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

Sewage effluent is the carrier of huge amounts of N (۰.۰۹ to ۰.۱۶%), P (۰.۰۲۳ to ۰.۰۲۹ %), and K (۰.۱۱ to ۰.۱۸%) and as well as it is rich in organic carbon (۳.۲۷%). Transfer of the toxic trace metal (Pb) from the contaminated site can be seized out from the food chain through application of FeSO۴.۷H۲O and CaSO۴ in a larger area. The efficacy of the toxic metal immobilization through an application of FeSO۴.۷H۲O and CaSO۴ was studied in the laboratory and tested in the field. In batch experiments, application of FeSO۴ at the rate of ۵% (on soil weight basis) indicated a greater decrease in soil pH (from ۷.۵۴ to ۵.۵۵) in half an hour of shaking period as a result of which water soluble and exchangeable Pb concentrations decreased by ۱۰۰%. Application of CaSO۴ 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 FeSO۴ treated soils.

Keywords:

Chemical amendments , Long term irrigation , Pb accumulations , Sewage