IDENTIFYING CHANGES IN SOIL QUALITY: CONTAMINATION AND ORGANIC MATTER DECLINE
Soil is increasingly affected by applied agrochemicals, atmospheric pollutants, sewage sludge, and manures which can have adverse impacts on soil quality. The European Commission has embarked recently on a Thematic Strategy for Soil Protection that identifies eight threats to soil in Europe of which contamination and decline in organic matter are accorded high priority. To identify changes in soil quality it is important to have some baseline against which to measure that change. In the UK, a National Soil Inventory was made to provide an unbiased inventory of soil resources in Great Britain. Soil samples were taken on a national UTM grid and analysed for a range of physical and chemical properties. About 40% of the grid points in England and Wales were resampled providing an ideal data set from which to identify changes in soil properties, an essential requirement for ‘monitoring’. Geostatistics have been used to estimate the temporal change in several metal concentrations and in soil organic carbon (OC), the major constituent of soil organic matter. In almost all cases, a normally distributed random variable with outliers is shown to be a suitable statistical model to study the change in metal concentrations. A map of change in lead concentration, identifying ‘hotspots’, shows how these methodologies can be applied. It is also shown that the variation of the change in organic carbon is not spatially structured but that the rate of change depends on the initial OC level in the soil.
KeywordsOrganic Carbon Soil Organic Carbon Sewage Sludge Soil Quality Robust Statistic
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