A primary vortex, with negative spanwise vorticity, occurs within the canyon for all spacings and is driven by the flow above. The circulation region of this vortex extends above the level of the tops of the obstacles. For spacings of2h and greater, a secondary vortex with positive vorticity appears in the upstream corner of the canyon, and a tertiary vortex with negative spanwise vorticity first appears in the downstream corner of the canyon for an opening of6h. The spatial distribution of the level of turbulence within and around the canyon is indicated by the contours of two-dimensional turbulent kinetic energy,12(u2¯+v2¯). The region of elevated turbulence in the shear layer created by the upstream obstacle penetrates deeper into the canyon with increasing canyon opening. For all openings, the Reynolds shear stress is negative above the canyon. The vertical extent of the high negative stress region increases as the canyon opening increases, and it also penetrates well within the canyon. This region of negative stress is due to the transport, by the primary canyon vortex, of low momentum fluid from deep within the canyon upward and high momentum fluid from above the canyon downward.

Keywords: Concentration; Dispersion; Street canyon; Boundary layer; PIV; Obstacles

The chemistry of gaseous acids in medieval churches in Cyprus by G. Loupa; E. Charpantidou; E. Karageorgos; S. Rapsomanikis (pp. 9018-9029).

Indoor and outdoor concentrations of HCl, HNO₃, HCOOH and CH₃COOH were determined in two medieval churches in Cyprus, during July 2003 and March 2004. The high air exchange rate through the open windows and doors led to lower indoor, compared to outdoor, acid concentrations in July 2003. Indoor pollutant emissions and a low air exchange rate resulted in higher indoor compared to outdoors acid concentrations in both churches during March 2004. Indoor to outdoor inorganic acid ratios were higher than the corresponding indoor to outdoor organic acid ratios during July 2003, whilst the opposite trend was observed during March 2004. Direct acid emission from candle burning appears to play a major role in the observed indoor acid concentrations. Emissions of volatile organic compounds from other sources, like humans, cleaning products and incense, led also to formation or depletion of the gaseous acids via homogeneous photochemical, heterogeneous and dark reaction sequences. Chemical reaction pathways were extensively investigated and appear to explain the observed results. The apparent indoor acid deposition velocities ranged between 0.05 and 0.15cms⁻¹.

Keywords: Indoor air quality; Indoor chemistry; Acid emission rate; Deposition rate; Artwork conservation

Impact of building facades and ground heating on wind flow and pollutant transport in street canyons by Xiaomin Xie; Chun-Ho Liu; Dennis Y.C. Leung (pp. 9030-9049).

This paper investigates the impacts of building facades and ground heating on the wind flow and pollutant transport in street canyons using the computational fluid dynamic (CFD) technique. Street canyons of H/ W ( H representing the building height and W the street width) varied from 0.1 to 2, which covered the basic flow regimes of skimming flow ( H/ W=1 or 2), wake interference flow ( H/ W=0.5), and isolated roughness flow ( H/ W=0.1), were examined in a series of sensitivity tests. Heating that occurred on different surfaces, including ground surface and building façades, posed considerable effects on the street canyon wind flow and pollutant transport compared with those under isothermal conditions. The CFD results showed that the mechanically induced wind flow and pollutant transport were complicated by the buoyancy under temperature stratification. Individual street canyons of different H/ W and surface-heating scenarios exhibited their unique wind flow structure and pollutant transport behaviors. Two counter-rotating vortices were calculated in the street canyons of H/ W=1, in which the zone of higher pollutant concentration under isothermal conditions was switched from the leeward side to the windward side. In the street canyon of H/ W=2, the recirculating wind pattern was perturbed by surface heating that led to the development of either one primary vortex or three closely coupled vortices. Because of the complicated wind structure, the zones of higher pollutant concentration located either on the leeward or windward ground level were subjected to the surface-heating scenarios. Only two vortices were developed inside the street canyon of H/ W=0.5. The large primary vortex, centered inside the street canyon, extended above the roof level of the street canyon. Meanwhile, a small secondary vortex was found at the ground-level windward corner whose size results as a function of surface-heating configurations. Finally, in the street canyon of H/ W=0.1, an isolated clockwise-rotating vortex was developed beside the leeward building while the wind in the windward side blew in the prevailing wind direction. As a result, air pollutant emitted at the street centerline was unlikely to be carried into the leeward vortex. Instead, it was dispersed rapidly on the windward side before being removed from the street canyon.

Keywords: CFD; Skimming flow; Wake interference flow; Isolated roughness flow; Pollutant transport

Sensitivity of molecular marker-based CMB models to biomass burning source profiles by Rebecca J. Sheesley; James J. Schauer; Mei Zheng; Bo Wang (pp. 9050-9063).

To assess the contribution of sources to fine particulate organic carbon (OC) at four sites in North Carolina, USA, a molecular marker chemical mass balance model (MM-CMB) was used to quantify seasonal contributions for 2 years. The biomass burning contribution at these sites was found to be 30–50% of the annual OC concentration. In order to provide a better understanding of the uncertainty in MM-CMB model results, a biomass burning profile sensitivity test was performed on the 18 seasonal composites. The results using reconstructed emission profiles based on published profiles compared well, while model results using a single source test profile resulted in biomass burning contributions that were more variable. The biomass burning contribution calculated using an average regional profile of fireplace emissions from five southeastern tree species also compared well with an average profile of open burning of pine-dominated forest from Georgia. The standard deviation of the results using different source profiles was a little over 30% of the annual average biomass contributions. Because the biomass burning contribution accounted for 30–50% of the OC at these sites, the choice of profile also impacted the motor vehicle source attribution due to the common emission of elemental carbon and polycyclic aromatic hydrocarbons. The total mobile organic carbon contribution was less effected by the biomass burning profile than the relative contributions from gasoline and diesel engines.

Keywords: Wood smoke; Organic aerosols; Atmospheric particulate matter; Source apportionment; CMB

Mass concentrations and metals speciation of PM_2.5, PM₁₀, and total suspended solids in Oxford, Ohio and comparison with those from metropolitan sites in the Greater Cincinnati region by Bart Wojas; Catherine Almquist (pp. 9064-9078).

Ambient aerosols were sampled for a period of 12 months from January to December 2005 in Oxford, OH, which is a relatively small college town approximately 50 miles northwest of Cincinnati. The goal of this study was to compare the mass concentrations and metals speciation of ambient aerosols collected in Oxford, OH with those collected in three urban centers (Cincinnati, Middletown, and Hamilton) in the Greater Cincinnati region. A secondary goal was to compare the effects of meteorological conditions on PM_2.5 and PM₁₀. Three different sampling instruments were used to collect PM_2.5, PM₁₀, and total suspended solids (TSP) in Oxford.It was found that PM_2.5 mass concentrations in Oxford were approximately 10% lower than those measured in Cincinnati, Middletown, and Hamilton. It was also found that the PM_2.5 contributed ∼95% to PM₁₀ and >60% to TSP. Acid extraction of the filters followed by inductively coupled plasma (ICP) was used for metals speciation. It was found that arsenic, antimony, cobalt, and lead were predominantly contained in PM_2.5, whereas cadmium, chromium, iron, nickel, molybdenum, silicon, vanadium, and zinc were found predominantly in PM₁₀. The crustal elements, including aluminum, calcium, magnesium, manganese, and potassium, were found predominantly in TSP. Copper had relatively high concentrations in TSP samples in Oxford, which may be due to emissions from a local industry that manufactures copper-based products. The metals concentrations in Oxford were generally lower than those reported in for Cincinnati and Middletown. However, different analytical methods were used for metals speciation in those cities, which likely contributed significantly to observed differences.It was observed that PM concentrations increased with air temperature and decreased with increasing wind speed. Humidity, precipitation, and wind direction appeared to have very little effect on PM concentrations.

Keywords: PM; _2.5; PM; ₁₀; Greater Cincinnati

Spatial distribution and temporal variability of Harmattan dust haze in sub-Sahel West Africa by Anthony C. Anuforom (pp. 9079-9090).

The distributions of frequency of occurrence (FOO) of ‘thick dust haze’ (TDH) and of ‘light dust haze’ (LDH) with respect to latitude, longitude, elevation and distance from source during Harmattan season (from November to February) are investigated, using 30-year visibility data collected from 27 synoptic stations located in Nigeria between the West African Sahel and the coasts of Gulf of Guinea. This region lies along the Harmattan season trajectory of Saharan dust. Also investigated is the temporal variability of TDH and LDH on intra-seasonal and inter-annual timescales spanning three decades from 1971 to 2000. Dust haze distribution over the region is found to correlate with the four geographical variables to different extents, with latitude, distance from source and elevation showing strong correlations with both TDH and LDH. The investigation also shows that while FOO of TDH days increases with latitude (correlation coefficient, r_{lat,FOO_TDH}=0.88), FOO of LDH days decreases with latitude over the region (correlation coefficient, r_{lat,FOO_LDH}=−0.74). The correlation coefficients with longitude over the region are r_{lon,FOO_TDH}=0.44 and r_{lon,FOO_LDH}=−0.25, respectively, indicating weaker dependence of TDH and LDH on longitude. The average number of TDH days per month during the Harmattan season in the region ranges from about 0.5 in the humid coastal zone near the Gulf of Guinea in the south, to approximately 6 in the dry semi-arid zone near the West African Sahel. An empirical equation which shows that FOO of TDH increases exponentially with latitude over the region is derived. The FOO of TDH is found to be most variable in or near the Sahel zone and decreases southwards towards the Gulf of Guinea. The average of the standard deviations is 1.13 for the six northernmost synoptic stations and decreases to 0.51 over the six coastal and southernmost locations. In contrast, the FOO of LDH is most variable in the south (with standard deviation of 2.11 (over the six southernmost and coastal stations) and decreases to an average of 0.30 (over six of the extreme northern stations). The observed patterns of TDH and LDH distribution are attributed to distance from dust source region, decrease in dust particle size and wind speed from north to south, increase in atmospheric humidity and vegetation cover from the Sahel in the north to the coastal zone in the south, as well as inter-annual variability of Sahel rainfall.

Keywords: Dust haze; Frequency of occurrence; Temporal variability; Sahel; Gulf of Guinea

Trends over a 20-year period from 1987 to 2007 in surface ozone at the atmospheric research station, Mace Head, Ireland by R.G. Derwent; P.G. Simmonds; A.J. Manning; T.G. Spain (pp. 9091-9098).

Hourly measurements of baseline ozone at the Mace Head Atmospheric Research Station on the Atlantic Ocean coast of Ireland are observed when unpolluted air masses are advected to the station from across the North Atlantic Ocean. Monthly mean ozone mixing ratios in baseline air masses have risen steadily during the 1980s and 1990s reaching unprecedented levels during the early months of 1999. During the 2000s, baseline ozone mixing ratios have shown evidence of decline and stabilisation. Over the entire 20-year 1987–2007 period, the trend in annual baseline ozone has been +0.31±0.12(2− σ)ppbyear⁻¹ and is highly statistically significant. Trends have been highest in the spring months and lowest in the summer months, producing a significant increase in the amplitude of the seasonal cycle. Over the shorter 1995–2007 period, we demonstrate how the growth to peak in 1999 and the subsequent decline have been driven by boreal biomass burning events during 1998/1999 and 2002/2003. The 2000s have been characterised by relatively constant baseline ozone and CH₄ levels and these may be a reasonable guide to future prospects, at least in the short term.

Keywords: Baseline mixing ratios; Surface ozone; Long-term trends; Biomass burning

On-road remote sensing of liquefied petroleum gas (LPG) vehicle emissions measurement and emission factors estimation by Z. Ning; T.L. Chan (pp. 9099-9110).

In the present study, the real-world on-road liquefied petroleum gas (LPG) vehicle/taxi emissions of carbon monoxide (CO), hydrocarbon (HC) and nitric oxide (NO) were investigated. A regression analysis approach based on the measured LPG vehicle emission data was also used to estimate the on-road LPG vehicle emission factors of CO, HC and NO with respect to the effects of instantaneous vehicle speed and acceleration/deceleration profiles for local urban driving patterns. The results show that the LPG vehicle model years and driving patterns have a strong correlation to their emission factors. A unique correlation of LPG vehicle emission factors (i.e., gkm⁻¹ and gl⁻¹) on different model years for urban driving patterns has been established. Finally, a comparison was made between the average LPG, and petrol [Chan, T.L., Ning, Z., Leung, C.W., Cheung, C.S., Hung, W.T., Dong, G., 2004. On-road remote sensing of petrol vehicle emissions measurement and emission factors estimation in Hong Kong. Atmospheric Environment 38, 2055–2066 and 3541] and diesel [Chan, T.L., Ning, Z., 2005. On-road remote sensing of diesel vehicle emissions measurement and emission factors estimation in Hong Kong. Atmospheric Environment 39, 6843–6856] vehicle emission factors. It has shown that the introduction of the replacement of diesel taxis to LPG taxis has alleviated effectively the urban street air pollution. However, it has demonstrated that proper maintenance on the aged LPG taxis should also be taken into consideration.

Keywords: On-road vehicle emissions; Remote sensing measurement technique; Emission factors; Liquefied petroleum gas; Regression analysis

Models for gas/particle partitioning, transformation and air/water surface exchange of PCBs and PCDD/Fs in CMAQ by Fan Meng; Baoning Zhang; Philip Gbor; Deyong Wen; Fuquan Yang; Chune Shi; Jonatan Aronson; James Sloan (pp. 9111-9127).

We have added the capability to simulate polychlorinated biphenyls (PCBs) and polychlorinated dibenzo [p] dioxins and polychlorinated dibenzo-furans (PCDD/Fs) to the Community Multiscale Air Quality (CMAQ) modeling system, thus taking advantage of the latter's capability to simulate atmospheric advection, diffusion, gas-phase chemistry, cloud/precipitation, and aerosol processes. The modifications reported here include the addition to the CMAQ system of two gas/particle partitioning models options: the Junge–Pankow adsorption model and the K_OA absorption model, as well as chemical transformations and atmosphere/water surface exchange processes for these semi-volatile organics. Simulations for the purpose of model testing and validation were conducted for the years 2000 and 2002 on a domain covering most of North America. Both partitioning models give reasonable results when compared with available measurements. The model predictions of deposition and air concentrations also agree well with measurements. The modeling results also indicate that the long-range transport is important and anthropogenic emissions of PCBs and PCDD/Fs are dominant although surface exchange of PCBs may be important for some clean locations.

Keywords: Regional modeling; PCB; PCDD/F; CMAQ; Deposition

Determinants of indoor benzene in Europe by H.K. Lai; M.J. Jantunen; Kunzli N. Künzli; E. Kulinskaya; R. Colvile; M.J. Nieuwenhuijsen (pp. 9128-9135).

This study identified the key determinants associated with the indoor benzene concentrations that were measured between 1996 and 2000 using the EXPOLIS protocol in the residences of six European cities, including Athens (Greece), Basel (Switzerland), Helsinki (Finland), Milan (Italy), Oxford (United Kingdom), and Prague (Czech Republic). Two consecutive days of home indoor and home outdoor measurements of benzene were carried out at the homes of adult participants on different dates and seasons during the sampling period. Regression models, with interactions searched by all-possible subset method, were used to assess the city effects and the determinants of home indoor benzene (adjusted R²=0.57, n=412). Outdoor benzene concentrations, outdoor temperature, wind speed, the use of anti-moth products, and indoor smoking in terms of number of cigarettes consumed per day were shown to be the key determinants of indoor benzene concentrations. The model was further used to predict the indoor benzene levels in cities. Non-linear relationships were commonly found, indicating that a unit change in the indoor concentration cannot be simply estimated by a proportional change of the determinant, and the pattern of relationships could be differed in different places. This finding is important in formulating indoor air quality guidelines as well as calculating an accurate health risk estimate based on the estimates of population's lifetime exposure levels.

Keywords: Benzene; Indoor air; Leukaemia; Non-linearity; Smoking

The characteristics of Asian-dust storms during 2000–2002: From the source to the sea by Zhang Kai; Gao Huiwang (pp. 9136-9145).

About 42 Asian-dust storms influenced the mainland and China during 2000–2002. Based on the Micaps meteorology data provided by China Meteorological Administration, the basic characteristics, including the source, movement route and influenced areas were studied for each case. It was shown that about 70% Asian-dust storms that influence China came from Mongolia, and were strengthened during the way from west to east. In 2000–2002, there was about 63.9% Asian-dust weather that might have affected China seas through three different routes. The probability is affecting the Bohai Sea was 27.4%, the Yellow Sea 30.9%, the East China Sea 12.3%, the Korea Channel 20.2% and the Japan Sea 9.2%. Annual dry deposition flux to the Yellow Sea was about 0.13gm⁻²d⁻¹, and in spring was ∼0.20gm⁻²d⁻¹. The total amount of dry deposition to the Yellow Sea was ∼17.9Tgyr⁻¹.

Keywords: Keyword; Asian-dust aerosols; Movement route; Dry deposition flux; China seas

Improvement of receptor model use in analytical aspect by C.-F. Chu-Fang Wang; P.-C. Pen-Chi Chiang; M.-T. Man-Ting Cheng; H.-L. Hung-Lung Chiang (pp. 9146-9158).

In this study, four certified particle standards including NIST SRM 1648 urban particulate matter, BCR Reference Material No. 176 city waste incineration ash, NIST SRM 2709 San Joaquin soil, and NIST SRM 1633b coal fly ash were used to simulate ambient particulate matter. Twenty-five samples were prepared with the four certified particulate standards. A total of 23 elements were analyzed per sample, 19 by ICP-AES and ICP-MS, three by IC, and one element, Si, by spectrophotometer. Results showed that combining the three IC-analyzed ionic species with the 19 ICP-AES/MS analyzed elements into the CMB model did not improve the source identification significantly. In addition, when all 23 analyzed chemical species per sample were used in the CMB model, they were still not good enough to effectively make the parameters of the CMB model fit the statistical criteria. Some of high variation and low recovery chemical species, i.e. Cd, V, Sb, etc., may have caused poor CMB model simulation. Omitting some poor quality analyzed species (such as relative analysis error >20%) could improve the CMB model simulation. Therefore, high quality chemical species data are important for the CMB model. In addition, co-linearity of source profiles also affects the CMB model; combining the co-linear sources could enhance the solubility of the CMB model. In this study, a two-step procedure was developed for CMB model simulation to improve source identification.

Keywords: Chemical mass balance (CMB); Receptor model; Fingerprints

Intake-to-delivered-energy ratios for central station and distributed electricity generation in California by Garvin A. Heath; William W. Nazaroff (pp. 9159-9172).

In previous work, we showed that the intake fraction (iF) for nonreactive primary air pollutants was 20 times higher in central tendency for small-scale, urban-sited distributed electricity generation (DG) sources than for large-scale, central station (CS) power plants in California [Heath, G.A., Granvold, P.W., Hoats, A.S., Nazaroff, W.W., 2006. Intake fraction assessment of the air pollutant exposure implications of a shift toward distributed electricity generation. Atmospheric Environment 40, 7164–7177]. The present paper builds on that study, exploring pollutant- and technology-specific aspects of population inhalation exposure from electricity generation. We compare California's existing CS-based system to one that is more reliant on DG units sited in urban areas. We use Gaussian plume modeling and a GIS-based exposure analysis to assess 25 existing CSs and 11 DG sources hypothetically located in the downtowns of California's most populous cities. We consider population intake of three pollutants—PM_2.5, NO _x and formaldehyde—directly emitted by five DG technologies—natural gas (NG)-fired turbines, NG internal combustion engines (ICE), NG microturbines, diesel ICEs, and fuel cells with on-site NG reformers. We also consider intake of these pollutants from existing CS facilities, most of which use large NG turbines, as well as from hypothetical facilities located at these same sites but meeting California's best-available control technology standards. After systematically exploring the sensitivity of iF to pollutant decay rate, the iFs for each of the three pollutants for all DG and CS cases are estimated. To efficiently compare the pollutant- and technology-specific exposure potential on an appropriate common basis, a new metric is introduced and evaluated: the intake-to-delivered-energy ratio (IDER). The IDER expresses the mass of pollutant inhaled by an exposed population owing to emissions from an electricity generation unit per quantity of electric energy delivered to the place of use. We find that the central tendency of IDER is much greater for almost every DG technology evaluated than for existing CS facilities in California.

Keywords: Distributed generation; Electricity generation; Exposure assessment; Intake fraction; Intake-to-delivered-energy ratio

A study for development of emission factors for trace gases and carbonaceous particulate species from in situ burning of wheat straw in agricultural fields in india by Shivraj Sahai; C. Sharma; D.P. Singh; C.K. Dixit; Nahar Singh; P. Sharma; K. Singh; S. Bhatt; S. Ghude; V. Gupta; Raj K. Gupta; M.K. Tiwari; S.C. Garg; A.P. Mitra; Prabhat K. Gupta (pp. 9173-9186).

Major crops subject to field burning of crop residue (FBCR) generated an estimated 284 Tg of residue in India, of which 40% was contributed by wheat in the year 2000. About 7.5% of this total generated wheat straw was subjected to on-site burning, that is expected to emit large amounts of trace gases and particulate matter (PM) to the atmosphere, whose country-specific estimates and emission factors (EFs) are presently not available. An in situ experiment for wheat straw burning was undertaken for developing India specific EFs. The EFs ofCO2,CH4, CO,N2O,NOx, NO andNO2 were found to be1787±36,3.6±2.7,28.1±20.1,0.74±0.46,1.70±1.68,0.78±0.71 and0.56±0.47gkg-1, whereas those for organic carbon (OC), black carbon (BC) and total carbon (TC) were0.3±0.1,0.2±0.1, and0.5±0.2gkg-1, respectively. Although these EFs have been generated from a single field experiment nevertheless they address important information gap on FBCR in the region. Further, the total emissions ofCH4,CO2, CO,N2O,NOx, NO,NO2, OC, BC and TC from wheat straw burning in India for the year 2000 was estimated as68±51,34435±682,541±387,14±9,33±32,15±14,11±9,6±2,3±1 and10±4 Gg, respectively.

Keywords: Agricultural crop residue; Biomass; Inventory estimation; Greenhouse gases; Carbonaceous aerosols

Scavenging of SO₄⁻ radical anions by mono- and dicarboxylic acids in the Mn(II)-catalyzed S(IV) oxidation in aqueous solution by Grgic Irena Grgić; B. Podkrajsek Boštjan Podkrajšek; Paolo Barzaghi; Hartmut Herrmann (pp. 9187-9194).

The rate constants for reactions of the SO₄⁻ radical anion with some low molecular weight monocarboxylic acids (MCAs) and dicarboxylic acids (DCAs) and their anions using the laser flash photolysis-long path laser absorption (LFP-LPLA) technique were determined. The present study contains the first measured rate constants for SO₄⁻ reactions with glycolic, lactic, malic and malonic acid. The rate constants are found to be in the range from 10⁵ to 10⁷M⁻¹s⁻¹, with the lower values found for acids and higher values for their respective anions. In addition, the rate constants for scavenging of SO₄⁻ by all investigated organics in the Mn(II)-catalyzed S(IV) autoxidation at pH 4.5 and T=25°C were determined by means of the reversed rate method. The comparison between these rate constants and the rate constants obtained by direct measurements confirms the proposed inhibiting mechanism for the Mn(II)-catalyzed S(IV) autoxidation in the presence of monocarboxylic acids. In the case of formic acid, which causes the highest inhibition, this mechanism can explain the second part of kinetic traces (i.e. after the induction period). Surprisingly, although dicarboxylic acids are reactive toward SO₄⁻ they do not contribute to the inhibition of S(IV) oxidation (especially malic and malonic acids).

Keywords: Inhibition; Low weight carboxylic acids; Manganese; Sulfate radicals; Sulfur dioxide

Analysis of air quality within a street canyon using statistical and dispersion modelling techniques by Emily J. Westmoreland; Nicola Carslaw; David C. Carslaw; Andrew Gillah; Elizabeth Bates (pp. 9195-9205).

The dispersion model, ADMS-Urban, alongside the statistical modelling technique, generalized additive modelling, have been used to predict hourly NO _x and nitrogen dioxide (NO₂) concentrations at a busy street canyon location and the results compared with measurements. Generalized additive models (GAMs) were constructed for NO₂ and NO _x concentrations using input data required to run ADMS-Urban. Bivariate polar plots have been produced from the wind flow (speed and direction) and pollution data (measured and predicted concentrations) to provide further information regarding the complex wind-pollutant interactions in an urban street canyon. The predictions made with the GAMs show excellent agreement with measured concentrations at this location, reproducing both the magnitude of NO _x and NO₂ concentrations and also the wind speed-wind direction dependence of pollutant sources within the canyon. However, the predictions made with ADMS-Urban under-estimated the measured NO _x by 11% and NO₂ by 21% and there are clear differences in the bivariate polar plots. Several sensitivity tests were carried out with ADMS-Urban in an attempt to produce predictions in closer agreement to those measured at Gillygate. Increasing the primary NO₂ fraction in ADMS-Urban (from 10% to 20%) had a considerable effect on the predictions made with this model, increasing NO₂ predictions by ∼20%. However, the bivariate plots still showed major differences to those of the measurements. This work illustrates that generalized additive modelling is a useful tool for investigating complex wind-pollutant interactions within a street canyon.

Keywords: Urban air quality; Generalized additive models; ADMS-Urban; NO; ₂; NO; _x

Testing model accuracy measures according to the EU directives—examples using the chemical transport model REM-CALGRID by J. Flemming; R. Stern (pp. 9206-9216).

The paper presents a comprehensive model evaluation focusing on the meaning and shortcomings of accuracy measures used to determine model quality according to European Union (EU) directives on air quality. European wide simulations employing the chemical transport model REM-CALGRID for the year 2002 were compared with O₃, NO₂, SO₂ and PM₁₀ observations of the German measurement network.The EU model quality objective, which is based on maximum relative errors, tends to penalise (i) the overestimation of very low measured concentrations in the case of annual averages and (ii) the underestimation of extremely high measured concentrations in the case of short-term values. As a more robust alternative, a model accuracy measure is presented, which corresponds to the allowed number of exceedances of the corresponding short-term air quality limit values.The influence of the spatial heterogeneity of the observations in relation to the spatial resolution of the model is investigated by spatial averaging of observation data. Because of this heterogeneity, any model with a 25km resolution would fail to simulate about 20% of all NO₂ and SO₂ stations and 5–10% of all O₃ and PM₁₀ stations in Germany according to the EU model quality objectives for short-term averages.

Keywords: EU directives for air quality; Model evaluation; Model quality objectives; Representativeness of observations

Characterisation of Amazon Basin aerosols at the individual particle level by X-ray microanalytical techniques by Anna Worobiec; Szaloki Imre Szalóki; Osan Janos Osán; Willy Maenhaut; Elzbieta Elżbieta Anna Stefaniak; Rene Van Grieken (pp. 9217-9230).

As a part of the LBA/CLAIRE-98 project (LBA, Large-Scale Biosphere–Atmosphere Experiment in Amazonia; CLAIRE, Cooperative LBA Regional Experiment), an extensive aerosol characterisation study was performed. The field work for the study took place in the Amazon Basin from 23 March to 15 April 1998. The collected aerosol samples were analysed by conventional and thin-window electron probe X-ray microanalysis (EPMA) combined with principal component analysis (PCA). Intensive transport of soil dust particles from the Sahara was observed at the end of March and beginning of April. The absolute number concentration of fine soil dust particles (0.30μm−3. Changes in the total number of particles and reactions of the Saharan dust, i.e., agglomeration with sea salt above the Atlantic Ocean and with local particulate matter, were observed. Particle number concentrations were higher in the fine size fraction, with soil dust dominating in the first part of the campaign. A significant contribution of natural biogenic particles was observed in the last 2 weeks of the campaign, but only in the coarse size fraction. The organic part of the aerosol particles and their agglomeration with other types of particles was studied. The chemical transformation of airborne marine particles in the abundant presence of gaseous pollutants originating from biomass burning and biogenic emissions was observed as well, e.g. N-containing species such as sodium nitrate particles classified as aged sea salt. Carbon was present in almost all particle types.

Keywords: Individual aerosol particles; EPMA; Amazon Basin; Saharan dust; Cluster analysis; Principal component analysis

Source apportionment of fine particulate matter (PM_2.5) at a rural Ohio River Valley site by Myoungwoo Kim; Seemantini R. Deshpande; Kevin C. Crist (pp. 9231-9243).

Twenty four-hour averaged concentrations of fine particulate matter were collected at Athens, OH between March 2004 and November 2005 in an effort to characterize the nature of PM_2.5 and apportion its sources. PM_2.5 samples were chemically analyzed and positive matrix factorization was applied to this speciation data to identify the probable sources. PMF arrived at a 7-factor model to most accurately apportion sources of the PM_2.5 observed at Athens. Conditional probability function (CPF) and potential source contribution function (PSCF) were applied to the identified sources to investigate the geographical location of these sources. Secondary sulfate source dominated the contributions with a total contribution of 62.6% with the primary and secondary organic source following second with 19.9%. Secondary nitrate contributed a total of 6.5% with the steel production source and Pb- and Zn-source coming in at 3.1% and 2.9%, respectively. Crustal and mobile sources were small contributors (2.5% each) of PM_2.5 to the Athens region. The secondary sulfate, secondary organic and nitrate portrayed a clear seasonal nature with the sulfate and secondary organic peaking in the warm months and the nitrate reaching a high in the cold months. The high percentage of secondary sulfate observed at a rural site like Athens suggests the involvement of regional transport mechanisms.

Keywords: Source apportionment; PM; _2.5; PMF; PSCF; CPF; Ohio River Valley

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Atmospheric Environment (v.41, #39)