Dissolved mercury (Hg) in groundwater poses underrecognized risks in industrial regions of South Asia. We assessed Hg occurrence, sources, and dynamics, with co-occurring metals, in the mid-Gangetic Plains (Kanpur), India. Hg was detected in all groundwater samples (n = 39; 0.02–3.8 µgL⁻¹), with 20% exceeding 1 µgL⁻¹ guideline, reflecting complex hydrological-geogenic–anthropogenic interactions, whereas river water samples (n = 11) showed no exceedances. Ca²⁺-Mg²⁺-SO₄²⁻ type water indicates sulfur dominance linked to anthropogenic inputs (industrial emissions or coal combustion), creating sulfate-rich aquifer conditions under which Hg enrichment is observed. Hydrochemical patterns, elevated EC/TDS, and the proximity to irrigated land suggest that irrigation return-flow mediated evaporation-based enrichment may act as an important driver, contributing to Hg concentrations. Eh-pH analysis indicates aquifer redox conditions conducive to the stability of reduced dissolved Hg species. Probability exceedance shows a sharp decline in higher Hg levels, suggesting anthropogenic inputs, primarily atmospheric deposition. Health risk assessment indicates significant non-carcinogenic risks, especially for children (HQ > 2.5), dominated by arsenic (As) in river water. Co-contaminants As, U (uranium), Cr (chromium), and Fe (iron), and altered multivariate ionic clustering warrant further investigation. This study underscores the need for targeted regulation informed by hydrochemical diagnostics and public health risk frameworks.
Kumar et al. (Thu,) studied this question.
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