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.

     

Trace gas and aerosol measurements at a remote site in the northeast U.S.

This paper presents the results of continuous measurements of trace atmospheric gases and aerosol composition made at the summit of Whiteface Mountain, New York, for 28 days in July 1982. The gas phase species NO, NO_x ( = NO + NO₂ + PAN), HNO₃, SO₂ and NH₃ were measured, as well as aerosol SO₄²⁻, NO₃⁻, H⁺ and NH₄⁺. Mean and median NO_x concentrations were 1.1 and 1.0 ppb, respectively, with maximum and minimum values of 3.2 and 0.3 ppb. HNO₃ concentrations were variable, occasionally exceeding the simultaneously measured NO_x levels. Mean and median SO₂ were 0.8 and 0.3 ppb, with concentrations up to 12 ppb in pollution episodes. Mean and median NH₃ were both 2.2 ppb. Monthly mean SO₄²⁻ was 5.3 μg m⁻³, with values in clean air of about 1.5 μg m⁻³, and in polluted air up to 80 μg m⁻³. Trajectory calculations indicate that episodes of high pollutant concentrations occur in air masses arriving at Whiteface from the southwest. These episodes contributed most of the SO₄²⁻, HNO₃ and aerosol acidity, and about half the SO₂ and NO_x to which the site was exposed during the measurement period. Limited comparisons of air chemistry data with the composition of cloudwater collected during the program are also presented.     

Evaluation of the effect of long-range transport of air pollutants on coastal atmospheric monitoring sites in and around Taiwan

Long-range transport of pollution outflow from Asian mainland has been noticed and expected to play a significant role in Pacific background. Since 1993 the Taiwanese Environmental Protection Administration (TEPA) is conducting ground-based observations of various particulate and gaseous pollutants at 74 monitoring stations in Taiwan. One of these stations, Heng-Chun at the south coast of Taiwan can be considered as a background station with only negligible amounts of local pollution, and another one, Wan-Li at the north coast, predominantly receives air that has not passed over Taiwan, so that background air can be analysed by means of sectorisation. In this work, the sectorised 13-year time series of measurements of CO, SO₂, O₃, NO_x and PM₁₀, from the Wan-Li station are presen and compared to data from the Heng-Chun station and another TEPA background station off the coast of mainland China, Ma-Zu. The CO and O₃ measurements are also compared to data from the Yonaguni station, a Pacific island site, part of the Global Atmospheric Watch (GAW) network.The similarity of the sectorised data from the Wan-Li station with the data of the other station indicates that atmospheric measurements from the Wan-Li site can be used to make inferences about trends in western Pacific background air pollution and the effect of long-range transport of pollutants. The measurement time series from 1993 to 2006 do not indicate a significant trend in the monthly mean O₃ concentrations in accordance with other research about ozone in tropical latitudes. An increasing trend in CO concentrations of 2.8% per annum is observed between 1999 and 2006 for long-range transport to northern Taiwan, and a doubling of the SO₂ and NO_x concentrations observed at the Wan-Li and Heng-Chun sites within the period 2001–2006. SO₂ concentrations are found to quadruple at Ma-Zu within the same period. The data suggest that pollution from the Asian mainland enhances significantly the background air pollution over the Pacific.     

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     

Short-Term Effects of Gaseous Pollutants on Cause-Specific Mortality in Wuhan,China

Abstract

In Asia, limited studies have been published on the association between daily mortality and gaseous pollutants of nitrogen dioxide (NO₂), ozone (O₃), and sulfur dioxide (SO₂). Our previous studies in Wuhan, China, demonstrated long-term air pollution effects. However, no study has been conducted to determine mortality effects of air pollution in this region. This study was to determine the acute mortality effects of the gaseous pollutants in Wuhan, a city with 7.5 million permanent residents during the period from 2000 to 2004. There are approximately 4.5 million residents in Wuhan who live in the city’s core area of 201 km², where air pollution levels are highest, and pollution ranges are wider than the majority of the cities in the published literature. We used the generalized additive model to analyze pollution, mortality, and covariate data. We found consistent NO₂effects on mortality with the strongest effects on the same day. Every 10-μg/m³increase in NO₂daily concentration on the same day was associated with an increase in nonaccidental (1.43%; 95% confidence interval [CI]: 0.87–1.99%), cardiovascular (1.65%; 95% CI: 0.87–2.45%), stroke (1.49%; 95% CI: 0.56–2.43%), cardiac (1.77%; 95% CI: 0.44–3.12%), respiratory (2.23%; 95% CI: 0.52–3.96%), and cardiopulmonary mortality (1.60%; 95% CI: 0.85– 2.35%). These effects were stronger among the elderly than among the young. Formal examination of exposure-response curves suggests no-threshold linear relationships between daily mortality and NO₂, where the NO₂concentrations ranged from 19.2 to 127.4 μg/m³. SO₂and O₃were not associated with daily mortality. The exposure-response relationships demonstrated heterogeneity, with some curves showing nonlinear relationships for SO₂and O₃. We conclude that there is consistent evidence of acute effects of NO₂on mortality and suggest that a no-threshold linear relationship exists between NO₂and mortality.     

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%).     

Ion chromatographic determination of anions in rainwater

High acidity rainwater has recently become an issue in environmental pollution because of its great influence on ecological systems with special reference to the human environment. To solve this problem, the chemical behaviors of various pollutants in the air, particularly in the wet atmosphere must be studied. Ion chromatography was used for rapid analysis of trace amounts of anions.As a result, it was found that a combination of 2mM Na₂CO₃ and 5mM NaOH as an eluent was suitable for the separation of various anions. The reproducibility of determination of anions in standard solutions was found to be satisfactory with a coefficient of variation (CV) of 2–4% for F^?, Br^?, NO^?₃, SO^2?₃, SO^2?₄, and PO^3?₄, but not for NO^?₂. The determination of NO^?₂ was accomplished by preparing an eluent having almost the same composition and cencentration as that of the standard and sample solutions. The precision of the method with rainwater samples was less than 10%, and was considered to be usable for data analysis.In addition, a considerable number of ions in rainwater samples could be determined by using 1–3 ml of the sample without pretreatment. It was found that ion chromatography was one of the best means to obtain information on the chemical behaviors of trace amounts of anions in rainwater.     

Exposure to hazardous air pollutants along Oba Akran road, Lagos-Nigeria

We measured toxic air pollutants along Oba Akran road in Lagos to evaluate pedestrian exposure. PM₁₀, CO, O₃, NO₂, SO₂, CH₄, noise, wind velocity and temperature were measured simultaneously with portable analyzers. Our results showed that pedestrian exposure to PM₁₀ (with an average of 274.6 μg m⁻³ for all samples) and CO (with an average of 19.27 ppm for all samples) was relatively high. CO is a traffic-related pollutant, so the influence of the local traffic emissions on CO levels is strong. The high concentration of the PM₁₀ measured at the three environments also suggests that the traffic is a major source of ultrafine particles. The overall average concentrations for the 72-day experimental period for SO₂, NO₂ and O₃ are 101.2, 62.5 and 0.32 ppb respectively, all of which are below the US national ambient air quality standards. Strong traffic impacts can be observed from the concentrations of some of these pollutants measured in these three environments. Most clear is a reflection of diesel truck traffic activity rich in black carbon concentrations. The diurnal variation of O₃ and NO₂ also showed that NO₂ was depleted by photochemically formed O₃ during the day and replenished at night as O₃ was destroyed. A multivariate statistical analysis (Principal Component Analysis, Factor Analysis) has been applied to a set of data in order to determine the contribution of different sources. It was found that the main principal components, extracted from the air pollution data, were related to gasoline combustion, oil combustion and ozone interactions.     

Ionic composition of TSP and PM2.5 during dust storms and air pollution episodes at Xi'an,China

TSP and PM_2.5 samples were collected at Xi'an, China during dust storms (DSs) and several types of pollution events, including haze, biomass burning, and firework displays. Aerosol mass concentrations were up to 2 times higher during the particulate matter (PM) events than on normal days (NDs), and all types of PM led to decreased visibility. Water-soluble ions (Na⁺, NH₄⁺, K⁺, Mg²⁺, Ca²⁺, F^?, Cl^?, NO₃^?, and SO₄^2?). were major aerosol components during the pollution episodes, but their concentrations were lower during DSs. NH₄⁺, K⁺, F^?, Cl^?, NO₃^?, and SO₄^2? were more abundant in PM_2.5 than TSP but the opposite was true for Mg²⁺ and Ca²⁺. PM collected on hazy days was enriched with secondary species (NH₄⁺, NO₃^?, and SO₄²) while PM from straw combustion showed high K⁺ and Cl^?. Firework displays caused increases in K⁺ and also enrichments of NO₃^? relative to SO₄^2?. During DSs, the concentrations of secondary aerosol components were low, but Ca²⁺ was abundant. Ion balance calculations indicate that PM from haze and straw combustion was acidic while the DSs samples were alkaline and the fireworks' PM was close to neutral. Ion ratios (SO₄^2?/K⁺, NO₃^?/SO₄^2?, and Cl^?/K⁺) proved effective as indicators for different pollution episodes.     

Spatial and seasonal variations of elemental and ion components in air particulate matters in three mega-cities in China

Beijing–Tianjin–Hebei region is one of the most important political, economic and cultural centers of China. The rapid development of economy in last decades has caused severe air pollution problems, which has resulted in considerable harm to local ecological environment and human health. In this study, total 671 air samples were collected from Beijing, Tianjin and Shijiazhuang (the capital city in Hebei province), one reference site and four background sites in four seasons. Particulate matters (PMs) with different sizes, elements and dissolvable ions in PMs were analyzed. Pollutant concentrations, characteristics and seasonal variations were discussed in order to describe the pollution status and the possible sources in this region. Enriched factors of K, Ca, Cr, Fe, Cu, Zn, As, Cd and Pb were all higher than 10. Concentrations of dissolvable ions were in the order of NO₃^–, SO₄^2–>NH₄⁺>Cl^–>Ca²⁺, K⁺, Na⁺>Mg²⁺, F^–. NO₃^–, SO₄^2–, NH₄⁺, Cl^– were the most important ion pollutants in the three cities which accounted for 90.3–92.3% of total 9 ion concentrations. Ion concentrations in the PMs were in the order of PM₁>PM_1–2.5>PM_2.5–10>PM₁₀>TSP. More than 50% of the dissolvable ions exist in PM1 and the percentage increases to 73.9–94.8% in PM_2.5. Human activities should be the main sources of the metallic pollutants, among which coal combustion was identified as the primary one.     

Study of aerosol transport through precipitation chemistry over Arabian Sea during winter and summer monsoons

Precipitation samples over the Arabian Sea collected during Arabian Sea Monsoon Experiment (ARMEX) in 2002–2003 were examined for major water soluble components and acidity of aerosols during the period of winter and summer monsoon seasons. The pH of rain water was alkaline during summer monsoon and acidic during winter monsoon. Summer monsoon precipitation showed dominance of sea-salt components (∼90%) and significant amounts of non-sea salt (nss) Ca²⁺ and SO₄²⁻. Winter monsoon precipitation samples showed higher concentration of NO₃⁻ and NH₄⁺ compared to that of summer monsoon, indicating more influence of anthropogenic sources. The rain water data is interpreted in terms of long-range transport and background pollution. In summer monsoon, air masses passing over the north African and Gulf continents which may be carrying nss components are advected towards the observational location. Also, prevailing strong southwesterly winds at surface level produced sea-salt aerosols which led to high sea-salt contribution in precipitation. While in winter monsoon, it was observed that, air masses coming from Asian region towards observational location carry more pollutants like NO₃⁻and nss SO₄²⁻ that acidify the precipitation.     

Assessment of contribution of SO2 and NO2 from different sources in Jamshedpur region, India

Contribution of pollution from different types of sources in Jamshedpur, the steel city of India, has been estimated in winter 1993 using two approaches in order to delineate and prioritize air quality management strategies for the development of region in an environmental friendly manner. The first approach mainly aims at preparation of a comprehensive emission inventory and estimation of spatial distribution of pollution loads in terms of SO₂ and NO₂ from different types of industrial, domestic and vehicular sources in the region. The results indicate that industrial sources account for 77% and 68% of the total emissions of SO₂ and NO₂, respectively, in the region, whereas vehicular emissions contributed to about 28% of the total NO₂ emissions. In the second approach, contribution of these sources to ambient air quality levels to which the people are exposed to, was assessed through air pollution dispersion modelling. Ambient concentration levels of SO₂ and NO₂ have been predicted in winter season using the ISCST3 model. The analysis indicates that emissions from industrial sources are responsible for more than 50% of the total SO₂ and NO₂ concentration levels. Vehicular activities contributed to about 40% of NO₂ pollution and domestic fuel combustion contributed to about 38% of SO₂ pollution. Predicted 24-h concentrations were compared with measured concentrations at 11 ambient air monitoring stations and good agreement was noted between the two values. In-depth zone-wise analysis of the above indicates that for effective air quality management, industrial source emissions should be given highest priority, followed by vehicular and domestic sources in Jamshedpur region.     

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⁻.     

The chemical composition of cloud and rainwater. Results of preliminary measurements from an aircraft

Using an aircraft, preliminary investigations have been carried out into the chemical composition of clouds. The emphasis was on testing the sampling devices under several conditions. The results clearly show a considerable spatial distribution in pollutant concentrations that must have been caused by the contribution of many plume sources and the inhomogeneity of cloudwater density as well. Rather high concentrations of H₃O⁺. Cl⁻, NO⁻₃, SO²⁻₄, NH⁺₄ and H₂O₂ were measured. Except for H₂O₂, these components are scavenged very fast during travel over short distances over source regions. Moreover H₃O⁺, NO⁻₃ and SO²⁻₄ are likely to be formed by chemical reactions of gaseous precursors with oxidants in the liquid phase. This may explain the marked decrease in high background H₂O₂ concentrations (ppm range). Relatively high (molar) NO⁻₃ /SO²⁻₄ ratios mainly varying from 1 to 2 were measured over The Netherlands near source areas. The lower values found during a flight over southern Scandinavia are in agreement with data from literature. Occasionally the chloride concentration was found to be much higher than could be expected from rain network data.     

Five years of air chemistry observations in the Canadian Arctic

Arctic air chemistry observations made in Canada between 1979 and 1984 are discussed. The weekly average concentration of 25 aerosol constituents has been measured routinely at three locations. Anthropogenic pollution typified by SO₄²⁻ and V has a persistent seasonal cycle. SO₄²⁻ concentrations are similar at all three locations, although they tend to be somewhat higher at Alert than at Mould Bay and Igloolik. The seasonal variation of an aerosol constituent depends on its source. There are four distinctive seasonal variations for:

• 1.(i) anthropogenic constituents Cr, Cu, Mn, Ni, Pb, Sr, V, Zn, H⁺, NH₄⁺, SO₄²⁻, NO₃⁻,
• 2.(ii) halogens (excepting Cl) Br, I, F,
• 3.(iii) sea salt elements Na, Mg, Cl and
• 4.(iv) soil constituents Al, Ba, Ca, Fe and Ti. In the Arctic winter, the mean concentrations of anthropogenic aerosol constituents, except SO₄²⁻, are 2–4 times lower than annual mean concentrations in southern Sweden near a major source region. SO₄²⁻ concentrations are only 30% lower mainly because of production from SO₂. Light scattering (b_scat) and SO₄²⁻ observations indicate that the SO₄²⁻ fraction of the fine particle mass fluctuates between 3 and 65% during the polluted winter months. Daily mean b_sact, at Mould Bay that exceeds 50 × 10⁻⁶m⁻¹ is associated with air originating from the northwest. The soluble major ion composition of aerosols during winter varies markedly with particle size. H⁺, NH₄⁺ and SO₄²⁻ dominate submicrometre particles while sea-salt ions Mg²⁺, Na⁺ and Cl⁻ predominate in supermicrometre particles. Winter SO₂ concentrations at Mould Bay and Igloolik ranged from 0.2 to 1.5 ppb
• 5.(v). The fraction of airborne S as SO₂ ranged from 20 to 90% and peaked in late December-early January. The concentration of total NO₃⁻ (0.025–0.090 ppb(v)) is much lower than that of SO₄²⁻ (0.3–1.2 ppb (v)).

     

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.     

Arctic air pollution: An overview of current knowledge

From December to April, the Arctic air mass is polluted by man-made mid-latitudinal emissions from fossil fuel combustion, smelting and industrial processes. In the rest of the year, pollution levels are much lower. This is the outcome of less efficient pollutant removal processes and better south (S) to north (N) transport during winter. In winter, the Arctic air mass covers much of Eurasia and N. America. Meteorological flow fields and the distribution of anthropogenic SO₂ emissions in the northern hemisphere favor northern Eurasia as the main source of visibility reducing haze. Observations of SO₄²⁻ concentrations in the atmosphere throughout the Arctic yield, depending on location and year, a January–April mean of 1.5–3.9 μg m⁻³ in the Norwegian Arctic to 1.2–2.2 μg m⁻³ in the N. American Arctic. An estimate of the mean vertical profile of fine particle aerosol mass during March and April shows that, on average, pollution is concentrated in the lower 5 km of the atmosphere. Not only are anthropogenic particles present in the Arctic atmosphere but also gases such as SO₂, perfluorocarbons and pesticides. The acidic nature and seasonal variation of Arctic pollution is reflected in precipitation, the snowpack and glacier snow in the Arctic. A pH of 4.9–5.2 in winter and ~ 5.6 in summer is expected in the absence of calcareous wind blown soil. Glacial records indicate that Arctic air pollution has undergone a marked increase since the mid 1950s paralleling a marked increase in SO₂ and NO_x emissions in Europe. Effects of Arctic pollution include a reduction in visibility and perturbation of the solar radiation budget in April–June. Potential effects are the acidification and toxification of sensitive ecosystems.     

Declining ambient air pollution and lung function improvement in Austrian children

Three thousand four hundred fifty-one Austrian elementary school children were examined (between 2 and 8 times) by spirometry by standardized methods, over a 5 yr period. The districts where they lived were grouped into those where NO₂ declined during this period (by at least 30 μg/m³ measured as half year means) and those with less or no decline in ambient NO₂. In both groups of districts, SO₂ and TSP fell by similar amounts over this period. A continuous improvement of MEF25 (maximum exspiratory flow rate at 25% vital capacity) was found in districts with declining ambient NO₂. Populations did not differ in respect of anthropometric factors, passive smoking or socioeconomic status. A birth cohort from this study population which was followed up to age 18 confirmed the improved growth of MEF25 with decline in NO₂, while the improved growth of forced vital capacity was more related to decline in SO_2. This study provides the first evidence that improvements in the outdoor air quality during the 1980s are correlated with health benefits, and suggest that adverse effects on lung function related to ambient air pollution are reversible before adulthood. Improvement of small airway functions appeared to be more dependent on reductions of NO₂ than reduction in SO₂ and TSP.     

The characterization of water-soluble inorganic ions in PM2.5 during a winter period in Xi'an,China

The characteristics of water-soluble inorganic ions (WSIIs) during a winter period in a suburb of Xi'an, China, were investigated. Our results show that the total mass concentration of the dominant WSIIs (8) was 91.27 µg m^–3, accounting for 50.1% of the total mass concentration of PM_2.5 (particulates with a size of 2.5 µm or less). Secondary inorganic aerosols (SO₄^2?, NO₃^? and NH₄⁺) were the most abundant ions, accounting for up to 95.12% of the total ions. By using the anion and cation equivalence ratio method, PM_2.5 was shown to have weak alkalinity, and the chemical forms of WSIIs were mainly (NH₄)₂SO₄ and NH₄NO₃. The sulfur oxidation ratio (SOR) and nitrogen oxidation ratio (NOR) suggested that larger proportions of SO₄^2? and NO₃^? were formed by gas-phase SO₂ and NO₂ in the sampling site. Ratio analysis also indicated that anthropogenic sources significantly contributed to WSII pollution. Among the anthropogenic sources, fixed pollution sources were found to be dominant over mobile sources.