Seasonal and spatial investigation of groundwater contamination of potential toxic elements (PTEs) and associated health risks of southern region of Delhi, India

PTEs contamination in drinking water has gained attention since it endangers human health. This study was attempted in southern region of Delhi, India as the region has remained unexplored and unexamined for groundwater contamination of PTEs. Spatially, PTEs concentrations and their distribution was analysed in groundwater with potential sources, probable toxicity, and related human health risks during pre-monsoon (PRM) and post-monsoon (POM) season of 2022-23. In both the seasons, mean value of Si is found higher followed by Fe, Al, Zn, Mn, B, Cu, Ni, Pb, Cr, As and Cd. Moreover, PTEs concentration found slightly higher during POM season. Principal Component Analysis (PCA) based loadings and scores determined the pollution sources mostly influencing south-eastern and northern plains where industrial effluent, residential discharge and landfill site leachate activities are prevalent in the region. It was observed that As, Fe, Mn, Al, Zn and Si derived from natural sources, whereas B, Ni, Pb, Cd, Cu and Cr originated from mixed sources. Likewise, pollution indices Heavy metal Pollution Index (HPI), Heavy metal Evaluation Index (HEI), Degree of Contamination (C_d) and Heavy metal Contamination Index (HCI) showed that groundwater is unfit for consumption for the similar regions. Among all the indices, HCI specifically identify pollution causing metals (Pb, Al, Cr, Fe, Ni) and toxicity level, which could be maintained within the BIS and WHO limits by diluting the water. Human health risk assessment has been computed by non-carcinogenic and carcinogenic risk. Non-carcinogenic assessment indicates that exposure of Fe and As may cause non-cancerous risk to children and carcinogenic risk (CR) assessment shows exposure of Pb, Cr and Ni may cause cancer risk to the overall population. Therefore, extensive groundwater quality monitoring and treatment would support the preventive action plan to safeguard drinking water quality and public health in the contaminated regions of study area.