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1.
There is currently much interest in mapping critical loads for nitrogen deposition as part of a strategy for controlling nitrogen emissions. While nitrogen deposition may cause acidification and excess nutrient effects, the former were considered previously in studies of sulphur deposition. In the UK, work on developing nutrient nitrogen critical loads maps has used several methods and databases. Two approaches are described here, one a steady state calculation using a nitrogen saturation limit for soil systems, the other an empirical estimate of critical loads set to prevent changes to vegetation communities. The empirical method uses national species records and land cover data derived from satellite imagery. Maps drawn from the available data are dependent upon a number of factors which reflect the approach used. To apply the nutrient critical loads to a strategy for future abatement measures, the nutrient nitrogen values for soils have been incorporated within a “critical loads function” which takes into account both acidity and nutrient effects as related to deposition loads for sulphur and nitrogen. This function may be used with deposition data to identify the need for sulphur and nitrogen emission reductions.  相似文献   

2.
A critical load data base was developed for Europe and Northern Asia using the latest data bases on soils, vegetation, climate and forest growth. Critical loads for acidity and nutrient nitrogen for terrestrial ecosystems were computed with the Simple Mass Balance model. The resulting critical loads are in accordance with critical loads from previous global empirical studies, but have a much higher spatial resolution. Critical loads of acidity are sensitive to both the chemical criterion and the critical limit chosen. Therefore a sensitivity analysis of critical loads was performed by employing different chemical criteria. A critical limit based on an acid neutralizing capacity (ANC) of zero resulted in critical loads that protect ecosystems against toxic concentrations of aluminium and unfavourable Al/Bc ratios, suggesting that ANC could be an alternative to the commonly used Al/Bc ratio. Critical loads of nutrient nitrogen are sensitive to the specified critical nitrate concentration, especially in areas with a high precipitation surplus. If limits of 3–6 mg N l?1 are used for Western Europe instead of the widely used 0.2 mg N l?1, critical loads double on average. In low precipitation areas, the increase is less than 50%. The strong dependence on precipitation surplus is a consequence of the simple modelling approach. Future models should explore other nitrogen parameters (such as nitrogen availability) instead of leaching as the factor influencing vegetation changes in terrestrial ecosystems.  相似文献   

3.
The Abatement Strategies AssessmentModel, ASAM, has been used to investigateEuropean emission abatement policies for ammoniaand oxides of sulphur and nitrogen. Thesepolicies are designed to reduce the depositionof acidifying substances towards critical loadsdefining the deposition which ecosystems cansustain. Since critical loads are not allattainable the model has been set up to reachvarious intermediate target loads. This paperuses the model to illustrate the sensitivity ofthe derived abatement strategies to the choiceof target load. Particular attention is paidto the various methods of `gap closure',designed to calculate target loads. Thesemethods have been discussed within the frameworkof the UN ECE Task Force on IntegratedAssessment Modelling in its preparations for thenew UN ECE `multi-pollutant multi-effectprotocol' and involve the reduction of the gapbetween the situation in 1990 and the criticalloads. The `gap' can be measured using variousmethods, `area', `ratio' and `accumulatedexceedance'. It is shown that the methods ofdefining target loads have an important bearingon the nature of abatement strategies forpollutants, in terms of the distribution acrosscountries of both costs and benefits. The`accumulated exceedance' approach reflects boththe differing sizes of ecosystem areas indifferent parts of Europe and the differentamounts by which their critical loads areexceeded. It probably reflects much morerealistically the relationship betweendeposition levels and damage to ecosystems.  相似文献   

4.
The goal of this study is to give a comprehensive and quantitative estimation of the uncertainty of computed in different scale nitrogen (N) and sulphur (S) critical loads (CL) values for terrestrial ecosystems of the Northern Asia, European part and the North-Western regions of Russia. The CL values are used to set goals for future deposition rates of acidifying compounds so that the environment is protected. In this research CL values for terrestrial ecosystems are determined using the expert-modelling geoinformation system (EM GIS) approach. UNCSAM software package is used as the tool for uncertainty analysis. The analysis presented here focuses on the estimation and effect of the input source uncertainties and sensitivities on the CL values in various regions under study. In spite of the region, nitrogen uptake by vegetation, nitrogen leaching from terrestrial ecosystems and the difference between deposition and uptake by plants of base cations (BC) are the most influential factors for all terrestrial ecosystems of Russia.  相似文献   

5.
In contrast to Europe and North America, air pollution in Asia is increasing rapidly, resulting in both local air quality problems and higher acidic depositions. In 1989, an east-west group of scientists initiated a multi-institutional research project on Acid Rain and Emissions Reduction in Asia, funded for the past two years by the World Bank and the Asian Development Bank. Phase I, covering 23 countries of Asia, focussed on the development of PC-based software called the Regional Air Pollution INformation and Simulation Model (RAINS-ASIA). A 94-region Regional Energy Scenario Generator was developed to create alternative energy/emission scenarios through the year 2020. A long-range atmospheric transport model was developed to calculate dispersion and deposition of sulfur, based upon emissions from area and large point sources, on a one-degree grid of Asia. The resulting impacts of acidic deposition on a variety of vegetation types were analyzed using the critical loads approach to test different emissions management strategies, including both energy conservation measures and sulfur abatement technologies.  相似文献   

6.
Critical loads of acid deposition for ecosystems in South China are derived by synthesizing the critical loads of acid deposition for soils, the critical loads of SO2 dry deposition for ecosystems, as well their exceedance. The results show in the southeast of Sichuan province around Chongqing municipality, the central and north of Guizhou province around Guiyang municipality, and the most areas of Jiangsu province, both the critical loads for soils and critical loads of SO2 dry deposition are exceeded. In Guangxi Zhuang Autonomous Region and some areas among Jiangxi, Zhejiang and Anhui provinces, the critical loads of SO2 dry deposition is the only restricting factor. There is no area where the critical load for soil is the only restricting factor in South China, so only the critical load for soil is not enough to be the basis to make sulfur abatement scheme.  相似文献   

7.
Acidification has the potential to become a widespread problem in parts of Asia. Just how widespread this risk may be is discussed by comparing sulphur deposition to critical load estimates, taking into account neutralising base cation deposition from soil dust. Two scenarios for the sulphur emission in 2025 are used as inputs to the MATCH atmospheric transfer model to estimate sulphur deposition scenarios. Net acidic deposition using a low and high base cation deposition input is compared to a map of sensitivity of terrestrial ecosystems to acidic deposition. Two ranges of critical loads assigned to this sensitivity map are used. The variability in the maps showing risks of acidification using low and high estimates for critical loads and base cation deposition for two different development pathways is discussed. Certain areas are shown to be at risk in all cases whereas others are very sensitive to the values used to estimate risk.  相似文献   

8.
Critical loads have been used in the revision of the Sulphur Protocol of the Convention on Long Range Transboundary Air Pollution (LRTAP) of the United Nations Economic Commission for Europe (UN/ECE). Critical loads, i.e. maximum allowable depositions which do not increase the probability of damage to forest soils and surface waters, have been computed and mapped for Europe by means of the Steady-state Mass Balance Method, using national data and, if national data were unavailable, using a European database. Results show that areas with low critical loads are located mostly in northern and central Europe. The reduction of the excess of sulfur (S) deposition over critical loads was a starting point for negotiations leading to the Oslo Protocol on Further Reduction of Sulphur Emissions (the “Second Sulphur Protocol”). The new protocol protects about 81%, 86% and 90% of the ecosystems' area in 2000, 2005 and 2010, respectively. In addition, the total European area in which sulphur deposition exceeds critical loads by more than 500 eq ha?1 yr?1 will be reduced from about 19% in 1980 to practically zero in 2010. Besides these results, a methodology is presented which allows the combined assessment of the acidifying effects of S and N as well as the eutrophying effects of N deposition on ecosystems (so-called critical load functions and the protection isolines derived from them). This methodology is well suited to integrate ecosystem sensitivities into future negotiations on the reductions of nitrogen (N) compounds, taking into account present or anticipated S emissions.  相似文献   

9.
We assessed critical loads of acid deposition and their exceedance for soils in the Kola Peninsula using a simple balance method and mapped them within 1.0° × 0.5° longitude/latitude grid cells. Critical loads of acidity vary from 200 to 800 molc/ha/y with the type of soil, parent rock, vegetation and climatic conditions. The critical deposition values are dominated by S contribution. Present sulphur depositions are higher than critical values in the large part of the Kola Peninsula (about 40% of total area). The greatest excess (800–1200 molc/ha/y) occur in north-western and western parts, especially in surroundings of nickel smelter in Nickel. Terrestrial ecosystems in the north-western Kola Peninsula are particularly susceptible to acid deposition damage due to relatively high soil sensitivity and heavy sulphur deposition.  相似文献   

10.
Critical loads are estimated in the UK by the Department of Environment's Critical Loads Advisory Group and sub-groups. The Mapping and Data Centre at ITE Monks Wood acts as the National Focal Centre for the UNECE programme for mapping critical loads. The centre is responsible for the generation of UK data sets and their application for national and European purposes. To make effective use of these data, it is necessary to draw upon other environmental data and examine the issues of scale, uncertainty and the way that data are presented. This paper outlines the methodologies which have been employed to derive national maps. Early critical load maps were not vegetation specific, but now critical loads for acidity and for nutrient nitrogen for soils, critical levels maps for ozone and sulphur dioxide, and sulphur deposition maps, have been generated on a vegetation or ecosystem specific basis. These have been used to derive a number of different types of critical load and exceedance maps. The results show the importance of the method selected and the data used for the interpretation. The visualisation of critical loads and the corresponding exceedance data is an important aspect in producing information for pollution abatement strategies.  相似文献   

11.
Critical loads for sulphur and nitrogen are defined to produce effective control strategies over Europe, such as those of the new sulphur protocol. To determine the critical load exceedances on the European scale it is necessary to simplify and generalize. The spatial variation on a scale smaller than the 150 × 150 km EMEP grid squares is considered for critical loads, via a cumulative frequency distribution and the 95 percentile for the grid square is determined. The deposition is assumed to be uniform over the area and the exceedance over the 95 percentile critical load is determined. In reality, the spatial variation is considerable for critical loads as well as for deposition. Calculations based on the frequency of local critical load exceedances have been made for two grid squares in southern Sweden. Local critical loads for acidity are compared to local deposition. Deposition variations due to pollution gradients within the square and to ecosystem structure have been considered. The results are similar for the two squares. The calculations based on local exceedances on 50×50 km grid squares and consideration to landuse variability, indicate that in order to protect 95% of the ecosystems in the square, emission reductions 25% greater than the large-scale European approach are needed. The effect of enhanced deposition at forest edges is of relatively small importance for the total exceedance.  相似文献   

12.
Critical loads of nutrient and acidifying nitrogen, as well as of sulphur and acidity, were derived for various ecosystems in China using the steady state mass balance (SSMB) equations. The weathering rates of major soils necessary for applying SSMB were calculated through the PROFILE model on the basis of mineralogical data from experimental analysis. The growth uptakes of nitrogen and base cations were also derived by multiplying the annual increases in biomass with the element contents of the vegetation. Using a geographical information system (GIS), 1°(latitude)×1°(longitude) critical load maps of China with different percentiles were compiled. Results indicate that low critical loads of S (< 0.5 keq·ha?1·a?1) occurred predominately in southwest and northeast China, and the critical loads of southeast China were intermediate and in the range of 0.5～1.0 keq·ha?1·a?1. In addition, the critical loads of N were very low for desert ecosystems in northwest China and high for agricultural ecosystems in east China. Among the ecosystems with intermediate critical load of N, coniferous forests may be more sensitive to N deposition than broad-leaf forests and temperate steppes.  相似文献   

13.
The impact of acid deposition, attributable to sulphur and nitrogen pollutants, on the soils of Scotland has been analysed using a critical loads approach. The critical load of a soil (as an indicator of ecological damage) is calculated from the soil parent material controlling weathering and soil development. Using existing soil survey information national maps for critical loads of acidity and the sulphur fraction are presented for soils under natural and semi-natural ecosystems. The results show that highly sensitive soils, that is those derived from quartzite and granite are limited in occurrence. However, there are large areas of sensitive soils predominantly to the north and west of the Midland Valley and in the Southern Uplands, in receipt of acid deposition in excess of their critical load. Enhanced soil acidification should be widespread in these areas and consequently the ecosystems which they support will be adversely affected. The least sensitive soils, overlying limestone or marl, are restricted in occurrence and are confined to the major deposits of marine alluvium. The results of the analysis may be used to help policy makers derive emission abatement strategies in the context of the European Sulphur protocol renewal in 1993. In Scotland the maps may be used to aid the planning of large scale afforestation.  相似文献   

14.
Critical loads of acidity were calculated using the PROFILE model to assess the forest ecosystem sensitivity to acid deposition in the Asian part of Russia — Siberia. The main input parameters and the output were mapped. At present atmospheric inputs of acid forming pollutants to the study territory are mainly related to transregional and transboundary pollution from Europe. It was shown that the most sensitive to acid loading are ecosystems of the Tundra zone and of the East Sayan mountains' coniferous forests with dystric cambisols and gleysoils, critical loads of actual acidity (CL(Ac)) = 0–0.3 keq/ha/yr. The most tolerant ecosystems are ecosystems of deciduous forests with podsoluvisols, luvisols and humic luvisols of South Taiga zone in West Siberia, CL(Ac) = 3.5–7.0 keq/ha/yr. Generally the values of critical loads are increasing from the North to the South and from the East to the West following the bioproductivity, annual soil temperature and alkalinity of deposition increases.  相似文献   

15.
Critical loads are used in international negotiations to reduce acid deposition resulting from emissions of sulphur and nitrogen compounds within Europe. For freshwater ecosystems, the First-order Acidity Balance (FAB) model is used to generate national maps of critical loads and exceedances for both sulphur (S) and nitrogen (N). In Wales, two survey datasets have been used to calculate critical loads and exceedances; one based on water bodies selected to be "most-sensitive" to acidification within a 10 km grid and the other based on a random selection of standing waters. Both datasets indicate that critical loads were exceeded in 1990 in a significant proportion of Welsh lakes and streams; 36% of sites in the grid-based survey and 31% of sites in the random survey. However, implementation of the Gothenburg Protocol would protect all but 6% of sites in the grid-based survey and all sites in the random survey. Assessment of the relative success of the Gothenburg Protocol in protecting Welsh freshwater ecosystems therefore depends on the site selection strategy employed.  相似文献   

16.
Many natural and semi-natural vegetation communities are sensitive to eutrophication; most eutrophication is caused by human activities. Critical loads have been developed in Europe to provide an effects-based approach to pollutant abatement including nitrogen deposition. Critical loads to protect ecosystems from eutrophication from excess nitrogen are only specified for very broad habitat types (e.g., ‘dry heaths’) and as a range of values (e.g., between 10 and 20 kg N ha?1 year?1). There may be considerable variation in vegetation communities within a broad habitat and there is a requirement (e.g., from conservation agencies, etc.) for more precise critical loads for more clearly specified receptors (habitats, vegetation communities). This paper demonstrates the use of endorsement theory to rationalise incomplete, qualitative and conflicting information on abiotic parameters (e.g., climate, management) that may influence the vegetation response to nitrogen deposition and hence, the critical loads. The endorsement theory approach is tested for 22 heathland community types in the UK (as described by the National Vegetation Classification of Rodwell, Cambridge University Press, vol. 3, 1991) to determine if the critical load for a community should be nearer the upper or lower limit of the published ranges. The results give a ‘confident’ endorsement for one heath community and a ‘likely’ endorsement for a further 13 communities for a critical load at the lower limit. The endorsements suggest that the critical load for most heaths should be at the lower end of the range meaning that current estimates of the exceeded area calculated using the mid-point of the range is an underestimate.  相似文献   

17.
Tao  Fulu  Feng  Zongwei 《Water, air, and soil pollution》2000,124(3-4):429-438
The critical loads of SO2 dry deposition in South China,which is transferred from critical level, as well the excess ofcritical loads are computed and mapped. The areas with thelowest critical load and the highest excess are, respectively,identified. The research is complementary to the previousresearches on critical loads for soils, and expected to beintegrated with them to make efficient sulfur emission abatement strategy.  相似文献   

18.
This paper presents an explorative, quantitative analysis of acidification and eutrophication of natural terrestrial ecosystems caused by excess sulfur (S) and nitrogen (N) deposition. The analysis is based on a steady-state approach, involving the comparison of deposition fluxes with critical loads to identify areas where critical loads are exceeded. Deposition fields for sulfur and nitrogen were obtained from the STOCHEM global chemistry-transport model, and they were combined with estimated base cation deposition to derive net acid deposition fluxes. The results indicate that the critical loads for acidification are exceeded in 7–17% of the global area of natural ecosystems. In addition, comparison of nitrogen deposition with critical loads for eutrophication yielded an exceedance in 7–18% of the global natural ecosystems. Apart from serious problems in the heavily industrialized regions of eastern USA, Europe, the former Soviet Union, and large parts of Asia, risks are also found in parts of South America, and West, East and Southern Africa. Both acidification and eutrophication risks could significantly increase in Asia, Africa and South America in the near future, and decrease in North America and Western Europe. Accounting for the effects of N in the analysis of acidification significantly enlarges the potentially affected areas and moves them away from highly industrialized areas compared to studies considering S deposition alone. Major uncertainties in the approach followed are associated with upscaling, the estimates of S, N and base cation emission and deposition fluxes, the critical loads to describe ecosystem vulnerability and the treatment of soil N immobilization and denitrification.  相似文献   

19.
Acidic deposition is considered a problem in Europe and North America but the potential for ecosystem damage from this pollution is also increasing rapidly in many developing countries. It is therefore important to assess current and future risks of ecosystem effects due to acidic deposition in these areas. It is possible to indicate risk areas by linking an assessment of sensitivity to net acidic input rates derived from deposition estimates for sulphur and nitrogen compounds and base cations. A method to assess and map a relative scale of terrestrial ecosystem sensitivity using international datasets is presented. The assessment relies on the determination of buffering mechanisms that prevent effects related to acidic deposition. Land-cover data, edaphic and climate datasets are combined using a GIS. Large areas are assessed as highly sensitive to acidic deposition in tropical regions of Asia, South and Central America and Africa, and also in the Boreal forests of northern Asia. Sensitive areas cover forest and non-forest ecosystems and some areas of agricultural production. Critical loads are not evaluated in this project but initial estimates will be applied to sensitivity classes at a further stage which will allow estimation of areas at risk by comparison with deposition.  相似文献   

20.
The scientific support of negotiations on emission reductions under the framework of the Convention on Long-range Transboundary Air Pollution of the UN Economic Commission for Europe has been based during the last decade on the integrated assessment of sources, including abatement costs, and risks to receptors (e.g. forests, lakes) quantified by critical loads. The shift from a single-pollutant (sulfur) protocol in 1994 to a multi-pollutant protocol in 1999 necessitated an extension of the methods by which critical loads were computed and mapped. Instead of a single critical load for acidification, methods were now developed to assess the risk of acidifying effects of both sulfur and nitrogen deposition as well as the eutrophying effects of nitrogen on sensitive elements of the environment. Collaboration with a scientific network of 24 national institutions ensured a successful implementation of the proposed methodology across countries. This paper summarizes the methodology, describes the latest input data and presents critical load maps on the basis of which about 98% and 78% of European ecosystems would be protected against acidification and eutrophication, respectively, by the year 2010 according to the multi-pollutant multi-effect protocol.  相似文献   

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