Chemical composition of the fine and coarse fraction of aerosols in the northeastern Mediterranean

Two-stage aerosol samples (PM_10–2.5 and PM_2.5) were collected at a coastal rural site located in the northeastern Mediterranean, between April 2001 and 2002. A total of 562 aerosol samples were analyzed for trace elements (Fe, Ti, Mn, Ca, V, Ni, Zn, Cr) and water-soluble ions (Na⁺, NH₄⁺, K⁺, Mg²⁺, Ca²⁺, Cl⁻, Br⁻, NO₃⁻, SO₄²⁻, C₂O₄²⁻ and MS⁻:methane sulfonate). PM₁₀, crustal elements, sea salt aerosols and NO₃⁻ were mainly associated with the coarse mode whereas non-sea salt (nss)SO₄²⁻, C₂O₄²⁻; MS⁻, NH₄⁺, Cr and Ni were found predominantly in the fine fraction. Concentrations of aerosol species exhibited orders of magnitude change from day to day and the aerosol chemical composition is heavily affected by dust events under the influence of airflow from North Africa. During the sampling period, 11 specific mineral dust events of duration varying from 1 day to a week have been identified and their influence on the chemical composition of aerosols has been studied in detail. Ionic balance analysis performed in the coarse and fine aerosol fractions indicated anion and cation deficiency due to CO₃²⁻ and H⁺, respectively. A relationship between nssSO₄²⁻ and NH₄⁺ denoted that sulfate particles were partially neutralized (70%) by ammonium. Excess-K/BC presented two distinct ratios for winter and summer, indicating two different sources: fossil fuel burning in winter and biomass burning in summer.     

Chemical characterization of particles in winter-night smog in Tokyo

Continuous measurement of PM₁₀, PM_2.5 and carbon (organic, elemental composition) concentrations, and samples of PM₁₀ and PM_2.5 collected on a polycarbonate membrane filter (Nuclepore^®, pore size: 0.8 μm), were carried out during a period from December 1998 to January 1999 at Shinjuku in Tokyo in order to investigate the chemical characterization of particles in winter-night smog within a large area of the Japan Kanto Plain including the Tokyo Metropolitan area. These were measured using an ambient particulate monitor (tapered element oscillating microbalance—TEOM) and a carbon particulate monitor. Elemental compositions in the filter samples of PM₁₀ and PM_2.5 were determined by means of particle-induced X-ray emission (PIXE) analysis. Ionic species (anion: F⁻, Cl⁻, NO₃⁻, SO₄²⁻ and C₂O₄²⁻; cation: Na⁺, NH₄⁺, K⁺, Ca²⁺ and Mg²⁺) in the filter samples were analyzed by ion chromatography. The temporal variation patterns of PM_2.5 were similar to those of PM₁₀ and carbon. PM_2.5 made up 90% of the PM₁₀ at a high concentration, and 70% at a low concentration. Concentrations of 22 elements in both the PM₁₀ and PM_2.5 samples were consistently determined by PIXE, and Na, Mg, Al, Si, S, Cl, K, Ca, Fe, Zn and Pb were found to be the major components. Among these S and Cl were the most dominant elements of the PM_2.5 and PM₁₀ at high concentrations. Ionic species were mainly composed of Cl⁻, NO₃⁻, SO₄²⁻ and NH₄⁺. The component proportion of carbon, the other elements (total amount of measured elements other than S and Cl) and secondary-formed particles of PM_2.5 was similar to that of PM₁₀. The major component was carbon particles at a low concentration and secondary-formed particles at a high concentration. The proportion of NH₄NO₃ and NH₄Cl plus HCl in secondary-formed particles at a high concentration, in particular, was as high as 90%.     

Characterization of the major chemical species in PM2.5 in the Kaohsiung City,Taiwan

The concentrations and characteristics of the major components in ambient fine particles in the urban city of Kaohsiung, Taiwan were measured and evaluated. PM_2.5 samples were collected using a dichotomous sampler from November 1998 to April 1999 and analyzed for water-soluble ion species using ion chromatography and for carbonaceous species using an elemental analyzer. It was found that SO₄²⁻, NO₃⁻, and NH₄⁺ dominated the identifiable components, and occupied 42.2% and 90.0% of PM_2.5 mass and total dissolved ionic concentrations. Carbonaceous species (organic and elemental carbon) accounted for 20.8% of PM_2.5. The secondary aerosol formed through the NO₂/SO₂ gas-to-particle conversion was estimated based on the sulfur/nitrogen oxidation ratio (SOR/NOR), i.e., sulfate sulfur/nitrate nitrogen to total sulfur/total nitrogen. The average SOR and NOR values were 0.25 and 0.07 for PM_2.5. The high SOR and NOR values obtained in this study suggested that there existed a secondary formation of SO₄²⁻ from SO₂ along with NO₃⁻ from NO₂ in the atmosphere. The secondary organic carbon formed through the volatile organic compound gas-to-particle conversion was estimated from the minimum ratio between organic and elemental carbon obtained in this study, and was found to constitute 40.0% of the total organic carbon for PM_2.5 (6.6% of the particle mass). The results obtained in this study suggest that the formation of secondary aerosols due to conversion from gaseous precursors is significant and important in urban locations.     

PM2.5–10, PM2.5 and associated water-soluble inorganic species at a coastal urban site in the metropolitan region of Rio de Janeiro

The concentrations of PM_2.5−10, PM_2.5 and associated water-soluble inorganic species (WSIS) were determined in a coastal site of the metropolitan region of Rio de Janeiro, Southeastern Brazil, from October 1998 to September 1999 (n=50). Samples were dissolved in water and analyzed for major inorganic ions. The mean (± standard deviation; median) concentrations of PM_2.5−10 and PM_2.5 were, respectively, 26 (± 16; 21) μg m⁻³ and 17 (± 13; 14) μg m⁻³. Their mean concentrations were 1.7–1.8 times higher in dry season (May–October) than in rainy season (November–April). The WSIS comprised, respectively, 34% and 28% of the PM_2.5−10 and PM_2.5 masses. Chloride, Na⁺ and Mg²⁺ were the predominant ions in PM_2.5−10, indicating a significant influence of sea-salt aerosols. In PM_2.5, SO₄²⁻ (∼97% nss-SO₄²⁻) and NH₄⁺ were the most abundant ions and their equivalent concentration ratio (SO₄²⁻/NH₄⁺ ∼1.0) suggests that they were present as (NH₄)₂SO₄ particles. The mean concentration of (NH₄)₂SO₄ was 3.4 μg m⁻³. The mean equivalent PM_2.5 NO₃⁻ concentration was eight times smaller than those of SO₄²⁻ and NH₄⁺. The PM_2.5 NO₃⁻ concentration in dry season was three times higher than in rainy season, probably due to reaction of NaCl (sea salt) with HNO₃ as a result of higher levels of NO_y during the dry season and/or reduced volatilization of NH₄NO₃ due to lower wintertime temperature. Chloride depletion was observed in both size ranges, although more pronouncely in PM_2.5.     

Ambient suspended particulate matters and related chemical species study in central Taiwan,Taichung during 1998–2001

Ambient suspended particulate (PM_2.5, PM_2.5–10, TSP) was collected from June 1998 to February 2001 in Taichung, central Taiwan. In addition, the related water-soluble ionic species (Cl⁻, NO₃⁻, SO₄²⁻, Na⁺, NH₄⁺, K⁺, Mg²⁺, Ca²⁺) and metallic species (Fe, Zn, Pb, Ni) were also analyzed in this study. The results showed that the concentrations of particulate mass are higher in the traffic site (CCRT) than the other sampling sites in this study. Also, the fine particle (PM_2.5) concentration is the dominant species of the total suspended particles in Taichung, central Taiwan. The dominant species for PM_2.5 are sulfate and ammonium at all sampling sites during the period of 1998–2001. The results of diurnal variation at THUC sampling site are also discussed in this study. Overall, acidic and secondary aerosol (Cl⁻, NO₃⁻, SO₄²⁻ and NH₄⁺) is a more serious air pollutant issue in southern and central Taiwan than at several sites around the world. Therefore, ambient suspended particulate monitoring in Taichung, central Taiwan will be continuing in our following study to provide more information for the government to formulate environmental strategy.     

Chemical composition of rainwater and anthropogenic influences in the Piracicaba River Basin,Southeast Brazil

The influences of different kinds of anthropogenic activities on rainwater chemistry in a tropical area were studied during one uninterrupted year at Piracicaba River Basin (Southeast Brazil). A total of 272 rainwater samples collected continuously from August 1997 to July 1998 at four different sites were analyzed for F⁻, CH₃COO⁻, HCOO⁻, MSA, Cl⁻, NO₂⁻, Br⁻, NO₃⁻, SO₄²⁻, C₂O₄²⁻, PO₄³⁻, Na⁺, NH₄⁺, K⁺, Mg²⁺, Ca²⁺, DOC (dissolved organic carbon), DIC (dissolved inorganic carbon), pH and conductivity. The most abundant ion was H⁺ and rain acidity was significant at all sampling sites (average pH of 4.4–4.5). The sources of this free acidity differ among sites and appear to be correlated to the different land-uses. The composition of rainwater appeared to be controlled mostly by three sources: soil dust, sugar cane burning and industrial emissions.     

PM2.5 particles and size-segregated ionic species measured during fall season in three urban sites in Korea

Twelve hours integrated fine particles (PM_2.5) and 24-h average size-segregated particles were collected to investigate the chemical characteristics and to determine the size distribution of ionic species during October–December 1999 in three cities of different urban scale; Chongju, Kwangju, and Seoul, Korea. Concentrations of 5-min PM_2.5 black carbon (BC) and hourly criteria air pollutants (PM₁₀, CO, NO_x, SO₂, and O₃) were also measured using the Aethalometer and ambient air monitoring system, respectively.Highest PM_2.5 mass concentrations at Chongju, Kwangju, and Seoul sites were 63.0, 77.9, and 143.7 μg m⁻³, respectively. For the time period when highest PM_2.5 mass occurred, BC level out of PM_2.5 chemical species was highest at both Chongju and Kwangju, and highest NO₃⁻ (23.6 μg m⁻³) followed by BC (23.1 μg m⁻³) were observed at Seoul site, indicating that highest PM_2.5 pollution is closely associated with the traffic emissions. Strong relationships of Fe with BC and Zn at both Kwangju and Seoul sites support that the Fe and Zn measured there are originated partly from same source as BC, i.e. diesel traffics. However, it is suggested that the Fe measured at Chongju is most likely derived from dispersion of soil dust.The size distributions of SO₄²⁻, NO₃⁻, and NH₄⁺ ionic species indicated similar unimodal distributions at all sampling sites. However, different unimodal patterns in the accumulation mode size range with a peak in the smaller size (0.28–0.53 μm, condensation mode) in both Kwangju and Seoul, and in the relatively larger size (0.53–1.0 μm, droplet mode) in Chongju, were found. The potassium ion under the study sites dominates in the fine mode, and its size distribution showed unimodal character with a maximum in the size range 0.56–1.0 μm.     

An automatic rain gauge for continuous,real time determination of rainwater chemistry

An automatic rain gauge has been developed, capable of collecting rainwater and analysing it continuously for the ions H⁺, NH₄⁺, Na⁺, Ca²⁺, NO₃⁻, Cl⁻, SO₄²⁻ and for dissolved H₂O₂. The wet-only rain collector, based on an inverting V-tray arrangement, is mounted on the roof of a small caravan, which contains the analysis equipment. An indirect colorimetric method is used for SO₄²⁻ and a chemiluminescent method for H₂O₂, the other species being determined by ion-selective electrodes. The onset of rain is sensed either by a simple conductivity plate or by a modified float gauge. In addition, equipment is installed to determine simultaneously gas-phase O₃, NO, NO₂ and SO₂ and simple meteorological parameters. Data is recorded on disc by a microcomputer, which also handles automatic calibration and other control functions.The caravan as a whole is a fairly comprehensive, transportable air and rainwater monitoring package. The advantage of the rainwater sampling method is that instantaneous concentrations are measured continuously rather than daily or weekly averages; and that problems of deterioration of stored samples are eliminated.     

The water-soluble ionic composition of PM2.5 in Shanghai and Beijing,China

A year-long field study to characterize the ionic species in PM2.5 was carried out in Shanghai and Beijing, China, in 1999–2000. Weekly samples of PM2.5 were collected using a special low flow rate (0.4 l min⁻¹) sampler. In Shanghai, SO₄²⁻ NO₃⁻ and NH₄⁺ were the dominant ionic species, which accounted for 46%, 18% and 17% of the total mass of ions, respectively. Local SO₂ emissions were an important source of SO₄²⁻ in PM2.5 because the SO₄²⁻ concentration was correlated with the SO₂ concentration (r=0.66). The relatively stable SO₄²⁻/SO₂ mass ratio over a large range of temperatures suggests that gas-phase oxidation of SO₂ played a minor role in the formation of SO₄²⁻. The sum of SO₄²⁻ and NO₃⁻ was highly correlated with NH₄⁺ (r=0.96), but insufficient ammonium was present to totally neutralize the aerosol. In Beijing, SO₄²⁻, NO₃⁻ and NH₄⁺ were also the dominant ionic species, constituting 44%, 25% and 16% of the total mass of water-soluble ions, respectively. Local SO₂ emissions were an important source of SO₄²⁻ in the winter since SO₄²⁻ was correlated with SO₂ (r=0.83). The low-mass SO₄²⁻/SO₂ ratio (0.27) during winter, which had low humidity, suggests that gas-phase oxidation of SO₂ was a major route of sulfate formation. In the summer, however, much higher mass ratios of SO₄²⁻/SO₂ (5.6) were observed and were ascribed to in-cloud sulfate formation. The annual average ratio of NO₃⁻/SO₄²⁻ was 0.4 and 0.6 in Shanghai and in Beijing, respectively, suggesting that stationary emissions were still a dominant source in these two cities.     

Seasonal variations in atmospheric SOx and NOy species in the adirondacks

This paper reports the results of over 2 years of measurements of several of the species comprising atmospheric SO_x (=SO₂+SO₄²⁻) and NO_y (=NO+NO₂ + PAN + HNO₃+NO₃⁻+ organicnitrates + HONO + 2N₂O₅ …) at Whiteface Mountain, New York. Continuous real-time measurements of SO₂ and total gaseous NO_y provided data for about 50% and 65% of the period, respectively, and 122 filter pack samples were obtained for HNO₃, SO₂ and aerosol SO₄²⁻, NO₃⁻, H⁺ and NH₄⁺. Concentrations of SO₂ and NO_y were greatest in winter, whereas concentrations of the reaction products SO₄²⁻ and HNO₃were greatest in summer. The seasonal variation in SO₄²⁻ was considerably more pronounced than that of HNO₃and the high concentrations of SO₄²⁻ aerosol present in summer were also relatively more acidic than SO₄²⁻ aerosol in other seasons. As a result, SO₄²⁻ aerosol was the predominant acidic species present in summer, HNO₃was predominant in other seasons. Aerosol NO₃⁻ concentrations were low in all seasons and appeared unrelated to simultaneous NO_y and HNO₃concentrations. These data are consistent with seasonal variations in photochemical oxidation rates and with existing data on seasonal variations in precipitation composition. The results of this study suggest that emission reductions targeted at the summer season might be a cost-effective way to reduce deposition of S species, but would not be similarly cost-effective in reducing deposition of N species. kwAcid deposition, seasonal variation, sulfate, nitrate, nitric acid, sulfur dioxide, oxides of nitrogen, hydrogen peroxide, ozone, air pollution, Adirondack Mountains     

Deposition of sulphur,nitrogen and acidity in precipitation over Ireland: chemistry,spatial distribution and long-term trends

The chemical composition of pollutant species in precipitation sampled daily or weekly at 10 sites in Ireland for the five-year period, 1994–1998, is presented. Sea salts accounted for 81% of the total ionic concentration. Approximately 50% of the SO₄²⁻ in precipitation was from sea-salt sources. The proportion of sea salts in precipitation decreased sharply eastwards. In contrast, the concentration of NO₃⁻ and the proportion of non-sea-salt SO₄²⁻ increased eastwards reflecting the closer proximity to major emission sources. The mean (mol_c) ratio of SO₄²⁻:NO₃⁻ was 1.6 for all sites, indicating that SO₄²⁻ was the major acid anion.The spatial correlation between SO₄²⁻, NO₃⁻ and NH₄⁺ concentrations in precipitation was statistically significant. The regional trend in NO₃⁻ concentration was best described by linear regression against easting. SO₄²⁻ concentration followed a similar pattern. However, the regression was improved by inclusion of elevation. Inclusion of northing in the regression did not significantly improve any of the relationships except for NH₄⁺, indicating a significant increase in concentrations from northwest to southeast.The spatial distribution of deposition fluxes showed similar gradients increasing from west and southwest to east and northeast. However, the pattern of deposition shows the influence of precipitation volume in determining the overall input. Mean depositions of sulphur and nitrogen in precipitation were ≈30 ktonnes S yr⁻¹ and 48 ktonnes N yr⁻¹ over the five-year period, 1994–1998, for Ireland.Least-squares linear regression analysis indicated a slight decreasing trend in precipitation concentrations for SO₄²⁻ (20%), NO₃⁻ (13%) and H⁺ (24%) and a slight increasing trend for NH₄⁺ (15%), over the period 1991–1998.     

Assessing the Relationship between Personal Particulate and Gaseous Exposures of Senior Citizens Living in Baltimore,MD

ABSTRACT

We conducted a multi-pollutant exposure study in Baltimore, MD, in which 15 non-smoking older adult subjects (>64 years old) wore a multi-pollutant sampler for 12 days during the summer of 1998 and the winter of 1999. The sampler measured simultaneous 24-hr integrated personal exposures to PM₂₅, PM₁₀, SO₄ ^2-, O₃, NO₂, SO₂, and exhaust-related VOCs.

Results of this study showed that longitudinal associations between ambient PM_2.5 concentrations and corresponding personal exposures tended to be high in the summer (median Spearman's r = 0.74) and low in the winter (median Spearman's r = 0.25). Indoor ventilation was an important determinant of personal PM_2.5 exposures and resulting personal-ambient associations. Associations between personal PM₂₅ exposures and corresponding ambient concentrations were strongest for well-ventilated indoor environments and decreased with ventilation. This decrease was attributed to the increasing influence of indoor PM_{2 5} sources. Evidence for this was provided by SO₄ ^2-measurements, which can be thought of as a tracer for ambient PM₂₅. For SO₄ ^2-, personal-ambient associations were strong even in poorly ventilated indoor environments, suggesting that personal exposures to PM_2.5 of ambient origin are strongly associated with corresponding ambient concentrations. The results also indicated that the contribution of indoor PM_2.5 sources to personal PM_2.5 exposures was lowest when individuals spent the majority of their time in well-ventilated indoor environments.

Results also indicate that the potential for confounding by PM_2.5 co-pollutants is limited, despite significant correlations among ambient pollutant concentrations. In contrast to ambient concentrations, PM_2.5 exposures were not significantly correlated with personal exposures to PM_2.5-10, PM_2.5 of non-ambient origin, O₃, NO₂, and SO₂. Since a confounder must be associated with the exposure of interest, these results provide evidence that the effects observed in the PM_2.5 epidemiologic studies are unlikely to be due to confounding by the PM_2.5 co-pollutants measured in this study.     

Characteristics and origins of air pollutants in Wuhan,China, based on observations and hybrid receptor models

To identify the characteristics of air pollutants and factors attributing to the formation of haze in Wuhan, this study analyzed the hourly observations of air pollutants (PM_2.5, PM₁₀, NO₂, SO₂, O₃, and CO) from March 1, 2013, to February 28, 2014, and used hybrid receptor models for a case study. The results showed that the annual average concentrations for PM_2.5, PM₁₀, NO₂, SO₂, O₃, and CO during the whole period were 89.6 μg m^?3, 134.9 μg m^?3, 54.9 μg m^?3, 32.4 μg m^?3, 62.3 μg m^?3, and 1.1 mg m^?3, respectively. The monthly variations revealed that the peak values of PM_2.5, PM₁₀, NO₂, SO₂, and CO occurred in December because of increased local emissions and severe weather conditions, while the lowest values occurred in July mainly due to larger precipitation. The maximum O₃ concentrations occurred in warm seasons from May to August, which may be partly due to the high temperature and solar radiation. Diurnal analysis showed that hourly PM_2.5, PM₁₀, NO₂, and CO concentrations had two ascending stages accompanying by the two traffic peaks. However, the O₃ concentration variations were different with the highest concentration in the afternoon. A case study utilizing hybrid receptor models showed the significant impact of regional transport on the haze formation in Wuhan and revealed that the mainly potential polluted sources were located in the north and south of Wuhan, such as Baoding and Handan in Hebei province, and Changsha in Hunan province. Implications: Wuhan city requires a 5% reduction of the annual mean of PM_2.5 concentration by the end of 2017. In order to accomplish this goal, Wuhan has adopted some measures to improve its air quality. This work has determined the main pollution sources that affect the formation of haze in Wuhan by transport. We showed that apart from the local emissions, north and south of Wuhan were the potential sources contributing to the high PM_2.5 concentrations in Wuhan, such as Baoding and Handan in Hebei province, Zhumadian and Jiaozuo in Henan province, and Changsha and Zhuzhou in Hunan province.     

Major air pollutants in Bursa,Turkey: their levels,temporal changes,interactions, and sources

Bursa is one of the largest cities of Turkey and it hosts 17 organized industrial zones. Parallel to the increase in population, rapidly growing energy consumption, and increased numbers of transport vehicles have impacts on the air quality of the city. In this study, regularly calibrated automatic samplers were employed to get the levels of air pollution in Bursa. The concentrations of CH₄ and N-CH₄ as well as the major air pollutants including PM₁₀, PM_2.5, NO, NO₂, NO_x, SO₂, CO, and O₃, were determined for 2016 and 2017 calendar years. Their levels were 1641.62?±?718.25, 33.11?±?5.45, 42.10?±?10.09, 26.41?±?9.01, 19.47?±?16.51, 46.73?±?16.56, 66.23?±?32.265, 7.60?±?3.43, 659.397?±?192.73, and 51.92?±?25.63 µg/m³ for 2016, respectively. Except for O₃, seasonal concentrations were higher in winter and autumn for both years. O₃, CO, and SO₂ had never exceeded the limit values specified in the regulations yet PM₁₀, PM_2.5, and NO₂ had violated the limits in some days. The ratios of CO/NO_x, SO₂/NO_x, and PM_2.5/PM₁₀ were examined to characterize the emission sources. Generally, domestic and industrial emissions were dominated in the fall and winter seasons, yet traffic emissions were effective in spring and summer seasons. As a result of the correlation process between O_x and NO_x, it was concluded that the most important source of O_x concentrations in winter was NO_x and O₃ was in summer.     

The use of real-time monitoring data to evaluate major sources of airborne particulate matter

Real-time chemical measurements have been made as part of a field study of air quality in the city and harbour of Cork, Ireland. The data relate to the year 2008, with particular attention paid to the period between May and August. Eight air quality parameters were measured: NO, O₃, NO₂, SO₂, EC, OC, particulate SO₄^2? and PM_2.5. The data have been used in a novel way involving wind and temporal averaging, along with Principal Component Analysis (PCA) and Positive Matrix Factorisation (PMF) methodologies to extrapolate major source contributions for PM_2.5. It is demonstrated that continuous monitoring of standard air quality parameters, such as NO, NO₂, SO₂, along with EC, OC and particulate SO₄^2?, can be used to provide relevant, cost-effective initial estimates of source contributions to ambient PM_2.5 levels. It is also shown that the benefit of including OC and particulate SO₄^2? in the monitoring protocol is considerable. Three major source groups of ambient PM_2.5 mass in Cork were identified and quantified using this combined monitoring and modelling approach; road transport (19%), domestic solid fuel burning (14%) and oil-fired domestic and industrial boilers, including power generation plants (31%).     

The use of chemical and statistical methods to identify sources of selected elements in ambient air aerosols in Karachi,Pakistan

Concentrations of 23 elements plus NO₃⁻, SO₄²⁻ and Cl⁻ were determined for samples collected continuously every 3 or 6 h during 22–27 July, 1985 at a suburban site in Karachi, Pakistan. Concentrations of lithophilic elements and several anthropogenic elements were ~ 80 % higher during daytime than at night. These elevated levels were attributed to daytime increases in wind velocity and anthropogenic activity. Factor analysis showed that ~ 50% of the variance was associated with soil, and ~ 14 % each with oceanic Na and Cl⁻, anthropogenic Sb and Pb, and Zn, Se and SO₄²⁻. A cement (limestone/dolomite) factor was not separated even though Ca and Mg concentrations were unusually high and a cement factory was located nearby. This led to an investigation of a chemical approach to determine the sources. Concentrations of Na, Mg and Ca were determined in water-extracts of the samples. Assuming soluble Na (~ 92 % of total) to be sea derived, marine components of Mg, SO₄²⁻, Ca and Br were determined. Solubility considerations were then used to reveal the cement source and apportion the aerosol sources. On the average, approximately 48 % of the total aerosol mass could be accounted for by the ‘cement’ and ‘soil’ components; about 12 % by the ‘sea salt’, about 3% by the ‘fossil fuel’ SO₄²⁻ (as (NH₄)₂SO₄); about 1 % by the NO₃⁻ (as NH₄NO₃); the remaining 36 % of the aerosol mass was unassigned.     

Description and intercomparison of techniques to measure n and s compounds in the Western Atlantic Ocean experiment

The data set of N and S compound measurements from WATOX-85 has been examined in detail to assess that data quality and suitability for use in addressing the goals of the Western Atlantic Ocean Experiment. Accuracy estimates for particulate SO₄²⁻ and NO₃⁻, SO₂ and HNO₃ have been made on the basis of the investigators' estimates and the results of intercomparisons. Intercomparisons of ground-based particulate SO₄²⁻ and all filter SO₂ and HNO₃ measurements show them to be consistent with the 20% accuracies quoted by the investigators. Ground-based particulate NO₃⁻ and aircraft particulate SO₄²⁻ show inconsistencies such that the accuracies can be no better than 28% and the aircraft particulate NO₃ has an accuracy of no better than 60%.     

Characteristics of re-suspended road dust and its impact on the atmospheric environment in Beijing

A sampling campaign of re-suspended road dust samples from 53 sites that could cover basically the entire Beijing, soil samples from the source regions of dust storm in August 2003, and aerosol samples from three representative sites in Beijing from December 2001 to September 2003, was carried out to investigate the characteristics of re-suspended road dust and its impact on the atmospheric environment. Ca, S, Cu, Zn, Ni, Pb, and Cd were far higher than its crustal abundances and Ca²⁺, SO₄²⁻, Cl⁻, K⁺, Na⁺, NO₃⁻ were major ions in re-suspended road dust. Al, Ti, Sc, Co, and Mg in re-suspended road dust were mainly originated from crustal source, while Cu, Zn, Ni, and Pb were mainly derived from traffic emissions and coal burning, and Fe, Mn, and Cd were mainly from industrial emissions, coal combustion and oil burning. Ca²⁺ and SO₄²⁻ mainly came from construction activities, construction materials and secondary gas-particle conversions, Cl⁻ and Na⁺ were derived from industrial wastewater disposal and chemical industrial emissions, and NO₃⁻ and K⁺ were from vehicle emissions, photochemical reactions of NO_X, biomass and vegetable burning. The contribution of mineral aerosol from inside Beijing to the total mineral aerosols was ∼30% in spring of 2002, ∼70% in summer of 2002, ∼80% in autumn of 2003, ∼20% in PM₁₀ and ∼50% in PM_2.5, in winter of 2002. The pollution levels of the major pollution species, Ca, S, Cu, Zn, Ni, Pb, Fe, Mn, and Cd in re-suspended road dust reached ∼76%, ∼87%, ∼75%, ∼80%, ∼82%, ∼90%, ∼45%, ∼51%, and ∼94%, respectively. Re-suspended road dust from the traffic and construction activities was one of the major sources of pollution aerosols in Beijing.     

Ionic composition of precipitation at the Central Anatolia (Turkey)

Concentrations of major ions, SO₄²⁻, NO₃⁻, Cl⁻, H⁺, Ca²⁺, K⁺, Mg²⁺, Ca²⁺ and conductivity were measured in approximately 300 daily, wet-only rain samples collected at a permanent rural station between 1993 and 1998. Concentrations of anthropogenic ions NH₄⁺, SO₄²⁻ and NO₃⁻ were among the highest values reported in whole EMEP network, suggesting that the Anatolian plateau is under strong influence of distant emission sources. Although transport of pollutants have significant influence on the chemical composition of precipitation, average pH of the rainwater is 6.2 due to extensive neutralization of acidity. Approximately 95% of the acidity in collected samples is neutralized, particularly in summer season. The neutralizing agents are primarily CaCO₃ and NH₃. Concentrations of crustal ions are higher in summer season due to enhanced resuspension of soil particles from dry surface soil. Concentrations of anthropogenic ions SO₄²⁻ and NO₃⁻ do not change significantly between summer and winter due to higher intensity of rains in summer season. Although concentrations of ions measured in this study is among the highest reported in EMEP network, wet deposition fluxes are low compared to flux values reported for similar sites in Europe, due to low annual precipitation in the Anatolia. Wet deposition fluxes of all measured parameters are highly episodic. Source regions affecting chemical composition precipitation in the Central Anatolia is investigated using trajectory statistics.     

Influence of NO2 and dissolved iron on the S(IV) oxidation in synthetic aqueous solution

The influence of dissolved NO₂ and iron on the oxidation rate of S(IV) species in the presence of dissolved oxygen is presented. To match the conditions in the real environment, the concentration of iron in the reaction solution and trace gases in the gas mixture was typical for a polluted atmosphere. The time dependence of HSO₃⁻, SO₄²⁻, NO₂⁻ and NO₃⁻ and the concentration ratio between Fe(II) and total dissolved iron were monitored. Sulphate formation was the most intensive in the presence of an SO₂/NO₂/air gas mixture and Fe(III) in solution. The highest contribution to the overall oxidation was from Fe-catalysed S(IV) autoxidation. The reaction rate in the presence of both components was equal to the sum of the reaction rates when NO₂ and Fe(III) were present separately, indicating that under selected experimental conditions there exist two systems: SO₂/NO₂/air and SO₂/NO₂/air/Fe(III), which are unlikely to interact with each other. The radical chain mechanism can be initiated via reactions Fe(III)–HSO₃⁻ and NO₂–SO₃²⁻/HSO₃⁻.