Spatial distribution and the extent of heavy metal and hexavalent chromium pollution in agricultural soils from Jajmau, India

This study quantifies the extent of heavy metal pollution in the agricultural soils (57 samples) from Jajmau, Kanpur, India. Heavy metal concentrations (mg/kg) in agricultural soils, frequently irrigated with treated tannery effluent, are significantly higher: Cr 118–3142, Cr(VI): 2–87, Mn 341–821, Ni 24–47, Zn 78–427, V 73–110, Cd 2–13, Pb 15–69. Sludge embedded soil, mainly comprising of tannery sludge disposed in open ground, contains ~40,500 mg/kg Cr [and 1,400 mg/kg Cr(VI)], Zn (884), Cu (300), Cd (192), Pb (180) and Ni (68 mg/kg). Results show ~65 % of the total chromium is easily leachable from these soils under acidic conditions. Pollution assessment suggests that agricultural soils are highly polluted with Cr, Cu, Cd, Pb and Zn. Spatial distribution maps of heavy metals identifies specific areas that are heavily contaminated with Cr, Cu, Zn, Cd, Pb and Cr(VI), mostly along the length of the major canal constructed to distribute the treated tannery effluents. Principal component (PC) and cluster analysis suggest two principal components (or two clusters) that explain 83 % of data variability. PC1 positively correlates with Cr, Cu, Zn, Cr(VI), Pb, Cd and OM, which is attributed to anthropogenic activities, i.e. irrigation by treated tanneries effluent, open dumping of Cr sludge. PC2 strongly correlates with Fe, Ni, Co, V and Mn, which is attributed to weathering of parental materials. This study clearly reveals significant metal pollution including Cr(VI) pollution in Jajmau, which can lead to widespread soil and groundwater contamination.