Comparative hydrogeochemical characterization and environmental controls on groundwater quality, irrigation suitability, and health risk across northern and coastal hydrological settings of Bangladesh

Groundwater is a vital resource that supports human health, ecosystems, and agriculture, and its quality varies across Bangladesh due to differing geology, land use, and environmental pressures. This study aims to conduct a comparative hydrogeochemical characterization and assess the environmental controls affecting groundwater quality, irrigation suitability, and human health risks across northern (Dinajpur) and coastal (Barisal) hydrological settings in Bangladesh. Groundwater data were obtained from the Bangladesh Water Development Board (BWDB), covering 27 monitoring wells in Dinajpur and 24 in Barisal. Multivariate statistical analyses revealed that groundwater quality in Barisal is primarily influenced by salinity-related factors (EC, TDS, and Major Ions like Na + , Cl - ), reflecting coastal saline intrusion. In contrast, Dinajpur samples were associated with parameters like SAR, Si + , PO 4 3- , ORP, I⁻, CaCO 3 , and B, indicating geogenic influences from silicate weathering, carbonate dissolution, and fertilizer inputs from agriculture. The Water Quality Index (WQI) results showed that in Barisal, 20.83% of sites were excellent and 18% unsuitable for drinking, whereas in Dinajpur, 64.29% were excellent with no unfit sites. For irrigation suitability, Barisal had 75% excellent and 4.17% severely affected areas, while 44.44% excellent and 14.81% severely affected sites were observed in Dinajpur. Health risk assessment revealed significantly higher Hazard Index (HI) values in Barishal across all age groups compared to Dinajpur, indicating elevated potential health risks in the coastal region. Children were identified as the most vulnerable group, exhibiting higher HI values than males and females in both Barishal (HI = 0.38–57.29) and Dinajpur (HI = 0.34–4.41). The Pearson Correlation analysis indicated that in Dinajpur, environmental variables demonstrated negligible correlations with groundwater quality (WQI: r = –0.18 to 0.19; IWQI: NDVI r = 0.25, LST r = –0.20). Similarly, Barishal had negligible correlations, with the Water Quality Index (WQI) revealing a little link with NDVI and NDWI, respectively (r = 0.17–0.24), whilst the Integrated Water Quality Index (IWQI) indicated minimal impact across all indices (r = –0.03 to 0.19). Overall, the study highlights regional variations in groundwater quality and health risks, emphasizing the necessity for location-specific water resource management strategies.