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1.
On the basis of modified simple steady state mass-balance equations, the critical loads for nutrient and acidifying nitrogen as well as for sulphur and acidity have been calculated for various ecosystems of northern Asia using simplified expert-modelling GIS and grid cells 150×150 km. The minimal values of critical loads of nitrogen, CL(N), (<50eq a/yr)=" were=" shown=" for=" arctic=" and=" subarctic=" ecosystems=" and=" the=" maximal=" ones=" (=">300eq/ha/yr) for ecosystems of chernozemic and chernozem-like soils in southern Siberia and the Far East. The minimal values of critical loads of sulphur, CL(S), as well as acidity were shown predominantly in the northern part of east Siberia and in the Kamchatka peninsula and the maximal ones for ecosystems having neutral and alcaline soils. The corresponding exceedances were indicated for many regions of the northern part of Asia with maximal values for regions of Ural mountains, frontery of Kazakhstan, Altai, lower Yenisei river flow, Far East, Sakhalin and South-Kurilean islands.  相似文献   

2.
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   

3.
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   

4.
South Africa is the most industrialised country in southern Africa and stands at some risk from negative pollution impacts. To the authors' knowledge, this paper presents the first attempt to apply the critical loads approach on the African continent; although sensitivity mapping has been performed for Africa and the rest of the world (Kuylerstierna et al, this conference). Actual sulphate and base cation deposition loads in Mpumalanga (formerly the Eastern Transvaal province of South Africa) were mapped from 16 monitoring sites. The region is characterised by long, dry periods with little rain, high evaporation (up to 8 mm per day) and low run-off (15% of MAP). Provisional critical load and exceedance maps were produced for the surface waters using the Steady-State Water Chemistry Model and the Diatom model. Maps of soil sensitivity to acid deposition, based on bedrock lithology, soil chemical characteristics and land cover, were produced. A weathering rate of 0.39–0.86 keq/ha/year was calculated for the most sensitive sites and taken as the critical load, based on the assumption that the weathering rate represents the buffering ability of the system. The critical loads were contrasted with measures of actual deposition to examine potential scenario's for critical load exceedances. Akey factor in refining the sensitivity maps, and allowing estimation of the critical loads, is the accurate calculation of weathering rates under the warmer and more arid environmental conditions prevalent in South Africa. In a developing country such as South Africa, where research resources are limited, the critical loads approach is a valuable means of assessing the risk of potential impacts of atmospheric deposition.  相似文献   

5.
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   

6.
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   

7.
To investigate the weathering rates of different soil parent materials which occur in Scotland, a study has been undertaken in which detailed soil mineralogy has been used to calculate base cation release. To calculate base cation release, this data, and supplementary soil chemistry and physical attribute data, have provided the input to the PROFILE model. The model is a multi-layer, steady state, deterministic model in which the soil is represented by a series of mixed tank reactors, each of which has the mineralogical, physical and chemical attributes measured for individual soil horizons. The major parent materials from which Scottish soils have developed are glacial till, derived from acid to basic igneous rocks, schist and other metamorphic types, Lower Palaeozoic greywackes and shales, Old Red Sandstone sediments, Carboniferous sediments and Permo-Trias sediments. For each of the parent materials, three soil profiles were analysed and used with the PROFILE model. The base cation release rates, calculated for these parent materials in the top 50cm of the soil profile, varies between 0.2 and 3.2 keq/ha/yr, although, for a given parent material, the range was usually quite small. In general, these results compare very favourably with those suggested for the calculation of critical loads using an empirical approach proposed at Skokloster. In comparison with current rates of deposition, this suggests many of these soils are being acidified and that for many soil-plant combinations, the critical load may be exceeded.  相似文献   

8.
The project Comprehensive Control and Demonstration for Acid Deposition in Liuzbou area is a national key project in the 8th Five-year-plan, and the study on critical loads will provide scientific and quantitative accordance for formulating control strategy. In this paper, critical loads of acid deposition to soil in Lirzhou area, China, were calculated using the Steady State Mass Balance method (SMB and PROFILE) and dynamic modeling methods(MAGIC), based on data obtained from field investigations and physiochemical properties measured through experiments such as the organic content, cation exchange capacity, base saturation, sulfate adsorption capacity, gibbsite coefficient, biomass base cation uptake and selectivity coefficient for cations. Weathering rates necessary to calculate soil chemistry in applying SMB and MAGIC model were determined by computation with PROFILE using independent geophysical properties such as soil texture and mineralogy as the input data, or by the total soil base cation content correlation. The results have shown that the critical loads of acidity in this area are in the range of 0.7–6.0 keq ha–1 yr–1, indicating sulfur deposition should be cut down by 50–90 percent of the present level. The upper soil layer is the most sensitive. The maximum allowable deposition loading of this area is also presented in the paper.  相似文献   

9.
In spite of numerous experimental studies, it has, sofar, not been possible to link historic changes inforest growth to acid deposition at regional scales,partly due to difficulties in modeling the ecologicalcomplexity of forests. We analyzed radial incrementdata from increment cores from >31 000 spruce forestplots in southern Norway from 1954–1996. Using acombination of a bio-stratification model to controlconfounding factors, and a catchment model foracidification, we demonstrate for the first time aspatial and temporal co-variation between forestgrowth and both nitrogen deposition and acidification,as indicated by acidity critical loads exceedances.Increases in growth during the 1960–1970s, followed bya subsequent decline in the 1980–1990s, were bestexplained by combined actions of acidification,nitrogen deposition and climatic stress on forestgrowth. While forest conditions varyprimarily with natural growing conditions, the resultssuggest that boreal forests are sensitive to moderatelevels of nitrogen and sulphur deposition whereacidity critical loads are low, and that effects maybe observed over relatively short time scales.  相似文献   

10.
A critical load of a pollutant is the level of input below which no harmful ecological effects occur to a complex ecosystem. Critical loads are being used in policy decisions regarding air pollution emissions. In this paper, we applied four mass and charge balance methods of calculating critical loads to two northern hardwood forests in the northeastern United States. Critical loads for nitrogen deposition with respect to acidity ranged from 0–630 eq/ha-yr. Critical loads for nitrogen deposition with respect to effects of elevated nitrogen (eutrophication and nutrient imbalances) ranged from 0–1450 eq/ha-yr. At both the Hubbard Brook Experimental Forest (HBEF) and Huntington Wildlife Forest (HWF), the critical load for nitrogen with respect to acidity was exceeded. At the HBEF, due to reduced forest growth, the critical load for nitrogen with respect to nutrient imbalances and eutrophication was exceeded in recent years. At Huntington Wildlife Forest, the critical load with respect to nitrogen effects was also exceeded. This analysis demonstrated that the calculated critical load of nitrogen varies in response to changes in environmental conditions such as variations in atmospheric deposition of sulfate or changes in forest biomass accumulation.  相似文献   

11.
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   

12.
As a basis for experimentation, inputs and outputs of biogeochemicals were observed in coniferous stands in Denmark, the Netherlands, Germany and Ireland. The range of deposition observed is characteristic of populated regions of northwest Europe, from only moderately polluted Atlantic areas through decreasing marine influence and increasing deposition of anthropogenic nitrogen and sulphur. In intensive agricultural regions, ammonium inputs are high enough to cause nitrogen saturation of ecosystems, and nitrificationacidification is a major soil process. Co-deposition of ammonia and sulphur dioxide may be significantly increasing loads of N and S in forests in the region. Input-outputs are balanced for seasalts in the maritime sites, and sulphur outputs from the rooting zone also reflect the inputs to a large degree on these sites. Mobilisation of cations, notably aluminium, apparently occurs as a result of acidity generated by nitrogen transformations.  相似文献   

13.
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   

14.
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   

15.
Critical loads of acidity were estimated for upland forests in Eastern Canada using the steady-state Simple Mass Balance (SMB) Model. A consistent methodology was applied to the entire region, although critical loads were estimated separately for the Atlantic provinces (New Brunswick, Nova Scotia, Prince Edward Island and Newfoundland), Quebec and Ontario using different data sources. In this project, critical load estimates and steady-state exceedance values did not include the effect of forest fire and forest harvesting, which could have a considerable impact on critical loads in Eastern Canada. The observed soil pH – base saturation relationship for forest soils indicated that the constants used into the calculation of alkalinity leaching should be set to 10 (M/M) for the molar Bc/Al ratio in soil leachate and 109 (mol L?1)2 for the gibbsite dissolution constant. The area-weighted median critical load for each province varied between 519 (Quebec) and 2063 eq ha?1 y?1 (Prince Edward Island), with a median critical load value for Eastern Canada of 559 eq ha?1 y?1. It is estimated that approximately 52% of the mapped area is exceeded in terms of acidity according to the 1994–1998 average total (wet + dry) atmospheric deposition. Greatest exceedances occurred in Ontario and Quebec and in the south of Nova Scotia, due to low critical loads and high loads of acid deposition.  相似文献   

16.
SO4 2?, NO3 ? and H+ depositions are estimated in the Brazilian territory based on the existing rainfall chemical data and on annual rainfall distribution over the whole territory. Local and regional depositions are estimated. Rainfall chemical data over the Braziliian territory shows that the average pH values are usually low (between 4.0 and 5.5). These values are observed in the tropical Amazon forest as well as in urban areas. However, the rainwater acidity in the tropical forests are due to organic acids naturally produced by the vegetation while in urban areas the acidity is mainly due to acidic anion deposition (NO3 ? and SO4 2?). In some Amazonian areas, the average input values through rainfall for NO3 ? is about 0.06 keq.ha.yr?1 and for SO4 2? is between 0.23 and 0.54 keq.ha?1.yr?1. On the other hand, in some urban centers, such as São Paulo, values of .072 keq.ha?1.yr?1 for NO3 ? and 1.16 keq.ha?1.yr?1 of SO4 2? are found and in sites where sulfate sources (coal mining) are present, as for the area of Florianópolis, values as high as 5.59 keq.ha?1.yr?1 for SO4 2? are found.  相似文献   

17.
The essential parameters needed for the calculation of critical load of sulfur, CL(S), are base cation weathering rate, base cation uptake, acid neutralizing capacity leaching and base cation deposition. These parameters are estimated and mapped for the most area of terrestrial ecosystems of Thailand using data of national data soil survey. The values of CL(S) range from <200 to 2,225 eq.ha?1yr?1 and about 70% of terrestrial ecosystems are characterized by low values (<200 eq.ha?yr?1). These CL values reflect the sensitivity of Thai ecosystems to sulfur deposition.  相似文献   

18.
One of the major threats to the structure and the functioning of natural and semi-natural ecosystems is the recent increase in air-borne nitrogen pollution (NHy and NOx). Ecological effects of increased N supply are reviewed with respect to changes in vegetation and fauna in terrestrial and aquatic natural and semi-natural ecosystems. Observed and validated changes using data of field surveys, experimental studies or, of dynamic ecosystem models (the empirical approach), are used as an indication for the impacts of N deposition. Based upon these data N critical loads are set with an indication of the reliability. Critical loads are given within a range per ecosystem, because of spatial differences in ecosystems. The following groups of ecosystems have been treated: softwater lakes, wetlands & bogs, species-rich grasslands, heathlands and forests. In this paper the effects of N deposition on softwater lakes have been discussed in detail and a summary of the N critical loads for all groups of ecosystems is presented. The nitrogen critical load for the most sensitive ecosystems (softwater lakes, ombrotrophic bogs) is between 5–10 kg N ha–1 yr–1, whereas a more average value for the range of studied ecosystems is 15–20 kg N ha–1 yr–1. Finally, major gaps in knowledge with respect to N critical loads are identified.  相似文献   

19.
Simultaneous soil acidification and deposition of heavy metals is a major concern for forest and agricultural soils of the Black Triangle region of East Central Europe including southern former East Germany, northern Bohemia of the Czech Republic, and southern Poland. The objective of this project was to develop historical and future projections of acid and heavy metal deposition to soils (As, Cd, Pb, Zn) and to produce a preliminary map of soil sensitivity to cadmium pollution and uptake by crops. Ultimately, we wish to assess the relative hazard and recovery times of soils to metals deposition in the region. Emission and deposition data bases obtained from several models developed at IIASA were linked using the Geographical Information System ARC/INFO to produce soil maps of sensitivity to cadmium mobility based on metals deposition, soil type, soil texture, organic matter content, and acid deposition. RAINS 6.1 (Alcamo et al., 1990) was utilized to produce maps of acid deposition for EMEP grids (150 km x 150 km). The largest amount of acid load is deposited in southern East Germany. Sulfur deposition in that area was 10–12 gS/m2/yr in 1990, and S+N deposition exceeded 8000 eq/ha/yr. But the hot spot for metals deposition is further to the east, in the Silesia area of southern Poland. The TRACE2 trajectory model of Alcamo, Bartnicki, and Olendrzynski (1992) was used to estimate cumulative metals deposition since 1955 with scenarios to 2010. Pb has improved over Europe since 1970 when depositions in the Ruhr River Valley of West Germany exceeded 60 mg/m2/yr. But cadmium deposition in southern Poland (Katowice and Krakow) has now accumulated to 60–70 mg/m2 by atmospheric deposition alone. During base case simulations from 1955–87, approximately 1.8 mg/kg Pb and 0.12 mg/kg Cd have been added to the mixed plow-layer of 30 cm. If these emissions continue indefinitely, the accumulation of metals will become problematic for agriculture and the food chain.  相似文献   

20.
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   

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