Atmospheric Environment (v.36, #2)

Measurement of aerosol chemical, physical and radiative properties in the Yangtze delta region of China by Jin Xu; M.H. Bergin; X. Yu; G. Liu; J. Zhao; C.M. Carrico; K. Baumann (161-173).
In order to understand the possible influence of aerosols on the environment in the agricultural Yangtze delta region of China, a one-month field sampling campaign was carried out during November 1999 in Linan, China. Measurements included the aerosol light scattering coefficient at 530 nm, σ sp, measured at both dry relative humidity (RH<40%) and under ambient conditions (sample RH=63±19%), and the absorption coefficient at 565 nm, σ ap, for aerosol particles having diameters <2.5 μm (PM2.5). At the same time, daily filter samples of PM2.5 as well as aerosol particles having diameters <10 μm (PM10) were collected and analyzed for mass, major ion, organic compound (OC), and elemental carbon (EC) concentrations in order to determine which anthropogenic chemical species were primarily responsible for aerosol light extinction. The aerosol loading in the rural Yangtze delta region was comparable to highly polluted urban areas, with mean and standard deviation (S.D.) values for σ sp, σ ap and PM2.5 of 353 Mm−1 (202  Mm−1), 23 Mm−1 (14 Mm−1) and 90 μg m−3 (47 μg m−3), respectively. A clear diurnal pattern was observed in σ sp and σ ap with minimum values occurring in the middle of the day, most likely associated with the maximum midday mixing height. The ratio of the change in light scattering coefficient at ambient RH to that at controlled RH (RH<40%), F σ sp (RH), indicates that condensed water typically contributed ∼40% to the light scattering budget in this region. The mass scattering efficiency of the dry aerosol, Escat_2.5, and mass absorption efficiency of EC, Eabs_2.5, have mean and S.D. values of 4.0 m2  g−1 (0.4 m2  g−1) and 8.6 m2  g−1 (7.0 m2  g−1), respectively. PM2.5 concentrations in Linan and two other locations in the Yangtze delta, Sheshan and Changshu (which have monthly mean values ranging from ∼80 to 110 μg m−3), are all significantly higher than the proposed 24-h average US PM2.5 NAAQS of 65 μg m−3. Organic compounds are the dominant chemical species accounting for ∼50% of the PM2.5 mass at all three sites. The results indicate that aerosol loadings in the agricultural Yangtze delta region of China are relatively high, and suggest that aerosols have a significant impact on visibility, climate, crop production, and human health in this region.
Keywords: Light scattering coefficient; Light absorption coefficient; PM2.5; Organic compounds; Yangtze delta;

The MICS-Asia study: model intercomparison of long-range transport and sulfur deposition in East Asia by Gregory R. Carmichael; Giuseppe Calori; Hiroshi Hayami; Itsushi Uno; Seog Yeon Cho; Magnuz Engardt; Seung-Bum Kim; Yoichi Ichikawa; Yukoh Ikeda; Jung-Hun Woo; Hiromasa Ueda; Markus Amann (175-199).
An intercomparison study involving eight long-range transport models for sulfur deposition in East Asia has been initiated. The participating models included Eulerian and Lagrangian frameworks, with a wide variety of vertical resolutions and numerical approaches. Results from this study, in which models used common data sets for emissions, meteorology, and dry, wet and chemical conversion rates, are reported and discussed. Model results for sulfur dioxide and sulfate concentrations, wet deposition amounts, for the period January and May 1993, are compared with observed quantities at 18 surface sites in East Asia. At many sites the ensemble of models is found to have high skill in predicting observed quantities. At other sites all models show poor predictive capabilities. Source–receptor relationships estimated by the models are also compared. The models show a high degree of consistency in identifying the main source–receptor relationships, as well as in the relative contributions of wet/dry pathways for removal. But at some locations estimated deposition amounts can vary by a factor or 5. The influence of model structure and parameters on model performance is discussed. The main factors determining the deposition fields are the emissions and underlying meteorological fields. Model structure in terms of vertical resolution is found to be more important than the parameterizations used for chemical conversion and removal, as these processes are highly coupled and often work in compensating directions.
Keywords: Model intercomparision; Sulfur deposition; Long-range transport; Source–receptor relationships;

The high ozone episode in the greater Seoul area (GSA) for the period of 27 July–1 August 1997 was modeled by the California Institute of Technology (CIT) three-dimensional photochemical model. During the period, ozone concentrations around 140 ppb were observed for 2 days. Two sets of diagnostic wind fields were constructed by using observations from the weather stations operated by the Korea Meteorological Administration. One set of wind fields utilized only observations from the surface weather stations (SWS) and the other set also utilized observations from the automatic weather stations (AWS) that were more densely distributed than the SWS. The results showed that utilizing observations from the AWS could represent fine variations in the wind field such as those caused by topography. A better wind field gave a more reasonable spatial distribution of ozone concentrations. The model performance of ozone prediction was also improved to some extent, but only marginally acceptable owing to large day-to-day variations. Overshoots of primary pollutants particularly for NO2 were observed as pollutants were accumulated where low wind speeds were maintained. More precise information on diurnal and daily variations in emissions was warranted in order to better model the photochemical phenomena over the GSA.
Keywords: Photochemical model; Diagnostic wind field; Local variations; Spatial distribution; Performance evaluation;

Large point source (LPS) emissions from India: regional and sectoral analysis by A Garg; M Kapshe; P.R Shukla; D Ghosh (213-224).
Indian large point sources (LPS) contribute to CO2 and SO2 emissions to a large extent (above 65%) and to CH4, N2O and NO X emissions to some extent (around 10%). The former emissions are primarily from fossil fuel combustion while the latter have agriculture sector dominance, explaining the drastic difference in LPS contributions to all India emissions. The present paper covers 509 LPS for India. These are well distributed across the country. However, there are some regions of very few LPS (like the western desert and the hilly areas of north, northeast and coastal west) and some regions of high LPS concentration (Mumbai–Ahmedabad corridor, Delhi and near coal mine mouths). There is a dominance of power plants in Indian LPS emissions for CO2 and SO2 (47% each), with cement (9% and 5%) and steel (6% and 7%) plants being the other major contributors. Moreover, due to growing population, increasing urbanization and higher consumption levels, these LPS emissions are growing much faster than the national average. The present analysis would be useful for policy-making to mitigate these pollutants and their associated impacts.
Keywords: Emissions; Large point sources; Greenhouse gases; Local pollutants; Mitigation policy;

Investigation of indoor air quality at residential homes in Hong Kong—case study by Shun Cheng Lee; Wai-Ming Li; Chio-Hang Ao (225-237).
Indoor air quality (IAQ) has been a matter of public concern in Hong Kong. Recently, the Hong Kong Government has recognized the potential risk and problems related to indoor air pollution, and it is striving to establish IAQ objectives for different types of indoor environments. This study attempts to provide more information about the present IAQ of local resident flats. Air pollutants measured in this study included carbon dioxide (CO2), respirable suspended particulate matter (PM10), formaldehyde (HCHO), volatile organic compounds (VOCs) and airborne bacteria. The results of this study indicate that the 8-h average concentrations of CO2 and PM10 in the domestic kitchens investigated were 14% and 67% higher than those measured in the living rooms. The indoor air pollution caused by PM10 was more serious in domestic kitchens than in living rooms as almost all of the kitchens investigated had higher indoor levels of PM10. The majority of the domestic living rooms and kitchens studied had average concentrations of airborne bacteria higher than 500 CFU/m3. The mean total bacteria count recorded in kitchens was greater than that obtained in living rooms by 23%. In homes where occupants smoke, the negative impact of benzene, toluene and m,p-xylene on the IAQ was greatly enhanced. The use of liquefied petroleum gas (LPG) stove has more significant impact on indoor VOCs than the use of cooking stoves with natural gas as cooking fuel.
Keywords: Home; Hong Kong; Indoor air quality; Suspended particulate matter (PM10); Total bacteria count (TBC); Volatile organic compounds (VOCs);

The sources and formation of atmospheric particulate mercury, Hg(p), in the Tokyo metropolitan area were investigated. Nine municipal solid waste (MSW) incinerators are located within 10 km of the study site. Airborne particles >10 μm in diameter were collected on a quartz fiber filter, and Hg(p) was measured by AAS following thermal desorption and gold trap amalgamation. Total gaseous mercury (TGM) was also determined using a continuous analyzer employing gold trap amalgamation and AAS. An average Hg(p) level of 0.098±0.051 ng m−3 (3.5±1.4% for total Hg=Hg(p)+TGM) was observed during the period from April 2000–March 2001, and Hg(p) levels tended to decrease during the summer. We investigated the relationship between concentrations of Hg(p) and Pb, a marker element for particles from MSW incineration. The propriety of using Pb as the marker element was verified based on the lead isotope ratios and the relationship between Pb, Cd and Zn concentrations. The results showed that Hg(p) concentration was correlated positively with Pb concentration and negatively with air temperature. On the other hand, the results of chemical leaching treatment for airborne particles indicated that most of the Hg in the particles might exist in the elemental form, Hg0. This suggests that some of the Hg0 emitted from MSW incinerators was adsorbed onto MSW incinerator particles in the atmosphere due to an abrupt decrease in temperature after emission, depending on air temperature. Thus, it is likely that the Hg(p) level in the Tokyo metropolitan area is closely related to the gaseous Hg0 emissions from MSW incinerators. In addition, from the thermodynamic analysis, it is inferred that the formation of Hg(p) is governed by the physical adsorption equilibrium of Hg0 between gas and particle phases.
Keywords: Airborne particles; Heavy metals; Municipal solid waste incineration; Physical adsorption; Thermodynamic analysis;

Concentrations of PAHs in atmospheric particles (PM-10) and roadside soil particles collected in Kuala Lumpur, Malaysia by Nasr Yousef M.J Omar; M.Radzi Bin Abas; Kamal Aziz Ketuly; Norhayati Mohd Tahir (247-254).
The concentrations of polycyclic aromatic hydrocarbons (PAHs) in atmospheric particles and roadside soil particles were measured at eight locations in the city center and the suburb of Kuala Lumpur, Malaysia. Atmospheric particles were collected using high-volume PM-10 sampler on glass fiber filters over 24 h average sampling period. Both types of samples were extracted with dichloromethane by ultrasonic agitation. The extracts were then fractionated on an alumina–silica column and the aromatic fraction was subjected to gas chromatography–mass spectrometric (GC–MS) analysis. Total PAH concentrations in the atmospheric particles and roadside soil particles were found to be 6.28±4.35 ng m−3 and 0.22±0.11 μg g−1, respectively. Benzo[g,h,i]perylene and coronene were found to be the most abundant PAHs in airborne particles at all locations. The most abundant PAHs in the roadside soil particles were fluoranthene, pyrene and phenanthrene.
Keywords: Air pollution; Particulate matter; Polycyclic aromatic hydrocarbons; Vehicular emissions;

Vehicle exhaust is the major source of pollutant in modern cities. About half of Hong Kong residents are living in suburban or rural areas. They need to traverse through tunnels, highways, urban street canyons and other road conditions in different landuse areas when they traverse to work in urban centres or new towns. Also, there is increasing traffic, especially trucks across the border between Hong Kong and mainland China via several border highways. This study helps us in assessing the exposure level of suburban and cross border commuters. Carbon monoxide (CO) is used as a tracer for traffic emission. An experimental vehicle traversing major commuting corridors were used to measure CO levels in different landuse and roadway microenvironments including tunnels and highways. The air samples were taken simultaneously at the outside and inside of a travelling vehicle. Result indicates that the pattern of fluctuation of the out-vehicle and in-vehicle CO level vary with different landuse areas. The variation pattern of in-vehicle CO level is closely related to that of out-vehicle level. The effects of the out-vehicle CO concentration on the in-vehicle CO concentration under different roadway conditions in various landuse categories are examined. There is an indication that external air pollutants penetrated into the in-vehicle compartment through car body cracks, ventilation system. From our observation, the exhaust of a nearby petrol vehicle contributed significantly to the in-vehicle CO level. The use of low standard of diesel fuel from Shenzhen in mainland China leads to higher CO level near border area.
Keywords: CO; Exposure; Vehicle exhaust; Tunnel; Highway;

Indoor air particulate samples were collected in 34 homes and their adjacent outdoor environments in Hong Kong during the fall and winter seasons. It was found that the mean indoor PM2.5 and PM10 concentrations were 45.0 and 63.3 μg m−3, respectively. The corresponding mean outdoor levels were 47.0 and 69.5 μg m−3, respectively. The indoor particulate levels were found to be about 2–4 times higher than those in the homes in western countries where most are located in suburb areas with a much better ambient air quality. Pearson paired t-tests were conducted on the data and it was found that poor correlation was seen in the indoor and the outdoor particulate concentrations. This was probably due to the fact that windows were closed more often in the fall and winter seasons keeping the ventilation rate low, plus the factor that window type air conditioners were used commonly in Hong Kong, which again, constituted to a low air change rate. Both the indoor and the outdoor elemental compositions of the particulate samples collected in these 34 homes were identified by proton-induced X-ray emission analysis. Seventeen elements were identified. The mean inorganic elemental compositions in the indoor PM2.5 and PM10 samples were 6.4 and 10.2 μg m−3, respectively while those in the outdoor samples were 7.9 and 14.1 μg m−3, respectively. Enrichment factor analysis was performed and it was noted that those species existing in fine mode were highly enriched (bromine, lead, nickel, potassium, sulfur, vanadium and zinc) while those species existing in the coarse mode had their enrichment factors close to 1 (aluminum, calcium, iron, magnesium, silicon, sodium and titanium).
Keywords: PM10; PM2.5; Indoor air quality; Elemental species; Homes;

Characterization of dioxin emissions from two municipal solid waste incinerators in Taiwan by Moo Been Chang; Jung-Jeng Lin; Shu-Hao Chang (279-286).
Characterization of the dioxin removal efficiencies of the air pollution control devices (APCDs) at two existing municipal solid waste incinerators (MWIs) in Taiwan is conducted via stack sampling and analysis in this study. MWI-A (capacity: 300 ton/day-incinerator) is equipped with electrostatic precipitators (ESP) followed by wet scrubbers (WS) while MWI-B (capacity: 450 ton/day-incinerator) is equipped with cyclones, dry lime sorbent injection systems (DSI) and fabric filters (FF) as APCDs. Results indicate that the patterns of dioxin isomers at APCD inlet and stack are similar for both MWIs. The dioxin concentration at APCD inlet of MWI-B is 2.75 times higher than that of MWI-A, but the readings are quite close at stacks. This indicates that the concentration of dioxins generated as the gas stream flows through APCD at MWI-A is higher than that of MWI-B. Dioxin removal efficiency at MWI-A is negative because the operating temperature of the APCD falls in the de novo reaction window (200°C–350°C). The concentration of emitted dioxin decreases significantly at MWI-B after the injection of powdered activated carbon has been started in 1999. The dioxin removal efficiencies based on I-TEQ were significantly increased from 5.9 to 87.6% and 91.3%, respectively, compared to the condition without activated carbon injection. The dioxin removal efficiency reached 98.6% in 2000 after continuous injection of activated carbon (43.4 mg/Nm3) for one year. The lower efficiency achieved with activated carbon injection (ACI) in 1999 can be attributed to the memory effect, i.e. the dioxin or precursor desorbs slowly the flue gas and increases the dioxin concentration at stack, resulting in a lower dioxin removal efficiency than expected.
Keywords: Municipal waste incineration; Dioxin emission; Activated carbon injection; Retrofit technology; Stack sampling;

Erythemal ultraviolet irradiance in Córdoba, Argentina by Gustavo G. Palancar; Beatriz M. Toselli (287-292).
Biologically active solar Ultraviolet-B radiation (UVery, 280–315 nm) is monitored in Córdoba, Argentina (31°24′S, 64°11′W, 400 m a.s.l) using the Yankee Environmental Systems (YES) pyranometer, model UVB-1. Measurements of the solar broadband UV-B irradiances are presented for the period of November 1998–December 1999. The site selected for the measurements represents semi-urban conditions and is along the most frequent wind direction (NE–SW) with reference to downtown, following the direction of prevailing winds. For clear sky days, the measurements are in good agreement with results of a radiative transfer model. However, examination of the record of solar ultraviolet measurements showed substantial reduction of the UV-B radiation on days with high levels of air pollution, which are associated with high concentration of particulate matter. Particulate matter is the only pollutant that surpasses the air quality standard several times during the year in Córdoba City. In this work, we investigate the daily variation of the UV-B radiation to assess its response to air pollution, physical variables, and meteorological factors. The main findings are that tropospheric aerosol is the most important UV-B attenuating factor (up to 40%), whereas tropospheric ozone and other UV absorber air pollutants like SO2 are not important. The results are consistent with the fact that pollution in Córdoba has mostly primary character with CO, NO x , and PM10 being the most important air pollutants. The UV-B radiation correlates well with simultaneous records of total radiation, but the reduction factors reflect stronger effects on the UV radiation than on total radiation.
Keywords: Air pollution; Erythemal; Aerosol; Córdoba; Ozone absorption;

Cations (pH, potassium, sodium, calcium, magnesium, and ammonium) and anions (sulfate, nitrate, nitrite, and chloride) concentrations were measured in Santiago city rain and dew waters collected during the 1995 to 1999. Concentrations measured in dews are considerably higher than those measured in rains. The high ionic concentration present in dew waters could contribute to their corrosion potential. Natural dust makes an important contribution to the ions present in dews, but the presence of rather high sulfate concentrations (up to 900 μeq/l) indicate a significant contribution of anthropogenic sources.A peculiar characteristic of dew waters is the relatively high nitrite concentrations (up to 180 μeq/l). This nitrite can be resuspended into the boundary layer after dew water evaporation, possibly due to the relatively high volatily of ammonium nitrite. This upward flux could constitute an important source of hydroxyl radicals in the early morning, contributing so to the initial steps of the observed photochemical smog.
Keywords: Nitrite; Dew; Photochemical smog; Nitrous acid;

Some aspects of air pollution in Córdoba, Argentina by Luis E. Olcese; Beatriz M. Toselli (299-306).
Córdoba, as well as many other Latin American cities, is facing problems concerning air pollution. The increase in the number of cars, the poor control on emissions and the little use of catalytic converters, produce a great amount of toxic gases and particulate. Many cities have started air quality measurement programs being the size of the network strongly dependent on the available funds. In 1995, Córdoba started a measurement campaign with two mobile stations. A major part of the city has been characterized, mostly the city center and the suburban zone. Lack of data at the prevailing wind direction is the major shortcoming, but this is mainly a political decision. In this work, we review the air quality measurements performed, and we attempt to explain the causes for the low ozone values found.
Keywords: Air pollution; South America; Ozone; Nitrogen oxides; Mobile sources; Primary pollutants;

Polycyclic aromatic hydrocarbons in a bioassay-fractionated extract of PM10 collected in São Paulo, Brazil by Bruno S. De Martinis; Robert A. Okamoto; Norman Y. Kado; Lara A. Gundel; Lilian R.F. Carvalho (307-314).
Polycyclic aromatic hydrocarbons (PAHs) were measured in airborne particles (PM10) collected in an urban site of São Paulo City, Brazil. Samples were Soxhlet extracted sequentially with dichloromethane and acetone, followed by solid phase fractionation. Increasing polar fractions (A–K) of dichloromethane and acetone extracts were obtained. Fractionated extracts were analyzed by gas chromatography/mass spectrometry and Salmonella microsuspension bioassay. Sixteen PAH compounds were quantified in dichloromethane B and C fractions, nevertheless the D and E fractions presented higher mutagenic activities. Concentrations of the individual PAHs ranged from 0.8 ng m−3 (perylene) to 12.8 ng m−3 (benzofluranthene), reaching a total concentration of 95.5 ng m−3. BaP/BgP and Pyr/BaP ratios indicated the presence of vehicular emissions and BghiP/Ind and Chr/BeP ratios suggested a contribution of wood combustion emissions. Further investigation is still necessary for a better understanding of the PAH sources in the urban atmosphere of São Paulo City.
Keywords: Atmospheric particulate matter; Polycyclic aromatic hydrocarbons; Mutagenicity; São Paulo City;

Ambient monitored data at Santiago, Chile, are analyzed using box models with the goal of assessing contributions of different economic activities to air pollution levels. The period analyzed is 1990–2000, characterized by the introduction of air pollution emissions standards, shift to unleaded gasoline and compressed natural gas, and steady growth of the private and public fleet and the associated fuel consumption growth. The box models explicitly include the seasonal behavior of meteorological variables; the results show that dispersion conditions in fall and winter seasons are 20–30% of the summertime values. This result explains the poor air quality in those seasons and shows that significant emissions reductions are required in order to improve air quality in wintertime. Emissions of CO, NO x and SO2 are estimated from data on fuel consumption in the city; the estimated parameters are thus fleet-average or industry-average emission factors. In terms of contributions to ambient concentrations, older cars and diesel vehicles are the major contributors to CO and NO x impacts, with more than 60% and 50%, respectively. Ambient concentrations of SO2 are largely dominated by stationary sources, although long range contributions are not negligible. By contrast, CO and NO x pollution is dominated by local sources within the city boundaries. The box models can be used for forecasting purposes, and they can predict annual average concentrations within 20% of the observed values. The methodology requires data on ambient air quality measurements and fuel consumption statistics, and produces quantitative results, which can be combined with economic models to analyze environmental regulation and public policies.
Keywords: Primary pollutants; Transportation emissions; Cleaner fuels; Urban air quality; Ambient data analysis;

Ambient monitored data at Santiago, Chile, are analyzed using box models with the goal of assessing contributions of different economic activities to air pollution levels. The box modeling approach was applied to PM10, PM2.5 and coarse (PM10–PM2.5) particulate matter (PM) fractions; the period analyzed is 1989–1999. A linear model for each PM fraction was obtained, having as independent variables CO and SO2 concentrations, plus a term proportional to (wind speed)−1 that lumps together non-combustion emissions and secondary generation terms; wet scavenging is included as another independent variable. Model identification results show good agreement for the different parameters across monitoring stations. The washout ratios and scavenging coefficients agree with data published in the literature, being higher for the coarse PM fraction. The CO and SO2 coefficients fitted for 1989–1995 agree with a priori estimates for the same period. Background estimates for the PM fractions are in agreement with measurement campaigns in upwind sites. Results show that transportation sources have become the dominant contributors to ambient PM levels, while stationary sources have decreased their contributions in the last years. The relative importance of mobile sources to PM2.5 ambient concentrations has doubled in the last 10 years, whereas stationary sources have reduced their relative contributions to half the value in the early 1990s. Model estimates of regional background of PM2.5 and PM10 have decreased 50% and 22% in the last decade, respectively; coarse background has shown no significant change. The final conclusion is that there is room and need for a more intensive emission reduction strategy for Santiago, focusing on mobile sources. The approach pursued in this work is feasible for cities or regions where comprehensive, transport and chemistry models are not available yet, but estimates of air quality contributions are needed for policy purposes. The methodology requires data on ambient air quality measurements and surface meteorology.
Keywords: PM data analysis; Urban air quality; Wet deposition; Cleaner fuels; Transportation impacts;

Characterisation of aerosol particles in the São Paulo Metropolitan Area by Regina Maura de Miranda; Maria de Fátima Andrade; Anna Worobiec; René Van Grieken (345-352).
Aerosol samples were collected in the São Paulo Metropolitan Area, Brazil, during two periods (winter and summer) for fine and coarse particles; they were analysed by gravimetry, scanning electron microscopy, particle induced X-ray emission (PIXE) and electron probe X-ray micro analysis (EPXMA) in order to investigate the mass concentration, morphology and physico–chemical properties of the particles. The gravimetry and PIXE results confirmed that the aerosol concentration is higher in winter than in summer, as expected from the climatological conditions (dry winter and humid summer). Hierarchical cluster analysis of the EPXMA results showed the presence of metal compounds, silicon-rich particles, sulphates, carbonates, chlorides, organics and biogenic particles.
Keywords: Atmospheric aerosols; Sources of air pollution; Trace elements; Micro analysis techniques; Urban atmosphere;

The Krusne Hory mountain plateau has experienced serious forest die-back in the last three decades which has been linked to acidic deposition, though important deposition routes had not been established before this study. Aerosol and wet deposition (precipitation and cloud water) data are presented for samples collected on the plateau at 740 m a.s.l. over the period March 1995–1996 and November 1996–March 1997. Concentrations of all species analysed were high relative to other continental sites, but were particularly elevated in cloud and rime samples and when atmospheric transport arose from the nearby industrialised valley. The species SO4 2− and NO3 were particularly enriched in samples that were associated with transport from the industrialised valley, suggesting significant oxidation of SO2 and NO x during transport from sources to the mountain region. Cloud and rime deposition represents a substantial proportion of the total wet deposition.
Keywords: Czech Republic; Air pollution; Rain; Aerosol; Fog; Rime;

Determination of the PAHs in precipitation and runoff waters permits the identification of the ways of their dissemination in the environment. The task is complicated by the two forms with which the compounds are present in these samples, i.e. dissolved in water and adsorbed on solid particles (dust). The study presented in this paper includes tracing of 16 selected compounds from the PAHs group at 10 precipitation sampling sites and 5 runoff sampling sites located across the “Threecity” (Gdañsk–Sopot–Gdynia). The recovery was performed using the solid phase extraction technique. PAH determinations were carried out by means of a GC-MS system. Among the 16 compounds selected for the study, naphthalene, phenanthrene+anthracene, fluoranthene and pyrene were found most frequently and at top concentrations (from few ng l−1 up to several hundred ng l−1), while dibenzo(a,h)anthracene, indeno(1,2,3-c,d)pyrene, benzo(a)pyrene, and benzo(g,h,i)perylene were present at concentrations close to the detection limit only. An attempt to correlate PAHs concentration with the percentage of coal stoves used for heating in the area gave coefficient of correlation (R 2) equal to 0.85 and 0.78, for rainwater and runoff, respectively, while PAHs concentration vs. traffic intensity correlation yielded the respective values of 0.40 and 0.54.
Keywords: Bulk precipitation; PAHs; Urban runoff;

Concentrations of PCB congeners were determined in precipitation and the annual and seasonal depositional fluxes were calculated for 16 (mostly rural) stations around the Baltic Sea during 1990–1993. The concentrations of individual congeners in precipitation were found to be influenced by atmospheric concentrations of PCBs, ambient temperature, precipitation volume and physico-chemical properties of the compounds. Median levels of PCBs in precipitation differed one order of magnitude between stations. When analyzing all data together to obtain regional trends, concentrations of PCBs in precipitation decreased with increasing temperature. This relationship was the same for all stations but differed in the magnitude of the slope for individual congeners. Low chlorinated PCB congeners showed steeper slopes for the temperature relationship than did high chlorinated congeners, a result explained by high atmospheric concentrations of the low chlorinated congeners during low temperatures. Annual wash out ratios were between 31 and 72×103 and tended to be higher for the high chlorinated congeners. Wash out ratios decreased with increasing temperature for all congeners except PCB-33. At snow scavenging events, the wash out ratio of PCBs increased with a factor of 2. Latitudinal trends for PCB concentrations in precipitation and deposition were generally not statistically significant. The calculated yearly deposition of PCBs to the Baltic Sea was 390 and 5–18 kg for individual congeners, with PCB-138 having the highest flux. Deposition of PCB congeners varied seasonally, with a factor between 2 and 3, and was generally highest during fall. Relatively higher deposition of low chlorinated congeners compared to high chlorinated congeners was found during winter.
Keywords: Polychlorinated biphenyls; Wet deposition; Rain scavenging; Temperature; Snow;

The influence of Siberian forest fires on carbon monoxide concentrations at Happo, Japan by Shungo Kato; Pakpong Pochanart; Jun Hirokawa; Yoshizumi Kajii; Hajime Akimoto; Yoko Ozaki; Kinichi Obi; Takao Katsuno; David G. Streets; Nickolay P. Minko (385-390).
Surface CO and ozone data were obtained in 1998 at Happo (36.7°N, 137.8°E, altitude 1840 m) in Japan. Backward trajectory analysis was applied to get the origin of the air mass to the measuring site. The air mass is basically coming from the west over the Asian continent except during summer. A maritime air mass prevails in the summertime, due to a dominant high-pressure system in the Pacific. In most cases, the air mass from the west (from China and Korea) shows a higher CO concentration than the air mass from the north, and the air mass from the Pacific shows the lowest CO concentration. Forest fires in Siberia were highly enhanced in 1998. To assess the influence of these forest fires, air masses from Siberia (from the North/Northwest direction) are divided into two categories: those that passed over the forest-fire region in Siberia and those that did not. This is done using AVHRR/NOAA satellite data and isentropic backward trajectories. The average CO concentration difference between these two categories is about 30 ppbv in May. Similar analysis for ozone data also shows concentrations about 7 ppbv higher for the air masses that passed over the forest-fire region in Siberia. These results suggest that air pollutants emitted by forest fires in Siberia in 1998 could be transported and influence the air at Happo in springtime.
Keywords: Biomass burning; Ozone; Backward trajectory; Long-range transport; East Asia;

Area of representativeness (AR) of atmospheric aerosol measurements and horizontal dimensions of a cloud of particles are estimated by time series of aerosol particle size number spectrum measured simultaneously at two locations. The distances between sampling points are varied, 7, 30, 50, 100 or 375 km. The spectrum in form of 12 fraction concentrations is measured every 10 or 15 min during five 2–4 week measurement campaigns in Estonia. During one measurement campaign one measurement point was in Estonia (Tahkuse) and the other in Finland (Hyytiälä). Two electrical aerosol spectrometers (EAS) designed at University of Tartu, having diameter range 10 nm–10 μm, were used. At Hyytiälä, the particle size spectrum (d=3–500  nm ) was measured by two Hauke type differential mobility analysers (DMA). The transport of the submicron fraction (d=60  nm–1  μm ) of atmospheric aerosol is investigated during the time intervals when an air mass moves from the one measurement point towards the other or crosswise to this direction. Sample cross-correlation functions (SCCF) are calculated between prewhitened time series. The time lag corresponding to the mode of these functions are found to be 3–5 h for upwind–downwind case and zero for crosswind case. This time lag should indicate the mean time of pollution transport for upwind–downwind case. A certain minimal distance between sampling points should exist, when statistically significant correlation between the time series cannot be found. Considering this circumstance, the half-width of the AR is estimated. It is found to be more than 100 km but less than 375 km when the sampling points are located on the same line with the wind direction; and more than 50 km but less than 100 km when the sampling points are located on a straight line crosswise to the wind direction. The pollutant concentrations in the limits of AR are estimated by regression analysis. To support these results, the dispersion calculations by HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectories) model are used.
Keywords: Aerosol spectrum; Long range transport; Cross-correlation; Area of representativeness; HYSPLIT;