The aims of this paper are to present fundamental chemical reactions of metals in soils treated with industrial residues and to compare the two methods of trace elements phytoavailability estimation: sequential extraction method and plant bioassay method. Trace elements solubility and availability in land-applied industrial residues is governed by fundamental chemical reactions between metal constituent, soil and residual components. Organic matter, phosphates, carbonates, sulphides, iron, manganese and aluminium oxides are important sinks for trace elements in soil – residues system. The most important chemical property that govern trace elements availability, solubility, precipitation and sorption is pH of soil-residues system. Trace elements phytoavailability in soils treated with industrial residues is often estimated using soil /residues extraction methods. Spectroscopic studies shown that sequential extraction methods may not be accurate in soil-residues system. The best method to measure the effect of trace elements from industrial residues on phytoavailability seems to be plant bioassay. The key concepts use to describe  phytoavailability are: the salt effect, the plateau concept and the soil plant barrier. Metals availability in soils from metal salts addition is higher than availability of metals from industrial residues. Metals content in plant show plateau at high residual loadings corresponding to the residuals metal concentration and sorption capacity. The soil plant barrier limits transmition of many trace elements through the food chain. Cadmium, an important human health concern, can bypass the soil-plant barrier. For trace elements phytoavailability estimation we used sequential extraction of trace elements from soil treated with mining steril (industrial residue), and plant bioassay method. Results of many studies that support these concepts provides a basis for understanding the relationship between trace elements chemistry and phytoavailability in industrial residues treated soils. Researches are needed to determine mechanisms for trace elements retention in soils and predict the long term bioavailability of trace elements in soil – industrial residue system.

trace elements; metal bioavailability; chemical extraction procedures; industrial residues

Presentation: oral