Physicochemical characterization of groundwater and drinking suitability with nitrate-related health risk assessment in the El Hammam basin, semi-dry Mediterranean regions

Abstract

Groundwater represents the main freshwater supply used for potable purposes in semi-dry Mediterranean regions, yet its chemical status is progressively shaped by hydrogeochemical processes alongside anthropogenic stressors. The present research presents a field-based evaluation of groundwater conditions and nitrate-related non-carcinogenic health impacts in the El Hammam Basin, Khenifra (central Morocco). Eleven groundwater wells were sampled during a spring 2023 campaign and subjected to comprehensive analysis of major physicochemical variables. Groundwater quality was evaluated through hydrogeochemical characterization combined with the Water Quality Index (WQI), the Canadian Council of Ministers of the Environment Water Quality Index (CCME-WQI), and the Nitrate Pollution Index (NPI), while nitrate-related potential health impacts were assessed using hazard quotient (HQ) and hazard index (HI) calculations considering both oral ingestion and dermal contact exposure pathways. Piper diagram interpretation indicates that groundwater samples mainly fall within mixed Ca–Mg–HCO 3 –Cl hydrochemical facies, reflecting the combined influence of carbonate dissolution, cation exchange, and salinity-related processes. Both WQI and CCME-WQI results indicate that approximately 75% among the sampled wells meet drinking water suitability standards, although elevated electrical conductivity and total dissolved solids highlight localized mineralization. Nitrate concentrations remain below guideline thresholds throughout the investigated area, and the applied health risk evaluation indicates no nitrate-related non-carcinogenic risk for adult populations or children within the sampled wells during the sampling period. These results provide a baseline characterization regarding groundwater conditions and associated public health implications within this under-studied hydrogeological basin and emphasize the need for multi-seasonal monitoring to capture temporal variability and support sustainable groundwater management. The originality of this work is reflected in the integrated use of hydrogeochemical analysis, multiple water quality indices (WQI and CCME-WQI), and nitrate-specific health risk assessment, offering a robust framework applicable to comparable semi-arid Mediterranean groundwater systems facing increasing environmental and agricultural pressures.