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1.
Presently considerable effort is devoted to the development of methods for estimating critical loads of acidic deposition. In this paper a steady-state mass balance model for lakes is presented, allowing the simultaneous calculation of critical loads of acidifying S and N deposition and their exceedance. Special emphasis is given to the derivation of model inputs and parameters and the quantification of their uncertainties. The inclusion of rate-limited processes in the model leads to the dependence of the critical loads not only on catchment properties but also on the loading to the ecosystem. As a consequence, critical load values have to be re-calculated whenever deposition patterns change. The methods presented in this study are used in an accompanying paper to derive regional distributions of critical loads of S and N for lakes in Finland and to quantify their uncertainties.  相似文献   

2.
The roles of sulphur (S) and nitrogen (N) in causing critical loads exceedance across the UK show considerable spatial variability at the present time. Over much of lowland Britain it appears that the environment can only be protected by reducing N deposition, whilst in upland areas (e.g. most of Scotland and Wales) reductions in S deposition are the primary requirement. Using the Hull Acid Rain Model (HARM) the effects of current and possible future emissions control legislation on critical loads exceedance can be explored. Based on HARM output, the implementation of the UNECE Sulphur Protocol (1994) will bring about a substantial reduction in the amount of S being deposited in the UK, especially in central and southern parts of the country. Some areas will remain where additional reductions in S are required. Over most of the country, however, the need to reduce N deposition will become paramount. The changing contributions and significance of non-UK sources can be estimated.  相似文献   

3.
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   

4.
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5.
Metcalfe  S. E.  Derwent  R. G.  Whyatt  J. D.  Dyke  H. 《Water, air, and soil pollution》1998,107(1-4):121-145
It is now recognised that a multi-pollutant, multi-effect approach needsto be adopted to address the range of problems caused by atmosphericpollution. In this paper we use a relatively simple trajectory model (HARM)to explore the coupled behaviour of sulphur dioxide (SO2),oxides of nitrogen (NOx) and ammonia (NH3) andthe possible effects of future reductions in emissions of these pollutantson depositions of S and N across Great Britain. The performance of HARM withrespect to concentrations and depositions of NOy andNHx is assessed by comparison with data from nationalmonitoring networks. A range of emissions scenarios are modelled and theeffects of these reductions on critical loads exceedance are explored usingthe critical loads function (CLF), which allows both the acidification andeutrophication effects of S and N deposition to be explored simultaneously.Spatial variations in the reductions of deposition of S and/or N required tomeet critical loads are described. Reductions in emissions of the precursorsof strong acids (SO2 and NOx) yield benefits interms of ammonium deposition as a result of their coupled chemistry. Thedevelopment of strategies to control nitrogen deposition will need to take this non-linearity in to account.  相似文献   

6.
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   

7.
The excess of acidic and eutrophying depositions over critical loads (critical load exceedances) is considered a measure for the risk of harmful effects on sensitive elements of the environment. The magnitude and the geographical distribution of critical load exceedances over Europe vary with the extent to which national emissions of sulfur dioxide, nitrogen oxide and ammonia are reduced. The scientific support of negotiations on emission reductions in the framework of the Convention on Long-range Transboundary Air Pollution (LRTAP) of the UN Economic Commission for Europe has been based on the integrated assessment of sources, including abatement costs, and risks to receptors (e.g. forests, lakes) using critical load exceedances. 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 load exceedances are computed and mapped. The focus changed from the protection of the most sensitive ecosystem against excessive deposition of one pollutant, to an assessment of the accumulated exceedance by more pollutants of all ecosystems. This paper presents and compares the different characterisations ("gap-closure methods") used in those negotiations. It is shown that the approach finally used has several appealing features, but treats the exceedance as a linear damage function, thus going beyond the critical load definition as a simple on-off limit value.  相似文献   

8.
The model SONOX has been developed that replicates the sequence of events on the way from emission of sulfur and nitrogen to the potential risk to forest ecosystems as reflected by critical loads exceedance. The model produces a set of emission, deposition and critical load maps in various spatial resolutions as well as maps of critical loads exceedances dynamically generated in response to various sulfur and nitrogen emission scenarios. Optionally, also the share of forest areas protected or unprotected against acidification is spatially presented. The model provides a decision tool to develop strategies aimed at the abatement of excess sulfur and nitrogen emissions. The present version of the model has been tailored to and implemented for Polish conditions. This model has been used to analyse the trends in impacts of acid deposition on Polish forest ecosystems.  相似文献   

9.

Three years (1994-1996) of runoff, bulk deposition, and throughfall S and N data obtained from GEOMON, a network of 14 small forest catchments in the Czech Republic, are presented. In this paper, we assess regional differences and temporal trends in S and N fluxes under changing regional burdens. Decreases in S deposition have occurred in the emission-burdened northern and western parts of the Czech Republic, where remedial measures have been applied. For example, at the Uhlí?ská catchment (Jizerské hory Mtns., northern Czech Republic), throughfall S fluxes decreased from 72.7 to 48.5 kg ha-1 yr-1. In contrast, the relatively clean central and southern parts of the Czech Republic showed an increase in S deposition; for example at the Na lizu catchment (?umava Mtns., southern Czech Republic) throughfall S fluxes increased from 9.0 to 18.8 kg ha-1 yr-1. In burdened catchments with damaged forests, high runoff of N was observed. Using fluxes of S and N measured at the GEOMON sites, we calculated critical loads and exceedances for both S and N in the catchments. The critical loads of S ranged from 505 to 3,631 mol L-1 yr-1 during 1994-1996; in about 80% of the catchments the critical loads were exceeded by atmospheric deposition; half of the catchments showed an exceedance for N.

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10.
Water chemistry data on which all the investigations in the AL:PE 1 (Acidification of Mountain Lakes: Palaeolimnology and Ecology) and AL:PE 2 (Remote Mountain Lakes as Indicators of Air Pollution and Climate Change) projects are based, are available for 28 lakes in U.K. (Scotland), Italy, Norway and France (AL:PE 1) and in Svalbard (Norway), Ireland, Austria, Spain, Portugal, Poland, Slovakia, Slovenia and Russia (AL:PE 2). The results show high sulphate concentrations in some mountain lakes in all the countries. Nitrate and sulphate concentrations have different distribution patterns among the sites. A gradient in acidification from north (Norway) to central Europe (via U.K. to Italy) is identified for the AL:PE lakes by means of multivariate data analysis. Critical loads and their exceedance are calculated, where sufficient information is available, both according to the leaching of S, and of S plus N from the catchment. The pattern of critical load exceedance demonstrates an increasing importance of nitrate from Norway via U.K. to Italy. Leaching of N was of considerable importance to the acidification of lakes in the Italian Alps. The projects receive financial support from the European Union.  相似文献   

11.
This paper reports an uncertainty analysis of critical loads for acid deposition for a site in southern England, using the Steady State Mass Balance Model. The uncertainty bounds, distribution type and correlation structure for each of the 18 input parameters was considered explicitly, and overall uncertainty estimated by Monte Carlo methods. Estimates of deposition uncertainty were made from measured data and an atmospheric dispersion model, and hence the uncertainty in exceedance could also be calculated. The uncertainties of the calculated critical loads were generally much lower than those of the input parameters due to a “compensation of errors” mechanism – coefficients of variation ranged from 13% for CLmaxN to 37% for CL(A). With 1990 deposition, the probability that the critical load was exceeded was > 0.99; to reduce this probability to 0.50, a 63% reduction in deposition is required; to 0.05, an 82% reduction. With 1997 deposition, which was lower than that in 1990, exceedance probabilities declined and uncertainties in exceedance narrowed as deposition uncertainty had less effect. The parameters contributing most to the uncertainty in critical loads were weathering rates, base cation uptake rates, and choice of critical chemical value, indicating possible research priorities. However, the different critical load parameters were to some extent sensitive to different input parameters. The application of such probabilistic results to environmental regulation is discussed.  相似文献   

12.
The critical loads approach to quantifying areas at risk of damage requires deposition and critical loads data at the same spatial scale to calculate exceedance. While maps of critical loads for soil acidification are available at a 1 km scale no monitoring networks in Europe measure wet and dry inputs at this scale and, further, the models currently used to estimate deposition incorporate a number of assumptions which are not valid at the 1 km scale. Simulations of 1 km deposition from 20 km data show that the uncertainty introduced by using 20 km scale estimates of deposition is small, except in mountain areas where it can give misleading results, but a major problem is the uncertainty in estimates of deposition at the 20 km scale produced by the current models.  相似文献   

13.
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   

14.
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   

15.
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   

16.
The foliar N content of bryophytes and Calluna vulgaris (L.) has been shown to be an indicator of atmospheric N deposition in the UK at a regional scale (1000km) and more recently on a smaller scale in the vicinity of intensive livestock farms. This work extends the geographical scale of the relationship between foliar N concentration of Calluna vulgaris and other ericaceous shrubs and N deposition with 2 measurement transects, one extending from northern Finland to southern Norway (2000 km) and the other extending from central Sweden to Stockholm, south east Sweden (330 km). Included in the second transect is a region of complex terrain in the Transtrand uplands, where the variation in N deposition with altitude and canopy cover was quantified using 210Pb inventories in organic soil. The relationship between foliar N (FN) and N deposition was shown to increase linearly with N deposition (ND) over the range 0.8% N to 1.4% N according to FN = 0.040ND + 0.793 (r2 = 0.70). The data are entirely consistent with earlier studies which together provide a valuable indicator of critical loads exceedance, the threshold value being approximately 1.5% N, which is equivalent to a N deposition of 20 kg N ha?1 y?1.  相似文献   

17.
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   

18.
This study shows that it is questionable if critical load modelling can contribute in the search for harmful effects of acid deposition on forest health at present. Critical loads forS and N deposition were calculated using the MAGIC and PROFILE models for more than 100 monitoring plots in Norway spruce forestin south-east Norway. The two models gave different results, likely due to differences in the models, including differences in the time spans applied. The PROFILE model gave considerably more plots with exceedance than the MAGIC model.At plots where the CL was exceeded, calcium/aluminium (Ca/Al) ratios in the soil solutions were low. However, very few of theseplots had possible harmful values of the Ca/Al-ratio. More than 50 yr seems in most cases to be needed to bring Ca/Al ratios below 1.0. Present deposition was better correlated with measured forest condition variables such as crown condition and needle chemistry,than with modelled exceedance according to any of the two methods. The deposition of S and N was weakly, negatively correlated to foliar concentrations of P and Ca, and positivelyto foliar N concentrations and crown density.  相似文献   

19.
An overall level as well as seasonal changes of acidification of Tatra Mountains surface waters have been studied. Measurements carried out in the Tatra Mountains National Park were concentrated on two lakes: Dlugi Staw and Zielony Staw, situated in the crystalline, granitic part of the mountains. These lakes differ from each other in altitude (1784 m and 1632 m a.s.l. respectively) as well as in quantity and variety of flora and fauna living in and around them. The wet deposition of acidifying compounds of sulphur and nitrogen, and their seasonal variability in the area of the lakes were measured and compared with the critical loads of sulphur and nitrogen for these lakes and their catchments. Results showed that the critical loads of both sulphur and nitrogen in Dlugi Staw were exceeded all over the year and in Zielony Staw the acid deposition was roughly equal to critical load. A surprisingly high concentration of nitrogen compounds in acid deposition, well above the absorption ability of both the lakes and their catchments were ascertained. Nitrogen retention coefficients calculated for the lakes were as follows: Dlugi Staw — approximately 10%, Zielony Staw — approximately 50%. Seasonal variability in nitrate ions concentration in the lakes' waters reflected their prominent acidification caused by nitrogen compounds corresponding to stages 2 and 3 in the scale proposed recently by Stoddard (Stoddard, 1994).  相似文献   

20.
A Spatial Decision Support System (SDSS) is being developed for Her Majesty's Inspectorate of Pollution (HMIP). It enables the investigation of the spatial implications of different operating procedures from large point sources of pollution. The environmental effect of emissions is assessed using the critical loads methodology developed at ITE and modelled deposition “footprints”. This approach allows an “effect per unit emission” or “pollution potential” to be determined for each source. Individual sources are modelled and included within the SDSS if their current emissions are above a given threshold. The SDSS provides a graphical user interface (GUI) which facilitates a fast, efficient and effective means to specify and to examine the effect of different operating policies. Mapping, statistical and optimization facilities are provided to help describe the effect of any specified strategy. Maps may be produced as deposition rates or exceedance values. Statistics may be visualised as histograms and scatter plots. The optimization facility uses linear programming to minimise the total environmental impact (estimated from emissions and critical loads) or maximise power produced within environmental limits. The SDSS has been written in the Arc/Info Macro Language (AML) and provides an invisible interface with standard GIS facilities and programmes written in “C”.  相似文献   

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