Trends in wet and dry deposition of sulphur in the United Kingdom

UK data on sulphur deposition trends between the 1960's and 1990's are presented. Long term data sets of sulphur dioxide (SO₂) concentrations at two sites have been analysed and dry deposition determined using a resistance model. Wet deposition has been calculated from non-marine sulphate concentration and rainfall fields for 1978–80 and 1989–93. These maps have been interpolated and corrected for seeder feeder enhancement. The wet deposition of sulphur declined by about 43 % between 1979 and 1993 whereas emissions of sulphur declined by about 32 %. An indication of the trends in sulphur dry deposition is provided by data from Eskdalemuir, a site in southern Scotland where wet deposition and SO₂ concentration have been measured since 1979. Dry deposition at Eskdalemuir has decreased by 70 % and wet deposition by 48 %. Hence, while wet deposition has responded approximately linearly with the decline in UK emissions of sulphur dioxide, dry deposition has declined at twice the rate of decline in UK emissions.     

Wet and Dry Deposition of Sulphur at the Site Melpitz in East Germany. In memorium dedicated to Wolfgang Rolle

Sulphur concentrations in precipitation as sulphate and in air as sulphur dioxide were determined from October 1991 (May 1992), respectively, to December 1995. The total sulphur deposition was calculated from sum of the wet and dry deposition, using the concentration of sulphate and precipitation volume and the concentration and deposition velocity of sulphur dioxide, determined with the micrometeorological gradient method. The concentration of sulphur in precipitation decreased over the period by about 40% and in air about 70%. The wet deposition decreased over the period by about 30%. However there was no decrease in dry deposition despite the reduction in SO₂ concentrations because the deposition velocity varied from 0.16 cm s^-1 to 0.37 cm s^-1 during the period. Therefore no trend was observed in the total sulphur deposition.     

Orographic enhancement of wet deposition in the United Kingdom: Continuous monitoring

Continuous monitoring of cloud and rain samples at three mountain sites in the UK has allowed consideration of the long term impact of the enhancement of the wet deposition of pollutants by orographie effects, specifically the scavenging of cap cloud droplets by rain falling from above (the seeder-feeder effects). The concentration of the major pollutant ions in the cloud water is related to the relative proximity of each site to marine and anthropogenic sources of aerosol. In general, the concentrations of major ions in precipitation at summit sites exceed those in precipitation to low ground nearby by 20% to 50%. Concentrations in orographie cloud exceed those in upwind rain by between a factor of five and ten. The results are consistent with seeder-feeder scavenging of hill cloud by falling precipitation in which the average concentration of ions in scavenged hill cloud exceed those in precipitation upwind by a factor of 1.7 to 2.3 for sulphate and nitrate respectively at Dunslair Heights and 1.5 to 1.8 for sulphate and nitrate at Holme Moss. The results suggest that the parameterisation of this relationship with scavenged feeder cloud water concentrations assumed to exceed those in seeder rain by a factor of two for the production of predictive maps of wet deposition in mountainous regions of the U.K. is satisfactory.     

Long range transport and deposition of mineral matter as a source for base cations

Mineral dust in the atmosphere is generally alkaline, and is a source of base cations in precipitation. Annual emissions of particles from large combustion plants and industrial processes in Europe is of the order of 24 million tonnes, and the calcium content may be as high as 1.4 million tonnes. Emissions from diffuse sources such as agricultural activities, construction and quarrying are much less well known. Emissions of dust from the Sahara have been estimated to more than 200 tonnes, with a calcium content of 3–5%. In northern Europe, airborne concentrations of calcium and the concentration of calcium in precipitation are generally consistent with the anthropogenic emissions and their regional distribution. Transport of dust from Sahara is a major source of base cations in precipitation around the Mediterranean Sea, but the influence diminishes further north. The concentration of calcium in precipitation decreases from south to north and from east to west in Europe. Dry deposition of alkaline particles is not well documented, but may be at least as high as the input by precipitation in regions where there are large emissions. There are still large uncertainty gaps with respect to emissions, transport and deposition of calcium-containing particles.     

Local patterns of sulphur deposition around Halifax/Dartmouth,Nova Scotia: 1979–83.

Five years of sampling support earlier findings that SO₂ emissions from Halifax/Dartmouth, Nova Scotia (population 270,000) cause wet sulphate deposition within 40 or 50 km of the city to be twice regional values. The urban effect is greatest within the city itself. Mean monthly sulphate concentrations in precipitation are usually more highly correlated among stations than is monthly deposition; the highest correlations are among concentrations in and around the city. Month to month variations in sulphate concentration in the city and at Oyster Pond (50 km east of the city) appear to be affected mainly by urban influences; those at St. Margaret's Bay (25 km west of the city) appear to be affected by both urban and regional influences. The urban effect appears to have diminished somewhat during the 5 yr, possibly because the urban emissions have decreased by 35% since 1980.     

sulphur isotope composition of stream water,moss and humus from eight arctic catchments in the Kola Peninsula region (NW Russia,N Finland,NE Norway)

In summer 1994, stream water, moss and humus samples were collected for sulphur isotopic analysis from eight catchments located in the western Kola Peninsula region, where several industrial centres emit high loads of SO₂ and other elements to the atmosphere. Three potential sources of sulphur and their isotopic signatures were identified: (1) marine (δ ³⁴S+20 to +21‰ CDT), (2) anthropogenic emissions (<+10‰), and (3) geogenic (variableδ ³⁴S, mostly <+10‰). Averaged per catchment, the sulphur isotopic composition varies between +6.0 and +16.3‰ for stream water sulphate, +6.0 and +8.4‰ for moss sulphur, and +5.2 and +12.2‰ for humus sulphur. Theδ ³⁴S composition of stream water from the more remote catchments is quite variable, reflecting several natural (geogenic) sources, but it becomes restricted to the range +8 to +10‰ near the pollution sources. A plot ofδ ³⁴S vs. 1:SO₄ in stream water suggests that sulphate originating from the smelters has aδ ³⁴S value ≈+9.5‰, and is a dominant source. Sulphur isotope values for moss and humus are consistent with the deduced composition for the emitted sulphur, though for humus a component of geogenic sulphur incorporated via vegetation uptake may play a role. Further isotopic characterisation of atmospheric emissions, together with environmental samples, is needed to better understand sulphur sources and sinks in the area.     

Estimation of S and NOx-N deposition budgets for the United States and Canada

Extensive wet deposition monitoring data, along with much sparser dry deposition monitoring data and isolated field characterizations of droplet deposition, are used to produce an annual deposition budget for S and NO_x-N for each contiguous U.S. state and Canadian province. The contribution to wet deposition from natural sources is estimated, and wet deposition is adjusted accordingly, to focus the analysis on deposition associated with anthropogenic emissions. The budgets, which are appropriate for 1985–1987, include adjustments for increased local wet and dry deposition near point sources and urban areas, which are generally avoided in selecting monitoring sites. When aggregated over the United States and Canada, estimated wet, dry, and droplet deposition account for about 30, 29, and 4% of anthropogenic S emissions, respectively, implying that 37% is exported. For NO_x-N, estimated wet, dry, and droplet deposition account for 30, 43, and 4% of anthropogenic emissions, with 23% exported. Results are in general agreement with a variety of other observational analyses and regional modeling simulations, particularly for eastern North America, and are consistent with estimates of net horizontal mass fluxes of S and NO_x-N across the Atlantic coast of North America.     

Precipitation chemistry within Kvarner Bay area,Northern Adriatic (Croatia), 1984–1991

The results of rainwater analyses collected at five sampling sites within Kvarner Bay area are presented for the period 1984–1991. The samples were collected on a daily basis in open buckets thus representing bulk samples. Although measurements are referred to as wet deposition samples, they are actually an upper limit for the wet deposition. The rainwater was initially analysed for pH, sulphate and nitrate content, while during the period March 1990 — May 1991 the analyses were extended to major ion concentrations: hydrogen, sulphate, nitrate, chloride, ammonium, sodium, potassium, calcium and magnesium. The pH frequency distribution, pH medians and precipitation weighted average (PWA) concentrations of hydrogen, sulphate and nitrate are presented, as well as wet deposition rates of sulphur (as sulphate) and nitrogen (as nitrate). The dependence of hydrogen, sulphate and nitrate mean concentrations on wind directions and seasons for Site 1 is also given. The highest precipitation acidity is obtained at urban and industrial Site 1 (city of Rijeka) because of the local washout of the atmosphere and influence of dry deposition, and at remote Site 4 (Lake Vrana) due to long-range transport. The neutralizing potential of sea salt and soil dust is responsible for partial neutralization of rainwater at other sites. The influence of sea salt on chemical composition of rainwater is observed at all sites. The estimated wet deposition rates of sulphate and nitrate are close to the values reported for Southeast Europe. The wet deposition rate for ammonium ion at Site 1 is almost double comparative regional values.     

Surface water acidification in the UK; current status,recent trends and future predictions

Data collected at 22 lake and stream sites under the UK Acid Waters Monitoring Network, established in 1988, are assessed. Non-marine sulphate concentrations in surface waters largely reflect the sulphur deposition gradient across the country. Time series analysis indicates an increase in non-marine sulphate concentrations at sites in SW Scotland, the Lake District and in Wales. No similar trends have been detected in deposition data for the same period. Predictions of water chemistry response at each site to the new UNECE sulphur protocol have been made using a long-term, dynamic acidification model (MAGIC). The results indicate that the agreed emissions reductions will lead to recovery at many sites over a 15–20 year timescale but will have little effect at the most impacted sites, within the next 15 years.     

Atmospheric deposition in Fenno-Scandia: Characteristics and trends

Chemical analyses of daily precipitation samples from “background” stations in Europe are discussed together with measurements of airborne SO₂ and sulphate aerosol, and trends in energy usage and SO₂ emissions. Emission sources contributing to the major part of the concentrations of sulphate and nitrate in precipitation are mostly 500 to 1000 km from the receptor area. Although there are no general statistically significant trends in the precipitation chemistry data, minor changes point to an effect of reduced S02 emissions in some areas. The daily data can be used to infer general conclusions with respect to precipitation scavenging efficiency.     

Trends in Airborne Sulphur and Nitrogen Compounds in Norway during 1985–1996 in Relation to Air Mass Origin

Major reductions in emissions of sulphur dioxide and nitrogen dioxide in Europe have significantly reduced the ambient concentrations of both sulphur dioxide, particulate sulphate and nitrogen dioxide, as well as of sulphate in precipitation at Norwegian monitoring sites. In this study, trends in ambient air concentrations were studied in relation to air mass origin by sector analysis. Associated trends in ambient concentrations were derived by non-parametric statistical methods and evaluated on the basis of emission figures within the various sectors. The observed trends correspond well with reported trends in emissions.     

燃煤电厂周边土壤中汞的分布和累积研究进展

汞(Hg)是唯一以气态形式存在于大气环境中的有毒重金属污染物。燃煤电厂作为最重要的人为Hg排放源之一,其释放的Hg可随大气环流运输和转化,并通过干湿沉降进入到陆地和海洋生态系统,造成局域、区域和全球范围内的Hg污染。研究燃煤电厂排放的Hg在大气中的沉降规律及其在土壤中的累积特点,对于深入了解燃煤电厂Hg排放的生态影响具有重要意义。本文综述了燃煤电厂Hg排放污染土壤的途径,分析了电厂周围土壤Hg的浓度水平和空间分布特点,总结了影响土壤Hg分布的主要因素,并对将来的研究方向提出了展望。     

Measurements of precipitation composition at UK EMEP sites 1987–1992 and comparison with the HARM model

Precipitation composition has been measured daily at five UK EMEP sites since 1987. Sulphur dioxide and sulphate aerosol concentrations are also measured daily at the sites. Back trajectories and wind sectors calculated by the Norwegian Meteorological Institute have been used to characterise the variation in wet deposition in terms of air mass source. Contributions to wet deposition from various source regions have been estimated for Eskdalemuir. Observations from the EMEP sites have been compared with output from the Hull Acid Rain Model (HARM). HARM is a Lagrangian model using simplified meteorology but straight-line trajectories. Results are compared on a site-by-site and sector-by-sector basis and the model reproduces the general features of pollutant concentration and wet deposition indicated by the measurements. The possible effects of future reductions in emissions of SO₂ and NOx on precipitation concentrations by wind sector are described.     

The effects of the emissions of the Kostomuksha mining complex on the chemical composition of deposition and soil water in the surrounding pine forests

The Kostomuksha mining complex in Russian Karelia is a major emission point source surrounded by large forest areas near the Finnish border. The sulphur dioxide emissions of the complex are almost 60 000 tonnes and dust emissions about 5 000 tonnes a year. Research into the effects of emissions on the surrounding forests were started in a Finnish-Russian co-operation project in 1992. Deposition measurements during the two first years indicate that the effects of the emissions extend about 30 km to the west of the complex. The annual sulphur deposition near the mining complex has been about 300 mg/m² in bulk precipitation and about 500 mg/m² in throughfall. Sulphur emissions sometimes extend the eastern parts of Finland, but there the deposition is clearly smaller than near to the mining complex. The high calcium emissions neutralize the acidifying effect of sulphur near to the mine and smelter. The iron concentration in precipitation also increased near the complex. Sulphur and calcium decreased in percolation water on moving westwards.     

The status of wet deposition of nitrogen compounds in an intensive dairy farming area in central Japan

(pp. 47–52)

The wet deposition of nitrogen compounds in the intensive dairy farming area and its environs in the northern part of the Kanto region in central Japan was investigated from April 2003 to April 2005. Open-bulk samplers were used to collect open-bulk precipitation, which approximates the sum of wet and dry deposition. Furthermore, wet-only samplers were applied to collect the precipitation for every 1 mm in a rainfall, termed the wet sample. The concentrations of total nitrogen and ammonium ions in the open-bulk precipitation were high in the central part of the dairy farming area and low in the remote mountainous area more than 15 km away the concentrations were generally high during winter and spring, and low during summer and autumn. There was a large difference in the annual deposition of nitrogen between the farming area and the surrounding area. The annual deposition of nitrogen in the farming area was significantly high compared to the values of existing data in Japan and Europe. The concentrations of respective nitrogen compounds in the wet sample, which accounted for 40 of the total rainfalls events, were notably high at the beginning of precipitation and rapidly decreased by 8 mm of continuous precipitation. The nitrogen concentrations at the beginning of precipitation were high in the farming area, and relatively low in the surrounding area. It was thought that the cause of the large wet deposition in the farming area was due to ammonia emissions, mainly from cattle manure produced at dairy farms. The factors of the seasonal changes were considered to be the frequency and the amount of precipitation, and the change in ammonia emissions from manure management performed by dairy farmers.     

The Spatial and Temporal Distributions of Spheroidal Carbonaceous Fly-Ash Particles (SCP) in the Sediment Records of European Mountain Lakes

Sediment cores were taken from 31 mountain lakes in 11 countries across Europe. For each core a full spheroidal carbonaceous particle (SCP) profile was produced. SCP are derived from the high temperature combustion of fossil-fuels and provide an unambiguous record of the atmospheric deposition of anthropogenic pollutants. The data from the sediment cores were therefore able to show both temporal and spatial trends in pollutant deposition across the continent from Svalbard to southern Spain and from Ireland to the Tatra mountains. In general, the temporal trends throughout Europe were remarkably consistent and were seen to be in good agreement with known historical emissions, combustion figures and modelled historical pollutant patterns for source countries. Spatial patterns showed that highest concentrations and accumulation rates were in central Europe, with clear decreases northwards and southwards from the region. An east to west decrease was also apparent. SCP profiles can be converted to full post-Industrial inventories and normalised against a ²¹⁰Pb inventory to create a ‘pollution index’ covering the whole of the SCP record. Such indices take into account sediment variability and some catchment influences and are therefore better for inter-site comparisons. These results were seen to show a clear latitudinal pattern, with a maximum at around 50°N and declining to the north and south. This agrees with European sulphur emissions data and are generally consistent with EMEP modelled distribution patterns. In many cases the SCP temporal profiles could only be explained by using emission and combustion statistics from more than one country emphasising the transboundary nature of particulate transport throughout Europe, in general, supporting EMEP modelled ‘blame matrices’.     

Deposition around a coal-fired power station during a wintertime precipitation event

The contribution to local wet deposition of emissions from a coal-fired power station at Inkoo on the south coast of Finland has been investigated during a wintertime precipitation event. Making use of intensive radiosonde and weather radar observations of meteorological factors, concentrations of sulphur in deposition due to plume washout were predicted by a short-range deposition model. The model used the scavenging coefficient to parametrize the wet removal of pollutants, and it took into account the wind drift of falling precipitation particles within the plume. The model predictions were then compared with the chemical analysis results from snowfall samples collected within 10 km of the power station during the experiment.The experiment was performed ahead of a deeply-occluded front during a period with strong advection of long-range transported pollutants. No reliable sign of the influence of the power station on the sulphate deposition could be identified. On the other hand, the deviations of acidity from the mean pH-value of 4.1 were concentrated in one sector near the expected area of deposited plume pollutants. If local emissions were responsible for these deviations, the explanation may lie in a slightly incorrectly estimated plume direction or the effects of alkaline fly ash. Nevertheless, definite conclusions cannot be drawn, because only a few collectors happened to be sited in the modelled sector of plume washout and none in its maximum area.     

Sulphur isotope tests of seasalt correction factors in precipitation: Nova Scotia,Canada

Sulphate in precipitation is an index of atmospheric pollution but natural sources also contribute to its concentration. One of the dominant natural sources of sulphate is seasalt and reseachers have routinely calculated its proportion using reference species such as Cl^?, Na⁺ and Mg²⁺. Such a method of estimation assumes conservatism of, and a purely marine origin for, the reference species. The stable isotopes of sulphur were utilized to assess the validity of these assumptions for a coastal area in Canada by taking advantage of the sulphur isotopic signature of seasalt sulphate (+20‰). The seaspray component (PSS) was calculated for 39 coastal rain events using Cl^?, Na⁺ and Mg²⁺ as reference species and these parameters were plotted against the sulphur isotopic composition of sulphate in the sample. All three regression lines yielded a value of ≈ +4‰ for a sample containing no seasalt. The regression lines extrapolated to δ ³⁴S≈+20, +17 and +16‰ using Cl^?, Na⁺ and Mg²⁺ respectively for a theoretical sample whose sulphate was derived totally from seasalt. This observation confirms that for this locality, the marine component of precipitation sulphate utilizing Cl^? is isotopically equivalent to sea spray sulphate, suggesting that Cl^? is a suitable reference species. It also supports the use of δ ³⁴S_SO4 as a constraint on the selection of the correct reference species for estimation of the seasalt component in a particular study area.     

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.     

Spatial Distribution of Gaseous And Particulate Matter Emissions in Greece

The quantification of air pollutant emissions to theatmosphere, from anthropogenic and natural sources, in Greece is the main focus of the current work. Emissions are spatially and temporally disaggregated in a high resolution grid based on a methodology given in Atmospheric Emissions Inventory Guidebook, CORINAIR. The anthropogenic emissions are equal to those given by UNECE through the EMEP program and an estimation of their spatial distribution in a 5 × 5 km² grid is performed. Furthermore, natural emissions are calculated using the bottom-up approach and are distributed to the 5 × 5 km² grid. The methodology used for the estimation of the spatial and temporal distribution of the emissions is presented as well as the contribution of each individual source in the distribution of gaseous and particulate matter emissions in Greece. Energy production, agriculture and road transport have been recognized as the activities in Greece mainly contributing to the anthropogenic emissions. Other important sources include biogenic VOC and resuspended dust.