The Influence of Experimental Leaching Conditions for the Determination of the Soluble Element Content of Soil and Stream Sediment Samples

The Hungarian Geological Survey - Geological Institute of Hungary participated in an INCO-Copernicus project which was aimed at the harmonisation of analytical methods and finished recently. In the first phase, participating geological laboratories entered the International Soil Exchange (ISE) scheme. Laboratories determined total and leachable element contents of soil (and stream sediment) samples, using their own methods. This article in intended to summarise the problems and conclusions regarding the determination of leachable (mobile) elements. Using their own methodologies, laboratories obtained fairly divergent results, especially for some elements. In order to eliminate the variance originating from applying different methodology, a standardised common method was designed for aqua regia leaching. The spread of the results did not improve significantly because of the insufficient control of the applied open vessel method. The final conclusion was: in order to produce internationally comparable results, the use of well-defined and well-controllable digestion methods is strongly recommended. A typical example might be the use of the microwave assisted digestion methods for all geological institutes participating in international geochemical programmes.