Is Mehlich 3 soil extraction a suitable screening method for determination of some risk elements?

Abstract

Legislation limits for risk elements (As, Be, Cd, Co, Cr, Cu, Ni, Pb, V, Zn) in agricultural soil in the Czech Republic are given for the content of elements extracted by aqua regia. This extraction is time consuming and environmentally unfriendly. The regular soil survey is based on Mehlich 3 universal soil extractant and covers the simultaneous determination of macronutrients, sulphur, and micronutrients by inductively coupled plasma optical emission spectrometry (ICP-OES). Our study focused on the possibility to use Mehlich 3 extractant also for preliminary screening for the determination of the risk elements simultaneously with the other elements by the ICP-OES method. Mehlich 3 was confirmed as a reliable screening method for Cd regarding sensitivity, specificity and precision (> 0.8) when the cut-off value of 0.27 mg/kg in Mehlich 3 extracts was used for the prediction of soils to be above or below the legislation limit, which in turn is based on aqua regia extraction. Very good results were obtained for Be and promising results were received for As, Cu and V. But the available data were not sufficient for the determination of reliable cut-off values for Co, Cr, Ni, Pb and Zn.