Friday, 14 July 2006 - 11:45 AM
97-5

Impact of Effluent Contaminated Sewage on Underground Water, Soil, Crop Plants and Amelioration of Contaminated Soils.

Mukand Singh Brar and Gurmeet Singh. Punjab Agricultural University, Ludhiana, Ludhiana, India

Heavy metal concentration in underground and surface water, soil, and crop plants receiving irrigation with effluent contaminated sewage were investigated. The concentration of Pb, Cr, Cd, and Ni in effluent contaminated sewage water was 20, 118, 13 and 186 times higher than in shallow handpump water, and 21, 133, 280 and 300 times higher than in deep tube-well water, respectively. The concentration of Cd and Ni in shallow handpump underground water was significantly higher than in deep tube-well underground water. The concentration of Pb, Cr, Cd, and Ni in deep tube-well water was 0.017, 0.003, 0.0002 and 0.0002 mg L-1, respectively. Soils irrigated with sewage contaminated water had higher electrical conductivity, cation exchange capacity, organic C, and clay content, but had lower pH and calcium carbonate content compared to soils irrigated with deep underground water. The concentration of DTPA-extractable Pb, Cr, Cd, and Ni in soils irrigated with effluents contaminated water was 1.9, 35.5, 3.6 and 14.3 times higher than that in soils irrigated with deep underground water, respectively. The concentration of Pb, Cr, Cd, and Ni in crop plants growing on soils irrigated with effluent contaminated water was 4.88, 3.95, 0.25, and 3.68 mg kg-1, which was 1.2, 2.1, 6.2, and 2.2 times higher than in plants irrigated with deep tube-well water, respectively. The amounts of potentially toxic metals were significantly and positively correlated with cation exchange capacity and organic C content, and negatively correlated with pH of soil. Long term accumulation of toxic metals in soils and their uptake by plants has a high potential for phytotoxicity as well as for entering into the food chain. The results also indicated a trend in contamination of underground shallow drinking water through leaching of some mobile metal ions. Addition of farmyard manure (FYM) to contaminated soils decrease both DTPA extractable Cr in soils as well as its absorption by the plants. The effect was more pronounced in low clay soils (sandy) as compare to high clay soils (silty loam)


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