The evaluation of bioavailability of cadmium, lead, copper, zinc and chromium in heavily contaminated Fluvisoil

The relationships are analyzed between the contents of cadmium, lead, copper, zinc and chromium in soil extracts of strong mineral acids (total content), in 2 M HNO3 (potentially mobilizable), in extracts of 0.05 M EDTA (topically mobilizable), as well as in the extract of 0.01 M CaCl2 (mobile) and the contents of these risky heavy metals in spring barley, oat and silage maize obtained under conditions of vegetational pot experiments using a heavily contaminated fluvisoil. The soil investigated (the River Hornad valley in Stredny Spis region) was contaminated due to geopedogonic anomalous concentration of copper and immissions of a metallurgical factory (Kovohuty Works, Krompachy) as well. A heavy copper contamination is shown by exceeding the legislatively stated indicating value C for decontamination and the riskiness of soils by exceeding the reference value A, or Al defined for cadmium and zinc. Potentially and topically mobilizable forms of copper in soil are also extremely high, these forms of copper being more significant for the soil hygiene evaluation than the total content. A sequence of heavy metals extractability in different extraction agents was suggested. From the soil extractability of heavy metals it follows that their mobile contents are trace and the analytical determinations are highly demanding. Potentially mobilizable forms of different heavy metals vary from 99.34% Pb to 6.10% Cr and this can limit their suitability for assessment of the soil hygiene. 0.05 M EDTA is considered to be the best extraction agent for heavily contaminated soil (it refers to Pb, Cu, Cd and partially to Zn). The results from the determination of heavy metals in barley and oat grain showed that the contents of copper and cadmium are excessive, which does not fulfill the requirements of the Slovak Food Codes. In accordance with the valid legislation, however, the contents determined in grain and the above-ground biomasss are allowed for feeding. Based on the values of transfer coefficients, 0.05 M EDTA is the most suitable extractant for determining the bioavailability of Cu, Cd and Pb contents. The use of an universal extraction agent for the bioavailability evaluation of heavy metals is not possible