Deciphering groundwater pollution in the Lower Anayari Catchment: insights from using δ2H, δ18O, PMF, and APCS-MLR receptor model

Abstract

This research provides a comprehensive analysis of groundwater pollution in the Lower Anayari Catchment (LAC) through δ²H and δ¹⁸O isotopic analysis, along with positive matrix factorization (PMF) and PCS-MLR receptor models. Forty groundwater samples were collected from hand-dug wells and equipped boreholes across the LAC. Flame photometry for Na⁺ and K⁺, complexometric titration for Ca²⁺, ion chromatography for Cl^-, F^-, NO₃^-, SO₄^2-, and PO₄^3-, and atomic absorption spectrometry for Mg²⁺, Fe, Pb, Cd, As, and Ni were analytical techniques/instruments employed. In regard to cations, Na⁺ has the highest average concentration of 63.0 mg/L, while Mg²⁺ has the lowest at 2.58 mg/L. Concerning the anions and nutrients, Cl^- has the highest mean concentration of 18.7 mg/L, and Fl^- has the lowest at 0.50 mg/L. Metalloids were detected in trace amount with Fe displaying the highest mean concentration of 0.077 mg/L whereas Cd and As recorded lowest (0.001 mg/L). The average values for groundwater δ¹⁸O and δ²H were - 3.64‰ and - 20.7‰, respectively; the average values for rainwater isotopic composition were - 3.41‰ for δ¹⁸O and - 17.4‰ for δ²H. It is believed that natural geological features, particularly biotite granitoid and volcanic flow/subvolcanic rocks from the Birimian Supergroup, significantly influence groundwater mineralisation. Additionally, the impact of anthropogenic activities on water quality, with urban development and agricultural practices, may be attributed to increasing levels of certain contaminants such as Fe, Ni, NO₃^-, and PO₄^3-. This research contributes to the broader field of hydrological study and provides practical implications for managing and conserving water resources in similar contexts. The innovative combination of isotopic and statistical analyses sets a new standard for future studies in groundwater quality assessment, emphasising the need for comprehensive approaches that consider both geological characteristics and human impacts for sustainable water resource management.

Keywords: Birimian Supergroup; Environmental geochemistry; Hydrological research; Natural geological processes; Stable isotope (δ2H and δ18O); Water resource management.