Assessment of health risk and pollution load for heavy and toxic metal contamination from leachate in soil and groundwater in the vicinity of dumping site in Mid-Brahmaputra Valley, India

The leakage of leachate from highly contaminated Municipal Solid Waste (MSW) landfill sites to the soil and groundwater may severely impact human health. The present study aimed to rank the levels of harmful metals Zn, Cd, Cr, Pb, and Ni evolving through leachate in different environmental matrices. An old but not stable landfill site near Morabharali River in Tezpur town, India, was selected for the study. The nature of groundwater was found to be slightly acidic, while leachate was alkaline in nature. While both landfill employees and locals in the target region were at a safe level (HI < 1), the children's hazard index (HI)levels (ing and inh) were higher than adults. The Incremental Lifetime Cancer Risk (ICLR) rating for adults in the residential area was higher than that for children, however ILCR derm value found to be highest in children's bodies for Cr, Ni, Cd and Pb were 8.34 × 10⁻⁷,7.87 × 10⁻⁷, 7.09 × 10⁻⁷, and 9.02 × 10⁻⁷ respectively and may affect the skin of the children. A high Leachate Pollution Index (LPI) of 18.39 was observed, indicating that the waste dumped in the landfill has not yet attained stability and the LPI was highly influenced by total chromium. LPI was higher in a few sites, and in a few places, it was low to moderate. Groundwater's heavy metal pollution index was observed to be highest in Site 10 and Site 12 and the concentration of heavy metals in the water was in a sequence as Mn > Zn > Cr > Ni > Cu > Pb. The contamination index was found to be highest for manganese. Index of contamination for ground water categorized 30% of the sites to be “High” contaminated, 13% to be “Mid” contaminated, and 57% were found to be categorized as “Low” contamination. Correlation coefficient pairs for metals Zn, Cd, Cr, Pb, and Ni in soils ranged from 0.47 to 0.93. In contrast, it ranged from 0.92 to 0.96 in water samples which implied they were significantly positively correlated with each other at the 99% confidence level. The cluster analysis classified B, Cr, Co, Ni, Cu, Zn, Pb, E.C. and pH as anthropogenic in origin and Mn and dissolved oxygen from mixed (anthropogenic and lithogenic) sources. Since the landfill site is unstable and continuously leaches contaminants into the soils and groundwater, there is an urgent need to manage the site, and regular monitoring of surrounding groundwater is recommended.