Spatio-temporal distribution and carcinogenic assessment due to potentially toxic elements in aquifer water of Ganga and Yamuna River basins, India

Abstract

The spatial and temporal dispersion of potentially toxic elements (PTE) are evaluated for shallow groundwater samples of Delhi and Patna considering PTE pollution index (HPIPTE), evaluation index (HEIPTE), cancerous and non-cancerous effects, hazard coefficient index (HQI) and overall hazard index (HInc) considering fuzzy entropy weights and source identification is done through PCA. The evaluation of groundwater indicators as pH, TDS and PTE (As, Ni, Mn, B, Pb, Fe and Zn) indicated 6.67% and 3.33% of sampling stations exceeded the threshold limit, HPIPTE > 100 for arid and humid periods of Delhi, whereas 3.33% and 13.33% of sampling stations come under high contamination in the banks of the Ganga in arid and humid seasons respectively. The hazard coefficient index (HQI), only 18% and 21% of the specimens were in the grade of low pollution in both the seasons of Delhi and Patna. The trend of HQI is followed as, HQIAs>HQIPb>HQIFe>HQIMn>HQINi≥HQIZn>HQIB in Delhi region for both Young and elders in both seasons, while the sequence is followed as, HQIAs>HQIPb>HQIFe>HQIMn>HQIZn>HQINi>HQIB in the Ganga River basin area for elders and Young. The index (HInc) found 4 Young & 3 elders and 4 Young & 4 elders (Patna, arid and humid seasons) whereas 6 Young and 5 elders (Delhi, arid and humid seasons) affected as per the index per 1000 cases reported. The PC1 (As, Fe, Mn, and Pb) and PC2 (pH, As, Fe, and Pb) extracted from PCA pointed to the effects of evolution of contamination, hydrogeochemical reaction, disintegration of rocks, its dissolution, dispersion, and dilution in unconfined deep aquifers. Rapid depletion of groundwater table may cause the influx of As contamination in the shallow groundwater, whereas high Pb, Fe, Mn and Ni may be the reasons of nearby industries and improper waste disposal process. The findings and GIS mappings may put some light on the PTE over the Rivers which can help the local government and decision makers to formulate safe and protective bounds, to reduce the rate of contamination and to protect the water ecology and environmental system.