OPERATIONALLY DEFINED EXTRACTION PROCEDURES FOR SOIL AND SEDIMENT ANALYSIS - I - STANDARDIZATION

Environmental studies on soil and sediment analysis are often based on the use of leaching or extraction procedures (e.g. single or sequenti al extraction procedures) which enable broader forms or phases to be m easured (e.g. 'bioavailable' forms of elements) and which are, in most cases, sufficient for the purpose of environmental policy. However, t he lack of uniformity in the procedures used often hampers comparison of the results, owing to their 'operationally defined' character. This implies that the 'forms' of metals are defined by the determination o f extractable elements, using a given procedure and, therefore, the si gnificance of the analytical results is highly dependent on the extrac tion procedures used. The comparability of results can hence only be a chieved if similar procedures are applied, which justifies efforts tow ards standardization. This article describes case studies of standardi zation approaches for single and sequential extraction procedures appl ied to soil and sediment analysis. In particular, the strategy followe d by the Standards, Measurements and Testing program (formerly BCR) is fully described (feasibility study, interlaboratory studies and estab lishment of standardized protocols based on the results of tests and p articipants' experience). (C) 1998 Elsevier Science B.V.