Assessment of Chromium Pollution at Nuasahi-Baula Mines, Orissa

Abstract

There has been growing demand for chromite ores in recent years. In the opencast mines, the chromite as well as overburden material are dumped in the open ground without considering the environmental consequences. Hence, further leaching of chromium causes the environmental degradation in the vicinity of mines. This study is conducted in and around the chromite mines situated in the Nuasahi-Baula igneous complex for assessing the Cr pollution. Hexavalent chromium was found between 2 and 6 ppb in groundwater and 8 to 36 ppb in mine discharges. The total chromium ranged between 2 and 7 ppb in groundwater and 9 to 42 ppb in mine discharge water. The goethite rich overburden material at chromite mines is an efficient sink for the chromate anion. Leaching experiments using a saline solution, phosphate solution and tap water showed that phosphate solution release more hexavalent chromium compared to other two solutions. These results can be useful in evaluating natural attenuation of fertilizerderived pollutants in the agricultural land near chromite mines. From the mineralogy it was found that the lateritic cover contain more goethite compared to other minerals. The concentration of chromium is more in laterite than overburden and soil. The impact of chromium on the environment depends on the percentage of chromium in exchangeable fraction. The study shows that percentage of chromium is less in exchangeable fraction and more in residual fraction in the study area. So the Cr bioavailability is low and toxicity is less.