Remediation Of Reclamed Tidal Flat Soil Contaminated With Heavy Metal By Desulfurized Gypsum Leaching

Heavy metal not only may accumulate in organism, but also may easily recycle in the food chain. So it directly threatens humanity's grain security. This makes it of great significance to study soil heavy metal contamination. This paper used samples of tidal flat reclamation soil, and made heavy metal Cd, Cr, Cu, Ni, Pb and Zn as removing objects. By soil leaching experiment, the study probed the best conditions that leaching removes heavy metal pollutants, which was expected to provided theoretical foundation for restoration application. The main research results were as follows.Desulfurized gypsum has a significant removal for the heavy metal in 0-30cm plant root zone, which were 55.49%for Cd,35.24%for Cr,46.65%for Cu,44.35%for Ni,38.08%for Pb, 50.52%for Zn. The best conditions were:6.59 kg·m-2 desulfurized gypsum for Cd,6.64 kg·m-2 for Cr,7.36 kg-m-2 for Cu,4.68 kg·m-2 for Ni,6.47 kg·m-2 for Pb and 6.56 kg·m-2 for Zn respectively; application tiems of desulfurized gypsum was three, irrigation water was 186.63 L/m, leaching intervals was 7 days for Cd,27 days for Cr,25 days for Cu,6 days for Ni,21 days for Pb and 21 days for Zn respectively. Below 30cm soil layer, the heavy metal's content increases, indicating that the leached heavy metal from the top soil are adsorbed or precipitated in the substrate again. In addition to concentrations of Ni exceeded water quality IV standard of Quality Standard for Ground Water in eluent, concentrations of Cd, Cr, Cu, Pb and Zn were lower than the standard, No further pollution is obviously resulted in to the ground water during leaehing amelioration.