Effect of the addition of gypsum- and lime-rich industrial by-products on Cd, Cu and Pb availability and leachability in metal-spiked acid soils

In situ stabilization of metals in contaminated soils by addition of industrial by-products is an attractive remediation technique. In this work, mixtures of metal-spiked (Cd, Cu and Pb) samples from the Ap horizons of two acid soils and solid samples of 4 industrial by-products (red gypsum, phosphogypsum, sugar foam and dolomitic residue) were incubated in order to assess the efficiency of the by-products for the in situ remediation of contaminated soils. Single (DTPA extraction and TCLP test) and sequential chemical extraction procedures were used to examine the availability and potential mobility of the metals retained as a result of the treatments. Both the sugar foam and dolomitic residue reduced the availability and mobility of Cd, Cu and to a lesser extent, Pb. On the other hand, red gypsum and phosphogypsum proved effective in immobilizing Pb and, to a lesser extent, Cu. However, both gypsum-like by-products were not so effective in reducing Cd availability and mobility.