DELINEATION OF CADMIUM CONTAMINATED SOILS AROUND BUDDAH NALLAH (LUDHIANA) AND REMEDIAL MEASURES OF AFFECTED SOILS
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Date
2011
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PAU Ludhiana
Abstract
Cadmium is potentially toxic metal and is highly carcinogenic that enters the food chain from the soil through crop uptake resulting from various anthropogenic activities. The surface sewage irrigated soils collected laterally around Buddah Nullah irrespective of the sites had DTPA extractable cadmium 5.2 times more than the adjoining tube well irrigated soils. Considering the threshold value of 3 mg Cd kg-1 soil, about 11.3 per cent soils have crossed this limit and needs cleanup operation. However management option to rehabilitate such soils depends on pools of Cd responsible for phyto-toxicity and use of amendments able to influence these pools. A screen house experiment was conducted to assess the effect of (0, 2.5, 5 10, 20 and 40 mg Cd kg-1 soil) and CaCO3 (2.5 and 5%), FYM (1 and 2 %) and Phosphorous (20 and 40 P2O5 mg kg-1 soil) on the growth of pigweed on soil having DTPA-Cd 0.36 mg kg-1 soil. Dry matter yields decreased as a consequence of phytotoxic effect of Cd emanating from increased availability of Cd in soils and plants. The rate at which significant declined occurred was 10 mg kg-1. However application of different amendments viz (Calcium carbonate, FYM, Phosphorus) exhibited variable behavior as far as their remediation potential was concerned. Application of CaCO3, FYM and phosphorous at their highest rate reduced DTPA- Cd by 52.6 percent, 37.1 percent and 45.1 percent respectively. Consequently maximum enhancement in dry matter yields was observed with application of 5% CaCO3 among other amendments. The upper critical toxic level in soil and shoots of pig weed was found to be 4.38 mg kg-1 soil and 14.6 μg g-1 dry matter respectively. The interaction of Cd with Zn and Fe was found to be rate dependent. Cu and Mn in both shoots and roots was negatively correlated to the added Cd. All the fractions of Cd in soils increased significantly with cadmium application. Amendments decreased the EX+WS fraction, the maximum depressing effect observed with 5% CaCO3 because of concomitant increase in CARB fraction. FYM application decreased the CARB fraction where as it encouraged both OM-Cd and oxide bound fractions. Phosphorus application was effective in transforming Cd in to oxide bound fractions with little influence on carbonate and organic fractions.
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