Appraisal of heavy metals in groundwater in Chennai city using a HPI model.

Heavy metal contamination in Chennai city was evaluated using a heavy metal pollution index (HPI) model in conjunction with the spatial distribution maps. Metals such as Cd, Cr, Cu, Pb and Zn in the groundwater were determined using standard methods and the resultant data was utilized in the development of a HPI model. The metal concentrations showed a dominance in the order of Zn > Cu > Cr > Pb > Cd respectively. About 14.3 % of the samples (n = 2), exhibited high HPI (>38) and the highest value, HPI = 97.55, has been recorded from Thiruvanmiyur area. Statistical analysis revealed a positive correlation between metals such as Cd and Cr (r = 0.606), Cd and Cu (r = 0.601), Cr and Cu (r = 0.464) and Pb and Zn (r = 0.416), suggested their common origin. The spatial distribution maps of heavy metals and the HPI suggested that the SW region, especially Adyar and Thiruvanmiyur regions are highly contaminated with the metals. Industrialisation and improper waste dumping were identified as the major cause for the accumulation of metals in the groundwater of Chennai city.