Seasonal variations, hydrogeochemical processes and health risks of nitrate and fluoride in groundwater of greater Hyderabad, Telangana State

This study evaluates hydrogeochemical processes and associated health risks from nitrate and fluoride contamination in shallow hard-rock aquifers of the semi-arid Greater Hyderabad Municipal Corporation (GHMC) region, Telangana, South India. A total of 44 groundwater samples were collected from domestic, industrial and irrigation sources during the pre- and post-monsoon seasons of 2023. Spatial analysis showed elevated nitrate levels in the south-western, northern, and central areas, with 36% (pre-monsoon) and 40% (post-monsoon) of samples exceeding the permissible limit (45 mg/L). Fluoride concentrations were high in the northern, southern, and south-western zones, where 64% and 59% of samples exceeded the acceptable limit (1.0 mg/L) during pre- and post-monsoon periods, respectively. Gibbs diagrams indicated that rock–water interaction and evaporation are the dominant processes controlling groundwater chemistry. Statistical and factor analyses revealed that groundwater chemistry is primarily controlled by feldspar weathering, cation exchange processes, and a combination of geogenic and anthropogenic influences. Health risk assessment indicates that hazard quotient (HQ) values for fluoride and nitrate exceed the non-carcinogenic threshold (HQ > 1.0), particularly among children, underscoring their heightened vulnerability due to lower body weight and greater exposure per unit mass. These findings signify a substantial public health concern in the region.