Atmospheric Environment (v.35, #25)

Influence of air mass trajectories on the chemical composition of precipitation in India by M. Norman; S.N. Das; A.G. Pillai; L. Granat; H. Rodhe (4223-4235).
Chemical composition of precipitation was measured with wet-only samplers at a rural site at Bhubaneswar in eastern India during 1997–1998. All rain events were compared with trajectories and precipitation fields from the ECMWF. The pH and ionic concentrations were found to vary systematically with the origin of air and the amount of rainfall along the trajectory. A seasonal cycle for pH was found with a monthly median pH below 5.0 during October–December. The highest monthly median concentration of Ca2+ was found in May with 20 μmol l−1 and for SO4 2− in January with 52 μmol l−1. Samples with trajectories within 400 km from Bhubaneswar during the last 5 days were found to have a median pH slightly below 5.0 as an average. These samples also had the highest concentration for all measured ions, indicating large pollution sources within the region. Samples with continental origin showed a decrease of ∼70% in concentration if there had been rain during >50% of the last 5 days compared to rain during <50% of the last 5 days. High concentrations of Na+ and Cl were also found in continental samples. Resuspension of previously deposited sea salt is believed to be the reason. The data were compared with data from three other sites in western India and higher concentrations of almost all ions (NH4 + being the exception) compared to Bhubaneswar were found at the west coast in monsoon samples.
Keywords: Acidic deposition; pH; Sulfate; Ammonium; Calcium;

Very high weight ratios of S/K in individual haze particles over Kalimantan during the 1997 Indonesian forest fires by Miwako Ikegami; Kikuo Okada; Yuji Zaizen; Yukio Makino; Jorgen B Jensen; John L Gras; Hery Harjanto (4237-4243).
The elemental composition of individual aerosol particles of 0.15–3 μm radius, collected over Kalimantan during the 1997 Indonesian forest fire event, was analyzed using a transmission electron microscope equipped with an energy-dispersive X-ray analyzer (EDX). Although 60–90% of the particles collected at altitudes of 1–5 km contained K, they exhibited high weight ratios of S/K with median values of 9–18 independent of particle size. These were much larger than those (median values of 2–4) obtained from the forest fires in northern Australia. The high weight ratios over Kalimantan are considered to be due to the heterogeneous growth of particles through the oxidation of SO2. In addition to SO2 from the combustion of forest biomass, SO2 originating from the combustion of peat below the ground is believed to have been important in producing the high S/K ratios.
Keywords: Aerosol particles; Biomass burning; Indonesia; EDX analysis; Elemental composition; Peat combustion;

Very high concentration of suspended particulate matter (SPM) is observed at traffic junctions in India. Factor analysis-multiple regression (FA-MR), a receptor modelling technique has been used for quantitative apportionment of the sources contributing to the SPM at two traffic junctions (Sakinaka and Gandhinagar) in Mumbai, India. Varimax rotated factor analysis identified (qualitative) five possible sources; road dust, vehicular emissions, marine aerosols, metal industries and coal combustion. A quantitative estimation by FA-MR model indicated that road dust contributed to 41%, vehicular emissions to 15%, marine aerosols to 15%, metal industries to 6% and coal combustion to 6% of the SPM observed at Sakinaka traffic junction. The corresponding figures for Gandhinagar traffic junction are 33%, 18%, 15%, 8% and 11%, respectively. Due to limitation in source marker elements analysed about 16% of the remaining SPM at these two traffic junctions could not be apportioned to any possible sources by this technique. Of the observed lead in the SPM, FA-MR apportioned 62% to vehicular emissions, 17% to road dust, 11% to metal industries, 7% to coal combustion and 3% to marine aerosols at Gandhinagar traffic junction and about a similar apportionment for lead in SPM at Sakinaka traffic junction.
Keywords: Traffic junctions; Suspended particulate matter; Lead; Factor analysis; Multiple regression;

In order to assess the temporal variabilities of atmospheric mercury (Hg) from an area moderately impacted by man-made source processes, the concentrations of total gaseous mercury were measured routinely from an urban monitoring station during January 1999–August 2000. The mean hourly concentration of Hg from overall measurements was computed to be 5.26±3.27 ng m−3 (N=11, 572). Using these measurement data, we inspected various aspects on the temporal distribution of Hg. When analyzed over 24 h scale, the pattern was characterized by high concentration during nighttime relative to daytime (e.g., values approaching 9 ng m−3). This pattern was prominent during winter and seen persistently across fall, spring, and summer. When divided seasonally, the highest mean of 6.01 ng m−3 was observed during winter. It appears that such wintertime dominance is most likely to come from the anthropogenic sources such as household heating systems from late fall to early spring. A close inspection of the Hg data however indicated that the seasonal variation proceeded quite dynamically. Inspection of seasonally divided data groups generally showed substantial variabilities among different months. In order to analyze the factors affecting Hg distributions over different time scale, we conducted the correlation analysis. Whereas Hg generally exhibited strong correlations with such parameters as PM, SO2, and NO2, its relationship varied diurnally and seasonally. The overall results of the present study suggest that changes in its source signatures can vary over varying time scale under the influence of strong man-made source processes.
Keywords: Temporal; Anthropogenic; Urban; Residence time; Source signatures; Mercury;

Atmospheric particulate mercury in Changchun City, China by Fengman Fang; Qichao Wang; Ruhai Liu; Zhuangwei Ma; Qingju Hao (4265-4272).
From July 1999 to January 2000, the total suspended particulate matter (TSP) in the atmosphere collected by high-volume sampler was used to determine the particulate Hg of four function districts and one contrast district in the City of Changchun,China. The study results indicated that the value of the volume-based concentration and the mass-based concentration of each district during the heating period are higher than those of the nonheating period. The volume-based concentration of the urban districts is higher than that of the contrast district. Atmospheric Hg concentrations varied temporally and spatially. TSP is the critical factor of particulate Hg concentration; precipitation is the main meteorological factor affecting Hg (p) concentration in the atmosphere; coal combustion and wind-blown soil material are the important sources of atmospheric particulate Hg. During heating period, the coal combustion makes a greater contribution to Hg(p) than that of wind-blown soil materials.
Keywords: Atmospheric particulate Hg; Concentrations; Temporal and spatial distribution; Affecting factors; Sources;

One-year observation of urban mixed layer characteristics at Tsukuba, Japan using a micro pulse lidar by Weibiao Chen; Hiroaki Kuze; Akihiro Uchiyama; Yoshihide Suzuki; Nobuo Takeuchi (4273-4280).
One-year characteristics of the urban mixed layer is observed by an eye-safe, compact micro pulse lidar (MPL). Retrieval method of the mixed layer height (MLH) and the encroachment model of the mixed layer growing are presented. Two case studies are carried out using summer and late winter data. Comparisons are made between the aerosol optical thickness, the rawinsonde data and the model calculation. The development of the mixed layer exhibits temporal behavior similar to that of the aerosol optical thickness, but with a time difference of about 1–2  h . The growth rate of the MLH agrees well with the encroachment model only in the morning, with considerate deviation during the daytime because of the wind effect. One-year growth rate and the maximum MLH are estimated from the MPL measurement between May 1999 and May 2000. The results show that the properties of mixed layer are strongly correlated with the seasonal meteorological conditions. This work also demonstrates that an automated, compact lidar system such as a MPL is quite useful for long-term monitoring of the mixed layer.
Keywords: Urban mixed layer; Micro pulse lidar; Aerosol optical thickness; Encroachment model; Mixed layer growth;

Black carbon emissions in China by David G. Streets; Shalini Gupta; Stephanie T. Waldhoff; Michael Q. Wang; Tami C. Bond; Bo Yiyun (4281-4296).
Black carbon (BC) is an important aerosol species because of its global and regional influence on radiative forcing and its local effects on the environment and human health. We have estimated the emissions of BC in China, where roughly one-fourth of global anthropogenic emissions is believed to originate. China's high rates of usage of coal and biofuels are primarily responsible for high BC emissions. This paper pays particular attention to the application of appropriate emission factors for China and the attenuation of these emissions where control devices are used. Nevertheless, because of the high degree of uncertainty associated with BC emission factors, we provide ranges of uncertainty for our emission estimates, which are approximately a factor of eight. In our central case, we calculate that BC emissions in China in 1995 were 1342 Gg, about 83% being generated by the residential combustion of coal and biofuels. We estimate that BC emissions could fall to 1224 Gg by 2020. This 9% decrease in BC emissions can be contrasted with the expected increase of 50% in energy use; the reduction will be obtained because of a transition to more advanced technology, including greater use of coal briquettes in place of raw coal in cities and towns. The increased use of diesel vehicles in the future will result in a greater share of the transport sector in total BC emissions. Spatially, BC emissions are predominantly distributed in an east–west swath across China's heartland, where the rural use of coal and biofuels for cooking and heating is widespread. This is in contrast to the emissions of most other anthropogenically derived air pollutants, which are closely tied to population and industrial centers.
Keywords: Black carbon; China; Biofuels; Emission factors; Coal combustion;

Lidar and satellite retrieval of dust aerosols over the Azores during SOFIA/ASTEX by Patrick Chazette; Jacques Pelon; Cyril Moulin; François Dulac; Isabelle Carrasco; Walter Guelle; Philippe Bousquet; Pierre-Henri Flamant (4297-4304).
The synergy between active (airborne lidar) and passive (Meteosat) sensors is achieved with the help of a numerical transport model (TM2z) to derive optical properties of Saharan dust during a long range transport over the Azores. Measurements were taken in June 1992 during the surface of the ocean, fluxes and interaction with the atmosphere campaign, which took place during the Atlantic stratocumulus transition experiment. The dust source is identified to be in north Morocco from a TM2z back-trajectory analysis. Lidar observations over the Azores show that the dust is maintained in multiple thin layers (few hundred meters) up to 5 km altitude after a 4-day transport. Horizontal gradients are less marked, with a typical scale of variation of about 5 km. Lidar inversions yield dust optical thicknesses from 0.1 to 0.16 mainly due to two layers centered at 1.3 and 3.7 km. Since the weather was extremely cloudy over this region, the dust plume was not observable on the coincident Meteosat image. We thus processed the image taken two days earlier that clearly shows a dust plume between Azores and Spain. The Meteosat inversion was constrained by using the airborne lidar measurements in the marine boundary layer. The retrieved dust optical thicknesses are in good agreement with that retrieved from the lidar. Coherence of both lidar and radiometry measurements suggests that such a combined analysis is promising for retrieving the optical thickness of elevated dust layers as well as their spatial extent outside the source region even under cloudy conditions.
Keywords: Mineral dust; Airborne lidar; Meteosat; Azores; Sofia;

Diurnal and seasonal variation of short-lived radon progeny concentration and atmospheric temporal variations of 210Pb and 7Be in Egypt by A. EL-Hussein; A. Mohamemed; M. Abd EL-Hady; A.A. Ahmed; A.E. Ali; A. Barakat (4305-4313).
During a one-year period, from November 1998 upto October 1999, the atmospheric activity concentrations of the short-lived (222Rn)-progeny (218Po, 214Pb, 214Po) were measured every 4 h in the open air, using α-spectrometry. The concentration data of short-lived radon progeny together with meteorological variables (relative humidity, air temperature, and wind speed) were used for a comprehensive regression analysis of daily time variation of radioactivity in the air. The seasonal concentration pattern of all short-lived radon progeny shows the same trend for diurnal variation with higher values at night and early morning hours compared with lower values at noon and in afternoon. The activity concentrations were observed to be higher during the winter months (November–January) than in other seasons. The mean activity concentrations of 218Po, 214Pb and 214Po within the whole year were found to be 6.7±0.8, 4.9±0.5 and 4.4±0.3 Bq m−3, respectively.Also, within that time period, approximately 120 samples were analysed to determine the concentrations of the long-lived radon decay product 210Pb and the cosmogenic radionuclide 7Be using a single-filter technique. The course of 210Pb air concentration is characterized by higher values in autumn/winter season and lower values in spring/summer season. The seasonal concentration pattern of 7Be reaches regular maximum values in the spring to early summer months. The annual average concentration values of 210Pb and 7Be have been found to be 0.37±0.06 and 2.0±0.09 mBq m−3, respectively. A mean aerosol mass concentration of 36.6±6.2 μg m−3 was also determined during the measurements of the long-lived radionuclides. The majority of attached 210Pb and 7Be were observed at lower aerosol mass concentrations while small fractions of attached activities were found to be associated with the higher mass concentrations.
Keywords: Meteorological parameters; Radon daughters; 210Pb; 7Be; Aerosol mass;

Estimating PM10 air concentrations from dust storms in Iraq, Kuwait and Saudi Arabia by Roland R. Draxler; Dale A. Gillette; Jeffrey S. Kirkpatrick; Jack Heller (4315-4330).
A model for the emission of PM10 dust has been constructed using the concept of a threshold friction velocity which is dependent on surface roughness. Surface roughness in turn was correlated with geomorphology or soil properties for Kuwait, Iraq, part of Syria, Saudi Arabia, the United Arab Emirates and Oman. The PM10 emission algorithm was incorporated into a Lagrangian transport and dispersion model. PM10 air concentrations were computed from August 1990 through August 1991. The model predicted about the right number of dust events over Kuwait (events occur 18% of the time). The model results agreed quantitatively with measurements at four locations in Saudi Arabia and one in Kuwait for one major dust event (>1000 μg/m3). However, for smaller scale dust events (200–1000 μg/m3), especially at the coastal sampling locations, the model substantially over-predicted the air concentrations. Part of the over-prediction was attributed to the entrainment of dust-free air by the sea breeze, a flow feature not represented by the large-scale gridded meteorological data fields used in the model computation. Another part of the over-prediction was the model's strong sensitivity to threshold friction velocity and the surface soil texture coefficient (the soil emission factor), and the difficulty in accurately representing these parameters in the model. A comparison of the model predicted PM10 spatial pattern with the TOMS satellite aerosol index (AI) yielded a spatial pattern covering a major portion of Saudi Arabia that was quite similar to the observed AI pattern.
Keywords: Long-range transport; Southwest Asia; Resuspension; Aeolian movement; HYSPLIT;

Rainfall geochemistry in the Sahel region of northern Nigeria by I.B. Goni; E. Fellman; W.M. Edmunds (4331-4339).
Chemical data and stable isotope (δ 18O, δ 2H) results are presented for monsoon rains for several years during the 1990s from northern Nigeria in the Sahel region of Africa. The isotopic data from Garin Alkali (Nigeria) are related by a line δ2 H=6.33δ18 O+9.9 with a weighted mean value of −3.6‰ for δ 18O. The heaviest rains have the lightest isotopic compositions; the lighter rains’ enrichment is as a result of convection. The mean 1992 concentrations of Cl in rain ranged from 1.3 to 2.8 mg l−1 for the two stations in Nigeria. The early rains have higher Cl than the later events although Cl accumulations are in general directly related to rainfall amount. The Br/Cl ratios of all rains are enriched above marine values, which may in part be attributed to a preferential concentration of Br in smaller size particles, although more likely, is related to release from the biomass as the air masses pass over vegetated areas. The high Br/Cl ratios rule out dust from halite sources during the monsoon. The ratios of Na and Cl are similar to those in sea water, although all other elements (especially Ca, SO4, NO3 and K) are enriched relative to marine aerosols and indicate continental sources. The element ratios (Ca/SO4); K/Mg; K/Na) are remarkably similar to those in ash leachates from tropical vegetation and this is proposed as the main solute source in the present day monsoon rains, reinforcing the evidence of Br/Cl ratios. The chemical results show the considerable terrestrial influence and are in line with isotopic evidence, which demonstrates considerable modification by convective circulation and continental influence as the monsoon air masses track northwards over the Sahel.
Keywords: Rainfall; Chemistry; Bromide; Isotopes; Africa; Sahel;

Surface ozone concentrations in Eastern Highlands of Zimbabwe by S.B Jonnalagadda; J Bwila; W Kosmus (4341-4346).
The communication covers various aspects of the surface ozone–monitoring project, which was carried over a period of 2 1 2 years in the Eastern Highlands of Zimbabwe. Using the passive samplers (candle method)—indigo impregnated paper and exposing for 7-day duration, the ambient ozone levels were monitored, which is calibrated by KI method. The surface ozone concentration was monitored at 14 sites situated at different altitudes in Eastern Highlands of Zimbabwe. Seasonal trends were observed. Marginal variations were observed between the years (1991 and 1993) at any sampling station. Mean ozone levels at various sites varied between (33 and 48) ppbv. The observed seasonal trends in ozone levels were discussed.
Keywords: Surface ozone; Air quality; Indigo method; Zimbabwe; Africa;

Size resolved chemical mass balance of aerosol particles over rural Hungary by D Temesi; A Molnár; E Mészáros; T Feczkó; A Gelencsér; G Kiss; Z Krivácsy (4347-4355).
The mass size distribution of atmospheric aerosol particles was determined by means of an electric low pressure impactor (ELPI) in rural air in Hungary. The particles captured on different stages of the impactor were chemically analyzed by capillary zone electrophoresis to quantify ionic components as well as by catalytic combustion method to detect total carbon in the samples. The results show that fine aerosol consists mainly of ammonium sulfate and organic carbon. These two species have rather different size distributions since very small particles are composed almost of carbon compounds. The analysis of fine aerosol samples collected simultaneously on filters indicates that an important part of organics is soluble in water. The mass balance of fine particles as a function of their size is estimated by taking into account the liquid water adsorbed by ammonium sulfate and by converting the mass of carbon to the mass of carbon compounds. Finally, the size resolved mass balance of fine aerosol particles is presented and discussed as a function of the origin of air masses.
Keywords: Mass balance; Fine particles; Rural air; Hungary;

Change of the ambient particle size distribution in East Germany between 1993 and 1999 by M. Pitz; W.G. Kreyling; B. Hölscher; J. Cyrys; H.E. Wichmann; J. Heinrich (4357-4366).
Size distribution of particle number concentrations in the geometric equivalent diameter range 0.01–2.5 μm were determined in three communities, Zerbst, Bitterfeld and Hettstedt of the state of Sachsen-Anhalt in Eastern Germany, in the first half of 1993 and 1999. A Mobile Aerosol Spectrometer (MAS) consisting of a differential mobility particle spectrometer (DMPS) and a laser aerosol spectrometer (LAS-X) were used for size-selective particle number concentration measurements from which mass concentrations were derived based on an apparent mean density of the ambient aerosol of the closely situated city of Erfurt.The total number concentration was governed by ultra-fine particles (<0.1 μm) (81% in 1993 and 90% in 1999) and 0.1–0.5 μm size fraction dominates total mass concentration (approximately 80%). While the mass concentration of fine particles (PM2.5) decreased from 39 to 19 μg m−3, the geometric means of total number concentration showed constant concentration (13.3×103  cm−3 in 1993 and 13.3×103  cm−3 in 1999, p=0.975) and the geometric means of number concentration of ultra-fine particles (UP) between 10 and 30 nm increased from 5.9×103 to 8.2×103  cm−3 from 1993 to 1999 (p=0.016). The temporal changes of number and mass concentrations in the three communities are similar. The clear shift to smaller particle sizes within this six years period was caused by changes of the most prominent sources, traffic and domestic heating, since formerly dominating industries in Bitterfeld and Hettstedt had vanished grossly.
Keywords: Ambient aerosol; Particle number concentration; Particle mass concentration; Aerosol spectrometer; Ultra-fine particles;

As part of an air pollution project in Budapest, aerosol samples were collected by stacked filter units and cascade impactors at an urban background site, two downtown sites, and within a road tunnel in field campaigns conducted in 1996, 1998 and 1999. Some criteria pollutants were also measured at one of the downtown sites. The aerosol samples were analysed by one or more of the following methods: instrumental neutron activation analysis, particle-induced X-ray emission analysis, a light reflection technique, gravimetry, thermal profiling carbon analysis and capillary electrophoresis. The quantities measured or derived include atmospheric concentrations of elements (from Na to U), of particulate matter, of black and elemental carbon, and total carbonaceous fraction, of some ionic species (e.g., nitrate and sulphate) in the fine (<2  μm equivalent aerodynamic diameter, EAD) or in both coarse (10–2  μm EAD) and fine size fractions, atmospheric concentrations of NO, NO2, SO2, CO and total suspended particulate matter, and meteorological parameters. The analytical results were used for characterisation of the concentration levels, elemental composition, time trends, enrichment of and relationships among the aerosol species in coarse and fine size fractions, for studying their fine-to-coarse concentration ratios, spatial and temporal variability, for determining detailed elemental mass size distributions, and for examining the extent of chemical mass closure.
Keywords: Urban aerosol; Size-fractionated aerosols; Aerosol properties; Chemical composition; Mass size distribution; Chemical mass closure; PM2.5;