Geochemical characteristics, mechanisms and suitability for sustainable municipal and agricultural water supply of confined groundwater in central North China Plain

Confined groundwater is a prior water resource for urban and rural water supply in arid and semiarid regions. A total of 53 groundwater samples were collected from a typical region of the Central North China Plain to get hydrogeochemical insights into the development and utilization prospects of confined groundwater in arid regions. The results show the confined groundwaters are with mainly fresh hydrochemical facies of HCO3-Na and mixed HCO3-Na·Ca. The toxic elements including F, I, Fe exceed the drinking water permissible limits and potentially pose non-carcinogenic risks to all populations. High Fluoride is mainly responsible for the potential health risk, and followed by high iodine. For irrigation, confined groundwater of the study area may cause potential sodium, magnesium hazard and permeability issues to soil in long-term agricultural practice. The hydrochemistry of confined groundwater is dominantly governed by natural water-rock interactions including evaporates dissolution, silicate weathering and ions exchange. The high fluoride and iodine originate from geogenic sources rather than anthropogenic inputs. This research suggests although confined groundwater has good quality regarding the salinity, the geogenic toxic substances may damage its quality for drinking. Anthropogenic influences on confined groundwater chemistry are limited, but should be concerned for sustainable development of confined groundwater.