Hydrogeochemical Modelling and Probabilistic Health Risk Assessment of Nitrate and Fluoride in the Groundwater of Kota Stone Mines regions

Abstract

Groundwater serves as the main source of drinking water, especially in rural India. The primary threats to human health and water quality are pollutants like nitrate and fluoride. To determine the concentration of fluoride and nitrate, as well as their geographical distribution and possible sources, the current study examines the hydrogeochemical properties of groundwater in the Kota Stone mining regions in Kota, Rajasthan, India. In the study multivariate statistics, Health Hazard Assessment and the Entropy Water Quality Index (EWQI) were also carried out. Around 84% of the samples had fluoride contents above than the threshold limit for drinking water (1.5 mg L-1). Similarly, nitrate contents were 25.5% and 33.3% higher in pre-monsoon and post-monsoon, respectively, than the permissible limit for drinking water quality (45 mg L-1). Considering EWQI, nearly 19.6% and 21.6% of the groundwater samples were poor and very poor, respectively, hence unfit for drinking in pre-monsoon. While in the post-monsoon period, rainfall-induced dilution exerts a significant positive influence on groundwater quality by reducing the concentration of dissolved contaminants. The average value of Hazard Quotient (HQ) of fluoride through groundwater ingestion for adults (children) in the before and after monsoon seasons was 2.29±0.31 (3.03±0.41) and 2.19±0.30 (2.89±0.39), respectively, hence associated with non-carcinogenic risk to people, which is a severe concern. In this study, elevated fluoride levels were found in groundwater, likely due to the dissolution of fluoride-bearing minerals at higher temperatures and extended residence times, which encourages fluoride weathering in semi-arid regions. The study's findings would be useful for managing groundwater resources strategically, while preserving groundwater quality and reducing health hazards.