Application of single and sequential extraction procedures to polluted and unpolluted soils

Details are given of extractants and extraction conditions, employed in soil testing. Three investigations are described. These include the following: (a) extractability, using chelating agents, of trace metals, Cd, Cr, Cu, Ni, Pb and Zn from unpolluted Irish agricultural soils, (b) extractability using chelating agents and a sequential extraction scheme for Cd, Cu, Ni and Zn in geochemically polluted soils together with a pot experiment to study uptake of Cd by herbage and (c) geographic delineation of an extensive area in the Irish mid-west for elevated soil Cd using EDTA extraction. Amount of trace metal extracted by chelating agents was significantly (P less than or equal to 0.001) related to total metal in soil for Cd, Cu and Ni only: amount of Zn extracted, but not total zinc, was significantly (P less than or equal to 0.001) correlated to soil organic carbon. A number of soils in an area known to contain elevated soil Se have been shown to also contain elevated (up to 110 mu g g(-1)) Cd. This area is part of a much more extensive area with widespread mild geochemical pollution. Extractability and plant uptake characteristics of Cd in the more polluted soils were broadly as expected.