Chromium contamination in soil and groundwater due to tannery wastes disposals at Vellore district of Tamil Nadu

摘要

Survey has shown the existence of hundred of ‘Hot-spots” of Cr contaminated agricultural lands in Vellore district where clusters of tanneries are located. The indiscriminate disposal of tannery wastes had resulted in the widespread contamination of soil and waters. It is found that most (>90%) of the soil samples from 65 locations in Vellore district had high concentration of Cr (>200 mg kg-1) which exceeds the maximum permissible limit prescribed by many Environmental Protection Agencies. Further, traces (below detectable level) to high (36.7 mg L-1) concentration of Cr were recorded in the ground waters. The Cr contaminated soil and water have also shown greater hazards due to sodium and other salts (salinity), besides Cr. The BOD and COD of the groundwater were not beyond the permissible limit. Most of the Cr contaminated water exhibited greater risk in terms of both salinity and sodicity hazards and were found unsuitable for both human consumption and irrigation purpose. The present study deals the chromium concentration in water and agricultural soil which was compared with previous year data. The soil chromium concentration was decreased at the same time water chromium was increased due to leaching process. The chromium was leached from upper layer of soil to deeper layer of aquifer.