Current interlaboratory precision of exchangeable soil fraction measurements

In addition to conventional aqua regia and EDTA extracts for monitoring tra ce metals in soils, the technique of examining exchangeable soil fractions has been suggested to estimate soil contamination and trace metal availabil ity to plants. In order to establish a useful method for soil monitoring, i nterlaboratory precision as a primary selection criterion has been investig ated. In order to assess the quality of data provided by laboratories parti cipating in the organization of the Austrian Governmental Agricultural Rese arch Institutes (ALVA), three soil samples have been analysed in a common r ing test, annually, for the last 20 years. In addition to the annual list o f parameters used for soil monitoring, within ALVA two NH4-acetate extracts were run in 1994, three NH4-acetate and NH4NO3 extracts in 1995 and three LiCl extractions in 1998. The procedures were tested for analytical precisi on and environmental indications in up to 12 laboratories, with respect to Cd, Cr, Cu, Ni, Pb and Zn. Due to the low extraction efficiency, for determ inations in the resultant solutions, graphite furnace AAS was preferably se lected, except for Zn and Cu. Flame-AAS and ICP-OES were not sensitive enou gh for non-contaminated sites. Interlaboratory precision of the data was in the range 10-65% coeff.var., and thus within the range of data given in th e appendix of DIN 19730 (NH4NO3), as well as in a previous BCR report. Indi cations from exchangeable fractions seemed to be good for Zn and Cu, wherea s they were impossible for Cr.