Assessment of metal pollution in groundwater using a novel multivariate metal pollution index in the mining areas of the Singhbhum copper belt

Groundwater samples were collected from 22 locations for 3 seasons in mining areas of Singhbhum copper belt. The concentrations of Al, As, Ba, Co, Cu, Fe, Mn, Ni, V and Zn were evaluated using inductively coupled plasma mass spectrometry to assess the metal pollution using conventional heavy metal pollution index (HPI) and multivariate indexing approaches. Considering all the seasons, metal concentrations exceeded the drinking water standards for Fe and Mn for most of the locations and Al, Cu, Ni and Zn at some of the locations. An assessment using principal component analysis suggested that metals in groundwater in the area are derived from both geogenic and anthropogenic sources. The PCA-based index (PMI) was computed using the factor scores, which does not need any permissible limits or standards for its calculation. A classification of the index is also done using the terciles (3 quantiles) to demarcate the locations into low, moderate and high pollution classes. Marked differences could be identified between the results of HPI and the PCA-based index, of which the latter was found to be robust and more suitable for the study.