INTERLABORATORY COMPARISON OF EDTA AND DTPA PROCEDURES PRIOR TO CERTIFICATION OF EXTRACTABLE TRACE-ELEMENTS IN CALCAREOUS SOIL

The use of single extraction schemes far soil studies is widely recogn ized. These procedures are currently performed in many laboratories to assess the bioavailable metal fraction (and related phyto-toxic and n utritional deficiency effects) and the accessability to the environmen t (e.g., contamination of ground waters). Owing to the need for valida tion of the extraction schemes used and of the analytical techniques, the EC Measurements and Testing Programme (formerly BCR) has organized a project for improving the quality of determinations of extractable trace metal contents in two soils (sewage sludge-amended and terra ros sa soils), the first step of which was an interlaboratory study follow ed by a certification campaign for EDTA- and acetic acid-extractable t race metal contents. This project was complemented by an interlaborato ry study on EDTA and DTPA extraction schemes applied to a calcareous s oil reference material. The latter study was actually a feasibility st udy which allowed the necessary precautions to be set up for the use o f these schemes prior to certification of a calcareous soil. This pape r presents the results of this intercomparison.