Appraising groundwater quality and probabilistic human health risks from fluoride-enriched groundwater using the pollution index of groundwater (PIG) and GIS: a case study of adama town and its vicinities in the central main Ethiopian rift valley

Abstract

This research's main objective is to identify the level of contamination in drinking water in Adama town and its environs by employing PIG, GIS and HHRA. The physical–chemical parameters of groundwater were determined, and the results were compared to regional and global drinking water quality guidelines. The pH of groundwater is alkaline, and the contents of Ca²⁺, Na⁺, HCO₃⁻, and F⁻ in the majority of samples surpassed the permissible drinking limit. The hydrochemical facies were identified in the following order: Ca–Mg–HCO₃, Na–Ca–HCO₃, and Na–HCO₃. Cation exchange and Rock–water interaction are the major dominant natural mechanisms controlling groundwater chemistry. Using IDW interpolation methods with Arc GIS 10.8, spatial analysis of the physico-geochemical content of water divulged that TDS, pH, TH, EC, Mg²⁺, Ca²⁺, K⁺, Na⁺, Cl⁻, HCO₃⁻, F⁻, and SO₄²⁻ all exhibit a positive trend in the direction of groundwater flow from the upland to the lowland (rift floor). As per PIG, the results show that 57%, 33%, 7% and 3% of the samples were found in the insignificant, low, moderate and high, correspondingly. The total hazard index (THI) is calculated from hazard quotients (HQIntake and HQDermal) results showing 83%, 73%, and 57% of the samples exceed the non-carcinogenic health threat of fluoride THI >1 in drinking water for children, women and men. Children are more susceptible to danger than either males or women, according to the THI data, based on body weights and consumption rates. Similarly, females are also more vulnerable to health risks than men.