Presence of alkyllead in rural and urban air: Evaluation of some sources of alkyllead pollution of the atmosphere in Norway

Concentrations of alkyllead in ambient air were measured, as well as in car exhaust and in gasoline vapours. In Oslo the concentration in air ranged from 0.010 to 0.100 μg Pb m⁻³, and these values were compared to the concentrations (< 0.001 μg Pb m⁻³) measured in a low traffic rural area of Norway. The amount of alkyllead in car exhaust varied between 0.1 and 15 μg Pb m⁻³, which was between 0.01 and 0.5% of the amount of inorganic lead in exhaust. Evaporation of alkyllead from parked cars was estimated at 0.5 mg Pb per day per car. The concentrations of alkyllead in saturated gasoline vapour were found to be 10–20 mg Pb m⁻³ at ambient air temperatures.     

An experimental study of the dry deposition of gaseous nitric acid to snow

A chamber placed in a constant temperature freezing room was used to study the surface resistance during deposition of HNO₃ to a snow surface. The resistance decreased with increasing temperature from larger than 5 s mm⁻¹ at − 18°C to about l s mm⁻¹ at −3°C. Measurements of gaseous and particulate nitrate concentrations during winter at a rural site in south central Sweden gave concentrations in the range of 0.4–5 μg HNO₃ m⁻¹ and 0.3–3 μg NO⁻₃ m⁻³ with a mean value of 1.3 μg HNO₃ m⁻³ and 0.7 μg NO⁻₃ m⁻³, respectively. The results indicate that for periods with temperatures below − 2°C estimated dry deposition of HNO₃ to snow is at most 4 % of measured wet deposition of nitrate in the area.     

The relationship between dimethyl sulfide and particulate sulfate in the mid-atlantic ocean atmosphere

Dimethyl sulfide (DMS) and atmospheric aerosols were sampled simultaneously over the Atlantic Ocean in the vicinity of Bermuda using the NOAA King Air research aircraft. Total and fine (50% cutoff at 2 μm diameter) aerosol fractions were sampled using two independent systems. The average nonsea-salt (nss)SO₄²⁻ concentrations were 1.9 and 1.0 μg m⁻³ (as SO₄²⁻) for the total and the fine fractions in the boundary layer (BL) and 0.53 and 0.27 μg m⁻³ in the free troposphere (FT). Non-sea-salt SO₄²⁻ in the two aerosol fractions were highly correlated (r = 0.90), however a smaller percentage (55%) was found in the fine aerosol near Bermuda relative to that (90%) near the North American continent. The BL SO₄²⁻ concentrations measured in this study were higher than those measured by others at remote marine locations despite the fact that the 7-day air mass back trajectories indicated little or no continental contact at altitudes of 700 mb and below; the trajectories were over subtropical oceanic areas that are expected to be rich in DMS. DMS concentrations were higher near the ocean surface and decreased with increasing altitude within the BL; the average DMS concentration was 0.13 μg m⁻³. Trace levels of DMS were also measured in the FT (0.01 μg m⁻³). Computer simultation of the oxidation and removal of DMS in the marine atmosphere suggests that <50% of the SO₄²⁻ observed could be related to the natural S cycle.     

Washout ratios of nitrate,non-sea-salt sulfate and sea-salt on Virginia key,Florida and on American Samoa

On Virginia Key, Miami, Florida, 257 rainwater samples were collected on a event basis from May 1982 to April 1985. At the same site, 171 aerosol samples were collected throughout 1984. All of these samples were analyzed for nitrate, non-sea-salt (NSS) sulfate and sodium to assess the temporal variations in the concentrations and to determine the washout ratios of each of the constituents. The annual volume-weighted mean concentrations in rainwater are: nitrate—0.51 μg ml⁻¹; NSS sulfate—0.74 μg ml⁻¹; Na—1.93 μg ml⁻¹. Only sodium exhibited a significant seasonal cycle; its concentrations were markedly higher during the winter. In aerosols, the mean concentrations are: nitrate—1.9 μg m⁻³; NSS sulfate—2.8 μg m³; Na—3.7 μg m⁻³. Nitrate and NSS sulfate exhibit consistent seasonal cycles with concentrations being significantly higher during the winter and spring. We estimate that wet deposition accounts for the majority of the total fluxes of each constituent: 80% for nitrate, 95 % for NSS sulfate, and 67% for Na. Annual washout ratios at Virginia Key arc similar for nitrate and NSS sulfate, 330 and 290, respectively. That for Na is about a factor of two higher, 550. Comparable long-term ratios were calculated for American Samoa based on aerosol data from the SEAREX program and rainwater data from the National Atmospheric Deposition Program: 270 for nitrate, 420 for NSS sulfate, and 520 for Na. The comparability of the Virginia Key and Samoa results suggest that these ratios may be applicable over a wide area of the world ocean. Estimates from nonconcurrent data for the washout ratios at Bermuda were factors of two to four higher. Regression equations for washout ratio vs event rainfall (logW = loga + blogR) at Virginia Key were essentially the same for all three constituents with ‘a’ ranging from 1100 to 1300 and ‘b’ ranging from −0.26 to −0.29. The coefficients for American Samoa were markedly different: ‘a’ ranged from 2900 to 3600 and ‘b’ ranged from −0.51 to −0.56.     

Development of a modified factor analysis/multiple regression model to apportion suspended particulate matter in a complex urban airshed

A modified factor analysis/multiple regression (FA/MR) receptor-oriented source apportionment model has been developed which permits application of FA/MR statistical methods when some of the tracers are not unique to an individual source type. The new method uses factor and regression analyses to apportion non-unique tracer ambient concentrations in situations where there are unique tracers for all sources contributing to the non-unique tracer except one, and ascribes the residual concentration to that source. This value is then used as the source tracer in the final FA/MR apportionment model for ambient paniculate matter. In addition, factor analyses results are complemented with examination of regression residuals in order to optimize the number of identifiable sources.The new method has been applied to identify and apportion the sources of inhalable particulate matter (IPM; D₅₀15 μm), Pb and Fe at a site in Newark, NJ. The model indicated that sulfate/secondary aerosol contributed an average of 25.8 μ⁻³ (48%) to IPM concentrations, followed by soil resuspension (8.2 μ⁻³ or 15%), paint spraying/paint pigment (6.7/gmm⁻³or 13%), fuel oil burning/space heating (4.3 μ⁻³ or 8 %), industrial emissions (3.6 μm⁻³ or 7 %) and motor vehicle exhaust (2.7 μ⁻³ or 15 %). Contributions to ambient Pb concentrations were: motor vehicle exhaust (0.16μm⁻³or 36%), soil resuspension (0.10μm⁻³ or 24%), fuel oil burning/space heating (0.08μm⁻³or 18%), industrial emissions (0.07 μ⁻³ or 17 %), paint spraying/paint pigment (0.036 μm⁻³or 9 %) and zinc related sources (0.022 μ⁻³ or 5 %). Contributions to ambient Fe concentrations were: soil resuspension (0.43μ⁻³or 51%), paint spraying/paint pigment (0.28 μm⁻³or 33 %) and industrial emissions (0.15 μ⁻³or 18 %). The models were validated by comparing partial source profiles calculated from modeling results with the corresponding published source emissions composition.     

Identification of haze-creating sources from fine particulate matter in Dhaka aerosol using carbon fractions

Fine particulate matter (PM_2.5) samples were simultaneously collected on Teflon and quartz filters between February 2010 and February 2011 at an urban monitoring site (CAMS2) in Dhaka, Bangladesh. The samples were collected using AirMetrics MiniVol samplers. The samples on Teflon filters were analyzed for their elemental composition by PIXE and PESA. Particulate carbon on quartz filters was analyzed using the IMPROVE thermal optical reflectance (TOR) method that divides carbon into four organic carbons (OC), pyrolized organic carbon (OP), and three elemental carbon (EC) fractions. The data were analyzed by positive matrix factorization using the PMF2 program. Initially, only total OC and total EC were included in the analysis and five sources, including road dust, sea salt and Zn, soil dust, motor vehicles, and brick kilns, were obtained. In the second analysis, the eight carbon fractions (OC1, OC2, OC3, OC4, OP, EC1, EC2, EC3) were included in order to ascertain whether additional source information could be extracted from the data. In this case, it is possible to identify more sources than with only total OC and EC. The motor vehicle source was separated into gasoline and diesel emissions and a fugitive Pb source was identified. Brick kilns contribute 7.9 μg/m³ and 6.0 μg/m³ of OC and EC, respectively, to the fine particulate matter based on the two results. From the estimated mass extinction coefficients and the apportioned source contributions, soil dust, brick kiln, diesel, gasoline, and the Pb sources were found to contribute most strongly to visibility degradation, particularly in the winter.

Implications: Fine particle concentrations in Dhaka, Bangladesh, are very high and cause significant degradation of urban visibility. This work shows that using carbon fraction data from the IMPROVE OC/EC protocol provides improved source apportionment. Soil dust, brick kiln, diesel, gasoline, and the Pb sources contribute strongly to haze, particularly in the winter.     

Comparative analysis of organic and elemental carbon concentrations in carbonaceous aerosols in three European cities

Sampling and analysis of carbonaceous compounds in particulate matter presents a number of difficulties related to artefacts during sampling and to the distinction between organic (OC) and elemental carbon (EC) during analysis. Our study reports on a comparative analysis of OC, EC and WSOC (water-soluble organic carbon) concentrations, as well as sampling artefacts, for PM2.5 aerosol in three European cities (Amsterdam, Barcelona and Ghent) representing Southern and Western European urban environments. Comparability of results was ensured by using a single system for sample analysis from the different sites. OC and EC concentrations were higher in the vicinity of roads, thus having higher levels in Amsterdam (3.9–6.7 and 1.7–1.9 μg m⁻³, respectively) and Barcelona (3.6–6.9 and 1.5–2.6 μg m⁻³) than in Ghent (2.7–5.4 and 0.8–1.2 μg m⁻³). A relatively larger influence of secondary organic aerosols (SOA), as deduced from a larger OC/EC ratio, was observed in Ghent. In absolute sense, WSOC concentrations were similar at the three sites (1.0–2.3 μg m⁻³). Positive artefacts were higher in Southern (11–16% of the OC concentration in Barcelona) than in Western Europe (5–12% in Amsterdam, 5–7% in Ghent). During special episodes, the contribution of carbonaceous aerosols from non-local sources accounted for 67–69% of the OC concentration in Western Europe, and for 44% in Southern Europe.     

PCB in the U.K. environment — A preliminary survey

Data on PCB levels in soil and grass samples from rural and urban locations in the United Kingdom are presented, on a dry weight basis. Average PCB concentrations for rural areas are 8 μg kg⁻¹ in soil (range 1 to 23 μg kg⁻¹) and 9 μg kg⁻¹ in grass (range 7 to 16 μg kg⁻¹); for urban areas, 43 μg kg⁻¹ in soil (range 11 to 141 μg kg⁻¹) and 40 μg kg⁻¹ in grass (one value); for industrial locations, 41 μg kg⁻¹ in soil (range 20 to 67 μg kg⁻¹). The levels fall within the range of values reported for other countries.     

Continuous measurement of particulate and sulfur dioxide concentrations in Junk Bay,Hong Kong

As part of an environmental impact assessment for building a new town in Junk Bay, continuous measurement of SO₂ and particulate concentrations was carried out from October 1981 to June 1982 at three sites in Junk Bay to study the air quality in the area. Flame photometric SO₂ analyzers were used to measure ambient SO₂ level, whereas tape monitors were used to measure the ambient suspended particulate level (in terms of soiling index, or coefficient of haze per 1000 feet). It was found that the mean SO₂ concentrations at the three monitoring sites ranged from 5μg m⁻³ to 35μg m⁻³. Maximum daily values up to about 250 μg m⁻³ and hourly values up to 800 μg m ⁻³ had been recorded on occasion. Comparison of the hourly meteorological data and the hourly SO₂ concentrations in four high-SO₂-level days suggested that the ‘sulfur dioxide episodes’ were all associated with very light wind speeds and local sources. The mean coefficient of haze level in Junk Bay was less than one, which corresponded to very slight particulate pollution.     

Multiple-year black carbon measurements and source apportionment using Delta-C in Rochester,New York

Black carbon (BC), an important component of the atmospheric aerosol, has climatic, environmental, and human health significance. In this study, BC was continuously measured using a two-wavelength aethalometer (370 nm and 880 nm) in Rochester, New York, from January 2007 to December 2010. The monitoring site is adjacent to two major urban highways (I-490 and I-590), where 14% to 21% of the total traffic was heavy-duty diesel vehicles. The annual average BC concentrations were 0.76 μg/m³, 0.67 μg/m³, 0.60 μg/m³, and 0.52 μg/m³ in 2007, 2008, 2009, and 2010, respectively. Positive matrix factorization (PMF) modeling was performed using PM_2.5 elements, sulfate, nitrate, ammonia, elemental carbon (EC), and organic carbon (OC) data from the U.S. Environmental Protection Agency (EPA) speciation network and Delta-C (UVBC_370nm – BC_880nm) data. Delta-C has been previously shown to be a tracer of wood combustion factor. It was used as an input variable in source apportionment models for the first time in this study and was found to play an important role in separating traffic (especially diesel) emissions from wood combustion emissions. The result showed the annual average PM_2.5 concentrations apportioned to diesel emissions in 2007, 2008, 2009, and 2010 were 1.34 μg/m³, 1.25 μg/m³, 1.13 μg/m³, and 0.97 μg/m³, respectively. The BC conditional probability function (CPF) plots show a large contribution from the highway diesel traffic to elevated BC concentrations. The measurements and modeling results suggest an impact of the U.S Environmental Protection Agency (EPA) 2007 Heavy-Duty Highway Rule on the decrease of BC and PM_2.5 concentrations during the study period.

Implications: This study suggests that there was an observable impact of the U.S EPA 2007 Heavy-Duty Highway Rule on the ambient black carbon concentrations in Rochester, New York. Aethalometer Delta-C was used as an input variable in source apportionment models and it allowed the separation of traffic (especially diesel) emissions from wood combustion emissions.     

Gaseous and particulate air pollution in the san gabriel mountains of southern california

In order to assess concentrations and daily patterns of air pollutants at a mountainous site in the South Coast Air Basin, a study was undertaken in the San Dimas Experimental Forest of the San Gabriel Mountains between April 1985 and October 1985. Continuous monitoring of O₃, NO, NO₂, SO₂, total S compounds and light scattering coefficient was conducted. Particulate aerosols were collected twice a week and concentrations of nitrate, ammonium and sulfate in fine (< 2.5 μm diameter) and coarse (> 2.5 μm diameter) modes were determined.For the June–August period, when the levels of photochemical smog were the highest, monthly 24-h average concentrations of the pollutants were: O₃, about 200 μg m⁻³; NO₂, 40–75 μg m⁻³; NO, 1–5 μg m ⁻³; and SO₂, 0.5–5 μgm⁻³. The concentrations of O₃ were about two times higher than in the neighboring stations of the South Coast Air Basin. O₃, SO₂ and total S concentrations peaked in the early afternoon, generally between 1500 and 1600 PST. Peak concentrations of NO occurred in the morning, generally between 1000 and 1100 PST. NO₂ concentrations typically peaked in the late afternoon between 1500 and 1800 PST, but occasionally (in 9 % of days) maximum NO₂ occurred in the morning, concurrently with the NO peaks. Daytime concentrations of the nitrate in fine aerosol fraction were generally between 100 and 600 nEq m ⁻³, those of ammonium between 50 and 300 nEq m ⁻³, and concentrations of sulfate between 60 and 250 nEq m⁻³. A 3-day denuder study showed that HNO₃can make up to 73 % of the total amount of total nitrate in the air. NO₂ was the most abundant N compound at Tan bark Flat (69–86% of the total amount of the monitored N compounds). Nitrate amounted to 9–15 %, HNO₃ to 4–11 %, ammonium to 3–9%, and NO to 1–2% of the total amount of the measured nitrogen compounds.     

Background levels of air and precipitation quality for Europe

This paper is intended to be used by specialists engaged in air and precipitation quality management on regional and continental scales. Major goals are to establish definition, methodology and specific values of background air and precipitation quality for sulfur (S) and nitrogen (N) species to be used in practical applications of air resources management. Major findings are the following:

• 1.(a) 69% of SO₂ and 63 % of NO₂ concentration over Europe originate from continental scale anthropogenic sources,
• 2.(b) 15% of precipitation sulfate and 11% of precipitation nitrate over Europe are contributed by hemispheric background,
• 3.(c) hemispheric background pollution values for Europe were found as 1.25 μg (SO₂-S)m⁻³, 0.80 μg (SO₄²⁻-S)m⁻³, 0.157 mg (SO₄²⁻-S)l⁻¹ and 0.04 mg (NO₃⁻-N)ℓ⁻¹.

     

PM10 concentration levels at an urban and background site in Cyprus: The impact of urban sources and dust storms

Air quality in Cyprus is influenced by both local and transported pollution, including desert dust storms. We examined PM₁₀ concentration data collected in Nicosia (urban representative) from April 1, 1993, through December 11, 2008, and in Ayia Marina (rural background representative) from January 1, 1999, through December 31, 2008. Measurements were conducted using a Tapered Element Oscillating Micro-balance (TEOM). PM₁₀ concentrations, meteorological records, and satellite data were used to identify dust storm days. We investigated long-term trends using a Generalized Additive Model (GAM) after controlling for day of week, month, temperature, wind speed, and relative humidity. In Nicosia, annual PM₁₀ concentrations ranged from 50.4 to 63.8 μg/m³ and exceeded the EU annual standard limit enacted in 2005 of 40 μg/m³ every year. A large, statistically significant impact of urban sources (defined as the difference between urban and background levels) was seen in Nicosia over the period 2000–2008, and was highest during traffic hours, weekdays, cold months, and low wind conditions. Our estimate of the mean (standard error) contribution of urban sources to the daily ambient PM₁₀ was 24.0 (0.4) μg/m³. The study of yearly trends showed that PM₁₀ levels in Nicosia decreased from 59.4 μg/m³ in 1993 to 49.0 μg/m³ in 2008, probably in part as a result of traffic emission control policies in Cyprus. In Ayia Marina, annual concentrations ranged from 27.3 to 35.6 μg/m³, and no obvious time trends were observed. The levels measured at the Cyprus background site are comparable to background concentrations reported in other Eastern Mediterranean countries. Average daily PM₁₀ concentrations during desert dust storms were around 100 μg/m³ since 2000 and much higher in earlier years. Despite the large impact of dust storms and their increasing frequency over time, dust storms were responsible for a small fraction of the exceedances of the daily PM₁₀ limit.

ImplicationsThis paper examines PM₁₀ concentrations in Nicosia, Cyprus, from 1993 to 2008. The decrease in PM₁₀ levels in Nicosia suggests that the implementation of traffic emission control policies in Cyprus has been effective. However, particle levels still exceeded the European Union annual standard, and dust storms were responsible for a small fraction of the daily PM₁₀ limit exceedances. Other natural particles that are not assessed in this study, such as resuspended soil and sea salt, may be responsible in part for the high particle levels.     

Attainment Flip-Flops and the Achievability of the Ozone Air Quality Standard

Abstract

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 μm (PM₁₀) and fine PM with aerodynamic diameter of less than 2.5 μm (PM_2.5) ranged from 32.2 to 76.6 μg m^-3 and 11.1 to 23.7 μg m^-3, respectively. OC (34%), SO₄ ⁼ (25.1%), EC (12.9%), and geological material (12.5%) were the major components of PM_2.5. For PM₁₀, geological material (57.9%), OC (17.3%), and SO₄ ⁼ (9.7%) were the major components. Coarse fraction (PM₁₀ –PM_2.5), geological material (81.7%), and OC (8.6%) were the dominant species, which amounted to 90.4%. Correlation analysis showed that sulfate in PM_2.5 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 PM_2.5 mass concentrations were similar to the submicron fraction concentrations. Furthermore, the correlation between EC in PM_2.5 and EC measured from an aethalometer was r² = 0.710. Temporal variations of SO₂ and nitrogen oxide were observed during a day when the maximum concentration of PM_2.5 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 μm.     

Urban impacts on regional carbonaceous aerosols: Case study in central Texas

Rural and background sites provide valuable information on the concentration and optical properties of organic, elemental, and water-soluble organic carbon (OC, EC, and WSOC), which are relevant for understanding the climate forcing potential of regional atmospheric aerosols. To quantify climate- and air quality-relevant characteristics of carbonaceous aerosol in the central United States, a regional background site in central Texas was chosen for long-term measurement. Back trajectory (BT) analysis, ambient OC, EC, and WSOC concentrations and absorption parameters are reported for the first 15 months of a long-term campaign (May 2011–August 2012). BT analysis indicates consistent north–south airflow connecting central Texas to the Central Plains. Central Texas aerosols exhibited seasonal trends with increased fine particulate matter (<2.5 μm aerodynamic diameter, PM_2.5) and OC during the summer (PM_2.5 = 10.9 μg m^?3 and OC = 3.0 μg m^?3) and elevated EC during the winter (0.22 μg m^?3). When compared to measurements in Dallas and Houston, TX, central Texas OC appears to have mixed urban and rural sources. However, central Texas EC appears to be dominated by transport of urban emissions. WSOC averaged 63% of the annual OC, with little seasonal variability in this ratio. To monitor brown carbon (BrC), absorption was measured for the aqueous WSOC extracts. Light absorption coefficients for EC and BrC were highest during summer (EC MAC = 11 m² g^?1 and BRC MAE₃₆₅ = 0.15 m² g^?1). Results from optical analysis indicate that regional aerosol absorption is mostly due to EC with summertime peaks in BrC attenuation. This study represents the first reported values of WSOC absorption, MAE₃₆₅, for the central United States.

Implications:Background concentration and absorption measurements are essential in determining regional potential radiative forcing due to atmospheric aerosols. Back trajectory, chemical, and optical analysis of PM_2.5 was used to determine climatic and air quality implications of urban outflow to a regional receptor site, representative of the central United States. Results indicate that central Texas organic carbon has mixed urban and rural sources, while elemental carbon is controlled by the transport of urban emissions. Analysis of aerosol absorption showed black carbon as the dominant absorber, with less brown carbon absorption than regional studies in California and the southeastern United States.     

Size-resolved sulfate and ammonium measurements in marine boundary layer over the North and South Pacific

Marine background levels of non-sea-salt- (nss-) SO₄²⁻ (5.0–9.7 neq m⁻³), NH₄⁺ (2.1–4.4 neq m⁻³) and elemental carbon (EC) (40–80 ngC m⁻³) in aerosol samples were measured over the equatorial and South Pacific during a cruise by the R/V Hakuho-maru from November 2001 to March 2002. High concentrations of nss-SO₄²⁻ (47–94 neq m⁻³), NH₄⁺ (35–94 neq m⁻³) and EC (130–460 ngC m⁻³) were found in the western North Pacific near the coast of the Asian continent under the influence of the Asian winter monsoon. Particle size distributions of ionic components showed that the equivalent concentrations of nss-SO₄²⁻ were balanced with those of NH₄⁺ in the size range of 0.06<D<0.22 μm, whereas the concentration ratios of NH₄⁺ to nss-SO₄²⁻ in the size range of D>0.22 μm were decreased with increase in particle size. We estimated the source contributions of those aerosol components in the marine background air over the equatorial and South Pacific. Biomass burning accounted for the large fraction (80–98% in weight) of EC and the minor fraction (2–4% in weight) of nss-SO₄²⁻. Marine biogenic source accounted for several tens percents of NH₄⁺ and nss-SO₄²⁻. In the accumulation mode, 70% of particle number existed in the size range of 0.1<D<0.2 μm. In the size rage of 0.06<D<0.22 μm, the dominant aerosol component of (NH₄)₂SO₄ would be mainly derived from the marine biogenic sources.     

Polychlorinated biphenyls and particulate organic/elemental carbon in the atmosphere of Chesapeake Bay,USA

Polychlorinated biphenyls (PCBs) and particulate organic/elemental carbon (OC/EC) differ as to sources, but are both elevated in major urban areas leading to loadings of proximate terrestrial and aquatic systems. Because of the dramatic difference in speciation, sources, and sinks of these compunds, gas+particulate phase PCBs and particulate OC/EC were measured in urban Baltimore, MD and over Chesapeake Bay at 4 and 12 h frequencies in July 1997. Gas phase ∑PCBs averaged 1180 pg m⁻³ for Baltimore and 550 pg m⁻³ for northern Chesapeake Bay. PCB homolog distributions in the gas phase differed between the land and over-water sites whereby the trichlorobiphenyls were higher in Baltimore compared to Chesapeake Bay. Autocorrelation analysis yielded a diurnal cycle for gas phase PCBs at Baltimore with the lowest concentrations observed during the day. Particulate organic and elemental carbon constituted 12.4% (17.4% organic matter) and 2.8% of total suspended particles (TSP) in Baltimore, and 15.0% (21.0% organic matter) and 5.3% over the Chesapeake Bay, respectively. Variability in PCB concentrations was not related to the variability in OC/EC concentrations. OC/EC ratios suggest that particulate organic carbon was mostly primary aerosol. Emissions of both classes of compounds into the Baltimore atmosphere and vicinity are major sources to the Bay.     

Benzene exposure in Helsinki,Finland

Personal exposures and microenvironmental concentrations of benzene were measured in the residential indoor, residential outdoor and workplace environments for 201 participants in Helsinki, Finland, as a component of the EXPOLIS-Helsinki study. Median benzene personal exposures were 2.47 (arithmetic standard deviation (ASD)=1.62) μg m⁻³ for non-smokers, 2.89 (ASD=3.26) μg m⁻³ for those exposed to environmental tobacco smoke in any microenvironment and 3.08 (ASD=10.04) μg m⁻³ for active smokers. Median residential indoor benzene concentrations were 3.14 (ASD=1.51) μg m⁻³ and 1.87 (ASD=1.93) μg m⁻³ for environments with and without tobacco smoke, respectively. Median residential outdoor benzene concentrations were 1.51 (ASD=1.11) μg m⁻³ and median workplace benzene concentrations were 3.58 (ASD=1.96) μg m⁻³ and 2.13 (ASD=1.49) μg m⁻³ for environments with and without tobacco smoke, respectively. Multiple step-wise regression identified indoor benzene concentrations as the strongest predictor for personal benzene exposures of those not exposed to tobacco smoke, followed sequentially by time spent in a car, time in the indoor environment, indoor workplace concentrations and time in the home workshop. Relationships between indoor and outdoor microenvironment concentrations and personal exposures showed considerable variation between seasons, due to differences in ventilation patterns of homes in these northern latitudes. Automobile use-related activities were significantly associated with elevated benzene levels in personal and indoor measurements when tobacco smoke was not present, which demonstrates the importance of personal measurements in the assessment of exposure to benzene.     

Background levels of polychlorinated biphenyls in British soils

The concentrations of PCBs in soil samples collected at rural and urban locations in Britain are reported. PCBs were detected in all samples analysed, within the range 2.3 to 444 μg kg⁻¹ (ppb), with a mean concentration of 22.8 μg kg⁻¹ and a median value of 7.2 μg kg⁻¹. A distinct sub-group of samples has a range of 2.3 to 19.2 μg kg⁻¹, with a mean of 7.5 μg kg⁻¹ and a median value of 6.8 μg kg⁻¹. These values are consistent with published data from other industrialised countries. Measurement was carried out using a two stage clean-up of soil extracts, with concentrated sulphuric acid and florisil, followed by gas chromatography and electron capture detection.     

Diesel emissions in Vienna

The aerosol in a non-industrial town normally is dominated by emissions from vehicles. Whereas gasoline-powered cars normally only emit a small amount of particulates, the emission by diesel-powered cars is considerable. The aerosol particles produced by diesel engines consist of graphitic carbon (GC) with attached hydrocarbons (HCs) including also polyaromatic HCs. Therefore the diesel particles can be carcinogenic. Besides diesel vehicles, all other combustion processes are also a source for GC; thus source apportionment of diesel emissions to the GC in the town is difficult.A direct apportionment of diesel emissions has been made possible by marking all the diesel fuel used by the vehicles in Vienna by a normally not occurring and easily detectable substance. All emitted diesel particles thus were marked with the tracer and by analyzing the atmospheric samples for the marking substance we found that the mass concentrations of diesel particles in the atmosphere varied between 5 and 23 μg m⁻³. Busy streets and calm residential areas show less difference in mass concentration than expected. The deposition of diesel particles on the ground has been determined by collecting samples from the road surface. The concentration of the marking substance was below the detection limit before the marking period and a year after the period. During the period when marked diesel fuel was used, the concentrations of the diesel particles settling to the ground was 0.012–0.07 g g⁻¹ of collected dust.A positive correlation between the diesel vehicle density and the sampled mass of diesel vehicles exists. In Vienna we have a background diesel particle concentration of 11 μg m⁻³. This value increases by 5.5 μg m⁻³ per 500 diesel vehicles h⁻¹ passing near the sampling location.The mass fraction of diesel particles of the total aerosol mass varied between 12.2 and 33%; the higher values were found in more remote areas, since diesel particles apparently diffuse easily.Estimates of diesel particle concentration by emission inventory or by using lead concentrations as an indicator for vehicle emissions gave similar values to those obtained in this study.Using available cancer risk data and diesel particle concentration found in this study, 1–2.6 additional lung cancers per 100,000 persons yr⁻¹ breathing diesel emissions in the measured concentration the whole lifetime can be expected.