Chemical Immobilization of Lead (Pb) in Long Term Sewage Irrigated Soil

Sewage effluent is the carrier of huge amounts of N (0.09 to 0.16%), P (0.023 to 0.029 %), and K (0.11 to 0.18%) and as well as it is rich in organic carbon (3.27%). Transfer of the toxic trace metal (Pb) from the contaminated site can be seized out from the food chain through application of FeSO4.7H2O and CaSO4 in a larger area. The efficacy of the toxic metal immobilization through an application of FeSO4.7H2O and CaSO4 was studied in the laboratory and tested in the field. In batch experiments, application of FeSO4 at the rate of 5% (on soil weight basis) indicated a greater decrease in soil pH (from 7.54 to 5.55) in half an hour of shaking period as a result of which water soluble and exchangeable Pb concentrations decreased by 100%. Application of CaSO4 also decreases soil pH, as well as Pb concentration in soil solution. Pot culture experiments with two flower and leafy vegetable plants also show decrease in bioavailability of Pb in FeSO4 treated soils