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In the UK the "critical loads" approach has been used to derive maps based on the 10km × 10km national grid. However, this grid based approach is inappropriate for catchment scale management and these maps cannot be used for "stock at risk" assessments of the number of water bodies or lengths of streams in a given area that may be vulnerable to acidification. Critical loads are determined across two large river catchments in England (The Duddon) and Wales (The Glaslyn). High resolution, digital datasets are used to characterise the attributes of each subcatchment in terms of land cover, soil, geology, topography and topology. Empirical models used to examine the relationship between these attributes and critical loads indicate that the former can be used to account for significant variation in the latter. However, these relationships can vary from catchment to catchment. Thus, although this approach provides the potential for identifying sensitive surface waters on a catchment wide basis, it is likely that models will need to be parameterised on a catchment specific basis. 相似文献
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Current applications of the critical loads concept are geared primarily toward targeting emission control strategies at a national and international level. Maps of critical loads for freshwaters have been produced in grid form based on water samples of representative sites within each grid square. However, the water chemistry data required to calculate freshwater critical loads are not always readily available at a national level and maps are therefore limited to catchments where such data exist. This paper describes the development of an approach that uses nationally available secondary data to predict freshwater critical loads for catchments lacking the appropriate water chemistry information. An empirical statistical model is calibrated using data from 78 catchments throughout Scotland. Water chemistry for each catchment has been determined. Each catchment is characterized according to a number of attributes. Redundancy analysis of these data shows clear relationships between catchment attributes and the critical load derived from the water chemistry. The key variables that explain most of the variation in critical load relate to soil, geology and land use within the catchment. Using these variables as predictors in a regression analysis, the critical load can be predicted across a broad gradient of sensitivity (R2 adj=0.81). The predictive power of the model was maintained when different combinations of explanatory variables were used. This accords the approach a degree of flexibility in that model parameterization can be geared toward availability of secondary data. There are limitations with the model as presently calibrated. However, the approach offers considerable scope for environmental managers to undertake national inventories of catchment sensitivity and specific assessments of individual catchments. 相似文献
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M. Kernan 《Water, air, and soil pollution》1995,85(4):2479-2484
Current applications of the critical loads concept are geared primarily towards targeting emission control strategies at a regional and international level. Freshwater critical maps in the UK have been produced at a resolution of 10 km grid squares and do not take into account variations of water chemistry within the mapping unit. They are therefore of limited use at the catchment scale. This paper assesses the potential for the development ofn empirical statistical model to predict catchment critical loads using readily available secondary data. Multivariate statistical analysis of existing critical loads chemistry data together with data obtained from the Institute of Terrestrial Ecology (ITE) identifies strong relationships between surface water chemistry composition and a variety of site-specific catchment attributes, particularly rainfall, altitude and site sensitivity. Although there were problems with the data used, particulaly in terms of noise, collinearity and spatial resolution, the strength of the relationships indicates that accurate prediction of catchment scale critical loads should be possible using a higher resolution, catchment specific dataset. 相似文献
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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
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J. M. Ullyett J. R. Hall M. Hornung M. Kernan 《Water, air, and soil pollution》2001,130(1-4):1235-1240
Environmental organisations in the UK have shown increasing interest in freshwater critical loads and acid sensitivity maps as a means of assessing pollution at the local and regional level. These maps can be used to identify sensitive areas when considering catchment management plans. The use of national data sets to map the sensitivity of freshwaters to acidification, highlighted the problems of relating national datasets to smaller, localised areas. The study described here investigated the use of detailed large-scale maps to predict the sensitivity of surface waters to acidification for two river catchments. Three large-scale acid sensitivity maps were produced and validated using measured freshwater critical loads. In addition, a score system relating to the buffering capacity for each soil and geology type was devised. The score value was found to have a better correlation with water chemistry and freshwater critical loads than the acid sensitivity maps. The study concluded that it was not necessary to use the largest scale data available in order to improve predictions of sensitive areas. 相似文献
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