Single extraction schemes for soil analysis and related applications

The different kinds of elemental soil analysis, for the determination of ‘total’, ‘pseudo-total’ and ‘extractable’ soil contents and their different purposes are reviewed. In particular, methods for assessing the trace element and heavy metal status of soils by selective chemical extraction procedures is considered in detail. Sampling, and sample preparation for extraction are discussed and the use of air-dried soils is justified. The range of extractants whose extractable soil contents correlate with plant growth, health or uptake is outlined and the nature of the soil phases and components extracted by different chemical extractants is discussed. Extraction is considered as a means of metal speciation, where species are defined functionally. The vital role of The Community Bureau of Reference (BCR) in coordinating and sponsoring the development and validation of agreed soil extraction schemes is revealed. The harmonisation of methodology achieved under the auspices of BCR will hopefully make available this year, 1995, two reference soils with certified extractable contents of a group of heavy metals as a major new contribution to quality control in this field.