MIGRATION AND CONTAMINATION OF MAJOR AND TRACE-ELEMENTS IN GROUNDWATER OF MADRAS CITY, INDIA

Groundwater samples collected from both open and bore wells in an area of about 270 km(2) from Madras City, India, have been analyzed for ma jor ions (HCO3, Cl, Si, Na, Ca, and Mg) and trace elements (As, Se, B, V, Cr, Fe, Co, Pb, Cu, Zn, Cd, Mn, Ni, Mo, and Ba). The study reveals that the quality of potable water has deteriorated to a large extent. Seawater intrusion into the aquifer has been observed in nearly 50 pe rcent of the study area. The toxic elements (As and Se) have already e xceeded the maximum permissible limits of drinking water in almost the entire city. A positive correlation of As and Se with other toxic met als such as V, Cr, Fe, B, etc., indicates that all these elements are anthropogenic in origin. Applying multivariate analysis, the source fo r trace elements in groundwater has been grouped into two major factor s: pollution and mobilization factors. The groundwater in the study ar ea is largely contaminated by organic effluents and reflects the inten sity of pollution caused by the overlying soil sediment and rapid infi ltration of the pollutants.