Fractionation of heavy metals in bottom sediments and sewage sludges using sequential extraction

Abstract

Comparison of heavy metal (Zn, Cu, Ni, Pb, Cd, Cr) fractionation methods was done. Two different sequential extraction methods were investigated: Te ssier, and BCR method. For the experiment following materials were used: sewage sludge were collected f rom mechanical-biological municipal wastewater trea tment plant located in Czestochowa, and bottom sediment f rom the Poraj Reservoir. After results comparison, it was stated that content of particular chemical forms of heavy metals in total amount in sewage sludge and bottom sediment vary depending on used extraction method. Also in sewage sludge and bottom sediment cadmium concentrations measured in exchangeable-carbonate, i organic-sulfide, and in residual (insoluble comp ounds) fractions after extraction according to Tessier met hod, did not equal to values obtained after use of BCR extraction method. This also applied to zinc and lead concentr ations in iron and manganese oxides fraction. The d iscrepancy between the results could be explained with both: u sed extractants, and extraction conditions (differe nt agents, temperature, and time). The results point out how i mportant is the choice of a proper extraction metho d depending on the aim of speciation analysis but also dependin g on the analyzed chemical forms of heavy metals.