Characterization of major chemical components of fine particulate matter in North Carolina

This paper presents measurements of daily sampling of fine particulate matter (PM2.5) and its major chemical components at three urban and one rural locations in North Carolina during 2002. At both urban and rural sites, the major insoluble component of PM2.5 is organic matter, and the major soluble components are sulfate (SO4(2-)), ammonium (NH4(+)), and nitrate (NO3(-)). NH4(+) is neutralized mainly by SO4(2-) rather than by NO3(-), except in winter when SO4(2-) concentration is relatively low, whereas NO3(-) concentration is high. The equivalent ratio of NH4(+) to the sum of SO4(2-) and NO3(-) is < 1, suggesting that SO4(2-) and NO3(-) are not completely neutralized by NH4(+). At both rural and urban sites, SO4(2-) concentration displays a maximum in summer and a minimum in winter, whereas NO3(-) displays an opposite seasonal trend. Mass ratio of NO3(-) to SO4(2-) is consistently < 1 at all sites, suggesting that stationary source emissions may play an important role in PM2.5 formation in those areas. Organic carbon and elemental carbon are well correlated at three urban sites although they are poorly correlated at the agriculture site. Other than the daily samples, hourly samples were measured at one urban site. PM2.5 mass concentrations display a peak in early morning, and a second peak in late afternoon. Back trajectory analysis shows that air masses with lower PM2.5 mass content mainly originate from the marine environment or from a continental environment but with a strong subsidence from the upper troposphere. Air masses with high PM2.5 mass concentrations are largely from continental sources. Our study of fine particulate matter and its chemical composition in North Carolina provides crucial information that may be used to determine the efficacy of the new National Ambient Air Quality Standard (NAAQS) for PM fine. Moreover, the gas-to-particle conversion processes provide improved prediction of long-range transport of pollutants and air quality.     

PCDD/Fs and PCBs in ambient air in a highly industrialized city in Northern Italy

Ambient air samples were collected in five locations around a polychlorobiphenyl (PCB) production plant in a highly industrialized city in the north of Italy, for the analysis of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) and PCBs.PCDD/F atmospheric concentrations were lower than those generally detected in urban areas, while PCB concentrations were higher than in urban and industrialized areas in other countries, especially in the locations closest to the plant. To identify source emissions responsible for air pollution we used principal component analysis (PCA) to compare the “fingerprint” of the air in Brescia with some source-related experimental and published data. This analysis showed that the PCDD/F fingerprints were more similar to steel plant emission data, while none of the PCB air patterns were comparable to emission profiles, indicating that different sources are responsible for the concentration of these two pollutants. The highest PCB concentrations detected in the areas closest to the chemical plant are indicative of its impact on the surrounding environment.     

Evidence of enhanced atmospheric ammoniacal nitrogen in Hells Canyon national recreation area: implications for natural and cultural resources

Agriculture releases copious fertilizing pollutants to air sheds and waterways of the northwestern United States. To evaluate threats to natural resources and historic rock paintings in remote Hells Canyon, Oregon and Idaho, deposition of ammonia (NH3), nitrogen oxides (NOx), sulfur dioxide (SO2), and hydrogen sulfide (H2S) at five stations along 60 km of the Snake River valley floor were passively sampled from July 2002 through June 2003, and ozone data and particulate chemistry were obtained from the Interagency Monitoring of Protected Visual Environments (IMPROVE) station at Hells Canyon. NH3 concentrations were high; biweekly averages peaked at 5-19 ppb in spring and summer and the nutrient-laden Snake River is a likely source. Fine particulate ammonium nitrate (NH4NO3) averaged 2.6 microg/m3 during the 20% of worst visibility days with winter drainage of air masses from the Snake River Basin and possibly long distance transport from southern California. Other pollutants were within background ranges. NH3 is corrosive to clay-based pictographs; nitrogen deposition can alter natural biotic communities and terrestrial ecosystem processes at levels reported here.     

Semicontinuous PM2.5 sulfate and nitrate measurements at an urban and a rural location in New York: PMTACS-NY summer 2001 and 2002 campaigns

Several collocated semicontinuous instruments measuring particulate matter with particle sizes < or =2.5 microm (PM2.5) sulfate (SO4(2-)) and nitrate (NO3-) were intercompared during two intensive field campaigns as part of the PM2.5 Technology Assessment and Characterization Study. The summer 2001 urban campaign in Queens, NY, and the summer 2002 rural campaign in upstate New York (Whiteface Mountain) hosted an operation of an Aerosol Mass Spectrometer, Ambient Particulate Sulfate and Nitrate Monitors, a Continuous Ambient Sulfate Monitor, and a Particle-Into-Liquid Sampler with Ion Chromatographs (PILS-IC). These instruments provided near real-time particulate SO4(2-) and NO3- mass concentration data, allowing the study of particulate SO4(2-)/NO3- diurnal patterns and detection of short-term events. Typical particulate SO4(2-) concentrations were comparable at both sites (ranging from 0 to 20 microg/m3), while ambient urban particulate NO3- concentrations ranged from 0 to 11 microg/m3 and rural NO3- concentration was typically less than 1 microg/m3. Results of the intercomparisons of the semicontinuous measurements are presented, as are results of the comparisons between the semicontinuous and time-integrated filter-based measurements. The comparisons at both sites, in most cases, indicated similar performance characteristics. In addition, charge balance calculations, based on major soluble ionic components of atmospheric aerosol from the PILS-IC and the filter measurements, indicated slightly acidic aerosol at both locations.     

Chemical characterization of rainwater at Singapore

A short term study of the chemical composition of rainwater was carried out from November 1999 to October 2000 in Singapore. The rainwater was typically acidic with a mean pH of 4.2. Sulfate was the most abundant ion and comparable to the results reported for other industrialized regions. The concentrations of major ions (NH(4)(+), Ca(2+), K(+), Na(+), Mg(2+), SO(4)(2+), NO(3)(2-), Cl(-), HCOO(-), CH(3)COO(-)) varied monthly. Results show that local meteorological conditions influence the chemical compositions to a significant extent. The pollutants in rainwater were derived from long range and local (industry and traffic) sources.     

Fine and coarse particulate matter chemical characterization in a heavily industrialized city in central Mexico during Winter 2003

This paper presents the results of the first reported study on fine particulate matter (PM) chemical composition at Salamanca, a highly industrialized urban area of Central Mexico. Samples were collected at six sites within the urban area during February and March 2003. Several trace elements, organic carbon (OC), elemental carbon (EC), and six ions were analyzed to characterize aerosols. Average concentrations of PM with aerodynamic diameter of less than 10 microm (PM10) and fine PM with aerodynamic diameter of less than 2.5 microm (PM2.5) ranged from 32.2 to 76.6 [g m(-3) and 11.1 to 23.7 microg m(-3), respectively. OC (34%), SO4= (25.1%), EC (12.9%), and geological material (12.5%) were the major components of PM2.5. For PM10 geological material (57.9%), OC (17.3%), and SO4= (9.7%) were the major components. Coarse fraction (PM,, -PM2.5), geological material (81.7%), and OC (8.6%) were the dominant species, which amounted to 90.4%. Correlation analysis showed that sulfate in PM2.5 was present as ammonium sulfate. Sulfate showed a significant spatial variation with higher concentrations to the north resulting from predominantly southwesterly winds above the surface layer and by major SO2 sources that include a power plant and refinery. At the urban site of Cruz Roja it was observed that PM2.5 mass concentrations were similar to the submicron fraction concentrations. Furthermore, the correlation between EC in PM2.5 and EC measured from an aethalometer was r(2) = 0.710. Temporal variations of SO2 and nitrogen oxide were observed during a day when the maximum concentration of PM2.5 was measured, which was associated with emissions from the nearby refinery and power plant. From cascade impactor measurements, the three measured modes of airborne particles corresponded with diameters of 0.32, 1.8, and 5.6 microm.     

Modeling air quality during the California Regional PM10/PM2.5 Air Quality Study (CPRAQS) using the UCD/CIT source-oriented air quality model – Part III. Regional source apportionment of secondary and total airborne particulate matter

A comprehensive air quality modeling project was carried out to simulate regional source contributions to secondary and total (=primary + secondary) airborne particle concentrations in California's Central Valley. A three-week stagnation episode lasting from December 15, 2000 to January 7, 2001, was chosen for study using the air quality and meteorological data collected during the California Regional PM₁₀/PM_2.5 Air Quality Study (CRPAQS). The UCD/CIT mechanistic air quality model was used with explicit decomposition of the gas phase reaction chemistry to track source contributions to secondary PM. Inert artificial tracers were used with an internal mixture representation to track source contributions to primary PM. Both primary and secondary source apportionment calculations were performed for 15 size fractions ranging from 0.01 to 10 μm particle diameters. Primary and secondary source contributions were resolved for fugitive dust, road dust, diesel engines, catalyst equipped gasoline engines, non-catalyst equipped gasoline engines, wood burning, food cooking, high sulfur fuel combustion, and other anthropogenic sources.Diesel engines were identified as the largest source of secondary nitrate in central California during the study episode, accounting for approximately 40% of the total PM_2.5 nitrate. Catalyst equipped gasoline engines were also significant, contributing approximately 20% of the total secondary PM_2.5 nitrate. Agricultural sources were the dominant source of secondary ammonium ion. Sharp gradients of PM concentrations were predicted around major urban areas. The relative source contributions to PM_2.5 from each source category in urban areas differ from those in rural areas, due to the dominance of primary OC in urban locations and secondary nitrate in the rural areas. The source contributions to ultra-fine particle mass PM_0.1 also show clear urban/rural differences. Wood smoke was found to be the major source of PM_0.1 in urban areas while motor vehicle sources were the major contributor of PM_0.1 in rural areas, reflecting the influence from two major highways that transect the Valley.     

Bulk deposition in a rural area located around a large coal-fired power station, northeast Spain

This work focuses on bulk deposition in a rural area located around a large coal-fired power station in northeast Spain. Deposition chemistry was characterised by high concentrations of SO(4)(2-), Ca(2+) and NH(4)(+), which were relatively high when compared with other rural areas. Monthly bulk deposition evolution of major ions was the result of two superimposed patterns: one pattern related to the volume of precipitation and the other showed the seasonal influence of the major ionic sources. A major local origin was attributed to bulk deposition of SO(4)(2-), NH(4)(+), and Ca(2+), whereas a relatively higher contribution of an external source was deduced for NO(3)(-), Na(+) and Cl(-). The SO(4)(2-) concentrations showed a significant correlation with the local SO(2) emissions. High levels of Ca(2+) were due to the high alkalinity of soils in the study area, although an external origin was attributed to the frequent air mass intrusions from the Sahara. Sources of NH(4)(+) were related to intensive livestock farming in the area. Total suspended particles exert a marked influence over bulk deposition and neutralisation. Thus, despite the high emissions of SO(2) in the area, neutral pH values have always been attained given that the concentrations of Ca(2+) and NH(4)(+) account for the total neutralisation of NO(3)(-) and SO(4)(2-).     

Chemical composition of fogwater in an urban area: Strasbourg (France)

To investigate the acidity and to identify the predominant compounds, this work presents the chemical analysis of 18 fogwater samples collected during the year 1991 in Strasbourg, in the east of France. For each fog event, two droplet size categories (2-6 microm and 5-8 microm) have been separately collected and 16 ionic components have been analysed. These two fraction sizes were chosen because they correspond approximately to the size range that can penetrate the human lung and they may have possible health effects. The dominant species were NH4+, NO3-, SO4(2-) and Cl-, with a maximum level of 12,640, 17,270, 21,620 and 13,540 microeq litre(-1), respectively. For most of the fog events the highest concentrations of all analysed species were observed in the 2-6 microm droplets. pH values ranged between 2.79 and 5.70 and the fogwater acidity was governed by three strong acids, H2SO4, HNO3 and HCl and was partially neutralised by NH3 and probably by the presence of CaCO3 in the 'loess', which is the major constituent of soils in the upper Rhine valley. In other respects the acetate/formate ratio (methanoate/ethanoate), generally lower than 1, indicates an important pollution due to automobile exhaust, although the Pb concentrations are moderate due to the general use of unleaded gasoline in France since 1989.     

Airborne cadmium in the major monitoring locations in Korea between 1991 and 2004

Air quality monitoring data for cadmium (Cd) collected in 13 cities in Korea over a 14-year period (1991–2004) have been analyzed. In the course of this study, variation of Cd was examined over time and with location to learn about its sources, transport, and removal processes and to help improve air quality control. The results of this study indicate that the spatial distribution of Cd is clearly distinguishable between different cities and that such a pattern is sensitively reflected by such a factor as the level of industrialization. Comparison of the Cd data sets between different cities indicated that its concentration levels observed in highly industrialized cities approached or exceeded 10 ng m⁻³, while those of urban background cities were found to lie in a narrow range of 1–3 ng m⁻³. As such, Cd values determined from the polluted areas were notably higher than the relatively clean ones, at least by several times. The Cd data collected from all study sites were also evaluated with respect to temporal behavior. Inspection of seasonal patterns generally showed the occurrences of the highest Cd value during spring (and winter) and the lowest one during summer. When the long-term pattern of Cd was assessed across all study years, the results differed greatly between different cities in relation to their pollution status. Although Cd concentrations tended to decrease rather abruptly in highly industrialized cities, its patterns for most cities were too variable to project a definitive trend. The results of this analysis thus suggest that Cd concentration levels in most urban areas of Korea are fairly comparable with those commonly seen in the urban background areas of western countries. Considering that most urban areas are affected by various pollution sources and that Cd concentrations have been reduced significantly through the years, more deliberate efforts are needed to further control Cd concentrations in the atmosphere.     

Source identification of atlanta aerosol by positive matrix factorization

Data characterizing daily integrated particulate matter (PM) samples collected at the Jefferson Street monitoring site in Atlanta, GA, were analyzed through the application of a bilinear positive matrix factorization (PMF) model. A total of 662 samples and 26 variables were used for fine particle (particles < or = 2.5 microm in aerodynamic diameter) samples (PM2.5), and 685 samples and 15 variables were used for coarse particle (particles between 2.5 and 10 microm in aerodynamic diameter) samples (PM10-2.5). Measured PM mass concentrations and compositional data were used as independent variables. To obtain the quantitative contributions for each source, the factors were normalized using PMF-apportioned mass concentrations. For fine particle data, eight sources were identified: SO4(2-) -rich secondary aerosol (56%), motor vehicle (22%), wood smoke (11%), NO(3-) -rich secondary aerosol (7%), mixed source of cement kiln and organic carbon (OC) (2%), airborne soil (1%), metal recycling facility (0.5%), and mixed source of bus station and metal processing (0.3%). The SO4(2-) -rich and NO(3-) -rich secondary aerosols were associated with NH(4+). The SO4(2-) -rich secondary aerosols also included OC. For the coarse particle data, five sources contributed to the observed mass: airborne soil (60%), NO(3-)-rich secondary aerosol (16%), SO4(2-) -rich secondary aerosol (12%), cement kiln (11%), and metal recycling facility (1%). Conditional probability functions were computed using surface wind data and identified mass contributions from each source. The results of this analysis agreed well with the locations of known local point sources.     

Particulate matter in California: part 2--Spatial, temporal, and compositional patterns of PM2.5, PM10-2.5, and PM10

Geographic and temporal variations in the concentration and composition of particulate matter (PM) provide important insights into particle sources, atmospheric processes that influence particle formation, and PM management strategies. In the nonurban areas of California, annual-average PM2.5 and PM10 concentrations range from 3 to 10 microg/m3 and from 5 to 18 microg/m3, respectively. In the urban areas of California, annual-averages for PM2.5 range from 7 to 30 microg/m3, with observed 24-hr peaks reaching levels as high as 160 microg/m3. Within each air basin, exceedances are a mixture of isolated events as well as periods of elevated PM2.5 concentrations that are more prolonged and regional in nature. PM2.5 concentrations are generally highest during the winter months. The exception is the South Coast Air Basin, where fairly high values occur throughout the year. Annual-average PM2.5 mass, as well as the concentrations of major components, declined from 1988 to 2000. The declines are especially pronounced for the sulfate (SO4(2-)) and nitrate (NO3-) components of PM2.5 and PM10) and correlate with reductions in ambient levels of oxides of sulfur (SOx) and oxides of nitrogen (NOx). Annual averages for PM10-2.5 and PM10 exhibited similar downwind trends from 1994 to 1999, with a slightly less pronounced decrease in the coarse fraction.     

Ionic composition of wet precipitation over the southern slope of central Himalayas,Nepal

Severe atmospheric pollution transported to Himalayas from South Asia may affect fragile ecosystem and can be harmful for human health in the region. In order to understand the atmospheric chemistry in the southern slope of central Himalayas, where the data is limited, precipitation has been sampled at four sites: Kathmandu (1,314 m), Dhunche (2,065 m), Dimsa (3,078 m), and Gosainkunda (4,417 m) in Nepal for over a 1-year period characterized by an urban, rural, and remote sites, respectively. HCO₃ ^? is the dominant anion, while the NH₄ ⁺ is the dominant cation in precipitation at the four sites. Generally, most of ions (e.g., SO₄ ^2?, NO₃ ^?, NH₄ ⁺, HCO₃ ^?, and Ca²⁺) have higher concentrations in urban site compared to the rural sites. Neutralization factor calculation showed that precipitation in the region is highly neutralized by NH₄ ⁺ and Ca²⁺. Empirical orthogonal function and correlation analysis indicated that the precipitation chemistry was mostly influenced by crustal, anthropogenic, and marine sources in Nepal. Among different sites, urban area was mostly influenced by anthropogenic inputs and crustal dusts, whereas remote sites were mostly from marine and crustal sources. Seasonal variations show higher ionic concentrations during non-monsoon seasons mainly due to limited precipitation amount. On the other hand, lower ionic concentrations were observed during monsoon season when higher amount of precipitation washes out aerosols. Thus, precipitation chemistry from this work can provide a useful database to evaluate atmospheric environment and its impacts on ecosystem in the southern slope of central Himalayas, Nepal.     

Simulated seasonal variations in wet acid depositions over East Asia

The air quality modeling system Regional Atmospheric Modeling System-Community Multi-scale Air Quality (RAMS-CMAQ) was applied to analyze temporospatial variations in wet acid deposition over East Asia in 2005, and model results obtained on a monthly basis were evaluated against extensive observations, including precipitation amounts at 704 stations and SO4(2-), NO3-, and NH4+ concentrations in the atmosphere and rainwater at 18 EANET (the Acid Deposition Monitoring Network in East Asia) stations. The comparison shows that the modeling system can reasonably reproduce seasonal precipitation patterns, especially the extensive area of dry conditions in northeast China and north China and the major precipitation zones. For ambient concentrations and wet depositions, the simulated results are in reasonable agreement (within a factor of 2) with observations in most cases, and the major observed features are mostly well reproduced. The analysis of modeled wet deposition distributions indicates that East Asia experiences noticeable variations in its wet deposition patterns throughout the year. In winter, southern China and the coastal areas of the Japan Sea report higher S04(2-) and NO3- wet depositions. In spring, elevated SO4(2-) and NO3-wet depositions are found in northeastern China, southern China, and around the Yangtze River. In summer, a remarkable rise in precipitation in northeastern China, the valleys of the Huaihe and Yangtze rivers, Korea, and Japan leads to a noticeable increase in SO4(2-) and NO3- wet depositions, whereas in autumn, higher SO4(2-) and NO3-wet depositions are found around Sichuan Province. Meanwhile, due to the high emission of SO2, high wet depositions of SO4(2-) are found throughout the entire year in the area surrounding Sichuan Province. There is a tendency toward decreasing NO3- concentrations in rainwater from China through Korea to Japan in both observed and simulated results, which is a consequence of the influence of the continental outflow from Eurasia. The same tendency is not found for SO4(2-).     

Regional variations in sulfate and nitrate on annual, seasonal, and synoptic time scales

Ambient data from Interagency Monitoring of Protected Visual Environments (IMPROVE) monitors are analyzed to evaluate the spatial structure of SO4 and NO3 aerosols in the mid-Atlantic region. Sub-weekly, seasonal, and annual data values are compared between the IMPROVE Washington, DC, site and three rural sites. Synoptic perturbations are compared between sites to quantify similarities in short-term temporal perturbations of SO4 and NO3. Based on these comparisons between the rural and urban IMPROVE monitors, the spatial structure of SO4 shows broad regional homogeneity that is recognizable from both the long-term average values and the short-term variations. NO3 data on a seasonal and annual basis show much larger spatial gradients between the urban Washington monitor and the three rural monitors than do SO4 data. Short-term NO3 perturbations at the three rural monitors also differ significantly from those at the Washington site. These dissimilarities in NO3 levels between the rural and urban IMPROVE monitors on both short-term and longer-term time scales indicate little homogeneity of NO3 aerosols in the mid-Atlantic region considered here. The volatility of NO3 aerosols and the removal rate of HNO3 via dry deposition could contribute to the spatial variability differences shown here between SO4 and NO3.     

Urban-Center CO Air Quality Projections

The distribution of mutagenic activity and nitroaromatic components of polycyclic organic matter (POM) in ambient air at industrial, urban, suburban, rural, and remote sites was studied using organic extracts from high volume aerosol samples. Direct-acting mutagens including 1-nitropyrene (1-NP), dinitropyrenes (DNP), and hydroxynitropyrenes (HNP) were measured by high performance liquid chromatography while the mutagenicity was determined in the Salmonella bioassay with strain TA-98. Benzo(a)pyrene (BaP), one of the possible precursors of nitroaromatic compounds in POM, was also measured. In comparing samples from a range of sites, TSP and the concentration of BaP per mass of particulate matter decreased, as expected, at greater distances from urban and industrial combustion sources. However, the concentrations of polar nitroaromatic POM compounds per mass of particles were higher at a remote site than in nonindustrial urban and suburban areas. The mutagenicity in particulate matter extracts from the remote area was predominantly (>90 percent) in the very polar fractions. There were also high atmospheric levels of nitroaromatic compounds and mutagenicity in heavily industrialized areas. These observations may reflect the influences of source emissions, atmospheric transformations of POM compounds, and ther atmospheric processes on the composition of ambient suspended particulate matter.     

Heterogeneous response of central European streams to decreased acidic atmospheric deposition

We investigated the relations between mountain streamwater chemistry and atmospheric pollution in an arca of 1611 km2 of the Czech Republic by comparing concentrations of SO4. NO3, Cl, Ca and the pH at 432 localities at the time of high (1984-1986) and relatively low (1996-2000) acidic atmospheric deposition. Medians of Cl. SO4, and NO3 decreased by 17, 96 and 60 microeq l(-1), or by 23, 17 and 49%, respectively, during 12 +/- 2 years. The decreased Cl corresponds to decreased emission of industrial Cl (as HCl). The decreased stream SO4 was proportionally lower than the 71% decrease in S-emissions due to leaching of previously accumulated SO4 from soils and non-zero background concentrations. Decreases of NO3 up to 60% in streamwaters with pH < or = 6 was greater than the decrease of N emission in central Europe, about 35%. Extensive regional decrease of NO3 is surprising and is probably described for the first time. The difference in NO3 concentrations between the two periods was probably enhanced by (a) an increase of mineralisation of forest floor in the mid-1980s and (b) by higher uptake of N in the late-1990s. The median pH of the 432 streams did not change but the pH of the sub-population with pH < 6 in the mid-1980s recovered substantially. The pH of circum-neutral streams (pH > 6.5) decreased even as acidic atmospheric deposition decreased.     

NO2 and SO2 dispersion modeling and relative roles of emission sources over Map Ta Phut industrial area, Thailand

Map Ta Phut industrial area (MA) is the largest industrial complex in Thailand. There has been concern about many air pollutants over this area. Air quality management for the area is known to be difficult, due to lack of understanding of how emissions from different sources or sectors (e.g., industrial, power plant, transportation, and residential) contribute to air quality degradation in the area. In this study, a dispersion study of NO2 and SO2 was conducted using the AERMOD model. The area-specific emission inventories of NOx and SO2 were prepared, including both stack and nonstack sources, and divided into 11 emission groups. Annual simulations were performed for the year 2006. Modeled concentrations were evaluated with observations. Underestimation of both pollutants was Jbund, and stack emission estimates were scaled to improve the modeled results before quantifying relative roles of individual emission groups to ambient concentration overfour selected impacted areas (two are residential and the others are highly industrialized). Two concentration measures (i.e., annual average area-wide concentration or AC, and area-wide robust highest concentration or AR) were used to aggregately represent mean and high-end concentrations Jbfor each individual area, respectively. For AC-NO2, on-road mobile emissions were found to be the largest contributor in the two residential areas (36-38% of total AC-NO2), while petrochemical-industry emissions play the most important role in the two industrialized areas (34-51%). For AR-NO2, biomass burning has the most influence in all impacted areas (>90%) exceptJor one residential area where on-road mobile is the largest (75%). For AC-SO2, the petrochemical industry contributes most in all impacted areas (38-56%). For AR-SO2, the results vary. Since the petrochemical industry was often identified as the major contributor despite not being the largest emitter, air quality workers should pay special attention to this emission group when managing air quality for the MA.     

Concentrations of carbonaceous species in particles at Seoul and Cheju in Korea

Concentrations of elemental carbon (EC) and organic carbon (OC) in particles at Seoul and Cheju Island, Korea were observed in 1994. PM₁₀ and PM_2.5 were collected by a modified SCAQS (Southern California Air Quality Study) sampler from Seoul during June 1994 and PM_2.5 were collected by a low-volume sampler at Cheju Island during July and August 1994. The selective thermal oxidation method with MnO₂ catalyst was used for analysis. The EC concentrations from Seoul were higher than those at Los Angeles, USA during the SCAQS study while the OC concentrations were comparable to those during the SCAQS study. At Cheju Island, the OC concentrations were higher than those at other clean areas in the world but the EC concentrations were lower than or comparable to those at other clean areas in the world. The OC to EC ratios of Seoul suggest that the carbonaceous species are mostly from primary emission sources. In Cheju, during July 1994 air pollutant levels were high and it was suggested that atmospheric transformation/transport of organics and biogenic emissions were main sources of carbonaceous species in particles. The carbonaceous species levels were low during August 1994 and it was suggested that the levels could be considered as marine background concentrations in the region during summer.     

Precipitation chemistry in the coast of the Metropolitan Region of Rio de Janeiro, Brazil

Precipitation chemistry was studied in the Metropolitan Region of Rio de Janeiro (MRRJ). This study reveals that rainwater in the MRRJ is affected by emissions of air pollutants and provides essential data for future estimates of regional biogeochemical cycles and the impacts of acid deposition on tropical ecosystems. The volume-weighted mean (VWM) pH was 4.77, varying from 3.50 to 6.85. Sea-salt aerosols were the dominant sources of the Na+, Cl- and Mg2+. Excess SO4(2-), Ca2+ and K+ comprised 82, 91, and 87% of their total VWM concentrations, respectively. There were very strong correlations (r > 0.75, P > 0.01) for NO3- and H+, NO3- and excess(exc-)SO4(2-), NH4+ and exc-K+, and exc-SO4(2-) and exc-Ca2+, suggesting causal relationships between these ion pairs. The VWM concentrations of all major ions, except H+, were higher in the dry season, with dry to wet VWM concentration ratios varying from 1.1 (NH4+) to 4.7 (for total K+).