Hydrochemical and health risk evaluation of the groundwater in Gonbad Kavus area, northeastern Iran

Abstract

Abstract Groundwater quality in arid and semi-arid regions is under increasing pressure from both natural and anthropogenic sources. This study presents a comprehensive assessment of groundwater quality in the Gonbad Plain, Iran, to determine its suitability for drinking and to identify the controlling hydrogeochemical processes. A total of 45 groundwater samples were analyzed for their physicochemical parameters, and the data were evaluated using an integrated approach combining hydrochemical facies analysis, geochemical modeling (PHREEQC), multivariate statistical techniques (Principal component analysis (PCA) and hierarchal cluster analysis (HCA)), and human health risk assessment (Heavy metal pollution index (HPI), Hazard quotient (HQ), Hazard index (HI)). The results reveal a hydrochemical evolution from fresh Ca-HCO₃ type water to saline Na-Cl type water, primarily controlled by three key mechanisms: (1) dissolution of evaporite minerals (halite and gypsum), (2) cation exchange, and (3) evaporation. The Gibbs diagrams confirmed that rock-water interaction and evaporation are the dominant processes governing water chemistry. Iron concentrations varied from 0.01 mg/L to 4.12 mg/L, with a mean of 0.46 mg/L and a standard deviation of 0.66 mg/L. The median iron concentration was 0.27 mg/L. Manganese concentrations ranged from 0.015 mg/L to 0.47 mg/L, with a mean of 0.09 mg/L and a standard deviation of 0.07 mg/L. The median manganese concentration was 0.08 mg/L. The HPI indicated a critical water quality crisis, with 77.8% of the samples being unsuitable for drinking (HPI > 100), primarily due to elevated concentrations of manganese. The non-carcinogenic health risk assessment revealed that while the dermal exposure pathway poses no significant risk, oral ingestion of groundwater presents a potential health hazard, particularly for children. The HI exceeded the safe limit of 1.0 in 11.1% of the samples for children, with manganese being the primary contributor to the risk. This is the first study apply integrated framework that combines multivariate statistics, geochemical modeling, and health risk indices to evaluate groundwater vulnerability in Gonbad-e Kavus. The study’s alignment with UN Sustainable Development Goal 6 (Clean Water and Sanitation).