Effect of Organic Matter, Zinc and Phosphorus on the Mobilisation of Lead in Soils.
Dilip Kumar Das, Sumita Subudhi, and Pintu Sur. Dept of Ag. Chem. and Soil Science, Bidhan Chandra Krishi Viswavidyalaya, B-5/50, Kalyani, Daigonal Road, Kalyani, 741 235, India
Laboratory experiments were conducted in five Aeric Haplaquept soils contaminated with Pb after collecting from high traffic density areas of Indian sub-tropics.The range of relevant physico-chemical properties of soils were: pH, 7.5-8.1; organic carbon,0.57-0.87%; CEC, 14-22 cmol(p+)/kg; soil texture,clay loam –clay; 0.005 M extractable Pb, 3.60-7.02 mg/kg). Four levels each of organic matter[O0(0mg/kg), O1(1%),O2(2%) and O3(3%)], and zinc [Zn0(0mg/kg), Zn1(5mg/kg),Zn2(10mg/kg) and Zn3(20mg/kg)] under two moisture regimes[ 60% water holding capacity(WHC) and saturated ] with different possible treatment combinations replicated thrice. Further, for the interaction effect between Pb and P , three levels of each Pb (0,5 and 10mg/kg) and P (0,15 and 30 mg/kg) were used in all possible combinations with three replications under saturated soil moisture condition. The results show that the amount of Pb content sharply decreased due to application of organic matter ,zinc and P applications. The magnitude of such decrease, however, varied with treatments, being highest decrease (86.70%) with 3% organic matter application under saturated soil moisture condition which was closely followed by 85.30% under 60% WHC moisture regime. The mobilization of Pb in soils was found to be decreased 84.23 and 35.39% when zinc and phosphorus were applied at 20 and 30 mg/kg respectively under saturated moisture condition. The greater immobilization or percent decrease of Pb in saturated soils receiving organic matter might be partly due to insoluble precipitates/adsorption of Pb onto organic colloids resulting from the greater intensity of soil reduction and also due to formation of insoluble Pb-organic complexes. Key words: Lead mobilisation, phosphorus, organic matter, zinc.