Heavy metals accumulation in soils irrigated by municipal and industrial effluent.

Four soil profiles have been exposed in municipal, industrial effluents and municipal wastes mixed with industrial wastes (mixed effluent) and tube well irrigated areas of Indore district of Madhya Pradesh. Soil samples were collected horizon wise and analyzed for pH, electrical conductivity (EC), organic carbon, CaCO3, clay content, cation exchange capacity (CEC), exchangeable sodium percentage (ESP) and heavy metals content viz. Fe, Mn, Zn, Cu, Cd, Cr, Co and Pb. Results showed all the heavy metals content decreased with increase in depth of soil profile. Municipal wastes / untreated sewage affected soil of Bhangarh village depicted highest content of heavy metals. The order of percentage availability of different heavy metals irrespective of the sources of irrigation is Pb>Co>Cr>Cd. However, continuous application of sewage indicated higher accumulation of heavy metals although the rate of accumulation was faster in case of industrial effluent within 2 years of irrigation. Organic carbon content had significant positive correlation with heavy metals except Cu and Zn, and negative correlation with pH and CaCO3. ESP had a negative correlation with all the metals. Zn, Mn, Cd and Co indicated significant negative correlation with the CEC of the soil. Inter-metallic correlation indicates a significant positive correlation in between Fe, Cu, Zn, Mn, Co, and Pb and among themselves.