Antimony availability in highly polluted soils and sediments – A comparison of single extractions

Forest/tilled soils and stream sediments from the highly polluted mining and smelting district of Příbram, Czech Republic, were subjected to single extraction procedures in order to determine the available contents of Sb and As. The results obtained from five widely-used 2-h single extraction tests were compared: deionised water, 0.01 M CaCl2, 1 M NH4NO3, 0.005 M diethylentriaminpentaacetic acid (DTPA) and 0.1 M Na2HPO4. The ICP-MS determinations of Sb and As in the extracts were coupled with measurements of pH and Eh and geochemical modelling (PHREEQC-2) to determine their speciation in extracts and possible solubility-controlling phases. According to the speciation calculations, Sb in extracts was present mainly as Sb(V) with the exception of the DTPA extracts from highly organic and acidic forest soils, where Sb(III) species accounted for up to 34% of total Sb speciation. The highest extractabilities were observed for the 0.1 M Na2HPO4 solution (up to 9% of the total Sb and up to 34% of the total As concentration). The other extracting media yielded statistically the same results (p < 0.05) with Sb extractabilities below 2% and As extractabilities below 8%. Thus, simple deionised water and 0.1 M Na2HPO4 extractions are preferred for quick estimates of easily-exchangeable and specifically-sorbed Sb, respectively.