Case Study of the Relationship betweenAqua RegiaandReal TotalContents of Harmful Trace Elements in Some European Soils

Abstract

Bothreal totalandaqua regiacontents of trace elements in soils are often denominated by the same word “total” though the results are not identical. The formulas would be helpful for recalculation ofaqua regiacontents toreal totals. Data for primary formulas were taken from the International Soil-Analytical Exchange Program of Wageningen Evaluating Programs for Analytical Laboratories. The degree of extractability DE of element in a sample was calculated by weighting the ratios of median contents inaqua regiato medianreal total contentsin different periods with weights proportional to the respective number of determinations. According to descending median values of DE (%) in ISE European soil samples the elements are arranged as follows: Hg(98), Cd(94), Cu(91), Zn(90), Mn(89), Ni(88), Co(86), As(82), Mo(82), Pb(79), V(61), Sn(57), Cr(56), Sb(53), Be(51), B(46), U(35), and Ba(21). These values can be used for approximate recalculation ofaqua regiacontents toreal totalsand adjustment of contamination assessment. An attempt to obtain more explicit prediction by fitting regression models and problems related to high leverage and possibly influencial points are discussed and their possible relation to the specificity of soil composition is pointed out.