Geostatistical and multivariate analysis of soil heavy metal contamination near coal mining area, Northeastern India

The spatial distribution and hazard assessment of heavy metals in the soils of surrounding agricultural fields affected by mine drainage of Ledo coal mining area of Tinsukia district, Assam, India, were investigated using statistics, geostatistics and geographic information system techniques. The amounts of Cr, Cd, Ni and Pb were determined from 83 soil samples collected within the contaminated area. The maps based on ordinary kriging showed that high concentrations of heavy metals were located in the low-lying paddy field and near coal mining site. Indicator kriged probability maps were prepared based on the concentrations to exceed permissible limit (MPL). It was seen that more than 95 % of the studied area has a higher than 50 % probability to exceed the MPL value of Pb and Ni. Multivariate statistical analyses and principal component analysis suggest that Cd and Pb are derived from anthropogenic sources, particularly coal mining activities, whereas Ni and Cr are derived from lithogenic and/or anthropogenic sources.