Spatial and Temporal Patterns of Chloride Deposition in Southern Sweden

Monthly bulk deposition of chloride at 49 stations in Southern Sweden between 1989 and 1995 was used to produce quarterly and annual deposition maps through ordinary block kriging. Generally, deposition decreases from the west coast and eastward and displays a large annual variation, governed by the frequency and intensity of midlatitude cyclones. The 1st quarter dominates the temporal pattern all years except 1992. The 4th quarter is the second most important and the 2nd and 3rd quarters have generallylow deposition. The spatial deposition maximum was often displaced from the west coast to the western fringe of the South Swedish highland, due to orographic enhancement of precipitation. On the western rise of the highland, deposition almost entirely co-variates with precipitation. On the west coast and in the eastern part of Southern Sweden, thetemporal pattern is a more complex result of precipitation and frequency of strong westerlies. Comparing the quarterly total dataset with precipitation and frequency of westerly gales shows that both the 3rd and 4th quarters have higher mean precipitation than the 1st quarter, but lower deposition, while the second quarter has substantially lower precipitation but almost equal deposition to the 3rd quarter. The frequency of westerly gales shows a clearer, linear relationship to quarterly deposition. The 1st quarter has the highest variability in deposition and precipitation as well as in frequency of westerly gales. The importance of single highlysalt laden cyclones to the annual deposition is obvious in the 1st quarter of 1993. Changes in cyclone activity due to climate change is therefore of vital importance for the chemical characteristics of the midlatitude atmosphere.     

Deposition of sulphur and nitrogen compounds in Croatia

Since precipitation is an efficient scavenger of pollutants, concentrations of major ions in precipitation reflect changes in chemistry of the atmosphere and in the subsequent exposure of various ecosystems to deposition. The National Atmospheric Precipitation Chemistry programme was initiated in 1978 and operated by Meteorological and Hydrological Service of Croatia to provide needed information on geographical patterns and temporal trends in precipitation chemistry in Croatia. To accomplish this, a network of about 20 stations, settled in different geographical regions, operates on a daily basis for 15 years now. Some monitoring stations are site- and study- specific; others are included in long-term, regional, or European monitoring networks (EMEP, GAW, MEDPOL, GEMS). The purpose of this work was to summarise existing data from the whole network for the period 1981–1992 and to compare data from measurements with EMEP model calculations of acid deposition. Results presented here show that annual average concentration and deposition values at remote sites agree reasonably well compared to modelled ones.     

Concentration and deposition of acidifying air pollutants over Sweden: Estimates for 1991 based on the match model and observations

The MATCH (Mesoscale Atmospheric Transport and CHemistry) model has been developed as a tool for air pollution assessment studies on different geographical scales. MATCH is an Eulerian atmospheric dispersion model, including physical and chemical processes governing sources, atmospheric transport and sinks of oxidized sulfur and oxidized and reduced nitrogen. Using a combination of air and precipitation chemistry measurements and the MATCH model, the national and long-range transport contributions to air pollution and deposition can be quantified in the model region. The calculations for the year 1991 show that the Swedish import was about 4.5 times larger than the export for sulfur and about six times larger for reduced nitrogen, while the Swedish import of oxidized nitrogen only exceeded the export by 10%. Using the MATCH system we estimate the long-range transport in an independent way compared to EMEP. Comparison between the EMEP and MATCH calculations for 1991 show that the total deposition of oxidized nitrogen over Sweden is similar, while the EMEP-values for total deposition of oxidized sulfur and reduced nitrogen are 25% respectively 40% smaller than what is obtained from MATCH.     

Global scale transport of acidifying pollutants

During the past few years several attempts have been made to use three-dimensional tracer transport models to simulate the global distribution of sulfur and nitrogen compounds from both natural and anthropogenic sources. We review these studies and show examples of estimated distributions of the total deposition of sulfur, oxidized nitrogen and ammonium as well as the pH of precipitation. The simulated patterns are compared with observations. Weaknesses in these estimates resulting from lack of knowledge of emissions, chemical transformations and removal processes are emphasized and discussed. We also show examples of how the models can be used to estimate past and future deposition patterns. In particular, we use the IPCC scenario IS92a to estimate the possible sulfur deposition around the world in the year 2050. A comparison with critical load values for sulfur deposition indicates that substantial parts of South and East Asia are at risk for acidification problems in the future.     

The acidifying potential of atmospheric deposition in Canada

It is proposed that the value of ([SO₄ ^??] - [Ca⁺⁺ + Mg⁺⁺]) in precipitation is a suitable way to describe the acidifying potential (AP) of the wet desposition. In eastern North America, the AP of precipitation varies from 20 to 85% of the total sulphate, the remainder of the sulphate being neutralized H₂SO₄, sulphate from salts in dust or from sea salt. The AP ranges from 20 to 80% of the H⁺ in the wet deposition. The rest of the H⁺ is contributed by the net effect of N compounds. Ammonium and nitrate ions from ammonia and NO_Xemissions do not represent a net acidic loading to the terrestrial ecosystem if they are taken up by vegetation. However, when N leaches from watersheds in the form nitrate, it constitutes an acidifying demand on the ecosystem. Therefore, the overall net acidifying potential (NAP) applied to the terrestrial ecosystem is defined by the value of ([SO₄ ^??] - [Ca⁺⁺ + Mg⁺⁺]) in precipitation plus [NO₃ ^??] in runoff from the watershed.     

Polycyclic aromatic compounds and microtox® acute toxicity in contaminated sediments in Sweden

Limnic and brackish aquatic sediments from contaminated locations in Sweden were analysed for polycyclic aromatic compounds (PACs) and tested for acute aquatic toxicity. The organic compounds were analysed in solvent-extractable and alkaline-treated fractions to complete the analysis of a set of priority pollutants according to the Swedish EPA. Additionally, the acute toxicity was measured by the solid phase Microtox test. The measured effects were correlated with sedimentological and chemical parameters. Analysis revealed no indication of a contribution of PACs to the acute sediment toxicity in highly contaminated sediments, with concentrations in the range of 11.3-307 μg SPAC_37/39/g dry matter. Despite a high ranking of 3 to 5 within the Swedish EPA list for coastal sediments, the acute toxicity results indicate a very low bioavailability of the analysed PACs from the creosote and combustion-contaminated sediments. A correlation of acute toxicity to elemental sulfur was indicated.     

Emissions of acidifying air pollutants in the North West region of England

Most estimates of emission are concerned with the nation state level. This paper will discuss methods utilised in the estimates of emissions to the atmosphere of sulphur dioxide, volatile organic compounds and oxides of nitrogen from a densely populated and heavily industrialised region of the United Kingdom. Data on power generation, industrial plant, fuel usage, air, sea and road transportation, and human population statistics have been integrated into a method to provide regional emission estimates. The resulting emission patterns are described in terms of sources and emission density. Spatial and temporal patterns are identified and major sources of emissions discussed in terms of national control programmes. Transportation is the dominant source of oxides of nitrogen emissions whilst power generation is the dominant source of sulphur dioxide. The relative importance of the North West as an emission source within the UK is assessed. The change in the strengths of acidifying emissions between 1987 and 1992 is discussed and the rate of change in emission magnitudes between the North West region and the UK as a whole compared.     

Deterioration of copper and bronze caused by acidifying air pollutants

The ‘ICP on effects on materials’ was launched in 1985, within the framework of the Convention on Long-range Transboundary Air Pollution with the aim to find an approach for clearing the main gaps in the knowledge about material degradation caused by environmental impacts. The project was organized as a staggered8 year's material exposure programme accompanied by an extensive measuring programme for environmental parameters. During the evaluation of the 4 years data set it took shape that the most efficient parameters for quantifying the material degradation are the mass loss and especially for copper the corrosion volumes. Bronze already reacts extremely sensitive on low SO₂ concentrations. The starting corrosion rate for copper is suprisingly high. A strong impact of chloride on the formation of pin holes for sheltered copper could be detected without showing high mass loss. At simultanous presence of ozone the corrosive action is catalysed by it's oxidation power and leads to severe mass loss. Based upon the 4 years data set for most of the materials preliminary dose-response-functions have been prepared. For the first time a synergetic effect of SO₂ and ozone has been demonstrated in a field exposure.     

Estimate of health impacts of acidifying air pollutants and tropospheric ozone in Europe

Based on combined information available from air quality monitoring data and long-range transport models, European population exposure to SO₂, NO₂ and O₃ has been estimated. This information has been combined with the results of epidemiological studies assessing strength of association between the exposure and health effects to estimate an impact of the pollution on health in Europe. The analysis indicates that a considerable number of health problems, ranging from mild irritation of the respiratory system to increased mortality, can be attributed to short-term peaks of pollution observed in Europe. Chronic impacts of prolonged elevated SO₂ levels on lung function are estimated to occur in close to10 million people in Europe.     

酸化软煮法制取胡萝卜汁的工艺

以新鲜胡萝卜为主要原料,研究了用酸化软煮法制取胡萝卜汁的加工工艺,并通过对比试验确定了最佳工艺参数。结果表明,用4％的NaOH,料液比1∶2,在95℃脱皮处理73 s,和添加0.5％柠檬酸,按料液比2∶1软煮45 min,可获得较好的脱皮和磨汁效果,并使其原料的利用率提高至80％以上。20%糖液和50%胡萝卜汁配成原浆含量15%的流态汁,在100℃杀菌处理20 min后,得到的胡萝卜汁色泽橙黄,口感细腻,流动性和稳定性较好;添加0.1％的琼脂和0.35％的羧甲基纤维素钠作为复合稳定剂,经高压均质杀菌处理,解决了产品沉淀问题。     

Liming in Sweden

Air-borne pollutants have acidified 90,000 km of running water and at least 18,000 of Sweden's 90,000 lakes. In 1977 a national liming program to mitigate the effects of acidification in surface waters started with governmental support. Governmental subsidies usually amount to 85 % of the total liming cost but can in rare cases be extended to 100 % when waters of great national interest are threatened. The main liming agent is limestone of the size 0 to 0,2 mm. In lakes lime is spread by pontoon boats, helicopters and other vehicles. In running waters dosers and diversion wells are used. By 1985, the national liming program has been able to lime approximately 3,000 lakes and 100 streams.     

Acidification trends in Sweden

A Swedish hydrochemical monitoring program, which was started during the International Hydrological Decade (1965–1975), has been evaluated with respect to trends and regional differences in acidic deposition and stream water quality. Despite the more than twofold decrease in S emissions in Sweden since the early 1970's, there was only a marginal decrease in sulphate level in precipitation, indicating that long-range transport dominates precipitation chemistry. Trend analyses of stream water data gave practically no evidence that surface water quality had been changing since the late 1960's, i.e., no time lagged or accumulating effects of acidic deposition during past decades could be demonstrated. The difference between the wet deposition of S in southern and northern parts of Sweden was found to be smaller than previously reported. In the northern catchment areas, the input of S was considerably larger than the output. The statistical uncertainty of the trend estimates raises questions about the effectivity of present hydrochemical monitoring programs in detecting environmental changes.     

The Importance of Calcium Deposition in Assessing Impacts of Acid Deposition in China

The extensive use of coal as an energy carrier in China has led to high deposition of sulfur in a large part of the country. In the southern part of China large areas receive acid deposition, while in the northern part of the country the acidity of the emissions is neutralized by alkaline dust from the desert areas. In this paper we demonstrate the importance of knowing the sources and deposition patterns of base cations when assessing the effects of changes in sulfur emissions. Regional-scale data of both sulfur and calcium deposition from modeling and monitoring are combined in order to demonstrate how the acidity of deposition in China has changed historically and may change in the future. The importance of base cation deposition is also demonstrated using the dynamic acidification model MAGIC with input data from an intensive monitoring site outside Guiyang. It is not known what fraction of the deposited base cations is of natural origin and anthropogenic origin, respectively. The relative source strength varies greatly between regions. Future effects of emission changes are highly dependent on the relative reduction in sulfur and base cation emissions.     

The compilation of measurement based European wet deposition maps of acidifying components and base cations

Precipitation concentrations in 1989 on a European scale were obtained from national organisations responsible for wet deposition monitoring in their countries and from the EMEP database. In total, results from about 750 monitoring locations scattered over Europe were gathered. Spatial analysis based on Regionalised Variable Theory revealed auto-correlation in all ion concentrations and reasonable bounded models were fitted to the experimental variograms. Maps of concentrations of acidifying components and base cations were compiled on a 50×50 km scale using the block-kriging interpolation technique. To obtain fluxes, concentrations were multiplied by long-term mean precipitation amounts from the EPA database. An extensive uncertainty analysis was performed to assess the quality of the maps.     

Exploring Ground Vegetation Change for Different Deposition Scenarios and Methods for Estimating Critical Loads for Biodiversity Using the ForSAFE-VEG Model in Switzerland and Sweden

The ForSAFE-VEG model was used to investigate the impacts of climate change and air pollution scenarios on soil chemistry and ground vegetations composition. In particular, the model involves a ground vegetation model incorporating plant changes to ambient site conditions in terms of climate and chemistry, but the model also incorporate competition between the different plant groups. The model was validated against observed values and reproduced observations of tree growth, soil chemistry, and ground vegetation compositions to satisfaction. The results show that the ground vegetation reacts strongly to changes in air pollution, in particular nitrogen as well as to climate change with major shifts in plant composition. A procedure for estimating critical loads for nitrogen, using ground vegetation biodiversity as criterion, was tested and the method seems operable. It suggests that if we want to protect the present biodiversity of the ground vegetation, this will face significant difficulties because of permanent climate change that induced changes in the ecosystem. We conclude that the reference state for ground vegetation biodiversity is rather to be sought for in the future, hopefully using models, than in the past or present.     

Time trend of wet deposition acidifying potential at five ecological monitoring sites in eastern Canada 1981–1993

The Acidifying Potential (AP) of wet deposition has been previously defined by the expression AP = SO₄ ^?-[Ca⁺⁺ + Mg⁺⁺]. The time series over the period 1981 to 1993 for sulphate, calcium plus magnesium and AP concentrations are examined at five ecological monitoring research sites in the eastern half of Canada. At all sites there was a reduction in the concentrations of all 3 parameters over the whole period. As a result the reduction in AP was between 70 and 80% of the sulphate reduction at the 4 sites where precipitation acidity is highest. The annual wet deposition of AP showed a substantial decline in the first half of the period, but has levelled off in the second half, in spite of continuing sulphate decline. In assessing the impact of acidic deposition on surface water systems it is, thus, important to account for the counteraction of sulphate decreases by base cation decreases. This is particularly important for simulation modelling, either diagnostic using past data, or predictive using future sulphur dioxide emission scenarios, where in general cations have been assumed to remain constant.     

A regional scale model for the calculation of episodic concentrations and depositions of acidifying components

An eulerian long-range transport model for the calculation of concentrations of SO₂, SO₄, NO _x , and NO₃ and wet and dry depositions of SO _x (sum of SO₂ and SO₄) and NO _y (sum of NO, NO₂ and NO₃) over Europe is presented. The model is developed in such a way that only routinely available, analyzed or prognostic meteorological fields are required as input data. In this way it is possible to obtain a forecast of the air quality during smog episodes. For evaluation of smog episodes the model provides a way to estimate the contributions of different sources and the effect of emission scenarios. The model has been evaluated for four winter and three summer episodes. The modeled concentrations of SO₂ and SO, are in agreement with the available measurements. A less good agreement is found for NO₂ and NO _x (sum of NO and NO₂) concentrations. For these components the model tends to underpredict the measured values.     

Trace metals in precipitation in Sweden

Trace metals (Cd, Cu, Fe, Mn, Pb, and Zn) concentrations in atmospheric precipitation have been routinely monitored in Sweden since the autumn of 1983. Concentrations are highest in southern Sweden and decrease northward. It is postulated that the long range transport of anthropogenic pollutants from the rest of Europe is the major source of Cd, Pb, and Zn in precipitation. Evidence for this hypothesis is that enrichment factors indicate anthropogenic origin, and Swedish atmospheric emissions of Zn and Cd are 2 to 3 times smaller than deposition fluxes. Also, Cd, Pb, and Zn concentrations are correlated in both space and time and are also well correlated with exSO₄ ⁺, a substance known to be of anthropogenic origin transported long distances.