Atmospheric Environment (v.39, #32)

Ultrafine particles (∼10–100 nm) were measured continuously for 18 months in an occupied townhouse. A major source was determined to be the gas clothes dryer. Although the dryer was vented to the outdoors it consistently produced an order of magnitude increase in the ultrafine concentrations compared to times with no indoor sources. Short-term peak number concentrations exceeded 100,000 cm−3 on a number of occasions. The source strength was conservatively estimated at about 6×1012  ultrafine particles produced per drying episode. These values are underestimates, since the part of the peak below 9.8 nm was not measured. Averaged over 150 h of operation, the number concentration showed a major peak at the smallest size measured (9.8 nm) and a secondary peak at 30 nm. Loss rates of the ultrafines due to diffusion, deposition, and particle growth (1–2 h−1) were high compared to losses due to air exchange (0.1–0.6 h−1). Considering the reported health effects of ultrafines, the widespread use of gas dryers, and the substantial amount of time that gas dryers are operated in many homes, it may be desirable to carry out further research to determine if the results reported here for a single dryer in one home are reproducible under different conditions.
Keywords: Ultrafine particles; Clothes dryer; Source strength; Vented gas appliance;

Airport related emissions and impacts on air quality: Application to the Atlanta International Airport by Alper Unal; Yongtao Hu; Michael E. Chang; M. Talat Odman; Armistead G. Russell (5787-5798).
In the last decade, air traffic has increased dramatically with a significant increase in emissions. Our goal is to quantify the impact of aircraft emissions on regional air quality, especially in regards to PM2.5 and ozone. Here the focus is on Hartsfield–Jackson Atlanta International Airport which is the busiest airport in the world based on passenger traffic.First, aircraft PM2.5 emissions are estimated based on the Smoke Number (SN) by using the “first order” method. The Emissions and Dispersion Modeling System (EDMS) is used for gaseous species. PM2.5 emissions are estimated once based on the characteristic SN and a second time using the mode-specific SN. Further, aircraft emissions are processed in two ways: (1) allocating the emissions at the airport itself, and (2) by accounting for flight paths, mode, and plume rise.When the more conservative emission estimates are used (i.e, the characteristic SN estimates allocated to the airport), results suggest that Hartsfield–Jackson airport can have a maximum impact of 56 ppb on ozone with a 5 ppb average impact over most of the Atlanta area. PM2.5 impacts are also estimated to be quite large with a maximum local impact of 25 μg m−3. Impacts over most of the Atlanta area are less than 4 μg m−3. The second set of emissions with detailed spatial allocation leads to a less intense ozone impact with a maximum of 20 ppb and an average of less than 1 ppb. PM2.5 impacts, in this case, are about 1 μg m−3 within a radius of 16 km around the airport. The difference in these two results shows the importance of how aircraft emissions are treated. The impacts on ozone and PM2.5 of ground support equipment at the airport are smaller compared to the aircraft impacts, with a maximum impact of 2 ppb for ozone and 9 μg m−3 for PM2.5.
Keywords: Aircraft emissions; Regional air quality; Ozone; Fine particulate matter;

An empirical orthogonal function (EOF) analysis is applied to two different data sets of tropospheric column ozone (TCO) and observed lightning flash rates over the tropical Atlantic for the period of 1996–2000. The first two dominant EOF modes of TCO values, explaining more than 65% of total variance are characterized by the seasonal cycle. The time series of EOF1 and EOF2 of TCO values are in phase with those of the EOF2 (16%) and EOF1 (63%) of the lightning, respectively. These relationships imply the influence of lightning on the tropical ozone maximum and the tropical ozone paradox. Moreover, the spatial distribution of the EOF modes and the horizontal wind field in the upper troposphere show that the highest lightning flash rates are located upstream of the region where high TCO values are found throughout the year.
Keywords: Tropospheric column ozone; Lightning; Large-scale transport; EOF; Seasonal variation;

To clarify nanoparticle behavior, observations of atmospheric aerosols, weather, and trace gases were carried out for about 1 month in summer and in winter at a region apart from major emission sources in Nagakute, Japan. The relation of nanoparticles with pollutants was clarified, and the potential of photochemical nucleation was pointed out based on the relation with meteorology and trace gas concentrations. The variation in particle size depends on the concentration of materials to be used in coagulation, condensation, and evaporation processes, except for photochemical nucleation. In winter, a minimum peak diameter of particle size distribution of about 40 nm was observed during the morning rush, and the growth rate of particle size during the morning was 7.6 nm h−1. On the other hand, the minimum size was recorded in the daytime in summer, and a large growth rate of 14.7 nm h−1 was obtained in the evening. The particle growth due to coagulation and condensation was thought to start with the morning rush and to continue until the next early morning in winter. The coagulation and condensation materials promoting particle growth were produced during the daytime, and a decrease in ambient temperature might contribute to particle growth during the night. In addition, a continuous particle growth was seen under a stable high atmospheric pressure for a few days. The average cyclic period of the particle growth and shrinkage of 81.9 h, which was calculated as a result of a Fourier analysis, was observed, and good correspondence was shown with the variation in atmospheric air pressure. The average growth rate during the time periods was 59.5 nm day−1 in winter and 103.3 nm day−1 in summer. The reason for the high value of the average growth in summer was thought to be the large amount of the materials produced which were used for particle growth through coagulation and condensation processes.
Keywords: Ultrafine particles; Nanoparticles; Particle size distribution; Particle growth; Photochemical nucleation; Air pollution; Meteorological influence;

Polycyclic aromatic hydrocarbons and nitropolycyclic aromatic hydrocarbons in urban air particulates and their relationship to emission sources in the Pan–Japan Sea countries by Ning Tang; Tetsuyuki Hattori; Rina Taga; Kazuhiko Igarashi; Xiaoyang Yang; Kenji Tamura; Hitoshi Kakimoto; Vasiliy F. Mishukov; Akira Toriba; Ryoichi Kizu; Kazuichi Hayakawa (5817-5826).
Airborne particulates were collected in seven cities in the Pan–Japan Sea countries, Shenyang (China), Vladivostok (Russia), Seoul (South Korea), Kitakyushu, Kanazawa, Tokyo and Sapporo (Japan), in winter and summer from 1997 to 2002. In addition, particulates from domestic coal-burning heaters and diesel engine automobiles were collected in Shenyang and Kanazawa, respectively. Nine polycyclic aromatic hydrocarbons (PAHs) and four nitropolycyclic aromatic hydrocarbons (NPAHs) in the extracts from the particulates were analysed by HPLC with fluorescence and chemiluminescence detections, respectively. The PAHs were fluoranthene, pyrene (Pyr), benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, benzo[ghi]perylene and indeno[1,2,3-cd]pyrene, and NPAHs were 1,3-, 1,6-, 1,8-dinitropyrenes, and 1-nitropyrene (1-NP). Mean atmospheric concentrations of PAHs in Shenyang and Vladivostok were substantially higher than those in Seoul, Tokyo, Sapporo, Kitakyushu and Kanazawa. However, the mean atmospheric concentrations of NPAHs were at the same levels in all cities except Kitakyushu. The expected seasonal variations (greater PAH and NPAH concentrations in winter than in summer) were observed in all cities. In order to study the major contributors of atmospheric PAHs and NPAHs, both cluster analysis and factor analysis were used and three large clusters were identified. Furthermore, the concentration ratios of 1-NP to Pyr were significantly smaller in Shenyang, Vladivostok and Kitakyushu and the values were close to those observed in particulates from coal stove exhaust. By contrast, in Seoul, Kanazawa, Tokyo and Sapporo the [1-NP]/[Pyr] ratio reached values similar to those of particulates released from diesel-engine automobiles. The [1-NP]/[Pyr] concentration ratio seemed to be a suitable indicator of the contribution made by diesel-engine vehicles and coal combustion to urban air particulates.
Keywords: NPAHs; PAHs; Airborne particulate; Contributor; Cluster analysis; Factor analysis;

Indirect N2O emission due to atmospheric N deposition for the Netherlands by Hugo Denier van der Gon; Albert Bleeker (5827-5838).
Nitrous oxide (N2O) is a potent greenhouse gas produced in soils and aquatic systems. The UNFCCC requires participants to report ‘indirect’ N2O emissions, following from agricultural N losses to ground- and surface water and N deposition on (other) ecosystems due to agricultural sources. Indirect N2O emission due to atmospheric N deposition is presently not reported by the Netherlands. In this paper, we quantify the consequences of various tiers to estimate indirect N2O due to deposition for a country with a high agricultural N use and discuss the reliability and potential errors in the IPCC methodology. A literature review suggests that the current IPCC default emission factor for indirect N2O from N deposition is underestimated by a factor ∼2. Moreover, considering anthropogenic N emissions from agriculture only and not from e.g., traffic and industry, results in further underestimation of indirect N2O emissions. We calculated indirect N2O emissions due to Dutch anthropogenic N emissions to air by using official Dutch N emission data as input in an atmospheric transport and deposition model in combination with land use databases. Next, land use-specific emission factors were used to estimate the indirect N2O emission. This revealed that (1) for some countries, like the Netherlands, most agricultural N emitted will be deposited on agricultural soils, not on natural ecosystems and, (2) indirect N2O emissions are at least ∼20% higher because more specific emission factors can be applied that are higher than the IPCC default. The results suggest that indirect N2O emission due to deposition is underestimated in current N2O budgets.
Keywords: Nitrous oxide; Greenhouse gases; N deposition; IPCC methodology; Emission factor;

Characteristics and determinants of ambient fungal spores in Hualien, Taiwan by Hsiao-Man Ho; Carol Y. Rao; Hsiao-Hsien Hsu; Yueh-Hsiu Chiu; Chi-Ming Liu; H. Jasmine Chao (5839-5850).
Characteristics and determinants of ambient aeroallergens are of much concern in recent years because of the apparent health impacts of allergens. Yet relatively little is known about the complex behaviors of ambient aeroallergens. To address this issue, we monitored ambient fungal spores in Hualien, Taiwan from 1993–1996 to examine the compositions and temporal variations of fungi, and to evaluate possible determinants. We used a Burkard seven-day volumetric spore trap to collect daily fungal spores. Air pollutants, meteorological factors, and Asian dust events were included in the statistical analyses to predict fungal levels. We found that the most dominant fungal categories were ascospores, followed by Cladosporium and Aspergillus/Penicillium. The majority of the fungal categories had significant diurnal and seasonal variations. Total fungi, Cladosporium, Ganoderma, Arthrinium/Papularia, Cercospora, Periconia, Alternaria, Botrytis, and PM10 had significantly higher concentrations (p<0.05) during the period affected by Asian dust events. In multiple regression models, we found that temperature was consistently and positively associated with fungal concentrations. Other factors correlated with fungal concentrations included ozone, particulate matters with an aerodynamic diameter less than 10 μm (PM10), relative humidity, rainfall, atmospheric pressure, total hydrocarbons, carbon monoxide, nitrogen dioxide, and sulfur dioxide. Most of the fungal categories had higher levels in 1994 than in 1995–96, probably due to urbanization of the study area. In this study, we demonstrated complicated interrelationships between fungi and air pollution/meteorological factors. In addition, long-range transport of air pollutants contributed significantly to local aeroallergen levels. Future studies should examine the health impacts of aeroallergens, as well as the synergistic/antagonistic effects of weather, and local and global-scale air pollutions.
Keywords: Aerobiology; Aeroallergens; Asian dust storms; Fungi;

Long-term urban aerosol simulation versus routine particulate matter observations by A. Hodzic; R. Vautard; B. Bessagnet; M. Lattuati; F. Moreto (5851-5864).
The ability of chemistry-transport models (CTMs) to accurately simulate particulate matter in urban areas is still to be demonstrated. This study presents a statistical evaluation of the performances of a mesoscale aerosol CTM over the Paris area, calculated over a long time period. Model simulations are compared to measured particulate matter PM10 and PM2.5 levels at monitoring ground stations. In summer, the PM10 daily mean levels are fairly well predicted by the model at all stations with correlation coefficients exceeding 0.67, relatively low biases (<2.5 μg m−3) and normalized errors (<27%). The relatively uniform negative biases suggest that the background PM10 levels are underestimated. In winter, discrepancies between the model and observations are more important, in particular at urban sites where several erroneous peaks are simulated. Consequently, the correlation coefficient drops down to 0.59 at urban sites and PM10 values are overestimated by about 10 μg m−3 with normalized errors exceeding 55%. We assume that discrepancies between simulated and observed PM levels are due to (i) TEOM (tapered element oscillating microbalance) measurement underestimation (35% in winter) caused by the evaporation of ammonium-nitrate, (ii) the underprediction of the model vertical mixing over the urban heat island and (iii) possible overestimation of local PM emissions. We use corrections for the urban boundary layer height and we subtract ammonium-nitrate from model PM10 concentrations. These modifications significantly improve the comparison statistics at urban sites in winter: the mean bias (<2 μg m−3) and normalized error (<30%) are reduced, while the correlation coefficient increased to 0.64. However, the overestimation at urban sites is inconsistent with the underestimation of PM10 background concentrations. The analysis of the total model biases at urban sites reveals that the underprediction of PM10 background levels is largely compensated by their local overprediction due to the overestimation of anthropogenic emissions.
Keywords: Aerosol modeling; PM10; Model error statistics; Urban aerosol; Model skill;

Wintertime PM10 samples collected in two New Zealand cities (Christchurch and Auckland) have been analysed for total carbon (TC), elemental carbon (EC), organic carbon (OC), water-soluble organic carbon (WSOC), and water-insoluble organic carbon (WIOC) as well as major inorganic ions. Christchurch, which is heavily influenced by residential wood and coal burning in winter, showed significantly higher ambient concentrations of carbonaceous materials than Auckland whose major sources of aerosols are sea-salt and vehicular emissions. In Christchurch, the mean concentrations of TC, EC, WSOC, and WIOC were 21, 6.0, 7.0 and 7.6 μg m−3, respectively. In contrast, those of Auckland were 5.0, 2.0, 1.3 and 1.7 μg m−3, respectively. On average, total carbonaceous materials (EC, water-soluble organic matter and water-insoluble organic matter) accounted for about 70% of PM10 mass in Christchurch but less than 30% in Auckland. Moreover, WSOC/EC and nss-K+/EC mass ratios in Christchurch were found to be substantially higher than those of Auckland. In contrast, nss-SO4 2−, NO3 and nss-Ca2+ concentrations in Auckland were dramatically enhanced relative to carbonaceous materials. This study suggests that fresh emissions from solid fuel burning are significantly more enriched with WIOC than WSOC, although a significant fraction of WSOC may be a secondary atmospheric product. It is estimated that only one-fifth to one-quarter of the measured OC was attributable to secondary organic aerosols in the two cities in winter.
Keywords: Chemical mass closure; Sea-salt; Secondary organic carbon; Wood and coal burning;

Aerosol modulation of small ion growth in coastal air by R.J. Wilding; R.G. Harrison (5876-5883).
Molecular cluster ions are produced throughout the troposphere by radon isotopes and cosmic rays, causing the slight electrical conductivity (σ) of atmospheric air. In a field campaign at the Weybourne Atmospheric Observatory on the Norfolk coast of the UK (52°57′23′′N 1°7′40′′E), aerosol size spectra were obtained simultaneously with σ measurements and background radioactivity, from 11th to 17th May 2004. σ varied with wind direction, from the modulation of the total aerosol number concentration Z rather than changes in ion production from radioactivity. σ was at its greatest when the air originated over the sea. Cluster ion properties were deduced using the σ data and the ion balance equation. The ion mobility μ decreased as Z decreased, corresponding to an increase in average cluster ion size. Using the attachment timescale of ions to aerosol as the typical time during which the ions can grow, negative ion growth occurred at ∼3 nm hr−1. Aerosol concentration changes modulate the time in which the ions can grow and the availability of condensable vapour.
Keywords: Atmospheric electricity; Cosmic rays; Ion mobility spectrometer; Solar variability;

Henry's law constants of 2,2,2-trifluoroethyl formate, ethyl trifluoroacetate, and non-fluorinated analogous esters by Shuzo Kutsuna; Liang Chen; Takashi Abe; Junji Mizukado; Tadafumi Uchimaru; Kazuaki Tokuhashi; Akira Sekiya (5884-5892).
Henry's law constants of two fluorinated esters [CF3CH2OC(O)H and C2H5OC(O)CF3] and four related non-fluorinated esters [CH3OC(O)H, C2H5OC(O)H, n-C3H7OC(O)H and C2H5OC(O)CH3] were determined at 278–298 K by a column-stripping method. From the van’t Hoff equation of H = H 298 exp [ - Δ H sol R ( 1 T - 1 298 ) ] , the H 298 (M atm−1) and ΔH sol (kJ mol−1) values obtained were 0.55±0.04, −39±3 (CF3CH2OC(O)H); 0.09±0.01, −41±5 (C2H5OC(O)CF3); 4.2±0.2, −33±2 (CH3OC(O)H); 3.4±0.2, −38±2 (C2H5OC(O)H); 2.6±0.1, −42±1 (n-C3H7OC(O)H); and 6.0±0.5, −49±3 (C2H5OC(O)CH3), respectively. Errors reported are at 95% confidence levels and represent precision only. Hydrolysis was observed only for C2H5OC(O)CF3. Replacement of CH3 by CF3 decreases H 298 values by 6, 11, and 67 times, respectively, for CF3CH2OC(O)H, CF3CH2OC(O)CH3, and C2H5OC(O)CF3, while the differences in the ΔH sol values were small with these substitutions. Sodium chloride salting-out effects are examined for all of the esters. C2H5OC(O)CF3 has the largest salting coefficient (0.74). The estimated lifetime of CF3CH2OC(O)H suggests that dissolution into seawater serves as a tropospheric sink for this compound. On the basis of the solubility and reactivity of the esters studied herein, clouds and the ocean are discussed as possible sinks for the dissolution of tropospheric CF3CF2OC(O)H, which is an atmospheric oxidation product of a substitute for hydrofluorocarbons as CF3CF2OCH3.
Keywords: Fluorinated esters; Solubility; Tropospheric sink; Salting-out; Lifetime;

Aerial observation of air pollutants and aerosols over Bo Hai, China by Shiro Hatakeyama; Akinori Takami; Wei Wang; Dagang Tang (5893-5898).
The first aerial observations of atmospheric pollutants over mainland China were performed as an international collaborative research effort in March, 2002. Observation flights over Bo Hai were made from Dalian to Dandong, Jinzhou, and Qingdao. High concentrations of gaseous pollutants (O3, SO2, and NO x ) were observed; SO2 and NO x showed a very good correlation. Comparing the chemical compositions of particulate pollutants showed that there was a high concentration of sulfate ions in fine particles. Concentrations of sulfate and nitrate ions showed good correlations with concentrations of both ammonium and calcium ions, suggesting that the aerosols over the Bo Hai area were well neutralized.
Keywords: Airborne observations; China air quality; Aerosol composition; Emission characterization;

Ozone and increased nitrogen supply effects on the yield and nutritive quality of Trifolium subterraneum by J. Sanz; R.B. Muntifering; V. Bermejo; B.S. Gimeno; S. Elvira (5899-5907).
The influence of ambient ozone (O3) concentrations and nitrogen (N) fertilization, singly and in combination, on the growth and nutritive quality of Trifolium subterraneum was assessed. This is an important O3-sensitive species of great pastoral value in Mediterranean areas. Plant material was enclosed in open-top chambers (OTCs). Three O3 levels were established: Filtered air with O3 concentrations below 15 ppb (CFA), non-filtered air with O3 concentrations in the range of ambient levels (NFA), and non-filtered air supplemented with 40 ppb O3 over ambient levels (NFA+). Similarly, three N levels were defined: 5, 15 and 30 kg ha−1. The increase in O3 exposure induced a reduction of the clover aerial green biomass and an increase of senescent biomass. Ozone effects were more adverse in the root system, inducing an impairment of the aerial/subterranean biomass ratio. Compared with the CFA treatment, nutritive quality of aerial biomass was 10 and 20% lower for NFA and NFA+ treatments, respectively, due to increased concentrations of acid detergent fiber, neutral detergent fiber and lignin. The latter effect appears to be related to senescence acceleration. The increment in N supplementation enhanced the increase of ADF concentrations in those plants simultaneously exposed to ambient and above-ambient O3 concentrations, and reduced the incremental rate of foliar senescence induced by the pollutant.
Keywords: Acid detergent fiber; Neutral detergent fiber; Crude protein; Lignin; Forage quality; Ozone; Trifolium;

Chemical composition of rainwater and dustfall was studied in two different stations of Bhubaneswar, located in the east coast of India. A wet-only and a bulk collector were placed at Regional Research Laboratory (RRL), a suburban area, during 1995–1997 and in the State Botanical Garden (SBG), a rural forest area, during 1997–1998. Of the rain events, 93% recorded alkaline pH (>5.6) at RRL while at SBG, 57% of the rain events were alkaline and the rest were acidic. Non-sea salt (nss) Ca2+ and NH3 were the primary neutralizing agents of rainwater acidity at both the locations. Low concentrations of alkaline constituents in the dustfall are an important finding in this study under Indian conditions. The Cl/Na+ ratio in rainwater at RRL was same as the seawater ratio (1.167) which indicates that sea salt contribution is local to RRL. It may be of indirect marine origin and resuspended locally. Rainwater samples were enriched with nss SO4 2−, nss Ca2+ and nss Mg2+ at both the sites. Most of the nss SO4 2− and NO3 were of anthropogenic origin, while a part of those might be soil derived.
Keywords: Acid precipitation; Ion balance; Neutralization factor; Non-sea-salt fraction; Suburban site;

A high-resolution emission inventory for eastern China in 2000 and three scenarios for 2020 by Xiaoping Wang; Denise L. Mauzerall; Yongtao Hu; Armistead G. Russell; Eric D. Larson; Jung-Hun Woo; David G. Streets; Alex Guenther (5917-5933).
We develop a source-specific high-resolution emission inventory for the Shandong region of eastern China for 2000 and 2020. Our emission estimates for year 2000 are higher than other studies for most pollutants, due to our inclusion of rural coal consumption, which is significant but often underestimated. Still, our inventory evaluation suggests that we likely underestimate actual emissions. We project that emissions will increase greatly from 2000 to 2020 if no additional emission controls are implemented. As a result, PM2.5 concentrations will increase; however O3 concentrations will decrease in most areas due to increased NO x emissions and VOC-limited O3 chemistry. Taking Zaozhuang Municipality in this region as a case study, we examine possible changes in emissions in 2020 given projected growth in energy consumption with no additional controls utilized (BAU), with adoption of best available end-of-pipe controls (BACT), and with advanced, low-emission coal gasification technologies (ACGT) which are capable of gasifying the high-sulfur coal that is abundant in China. Emissions of NH3 are projected to be 20% higher, NMVOC 50% higher, and all other species 130–250% higher in 2020 BAU than in 2000. Both alternative 2020 emission scenarios would reduce emissions relative to BAU. Adoption of ACGT, which meets only 24% of energy service demand in Zaozhuang in 2020 would reduce emissions more than BACT with 100% penetration. In addition, coal gasification technologies create an opportunity to reduce greenhouse gas emissions by capturing and sequestering CO2 emissions below ground.
Keywords: Air pollution; Particulate matter; CO2; Energy technology; Coal;

Non-methane volatile organic compounds (NMOC) that were most likely to contribute to ozone formation in the Houston, Texas area were measured by Texas Commission on Environmental Quality using AutoSystem Gas Chromatograph. Hourly, integrated NMOC measured between 9 pm and 6 am at the three monitoring sites (Deer Park, Haden Rd., and Clinton Dr.) in Houston were analyzed with Positive Matrix Factorization (PMF). Only NMOC data collected during the nighttime was utilized to minimize the influence of photochemistry, motor vehicles, and biogenic sources. A total of 401–883 samples and 38 to 40 NMOC species measured between July 2001 and October 2001 were analyzed. PMF identified seven sources at Deer Park (flare emissions, industrial source, petrochemical source, natural gas/propane, refinery, isoprene source, and motor vehicle), Haden Rd. (flare emissions, petrochemical source, industrial source, solvent, natural gas/propane, refinery, and motor vehicle), and Clinton Dr. (flare emissions, two industrial sources, refinery, natural gas/propane, motor vehicle, and isoprene source). Five similar source types were found among three sites although the sources were differently located. Conditional probability function analysis using surface wind data and identified source contributions aided the identifications of local point sources by providing indications of likely directions for the sources. The results agreed well with the locations of known local NMOC sources.
Keywords: Non-methane volatile organic compounds; Positive matrix factorization; Source apportionment; Conditional probability function;

Elemental composition and reflectance of ambient fine particles at 21 European locations by Thomas Götschi; Marianne E. Hazenkamp-von Arx; Joachim Heinrich; Roberto Bono; Peter Burney; Bertil Forsberg; Deborah Jarvis; Jose Maldonado; Dan Norbäck; Willem B. Stern; Jordi Sunyer; Kjell Torén; Giuseppe Verlato; Simona Villani; Nino Künzli (5947-5958).
We sampled fine particles (PM2.5) over a 1-year period at 21 central urban monitoring sites in 20 cities of the European Community Respiratory Health Survey (ECRHS). Particle filters were then analysed for elemental composition using energy dispersive X-ray fluorescence spectrometry and reflectance (light absorption). Elemental analyses yielded valid results for 15 elements (Al, As, Br, Ca, Cl, Cu, Fe, K, Mn, Pb, S, Si, Ti, V, Zn).Annual and seasonal means of PM2.5, reflectance, and elements show a wide range across Europe with the lowest levels found in Iceland and up to 80 times higher concentrations in Northern Italy. This pattern holds for most of the air pollution indicators. The mass concentration of S did constitute the largest fraction of the analysed elements of PM2.5 in all locations. The crustal component varies from less than 10% up to 25% across these cities. Temporal correlations of daily values vary considerably from city to city, depending on the indicators compared. Nevertheless, correlations between estimates of long-term exposure, such as annual means, are generally high among indicators of PM2.5 from anthropogenic sources, such as S, metals, and reflectance. This highlights the difficulty to disentangle effects of specific sources or PM constituents in future health effect analyses using annual averages.
Keywords: Air pollution; PM2.5; Elements; Reflectance; Long-term exposure assessment;

Indirect nitrous oxide emission from a nitrogen saturated spruce forest and general accuracy of the IPCC methodology by Bettina S. Höll; Hermann F. Jungkunst; Sabine Fiedler; Karl Stahr (5959-5970).
The relevance of indirect N2O emission is a controversial topic which is subject to much uncertainty. Only a small number of studies measure the indirect N2O emission at the interface from soil to stream. In addition, the majority of studies undertaken only cover a short-term period (<1 year). Therefore, limited information is available regarding the influence of seasonal or event effects, nor is there much information as to whether indirect N2O emissions are reflected by N2O in soil solutions. The present study aimed at clarifying these two questions along with the general relevance of dissolved nitrous oxide. A wetness gradient involving soil solutions of different soil types and surface waters within an N-saturated forest catchment (3.2 ha) was monitored over a period of 1 year. N2O concentrations in soil solutions (0.09–16.6 μg N l−1) were affected by events such as dry–wet cycles but did not reflect to the actual, indirect N2O emission at the soil-stream interface. It was assumed that N2O emission was due to N transformation processes. The N2O concentration at the spring was three times higher than the N2O concentrations in the soil solutions. Nevertheless, indirect N2O emission was still subordinate (<1%) to the direct emission of N2O. The weekly amount of indirect N2O emissions depended only on the stream flow rate (62% of the total annual amount). For this reason it was necessary to measure indirect N2O emission at short intervals and at the interface between soil and stream over a longer time period. Our results and the results of the reviewed studies show that the default IPCC emission factor (EF5-g=1.5%) overestimates the indirect N2O emission from ecosystems. The emission factor should therefore be lowered to about 0.1–0.3%. In addition, the results indicate that indirect N2O emission is an insignificant pathway in the N cycle of most ecosystems. However, final judgement will depend on long-term studies.
Keywords: N2O; N transformation; Hydromorphic soils; Event pattern; Stream flow; EF5-g;

Optical properties and size distribution of dust aerosols over the Tengger Desert in Northern China by Jinyuan Xin; Shigong Wang; Yuesi Wang; Jiuyi Yuan; Wenyu Zhang; Yang Sun (5971-5978).
A field experiment was performed during 1 April–30 September 2001 in the southeast Tengger Desert in Northern China to measure the solar radiant flux by a solar direct radiometer and a multi-wavelength sun-photometer. The observation and research results are as follows. On fine days, dust aerosols attenuate the direct solar radiant flux by 2.6–47.0%, with an average of 16.9%. On dusty days, dust aerosols attenuate the direct solar radiant flux by 10–90%, with an average of 38%. The mean atmospheric turbidity for broadband (300–4000 nm) flux is 0.26 for fine days and 0.74 for dusty days. Under the typical background, floating dust, and dust storm weather conditions, the aerosol optical depths (AODs; at 550 nm) are about 0.1, 0.9, and 2.0, and the Ångström exponents are about 2.0, 0.38, and −0.24, respectively. The mean AOD of the examples is 0.66, and 0.87 for the Ångström exponents. On dusty days, the aerosol number concentration is 2–10 times higher than that on fine days. The aerosol size distribution is a multi-normal distribution during dusty conditions, while the aerosol size distribution is a logarithmic normal distribution during fine weather.
Keywords: Dust aerosols; Atmospheric turbidity; Aerosol optical depth (AOD); Ångström exponent; Aerosol size distribution;

Volatile organic compounds in 43 Chinese cities by Barbara Barletta; Simone Meinardi; F. Sherwood Rowland; Chuen-Yu Chan; Xinming Wang; Shichun Zou; Lo Yin Chan; Donald R. Blake (5979-5990).
Whole air samples were collected in 43 Chinese cities in January and February 2001, and methane and nonmethane hydrocarbon (NMHC) concentrations for those samples are here discussed. In order to identify the main sources of the hydrocarbons in these cities, cross-correlations with the general combustion tracer ethyne and the gasoline marker i-pentane were investigated. Most of the identified NMHCs correlated with ethyne or i-pentane suggesting that their primary source is combustion or gasoline evaporation. To differentiate between vehicular and other combustion sources, the benzene to toluene ratio characteristic of the Chinese vehicular fleet was calculated using roadside samples (collected in 25 cities). Cities where the main source of the NMHCs was traffic related were identified. The slope resulting from the correlation of selected gases was used to identify the likely sources of the NMHCs measured. Vehicular emissions were found to be an important source of isoprene in some cities. Different VOC mixing ratio distributions throughout the country were also investigated. This paper gives a general overview of urban VOCs in many Chinese cities. Future more rigorous studies will be necessary to further characterize VOC sources in China.
Keywords: VOCs; Vehicular emissions; Urban air; Combustion; Gas-chromatography;

The percentage weighting polygon (PWP) method is proposed as an alternative to the classical arithmetic average (AA) method for calculating the average areal concentration (AAC) over an urban centre. The basis of the method is to divide the study area into a set of sub-areas by considering three adjacent air pollutants concentration percentages at a time. This method is more reliable and flexible than the AA method where the subareas remain the same independent of the measured air pollutants concentrations. In this paper, the PWP method is applied to the urban centre of Erzurum in Turkey for the first time, at six air quality monitoring stations. In the PWP method, higher air pollutant concentration values are represented with the smaller sub-areas than in the case of the AA method. It is observed that the PWP method yields a 16.5% smaller AAC value than the classical AA method.
Keywords: Average areal concentration; Percentage weighting polygon method; Sulphur dioxide; Erzurum;

Mt. Erebus, the largest point source of NO2 in Antarctica by C. Oppenheimer; P.R. Kyle; V.I. Tsanev; A.J.S. McGonigle; T.A. Mather; D. Sweeney (6000-6006).
We report here the first observations of NO2 emission from Mt. Erebus, a volcano with an active lava lake located on Ross Island, Antarctica. Erebus generates a persistent plume, which is entrained at an altitude of about 4 km above sea level. Its NO2 flux, measured by scattered light ultraviolet spectroscopy in December 2003, was equivalent to ∼0.6 Gg (N) yr−1. The total reactive nitrogen supply may be significantly higher than this since other NO y species are likely to have been present in the plume. We believe the NO2 is generated by thermal fixation of atmospheric nitrogen at the hot lava surface, forming NO, which then reacts rapidly with oxidants including ozone to yield NO2. Erebus volcano has displayed lava lake activity for many decades and may, therefore, play a significant long-term role in Antarctic tropospheric chemistry, and represent an important source of nitrogen deposited to the ice surface.
Keywords: Troposphere; Plume; NO x ; DOAS;

Carbon and nitrogen isotopic analysis of atmospheric organic matter by S.D. Kelly; C. Stein; T.D. Jickells (6007-6011).
A new method is presented to analyse the isotopic abundance of organic matter in aerosols. The method involves water extraction of aerosol filters, elution through an ion retardation resin to remove inorganic components and lyophilising the eluent to concentrate the fraction prior to isotopic analysis. Results of analyses of a series of aerosol samples collected in the UK, for the fraction of organic matter passing through the resin, are presented. Carbon and nitrogen isotopic abundances ranged from −23.0‰ to −35.5‰ (versus PDB) and −14.6‰ to +12.5‰ (versus AIR), respectively.
Keywords: Dissolved organic matter; Dissolved organic nitrogen; Nitrogen isotope ratios; Carbon isotope ratios;