Fluoride variability in groundwater: Hydro-geochemical influences and risk assessment in an arid region of Northwestern India

Abstract

This study examines the underlying hydrogeochemical mechanisms driving fluoride (F^-) enrichments in groundwater and its associated health risks in the arid region of Northwest India. Groundwater samples were systematically collected from multiple villages in the Ladnu block of Rajasthan during the pre-monsoon and post-monsoon seasons of 2023. Concentrations of F^- were analyzed to assess their spatial variability and the governing hydrogeochemical processes. The concentrations of F^- surpassed the Bureau of Indian Standards (BIS) 2012 and the World Health Organization (WHO) 2022 -permissible limits of 1.5 mg/L in 45 samples across 34 villages during both seasonal periods. The highest F^- content was observed in the eastern part of the study area, with peak values recorded in Tanwara village, while Datau village displayed the lowest concentrations. The alkaline nature of groundwater coupled with the semi-arid climate, enhances F^- mobilization. The water quality index (WQI) indicates seasonal fluctuations in groundwater quality, with elevated F^- levels presenting potential health hazards in the order of infants > children > adults. Multivariate statistical analysis, including PCA and other hydrochemical proxies, indicates that evaporation and rock-water interaction are the primary processes controlling F⁻ enrichment along with co-existing chemical species. The findings indicate that the groundwater in study area is under both quantitative and qualitative stress, requiring continuous monitoring and sustainable management strategies. Policy implementation aligned with Sustainable Development Goals (SDG) 6 is essential to mitigate F^- contamination and ensure the long-term sustainability of this vital resource.