Atmospheric Environment (v.40, #22)

Leaves of Pittosporum tobira as indicators of airborne trace element and PM10 distribution in central Italy by G. Lorenzini; C. Grassi; C. Nali; A. Petiti; S. Loppi; L. Tognotti (4025-4036).
Leaves of the evergreen ornamental shrub species Pittosporum tobira were used as a passive monitor to describe the distribution of selected elements in three coastal cities of central Italy (namely Livorno, Rosignano Marittimo and Piombino) differing for number of inhabitants and economical activities. Unwashed healthy mature leaves collected in June 2004 from 88 sampling sites covering the whole municipalities according to a systematic stratified unallineated sampling design were analysed by ICP-MS for Al, Ba, Be, Bi, Br, Ca, Cd, Cl, Co, Cr, Cs, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, Pb, Si, Ti, V and Zn. Values were normalised by subtracting baseline concentrations of biologically essential elements. Enrichment factors were calculated taking Al as crustal reference element. Factor analysis allowed to identify three main source groups of elements, namely crustal components, sea-salt spray and anthropogenic sources (vehicular traffic, industrial activities). SEM–EDX analyses were performed on 556 PM10 samples collected from the 88 sampling sites. High contributions of geological elements and marine aerosols were detected. Pb is no longer of environmental concern in the area. Results are discussed with emphasis on the potential role of vegetation for the removal of particulate pollution.
Keywords: Factor analysis; ICP-MS; Pollution removal; Pollution sources; SEM–EDX; Source apportionment;

An on-line monitoring method, jet resonance-enhanced multi-photon ionization (REMPI) with time-of-flight mass spectrometry (TOFMS), was used to measure emissions of organic air toxics from a medium-duty (60 kW) diesel generator during transient and steady state operations. Emissions of gas phase benzene, toluene, ethylbenzene, o-, m-, p-xylenes (BTEX), styrene and polycyclic aromatic hydrocarbons (PAHs) were measured at levels in the 10–500 ppb range with a measurement frequency of 10 s−1; this enabled rapid emission characterization as a function of operating conditions: cold starts, hot starts and load changes. The sensitivity, selectivity and real-time monitoring capabilities of the jet REMPI-TOFMS system discerned transient concentrations of organic air toxics (e.g., benzene and naphthalene) during cold starts exceeding 15 times their steady state levels. Time-integrated concentrations obtained by jet REMPI-TOFMS compared well with standard EPA methods. The jet REMPI-TOFMS system provides a means to rapidly characterize air toxic emission factors that enables users to alter operational procedures to minimize air toxic formation. The relative concentrations between startup and steady state emissions, as well as the transition period between these levels, were specific for each type of compound found in the diesel exhaust.
Keywords: Emission factor; Air toxics; Diesel; Startup; Emissions; REMPI-TOFMS;

Global anthropogenic mercury emission inventory for 2000 by Elisabeth G. Pacyna; Jozef M. Pacyna; Frits Steenhuisen; Simon Wilson (4048-4063).
The paper reviews the current state of knowledge regarding global emissions of mercury and presents a new inventory of global emissions of mercury to the atmosphere from anthropogenic sources for the year 2000. The largest emissions of Hg to the global atmosphere occur from combustion of fossil fuels, mainly coal in utility, industrial, and residential boilers. As much as two-thirds of the total emission of ca. 2190 ton of Hg emitted from all anthropogenic sources worldwide in 2000 came from combustion of fossil fuels. Emissions of Hg from coal combustion are between one and two orders of magnitude higher than emissions from oil combustion, depending on the country. Various industrial processes account for additional 30% of Hg emissions from anthropogenic sources worldwide in 2000. Major contribution to emissions from this source category comes from gold production using Hg technology. The Asian countries contributed about 54% to the global Hg emission from anthropogenic sources in 2000, followed by Africa (18%) and Europe, including the European part of Russia (11%). China heads the list of the 10 countries with highest Hg emissions from anthropogenic activities. With more than 600 ton of Hg, China contributes about 28% to the global emissions of mercury.It is expected that future changes of Hg emissions from anthropogenic sources worldwide until the year 2020 should be within ±20% of the current estimates, although this assessment should be treated with great caution.Emission estimates for various continents presented in this paper were used to prepare global emission maps. These maps are presented in a companion paper (Wilson et al., 2005. Spatial distribution of global anthropogenic mercury atmospheric emissions. Atmospheric Environment, in this issue).
Keywords: Anthropogenic emissions; Global inventory; Mercury; Emission projections;

Investigation of carbon pollution episodes using semi-continuous instrument in Incheon, Korea by Young J. Kim; Min Jeong Kim; Kwon Ho Lee; Seung Shik Park (4064-4075).
Hourly measurements of organic and elemental carbon (OC and EC) in fine particles (PM2.5) were conducted at an urban site of Incheon, Korea, between June 2004 and October 2004, using a Sunset Lab semi-continuous carbon field instrument with a continuous-flow non-dispersive infrared (NDIR) detector system. Analyses were performed using the NIOSH thermal-optical transmittance (TOT) protocol. Five-minute black carbon (BC) concentrations were also measured simultaneously using an aethalometer to compare with the thermal and optical EC measurements obtained from a Sunset Lab carbon analyzer.Close inspection of 1-h time-resolved OC and EC measurements reveals many carbon transients, which were mostly attributed to local traffic emissions. In this study, only three distinct carbon pollution episodes are discussed. The first episode was characterized by smoke plumes from forest fires that occurred in southeastern China, which resulted in enhanced OC concentrations. The second episode was strongly associated with regional haze over northeastern China and local stagnation conditions, which lead to highly elevated OC and EC levels throughout the episode. The third episode occurred at the weekend (Saturday and Sunday) was related to broad OC peak and the highest short-term OC excursion over the entire study period. Back trajectory analysis and Moderate Resolution Imaging Spectro-radiometer (MODIS) satellite image data were used to characterize potential source regions for the developed episodes and the transport pathways of the air masses. The measured EC concentrations for the three episodes were strongly associated with the optical EC ( R 2 = 0.90 – 0.98 ) and BC concentrations ( R 2 = 0.93 – 0.95 ). The slopes from the relationship between EC and BC varied with the classification of the pollution episodes, ranging from 0.79 to 1.22, suggesting that the attenuation coefficient used for the determination of the BC particle concentrations could depend on the time, sampling location, emission sources of carbon particles, etc.
Keywords: High time resolution; Carbonaceous species; MODIS satellite image; Forest fires; Regional haze;

A novel approach for structure quantification of fatty acids films on rain water by Adriana Z. Mazurek; Stanisław J. Pogorzelski; Anna D. Kogut (4076-4087).
A complete compositional or structural description of naturally occurring surfactants on rainwater is not currently feasible. A main limitation of previous work has been the lack of means for correlating force-area characteristics with the chemical makeup of the films. Instead of analyzing the chemical composition of rain water film-forming organics, it is postulated here to introduce the novel scaling procedures (2D virial equation of state and 2D polymer film scaling theory) applied to the surface pressure-area (πA) isotherms and surface pressure-temperature (πT) isochors, and resulting from generalized physical formalisms modified to a multicomponent surfactant film. A set of the introduced structural film state parameters could become sensitive indicators for surface-active source-specific organic matter pathways tracing, where the measurement of surfactant concentration and chemical analyses are avoided. Performed comprehensive film studies on rain, marine and snow-melted water samples exhibited significant and differentiated film structural parameters variability. The developed procedure allows one to recover the film parameters (π, Γ, A lim, E isoth) present originally at the raindrop surface from the Langmuir trough data supplemented with the simultaneously taken rain event characteristics (rain rate and rain drop diameter distribution). It requires the partitioning effect of the surfactant molecules between the surface and bulk phases to be estimated where the entering quantities are: the partitioning coefficient K p=Γ/c and a degree of the rain water interfacial system area development A r/V r evaluated here using the fatty acids concentrations as model input data. The latter parameter depends on the rain rate and the form of the drop size distribution function differing significantly from the Marshall–Palmer one at low I r (<1 mm h−1). The partitioning factor K p related to the physicochemical composition of the film-composing material exhibited a seasonal and source-specific features and varies in a rather narrow range (5.3–13.7 cm) being of secondary importance in comparison to the interface development term. Original rain drop films exhibited low surface pressures (1.9–5.4 mN m−1) characteristic of a quasi-ideal 2D gas behavior found in a diluted surfactant solution (with c≈10−3a) and are composed of slightly soluble immiscible components of mean molecular masses within 261–270 Da in agreement with chemical analyses. The concept is quantified using the Langmuir trough film and disdrometer data on a set of rainwater events observed at Gdańsk, Poland in May 2002.
Keywords: Source-specific surfactants; Rainwater film; Isotherm scaling; Structural parameters; Film state quantification;

Impacts of summer ozone exposure on the growth and overwintering of UK upland vegetation by Felicity Hayes; Gina Mills; Philip Williams; Harry Harmens; Patrick Büker (4088-4097).
The effects of ozone exposure on species of an upland grassland were assessed. Thirty-three species from Snowdonia, North Wales, UK, were exposed for 10 weeks to a weekly episodic ozone regime in solardomes representing predicted future concentrations. Two solardomes were used as controls, with ozone added to charcoal-filtered air to give a continuous ozone concentration of 30 ppb (O3(30)). A weekly episodic ozone regime was applied to two other solardomes, with concentrations rising for 8 h per day to 80 ppb on day 1, 100 ppb on days 2 and 3, and 80 ppb on day 4; ozone concentrations remained at 30 ppb at all other times (O3(30+peaks)). The control and background ozone concentrations of 30 ppb were maintained throughout the night as well as during the daytime. During exposure to the episodic ozone regime, some species were sensitive to ozone and showed ozone-specific leaf injury symptoms (e.g. Carex echinata) and/or premature senescence (e.g. Festuca rubra) and/or changes in above-ground biomass (e.g. Armeria maritima), whereas other species (e.g Holcus lanatus and Carex demissa) showed no effects. Some species, although showing no effects during the 10-week ozone exposure, showed carry-over effects on biomass the following spring, after a winter period of ambient ozone exposure (e.g. Galium saxatile, Nardus stricta and Saxifraga stellaris). The carry-over effects shown in this study indicate the potential ecological impact of ozone on semi-natural vegetation species and indicate the importance of longer-term studies on the effects of ozone on plants.
Keywords: Ozone; Carry-over effect; Ozone injury; Biomass; Upland vegetation;

Keywords: Vapor intrusion; Johnson and Ettinger model; Risk assessment; Volatile organic compounds;

A complex case study of down to the surface intrusions of persistent stratospheric air over the Eastern Mediterranean by Evangelos Gerasopoulos; Prodromos Zanis; Constantin Papastefanou; Christos S. Zerefos; Alexandra Ioannidou; Heini Wernli (4113-4125).
In this study, we present a complex case study of concurrent stratosphere-to-troposphere transport (STT) events down to the surface of a low topography region in Northern Greece, which occurred in spring 2000. Two surface stations at Livadi (850 m asl) and Thessaloniki (20 m asl) were influenced by intrusions of stratospheric air masses that persisted for a time period from 7 to 10 days within the troposphere before reaching the stations. Before reaching the surface stations in Greece, the air masses crossed the tropopause in different synoptic systems over Eastern Europe, N. America and the N. Atlantic. This is the first study, to our knowledge, that presents a down to the surface STT event in the Eastern Mediterranean. Observational evidence comes mainly from surface measurements of ozone rising by about 20 ppbv and the cosmogenic radionuclide 7Be exceeding 9 mBq m−3. Trajectory analyses, in conjunction with the evolution of the synoptic situation, were used to identify the stratospheric intrusions most likely to have impacted the surface sites and to estimate the volume fraction of surface air that has been transported from the stratosphere. The latter presented a maximum of 5.2% and allowed the investigation of the response of both ozone and 7Be to the presence of stratospheric air down to the surface.
Keywords: Statosphere-troposphere exchange/transport; Ozone; 7Be; Specific humidity; Potential Vorticity; Eastern Mediterranean;

PM10 modeling of Beijing in the winter by Yu Song; Minsi Zhang; Xuhui Cai (4126-4136).
The megacity of Beijing, China, has had an air pollution problem since the 1990s. The concentrations of particulate matter with an aerodynamic diameter less than 10 μm (PM10) in Beijing in the winter of 2000 were high; the average value of 188 μg m−3 was nearly four times the first grade national standard of 50 μg m−3. The CALPUFF modeling system was used to simulate PM10 dispersion from 1 January 2000 to 29 February 2000. We used near real-time landcover data from the moderate resolution imaging spectroradiometer (MODIS). Statistical evaluation indicated that the model agreed well with the observations. The fluctuations of 24-h PM10 concentrations followed the winter synoptic winds. Cold air from the northwest or north intruded over Beijing for average periods of 4 days in winter, accompanied by high wind speeds. PM10 was swept out of Beijing after the cold fronts and accumulated again once the winds stopped, until the next cold air intrusion. Capital Steel Corporation Limited contributed 46% of the PM10 mass concentrations observed in the Shijingshan industrial area, and had little effect on the eastern part or the center of Beijing. The other industrial regions distributed in southeastern Beijing accounted for an average of 18% of the PM10 in Beijing. Boilers associated with coal consumption mostly for winter heating contributed 31%. Motor vehicles and road dust contributed 5% and 13%, respectively. The total of residential heating in old houses and restaurants contributed approximately 7%. The primary PM10 emissions from electrical generating units were relatively low. Some suggestions are proposed for reducing PM10 pollution in Beijing.
Keywords: Beijing; Particulate matter; CALPUFF; MODIS; Synoptic winds;

Day-of-week trends in carbonaceous aerosol composition in the urban atmosphere by G.C. Lough; J.J. Schauer; D.R. Lawson (4137-4149).
The chemical composition of atmospheric particulate matter was measured at two sites near Los Angeles, California, over 3 weeks in July 2001, as part of the Gasoline/Diesel PM Split Study. Samples were composited for organic speciation analysis by day of week at each site to investigate weekly trends in chemical composition of the carbonaceous fraction of particulate matter. Observed weekly trends in elemental carbon (EC), hopanes, steranes, and polynuclear aromatic hydrocarbons (PAHs) indicate increased impacts of motor vehicle traffic on carbonaceous particulate matter concentrations on weekdays relative to weekends. Ambient average EC was approximately 4 times higher in the Friday samples than in Sunday samples at each site. Levoglucosan, a tracer species for biomass burning, and cholesterol, monopalmitin, and monostearin, tracers for food cooking operations, were all highest on Friday and lowest on Sunday. Late-week increases in aliphatic and aromatic diacids present in the particulate phase were also observed. Diacids in particulate matter have been seen to be indicators of secondary organic aerosol formation, and the day-of-week trend observed may be due to weekday increases in volatile precursor species present in the atmosphere.
Keywords: Organic; Ambient; Particulate matter; Source apportionment; Tracer compound;

Sesquiterpene emissions from loblolly pine and their potential contribution to biogenic aerosol formation in the Southeastern US by Detlev Helmig; John Ortega; Alex Guenther; Jeffrey D. Herrick; Chris Geron (4150-4157).
Sesquiterpene (SQT) and montoterpene (MT) emissions from loblolly pine (Pinus taeda L.) were studied by branch enclosure experiments at Duke Forest in Chapel Hill, NC. Four SQT (β-caryophyllene, α-bergamotene, α-humulene, β-farnesene), five MT (α-pinene, β-pinene, β-myrcene, β-phellandrene, limonene), and the oxygenated MT linalool were identified. Emission rates of both compound classes increased exponentially with temperature, albeit SQT temperature coefficients (0.12–0.18 K−1) were higher than for MT (0.068–0.15 K−1), resulting in an increased contribution of SQT to the overall biogenic volatile organic compound (BVOC) flux during warm temperature conditions. The highly correlated variables of light and temperature conditions preclude a rigorous characterization of their individual roles in driving these emissions. However, the observations indicate that there may be both temperature-only and temperature/light-dependent components contributing to SQT emission variations. When normalized to 30 °C using the best-fit temperature algorithm, total SQT basal emission rate was 450 ng g−1  h−1. The potential contribution of SQT from all pine trees (based on the loblolly pine emission factors) to secondary, biogenic organic aerosol in 12 southeastern US states was estimated to be 7×106  kg for the month of September which constitutes an appreciable portion of the overall PM 2.5 emission budget.
Keywords: Sesquiterpenes; Montoterpenes; Emission factors; Organic secondary aerosol;

The significance of the heterogeneous formation of particulate nitrate, rarely included in chemistry-transport models (CTMs), is investigated. According to several field campaigns, particulate nitrate in a coarse particle (2–10 μm) can be obtained by reaction of nitric acid with calcium and magnesium carbonates. This process significantly contributes to the total nitrate mass concentration over land, particularly in summer. We introduce this heterogeneous reaction in the CHIMERE CTM and analyze its impact on total nitrate, nitric acid and aerosol particles, by statistical comparison of one-year long simulations with EMEP measurements over Europe. Several values of the nitric acid uptake coefficient are tested in order to investigate the sensitivity to this parameter, and we propose an optimal value for our study. The model performance in simulating nitrates and PM10 significantly improves when the heterogeneous nitrate formation is included. This process also greatly improves the simulation of coarse nitrate by comparison with field campaign measurements near Paris city.
Keywords: Coarse nitrate; Heterogeneous formation of particulate nitrate; Mineral dust; Chemistry-transport models; PM10; Air quality;

Separation of slurry produces a solid fraction that is stored in manure heaps before being used as a fertiliser in crop production. Considerable amounts of ammonia (NH3) and greenhouse gases may be emitted during storage, which has deleterious environmental effects. The emission levels can be expected to depend on oxygenation level inside the bulk of the stored manure and therefore on storage conditions. An experiment was thus set up to study gaseous emissions during storage of the solid fraction, and the effects of the oxygenation of manure heaps on emissions of NH3 and various greenhouse gases. Emissions of NH3 and the greenhouse gases methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2) from an uncovered and covered heap of solids separated from pig slurry were compared, and related to the oxygenation level inside the manure heap. Approximately 15% of the initial nitrogen content was lost when separated solids were stored uncovered. Of the initial nitrogen content, 4.8% was lost as N2O, 0.3% was lost as NH3, while the 9.6% unaccounted for was assumed lost as dinitrogen (N2). Of the initial carbon content, 28% was lost during uncovered storage; the majority of this was emitted as CO2 (25%), while 1.3% was emitted as CH4. Oxygenation level inside the heap was found to influence the production and emission of greenhouse gases. Covering the heap with an airtight material delayed aeration of the bulk of the stored manure, which reduced the internal heat production, degradation of organic matter, and emission of NH3 and greenhouse gases. Emissions of NH3, N2O, and CH4 were reduced by 12%, 99%, and 88%, respectively, when the manure heap was covered with an airtight material.
Keywords: Solid manure; Separation; Ammonia; Methane; Nitrous oxide;

Molecular composition of PM2.5 organic aerosol measured at an urban site of Korea during the ACE-Asia campaign by Seung Shik Park; Min-Suk Bae; James J. Schauer; Young J. Kim; Sung Yong Cho; Seung Jai Kim (4182-4198).
Daily fine particulate matter (PM2.5) samples were collected at Gwangju, Korea, during the ACE-Asia campaign between 26 March and 4 May 2001, to characterize individual organic compounds. Daily air volumes per sample (∼24 m3) were too low for detailed organic analysis by gas chromatography–mass spectrometry (GC–MS), so were grouped based on their air mass trajectories. A total of 9 composites (Groups A–I), seven containing 4–6 daily samples and two containing 2 daily samples, were analyzed to determine the n-alkanes, n-alkanoic acids, dicarboxylic acids, aromatic acids, resin acids, PAHs, oxy-PAHs, and levoglucosan, etc. Two-day composite samples were formed during the Asian dust storm events (10–13 April) due to the high PM2.5 mass concentration.The concentrations of n-alkanes and n-alkanoic acids were highly elevated when air masses are transported through Korean peninsula (Group B), local anthropogenic pollution strongly impacted on the measurement site (Group C), or when a biomass burning event had occurred (Group H). Of the n-alkanoic acids, octadecanoic acid (C18) was the most abundant species in most of the composite samples, followed by hexadecanoic acid (C16), but with lower concentrations for the higher molecular weight acids (⩾C20), suggesting a greater contribution from petroleum-based emission sources, such as gasoline and diesel vehicles, fuel oil combustion, etc. Also, the concentrations of resin acids were enriched in Groups B and C. A high levoglucosan concentration was observed in the Group H, in which a biomass-burning plume passing through Korean peninsula was transported to the sampling region. For the periods with Asian dust events (Groups D and E), most of the organic species were less abundant than in the other composite sample groups.Additionally, two 12-h PM2.5 ambient samples, collected nearby an agricultural land during agricultural waste burning episode, were used to analyze individual organic species and examine the influence of agricultural burning on the ambient fine particulate matter concentrations. Very enhanced concentrations were observed for the PM2.5 mass, organic carbon and levoglucosan during this episode. An elevated carbon preference index (CPI) value (2.8) of n-alkanes and high wax n-alkanes contribution (50.7%) indicate a greater influence from biogenic emissions. The concentration of hexadecanoic acid (C16) among those of the n-alkanoic acids was highest, following by octadecanoic acid (C18).
Keywords: Ace-asia; Fine particles; Asian dust; Organic compounds; Agricultural waste burning; Levoglucosan;

Emissions of regulated pollutants from in-use diesel back-up generators by Sandip D. Shah; David R. Cocker III; Kent C. Johnson; John M. Lee; Bonnie L. Soriano; J. Wayne Miller (4199-4209).
Recent power outages have highlighted the need for reliable alternatives to the power grid such as diesel back-up generators (BUGs). As many BUGs are operated in close proximity to populations, there is a need for accurate emissions measurements from these units. This paper reports regulated emissions for diesel BUGs of varying model year, engine technology and manufacturer in the 60–2000 kW size and provides the largest emissions database for these engines. The average emission factors for oxides of nitrogen (NO x ) were determined to be approximately 41% and 47% lower than EPA's estimates in AP-42 for small and large BUGs, respectively. Average particulate matter (PM) emission factors were approximately 83% and 50% lower than AP-42 estimates for small and large BUGs, respectively. All BUGs tested had lower emissions than used in EPA's AP-42 emissions inventory for NO x and PM. Results indicate that decreases in NO x emission rates for BUGs paralleled the non-road and on-road emission standards. Minimal variation was noted for three engines of the same family and model year but with different hours of operation.
Keywords: Diesel emissions; NO x ; Diesel particulate matter; Off-road emissions; Regulated pollutants; Heavy-duty diesel;

The relationship between odor concentrations (olfactometry) and chemical concentrations (gas chromatography-mass spectrometry, GC-MS) was studied for the odorous air compositions of a rendering plant, a sanitary landfill and an industrial area with large petroleum and petrochemical industries. Samples taken from the university campus located in a non-industrial and non-urban area were also studied for several organic components for comparison. Ambient air samples were taken into special bags by using an odor sampling device designed for field sampling of odors. In the laboratory odorous chemicals in the samples were transferred into adsorbent tubes and analyzed using a combination of thermal desorption and GC-MS. Results point to different characteristics of the odorous gases and air in and around the urban and industrial sources.Among the 64 specific compounds studied, 49 volatile organic compounds (VOCs) were detected in rendering plant, 53 VOCs were detected in sanitary landfill and 44 VOCs were detected in petroleum and petrochemical industries. The compounds measured in the odorous gas composition are the alkanes, alkenes, carbonyls, arenes, chlorinated and other halogenated compounds and organic chlorides as well as the volatile fatty acids.
Keywords: Odor concentration; Olfactometry; GC-MS; Rendering plan; Sanitary landfill; Petroleum industry;

Scavenging properties of major and trace species in rainfall collected in urban and suburban Tokyo by Tadashi Shimamura; Takaya Wada; Masato Iwashita; Yuuichi Takaku; Hideo Ohashi (4220-4227).
Sequential rain collections were carried out for 93 rainfall events, with samples of 1 mm of precipitation. A total of 29 major and trace elements and major anions were determined for each fraction. The scavenging properties of these elements with rainfall depth were well approximated by a power law C = a R t - b , rather than an exponential law C = C 0 exp [ - λ * R t ] , where C is the concentration of a trace element in rain, C 0 is the initial concentration, Rt is rainfall depth, a and b are empirical constants and λ* is the scavenging coefficient. We propose a power exponent b as a scavenging index that is the slope of linear approximation of the log  C versus log  Rt plot and represents degree of scavenging efficiency. Elements such as Na, Mg, Ca, Sr, which are predominantly from natural sources, had large b values and were efficiently scavenged by raindrops, while elements such as Zn, Cu, Se, Sb, which are predominantly from anthropogenic sources, had intermediate b values and were scavenged less efficiently than natural source elements. On the other hand, Sn had a distinctly small b value compared to the other elements. The scavenging index b values correlate well with the aerodynamic diameter of aerosols that bear the respective elements. The size of aerosols bearing Sn could be extremely small, down to 0.05 μm.
Keywords: Rainwater; Sequential sampling; Power approximation; Scavenging process; Scavenging index; Trace element;

Using a mass balance method, we estimated the average Cd emission factors from artisanal zinc smelting using indigenous method in Hezhang, Guizhou, China, to be 1460 and 1240 g Cd t−1 of Zn produced from sulfide ore and oxide ore, respectively. These emission factors are much higher than the literature value used to estimate Cd emission from zinc smelting using pyrometallurgical method in developed countries, which is 50 g Cd t−1 of Zn produced. Based on the average Cd emission factors obtained in the study, annual Cd emission rates from artisanal zinc smelting in this area were calculated from 1989 to 2001. And up to 2003, approximately 450 t of Cd have been released to the ambient air from zinc smelting in a small area (<150 km2) in Hezhang district. Owing to a huge quantity of Cd atmospheric deposition, surface soils and mosses collected around the smelting areas were heavily contaminated. The highest total Cd concentrations in surface soils and naturally growing mosses were found to be 74 and 110 mg kg−1, respectively, exhibiting a local spatial pattern of Cd deposition from atmosphere.
Keywords: Cadmium; Emission; Zinc smelting; Soil; Moss; Hezhang; Guizhou; China;