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Atmospheric Environment (v.39, #22)

Editorial board (pp. i).

List for forthcoming papers (pp. i-ii).

Seasonal trends in PM2.5 source contributions in Beijing, China by Mei Zheng; Lynn G. Salmon; James J. Schauer; Limin Zeng; C.S. Kiang; Yuanhang Zhang; Glen R. Cass (pp. 3967-3976).

The 24-h PM2.5 samples (particles with an aerodynamic diameter of 2.5μm or less) were taken at 6-day intervals at five urban and rural sites simultaneously in Beijing, China for 1 month in each quarter of calendar year 2000. Samples at each site were combined into a monthly composite for the organic tracer analysis by GC/MS (gas chromatography/mass spectrometry). Compared to the data obtained from other metropolitan cities in the US, the PM2.5 mass and fine organic carbon (OC) concentrations in Beijing were much higher with an annual average of 101 and 20.9μgm⁻³, respectively. Over one hundred organic compounds including unique tracers for important sources were quantified in PM2.5 in Beijing. Source apportionment of fine OC was conducted using chemical mass balance receptor model (CMB) in combination with particle-phase organic compounds as fitting tracers. Carbonaceous aerosols and major ions (sulfate, nitrate and ammonium) constituted 69% of PM2.5 mass on average. The major sources of PM2.5 mass in Beijing averaged over five sites on an annual basis were determined as dust (20%), secondary sulfate (17%), secondary nitrate (10%), coal combustion (7%), diesel and gasoline exhaust (7%), secondary ammonium (6%), biomass aerosol (6%), cigarette smoke (1%), and vegetative detritus (1%). The lowest PM2.5 mass concentration was found in January (60.9μgm⁻³), but the contribution of carbonaceous aerosol to PM2.5 mass was maximal during this season, accounting for 57% of the mass. During cold heating season, the contributions from coal combustion and biomass aerosol to PM2.5 mass increased, accounting for 20.9% of fine particle mass in October and 24.5% in January. The contribution of the biomass aerosols peaked in the fall. In April 2000, the impact of dust storms was so significant that dust alone constituted 36% of PM2.5 mass. On average, the model resolved 88% of the sources of the PM2.5 mass concentrations in Beijing.

Keywords: Source apportionment; Fine particles; Organic tracers; CMB; China

Spatial distribution of submicrometre particles and CO in an urban microscale environment by N.S. Holmes; L. Morawska; K. Mengersen; E.R. Jayaratne (pp. 3977-3988).

Traffic is the major source of submicrometre particles in an urban environment but the spatial distribution of particles around an urban site has not been measured. The aim of this paper was to investigate the relationship of CO and particles at a busy central urban location surrounded by buildings. This study measured the concentration and size distribution of submicrometre particles at a fixed location and concentrations of submicrometre particles and CO at 10 locations around a square site in the Brisbane Central Business District (CBD). Changes in concentration were assessed as a function of traffic volume and wind direction and speed.Fixed site measurements of submicrometre particle number concentration varied between 7.9×10² (±40) and 2.6×10⁵ (±1.3×10⁴)cm⁻³ and showed a strong positive correlation with traffic flow rate, confirming that vehicles were the major source of urban submicrometre particles. The particle concentration decreased exponentially with increasing wind speed.Average particle concentrations around the site ranged between 19.7×10³ (±8.2×10³) and 32.5×10³ (±16.6×10³)cm⁻³. Analysis of the particle measurements around the site showed that time and location both had a statistically significant effect on mean particle concentration around the square over the period of the study.Around the site, CO concentration was relatively constant (within instrument error), ranging between 2.2 (±1.9) and 4.5 (±3.0)ppm. Again both time and location had a statistically significant effect on CO concentration during the measurement period. However, CO concentration was not significantly correlated to particle number concentration around the site and examination of between-site comparisons with the two pollutants showing different spatial and temporal trends.The significant difference in the concentration trends between the locations around the square indicates that there is considerable inhomogeneity in the particle concentration around the site. One implication of this is that careful thought must be given to locations of air intakes of air-conditioning systems in urban environments.

Keywords: Dispersion; Submicrometre; Particles; CO; Urban

Seawater solubility of natural and anthropogenic metals within ambient aerosols collected from Taiwan coastal sites by Shih-Chieh Hsu; Fei-Jan Lin; Woei-Lih Jeng (pp. 3989-4001).

To evaluate the bioavailability and environmental mobility of aerosol metals to the seas, ambient aerosol samples collected from two coastal sites, i.e., Hsiyu located at the southwestern tip of the Penghu Islands in Taiwan Strait and Santiaolun on the west coast of Taiwan were determined for the seawater solubility of Al, Fe, Mn, Zn, Ni, Cu, Pb and Cd. The experiment of dissolution kinetics suggested that almost all soluble fractions of studied aerosol metals could be released within 1h. Thereafter, dissolved particle-reactive metals like Al, Fe and Pb exhibited a slight decrease, suggestive of re-adsorption to residual particles. Seawater solubility of selected metals from Hsiyu aerosols showed the following order: Al (1.3%)=Fe (1.1%)crust), indicating that the dissolvable percentage is, to some extent, dependent on the anthropogenic contribution for specific aerosol metals and likely due to the presence of considerable contaminants such as organic, acidic and carbonaceous substances for anthropogenic aerosols. In addition, for Al, Fe, Zn and Pb, inverse power-law (log–log) correlations between solubilities and dust loadings have been observed, suggesting that particle scavenging may follow dissolution for certain metals in the marine environment. In conclusion, the dissolution of aerosol metals in seawater is predominantly controlled by which origins dominate their contributions (such as crustal or anthropogenic derivatives) and the behavior of a specific metal in seawater (such as dissolution/adsorption). Aerosol metals have substantial impacts on diverse eco-environments and accurate assessments of environmental impacts of eolian metal depositions must be based on such informative data. Thus more simulation experiments relevant to dissolution of aerosol metals in various natural waters are merited.

Keywords: Dissolution; Enrichment factor; Dust loading; Eco-environment; Taiwan

Evaluation of atmospheric benzene concentrations in the Helsinki Metropolitan Area in 2000–2003 using diffusive sampling and atmospheric dispersion modelling by Hellen H. Hell�n; J. Kukkonen; M. Kauhaniemi; H. Hakola; T. Laurila; H. Pietarila (pp. 4003-4014).

Ambient air concentrations of benzene were both measured and predicted in the Helsinki Metropolitan area. Two-weekly measurements were conducted in 2000, 2002 and 2003 at seven measurement stations using diffusive adsorbent sampling; additional two-hourly measurements were also performed. An urban dispersion modelling system was utilised for modelling the spatial concentration distributions of benzene for 2000. According to both measurements and predictions, the annual mean benzene concentrations were below the upper assessment threshold (3.5μgm⁻³) set by the European Union, while the lower assessment threshold (2μgm⁻³) was exceeded at one urban station (Töölö) during the year 2000. The concentrations measured in the Helsinki Metropolitan Area were also compared with those at rural and remote stations in Finland. In the winters of 2000 and 2003, the concentrations at the remote and rural stations of Utö, Hyytiälä and Pallas were close to the concentrations at the urban background station of Kallio, while in the summers of 2000 and 2003, the concentrations at Kallio were substantially higher. The predicted concentrations in 2000 were highest in the vicinity of major roads and streets, and at their junctions. At all the stations, the predicted yearly averaged concentrations agreed fairly well with the measured data; the differences between measured and predicted values ranged from 10 to 31%. According to the measurements, and also the emission and dispersion computations, the most important source categories were exhaust emissions from local vehicular traffic, and the long-range transported background.

Keywords: Diffusive sampling; Dispersion modelling; Benzene; Aromatic hydrocarbons; Urban air pollution; Traffic

Implementing the trajectory-grid transport algorithm in an air quality model by David P. Chock; Margaret J. Whalen; Sandra L. Winkler; Pu Sun (pp. 4015-4023).

Eulerian-based air quality models encounter a serious numerical problem in solving the advection equation. In addition, mass conservation is often violated when meteorological model output is used as input to air quality models. The trajectory-grid algorithm handles the advection and eddy-diffusion in the Lagrangian and Eulerian framework, respectively. It is very accurate and can be used to trivially solve the advection equation for molar mixing ratios to address (but not correct) the mass conservation issue. We incorporated the algorithm into the state-of-the-science comprehensive air quality model with extensions (CAMx). Applications of the model reveal the inaccuracy of the commonly used Bott advection scheme, and the subsequent compensating errors of the model. The results clearly call for a more reliable description of eddy diffusivity and emissions inventory in order to truly improve the reliability and predictive capability of air quality models.

Keywords: Air quality model; Trajectory-grid algorithm; Bott scheme; Advection equation; Mass conservation; Eddy diffusivity; Eulerian; Lagrangian; MM5; CAMx

A hybrid model for predicting carbon monoxide from vehicular exhausts in urban environments by Sharad Gokhale; Mukesh Khare (pp. 4025-4040).

Several deterministic-based air quality models evaluate and predict the frequently occurring pollutant concentration well but, in general, are incapable of predicting the ‘extreme’ concentrations. In contrast, the statistical distribution models overcome the above limitation of the deterministic models and predict the ‘extreme’ concentrations. However, the environmental damages are caused by both extremes as well as by the sustained average concentration of pollutants. Hence, the model should predict not only ‘extreme’ ranges but also the ‘middle’ ranges of pollutant concentrations, i.e. the entire range. Hybrid modelling is one of the techniques that estimates/predicts the ‘entire range’ of the distribution of pollutant concentrations by combining the deterministic based models with suitable statistical distribution models (Jakeman, et al., 1988). In the present paper, a hybrid model has been developed to predict the carbon monoxide (CO)²2CO has been used as an indicator in the vehicular exhaust emission modelling studies (Hickman and Colwill, 1982). concentration distributions at one of the traffic intersections, Income Tax Office (ITO), in the Delhi city, where the traffic is heterogeneous³3It consists of light vehicles, heavy vehicles, three- wheelers (auto rickshaws) and two-wheelers (scooters, motorcycles, etc). in nature and meteorology is ‘tropical’. The model combines the general finite line source model (GFLSM) as its deterministic, and log logistic distribution (LLD) model, as its statistical components. The hybrid (GFLSM–LLD) model is then applied at the ITO intersection. The results show that the hybrid model predictions match with that of the observed CO concentration data within the 5–99 percentiles range. The model is further validated at different street location, i.e. Sirifort roadway. The validation results show that the model predicts CO concentrations fairly well (d=0.91) in 10–95 percentiles range. The regulatory compliance is also developed to estimate the probability of exceedance of hourly CO concentration beyond the National Ambient Air Quality Standards (NAAQS) of India.

Keywords: Vehicular pollution modelling; Hybrid model; Extreme pollutant concentrations; Heterogeneous traffic conditions; Statistical distribution models; Log logistic distribution

Scaling properties of air pollution in Athens, Greece and Baltimore, Maryland by C. Varotsos; J. Ondov; M. Efstathiou (pp. 4041-4047).

Detrended fluctuation analysis is applied to the Athens air-pollution time-series consisting of hourly observations of ozone, nitrogen oxides, and particulate matter obtained at five air-pollution monitoring stations during 1987–2003.Persistent power-law correlations in the fluctuations of daytime and nighttime ozone concentrations with lag times ranging from 1 week to 5 years were detected with more intense correlations (“stronger memory�?) during daytime. The fluctuations of nitrogen oxide concentrations exhibit similar behavior. Finally, persistent power-law correlations from about 4h to 9 months were found in PM10 fluctuations in Athens. Long-range correlations for lag times from about 4h to 2 weeks were also detected for PM2.5 fluctuations in a 6-month data set collected at the University of Maryland “Supersite�? in East Baltimore.Although the origin of the long-range behaviour of air-pollution merits further investigation, these findings presumably, reflect short and longer term source/meteorological features that are probably related to the self-organized critical behavior of the atmosphere. These findings provide power-law relationships which may substantially contribute to the development of more reliable simulating models for the ozone, nitrogen oxides, and particulate matter fluctuations.

Keywords: Detrended fluctuation analysis; Ozone; Oxides of nitrogen; PM10; Air pollution prediction

A new laboratory test chamber for the determination of diffusive sampler uptake rates by Norbert Gonzalez-Flesca; Armelle Frezier (pp. 4049-4056).

Diffusive samplers are today widely used for air quality control in indoor and outdoor environments and for personal exposure studies as well. The uptake rate is a fundamental parameter of a sampler for the calculation of the concentration of the substance to be monitored depends directly on it. Uptake rates can be affected by numerous factors. Their values and the range of validity have to be determined in an appropriate exposure chamber.The laboratory test chamber presented here consists of a loop made of glass, stainless steel and PTFE containing the generated atmosphere in which diffusive samplers can be tested. It is possible to accommodate several samplers simultaneously and simulate various environmental conditions such as temperature, wind speed, wind direction, humidity, atmospheric composition, total pressure and exposure duration. All working parameters have to be monitored including the concentrations of the components of the generated atmosphere. It is shown that the expected concentration of a volatile compound like benzene can be reached very quickly whereas those of less volatile compounds like toluene or xylenes takes longer. The procedure for overcoming this difficulty is described in this paper.By means of an application it is also shown that exposure duration can unequally affect diffusive sampler uptake rates depending on sampler geometry and the nature of the adsorbent. It appears that a radial high-uptake rate diffusive sampler packed with a thermally desorbable material may be unsuitable for long-term monitoring of a volatile compound like benzene. However an axial low-uptake rate diffusive sampler, also packed with a thermally desorbable material, seems more appropriate for this application due to the higher stability of its uptake rate.

Keywords: Atmospheric simulation; Diffusive samplers; Air quality; Benzene; Toluene; Xylene

Gross alpha, gross beta activities and gamma emitting radionuclides composition of airborne particulate samples in an oceanic island by Hernandez F. Hern�ndez; Hernandez-Armas J. Hern�ndez-Armas; Catalan A. Catal�n; Fernandez-Aldecoa J.C. Fern�ndez-Aldecoa; L. Karlsson (pp. 4057-4066).

The radiometric compositions of airborne particulate samples, collected weekly during a 4 years period (1 January 2000 till 31 December 2003) at a site located 310m a.s.l. in Tenerife (Canary Islands), are analysed in this paper. To do this, measurements of gross alpha, gross beta,⁷Be,²¹⁰Pb,²²⁸Ac,²²⁶Ra,²¹²Pb,²¹⁴Pb,²⁰⁸Tl,²¹⁴Bi,²³⁵U,⁴⁰K,¹³¹I and¹³⁷Cs concentrations were carried out in 376 cellulose and polypropylene filters. The time variations of the different radionuclides concentrations have been discussed in relation with various meteorological factors and the mean values have been compared to those published in recent literature for other sites located at the same altitude but different latitudes.The weekly activities of⁷Be correlated linearly with the²¹⁰Pb activities (R=0.59). In disagreement with other published studies, the⁷Be activities did not correlate (R=-0.05) with the temperature and maximum values were not found during summer season. The gross beta activities showed correlations with the gross alpha (R=0.72) and²¹⁰Pb activities (R=0.52), but not with the⁷Be (R=0.16). The anthropogenic radionuclide¹³¹I, emitted from a nearby hospital, was detected slightly above detection limits (1.73×10⁻⁶Bqm⁻³) in 88 of the 210 weeks of measurement considered in this work.¹³⁷Cs was detected in 31 of those weeks. The 4-year average calculated for⁷Be and²¹⁰Pb were 3 and 0.3mBqm⁻³, respectively. These values are lower than those expected for a site at comparable latitude and altitude. In general, the radionuclides which appeared most frequently in the airborne particulate filters (⁷Be,²¹⁰Pb,²¹²Pb and⁴⁰K), did not correlate significantly with any of the meteorological parameters considered: rainfall, temperature, pressure, relative humidity, visibility, wind speed and direction. Therefore, no predictive model could be established with the available data as it has been done for continental sites. The long-range transport of aerosols from the Saharan desert showed to be an important source of¹³⁷Cs and⁴⁰K in the particulate filters after low-level atmospheric dust intrusions that reached the island.

Keywords: Aerosols; Atmospheric radionuclides; Surface air; Saharan dust; Tenerife

Mercury emissions from the Idrija mercury mine measured by differential absorption lidar techniques and a point monitoring absorption spectrometer by Gronlund Rasmus Grönlund; Hans Edner; Sune Svanberg; Joze Jože Kotnik; Milena Horvat (pp. 4067-4074).

Mercury emission measurements from the Idrija mercury mine in Slovenia were performed during an early November 2003 campaign, where the differential lidar technique was used to map mercury concentrations and an attempt was made to quantify the total mercury flux from the most contaminated area, the abandoned cinnabar roasting oven complex. Lidar concentration data were compared with data recorded with a Zeeman modulated atomic absorption instrument, operated from a vehicle equipped with a GPS localization system. Concentrations and fluxes were comparatively low due to low temperature and rainfall. The average flux from the distillation plant was measured to approximately 2gh⁻¹.

Keywords: DIAL; Atmospheric mercury flux; Idrija; Mercury mine; OPO

Simulation of long-range transport of air pollutants over Northeast Asia using a comprehensive acid deposition model by I.-S. Il-Soo Park; W.-J. Won-Jun Choi; T.-Y. Tae-Young Lee; S.-J. Suk-Jo Lee; J.-S. Jin-Seok Han; C.-H. Cheol-Hee Kim (pp. 4075-4085).

A comprehensive acid deposition modeling system (CADM) was developed to simulate the long-range transport of air pollutants and regional acidic deposition processes over Northeast Asia. The main objective of the CADM is to facilitate efficient assessment by providing explicit information on long-range transboundary processes. The implemented modeling system in CADM is composed of a numerical atmospheric model (CSU RAMS) and an Eulerian chemistry/transport/deposition model.For the model validation, CADM was used to simulate long-range transport over the Northeast Asian region during 5–12 March 2002, and the simulated concentrations were compared with both surface observations at background monitoring stations as well as aircraft measurements. Additional experiments were performed to examine the sensitivity of simulated concentrations to input fields (emission rate and meteorological fields). The simulated concentrations showed some encouraging agreements with some success for the temporal variation of surface SO₂ concentrations in comparison with both the observation at background monitoring stations and aircraft observation. However, disagreements were significant for NO _x and O₃ concentrations, showing large inconsistencies especially at higher levels. The magnitudes of this disagreement were found to have some dependence on both input fields of emission rate and meteorology.

Keywords: Long-range transport; Comprehensive transport/chemistry model; Observed concentrations; Verification; Sensitivity to inputs

Concentrations of ethene and formaldehyde at a valley and a mountain top site in the Austrian Alps by S. Smidt; H. Bauer; O. Pogodina; H. Puxbaum (pp. 4087-4091).

Ethene and formaldehyde concentrations were measured at two forest sites (valley, mountain top) in the Achen Valley (Austrian Alps, Tyrol) during three campaigns in 2001 and 2002. During the June/July campaign mean concentrations of ethene were above 9ppb_v at the valley station and 1.9ppb_v at the mountain top site; lower ethene concentrations were observed at the valley site during the April (1.4ppb_v) and the May campaign (3.1ppb_v). As 9ppb_v is the effect-related limiting value (= concentration of pollutants in the atmosphere, above which direct adverse effects on receptors may occur according to the present knowledge) of the Austrian Academy of Sciences for plants (1997) we found that ethene levels in valleys may come close to the limiting value. Formaldehyde concentrations were far below the effect-related limiting value of 16ppb_v. On the basis of the actual knowledge, ethene could be relevant as a phytotoxic component in alpine valleys.

Keywords: Ethene; Formaldehyde; Alps; Forest ecosystems

Effect of filter type and temperature on volatilisation losses from ammonium salts in aerosol matter by Lothar Keck; Klaus Wittmaack (pp. 4093-4100).

During a 10-month sampling period, cellulose acetate-nitrate (CA), quartz fibre (QF), Teflon (Tf), and glass fibre (GF) filters were used to collect 19 ambient PM2.5 aerosol samples at mean temperatures between –10 and +25°C. The standard procedure of sampling involved filters that were incorporated in monitor cassettes with cellulose support pads underneath. For comparison, measurements were carried out using a denuder-filter system. The samples were analysed for mass and major inorganic ions. At mean temperatures〈T〉 below 0°C, CA, QF and Tf filters were found to properly collect particulate ammonium nitrate and chloride. At〈T〉 above 0°C, the salts were lost from QF and Tf filters, more so the higher the temperature and with no significant difference between QF and Tf. The salts were lost completely from denuded QF filters above about 20°C, from undenuded QF and Tf filters above about 25°C. In contrast, the losses from CA filters were negligible or small up to 25°C, but positive artefacts due to gas retention could occur at high concentrations of gaseous nitrate (and ammonia). The cellulose support pads collected evaporating equimolar ammonia and nitric acid quantitatively and also a small fraction of (pure) ambient gaseous ammonia. With the exception of GF, the filter face velocity had no significant effect on the PM concentrations measured on front filters. The observed sampling artefacts are in accordance with our recently reported gas retention efficiencies derived from laboratory studies. We conclude that, without additional means, inert QF and Tf filters are not suited for routine sampling of particulate ammonium nitrate and chloride at temperatures exceeding ∼0°C.

Keywords: Aerosol filter; Sampling artefacts; Ammonium nitrate; PM2.5; Denuder

Evaluation of two types of diffusive samplers and adsorbents for measuring 1,3-butadiene and benzene in air by Bo Strandberg; A.-L. Anna-Lena Sunesson; Katarina Olsson; J.-O. Jan-Olof Levin; G. G�ran Ljungqvist; Margit Sundgren; Sallsten Gerd S�llsten; Lars Barregard (pp. 4101-4110).

1,3-Butadiene and benzene are common air pollutants, the former being a suspected and the latter an established carcinogen. Road traffic and industry emissions are sources of these compounds. In order to assess the risk posed to the general population by ambient levels of these pollutants, diffusive samplers capable of monitoring them over both long timescales (weeks) and shorter periods (8–24h) are needed. In this study, we evaluated a new diffusive sampler, the SKC-Ultra, and a partially validated sampler, the Radiello, both of which are compatible with thermal desorption. Two adsorbents, the graphitized carbon blacks Carbopack X and Carbograph 5, were also evaluated. Standard atmospheres of the target compounds were generated in order to determine uptake rates and to evaluate the effects of concentration, relative humidity, reverse-diffusion and storage of samplers. The samplers and adsorbents were also tested in a field study. Analysis and detection were performed using an automatic thermal desorber (ATD) connected to a gas chromatograph-flame ionization detector (GC/FID). Both samplers showed much higher uptake rates (ca. 25–50 fold) than those reported for the Perkin-Elmer sampler. The 24h uptake rates for 1,3-butadiene and benzene obtained using the SKC-Ultra filled with Carbopack X were 14.9±0.8 (SD) and 16.0±1.4 (SD) mLmin⁻¹, respectively, and the corresponding figures for the Radiello were 22.0±0.9 (SD) and 30.4±1.1 (SD) mLmin⁻¹. Varying the atmospheric concentrations of the compounds had no effect on the uptake rate for the Carbopack X adsorbent and the samplers could be stored up to one month after sampling. Uptake rates of 1,3-butadiene declined over longer periods (one week). This was probably due to reverse diffusion, and the effect was less pronounced with the SKC-Ultra sampler. In summary, we consider the two samplers to be suitable both for stationary and personal monitoring of 1,3-butadiene and benzene, for the general population and for workplaces.

Keywords: VOCs; Air contaminants; Diffusive samplers; Monitoring; Exposure

Influence of major African dust intrusions on the¹³⁷Cs and⁴⁰K activities in the lower atmosphere at the Island of Tenerife by Hernandez F. Hern�ndez; Alonso-Perez S. Alonso-P�rez; Hernandez-Armas J. Hern�ndez-Armas; E. Cuevas; L. Karlsson; P.M. Romero-Campos (pp. 4111-4118).

The influence of two intensive low-altitude atmospheric-dust intrusions on the activity levels of¹³⁷Cs and⁴⁰K as well as atmospheric particle matter (PM10) concentrations in the lower atmosphere of the Canary Islands are analysed here. These two events took place at the beginning of January 2002 and March 2004, respectively. 3D atmospheric back-trajectories indicated that the main source of dust material involved in the considered atmospheric intrusions came from NW Africa. A consequence of these dust intrusions was the major increase of PM10 concentrations in the lower atmosphere. Both episodes were characterised by having weekly averages of PM10 concentration surpassing 150μgm⁻³, higher than the daily PM10 limit value established by the EC/1999/30 directive for PM10 from 2005. Similarly, during these two events, both¹³⁷Cs and⁴⁰K activities increased by a factor of 6 and 13 as well as 13 and 14, respectively, over the basal values calculated for each radionuclide and time period (0.59±0.02 and 0.88±0.07μBqm⁻³ as well as 12±6 and 24±8μBqm⁻³).

Keywords: Aerosols; Back-trajectories; Atmospheric radionuclides; Saharan dust; Dust intrusions

Concentration characteristics of extractable organohalogens in PM2.5 and PM10 in Beijing, China by Diandou Xu; Mo Dan; Yan Song; Zhifang Chai; Guoshun Zhuang (pp. 4119-4128).

PM2.5 and PM10 samples were simultaneously collected at a downtown site in Beijing from May 2002 to April 2003 and analyzed by instrumental neutron activation analysis (INAA) and gas chromatography (GC) combined with organic solvent extraction method for the concentrations and distributions of extractable organohalogens (EOX), including extractable organo-chlorine (EOCl), -bromine (EOBr) and -iodine compounds (EOI), and organochlorinated pesticides (OCPs) and polychlorinated biphenyls (PCBs). The concentrations of EOX were increasing in the order of EOCl⪢EOBr∼EOI. EOCl accounted for 73–88% and 69–91% of EOX in PM2.5 and PM10, respectively, suggesting that EOCl was the major component of the organohalogens in the atmosphere. The relative proportions of the known organochlorines (such as HCHs, DDTs, chlordanes, and PCBs) to total EOCl were 0.04–0.7% and 0.06–0.3% in PM2.5 and PM10, respectively, which implied that most of EOCl measured in aerosol was unknown. The ratios ofα/γ-HCH (0.9–1.5) and p,p′-DDE+DDD/ p,p′-DDT (0.2–0.5) revealed the presence of the recent use of lindane and DDTs or impure dicofol in Beijing. In the plots of the logarithm of the OCPs concentrations versus reciprocal temperature(1/T), their linear relations were observed for PM2.5, which could be partly explained by temperature differences, but poor linearity for PM10.

Keywords: Organochlorinated pesticides; Polychlorinated biphenyls; Instrumental neutron activation analysis; Extractable organochlorine

Seasonal variations of black carbon aerosols and total aerosol mass concentrations over urban environment in India by K. Madhavi Latha; K.V.S. Badarinath (pp. 4129-4141).

Aerosol optical properties are one of the important global geophysical variables required in climate modeling studies. The largest variability and uncertainty in estimates of the effects of atmospheric aerosols on climate is their particle size distribution. The highest non-uniform spatial and temporal distribution of tropospheric aerosols on global scale is owing to their diverse sources, chemical compositions and lifetimes require more measurements for aerosol quantification. In the present study, changes in the response of near surface aerosol properties and their association with meteorological parameters have been studied during January–December over a tropical semiarid urban environment. Diurnal variations of black carbon (BC) aerosols showed a gradual build up in BC concentration from morning and a sharp peak occurs between 7:00 and 9:00 LT almost an hour after the local sunrise and a broad nocturnal peak from ∼21:00 to 02:00 local time. Total aerosol mass concentration showed positive correlation with air temperature and wind speed. Diurnal variation of coarse mode and accumulation mode particles showed a nocturnal high and daytime low. Aerosol mass size distribution showed possibly a multi-modal size distribution over the study area. Coarse mode particle loading observed to be high during summer and accumulation mode particles observed to be high during winter. Seasonal variations of BC aerosol mass concentration showed high concentrations during dry season and low concentrations during the monsoon season. Monthly average aerosol optical depth (AOD) values gradually increased from January to April and then decreased after May. The average share of BC to the total mass concentration has been observed to be 15% during January to December.

Keywords: Aerosol mass loading; Aerosol size distribution; Number density; Aerosol optical depth; Black carbon

Microbial population in cloud water at the Puy de D�me: Implications for the chemistry of clouds by Pierre Amato; Menager Matthieu M�nager; Martine Sancelme; Paolo Laj; Gilles Mailhot; A.-M. Anne-Marie Delort (pp. 4143-4153).

Airborne micro-organisms are ubiquitous in the atmosphere where they can remain alive and be transported over long distances, thus colonizing new environments. Despite their great importance in relation to ecological and socio-economical issues (bio-terrorism, health, etc.) very few studies have been carried out in this field.In this study, the structure of the microbial community present in atmospheric water samples from clouds at the Puy de Dôme (alt 1465m, Massif Central, France) is described and the metabolic potential of some bacteria is investigated. The total microflora has been quantified by epifluorescence microscopy, while the cultivable aerobic micro-organisms were isolated. Bacteria were identified by 16S DNA sequencing and fungi by morphological criteria. The total bacterial count reached about 3×10⁴cellsm⁻³ of cloud volume (1×10⁵cellsmL⁻¹ of cloud water), of which less than 1% are cultivable. Most of the isolated micro-organisms, including 12 fungal and 17 bacterial strains, are described here for the first time in atmospheric water. Many bacterial strains seem to be adapted to the extreme conditions found in cloud water (pH, T°, UV radiations, etc.). Comparison of the two samples (March 2003) shows that pH can be a major factor controlling the structure of this community: an acidic pH (Sample 1: pH=4, 9) favours the presence of fungi and spore-forming bacteria, while a more neutral pH (Sample 2: pH=5, 8) favours greater biodiversity. We have also shown, using in situ¹H NMR, that most of the isolated bacteria are able to degrade various organic substrates such as formate, acetate, lactate, methanol and formaldehyde which represent the major organic compounds present in cloud water. In addition, the detection of intermediates indicated preferential metabolic routes for some of the strains.

Keywords: Cloud water; Micro-organisms; NMR; Organic acids; Formaldehyde; Methanol; Biodegradation

Evolution of particle number distribution near roadways. Part III: Traffic analysis and on-road size resolved particulate emission factors by K. Max Zhang; Anthony S. Wexler; Debbie A. Niemeier; Yi Fang Zhu; William C. Hinds; Constantinos Sioutas (pp. 4155-4166).

On-road size-resolved particulate emission factors were computed using concurrently measured carbon monoxide (CO) as a freeway dilution indicator and correlating roadside particle measurements to CO measurements. The emission factors derived for the total particle number agree well with previous on-road investigations. However, this study extends this analysis to produce unique receptor-dependent, size-resolved, road and grid-level emission factor distributions. Both mileage- and fuel-based particle number and mass emission factors at road and grid levels, along with CO emission factors, are presented and the results from freeways with distinctly different percentages of heavy-duty diesel truck traffic are compared. The effects of plume processing on particle number near roadways are shown to be much more profound than on particle mass, further indicting that the adverse health effects observed near roadways are at least partially related to particle numbers.

Keywords: Carbon monoxide; Mobile emissions; Traffic; Transportation; Ultrafine particles; Aerosol

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Atmospheric Environment (v.39, #22)