西南岩溶地下河水化学特征及健康风险评价—以广西平江地下河为例OA

The groundwater system in the karst regions of Southwest China is crucial for ensuring water supply security in traditional agricultural areas and maintaining ecosystem health.Assessing the water quality and ecological risks of karst groundwater is therefore of strategic importance for regional ecological conservation and sustainable development.This study focused on the representative Pingjiang Underground River Basin.42 groundwater samples across high-flow,normal-flow,and low-flow periods were collected.A comprehensive hydrochemical analysis was conducted to identify the primary factors influencing groundwater chemistry,and the Objective Comprehensive Weight Water Quality Index(OCWQI)alongside human health risk assessment models were employed to evaluate groundwater quality and associated health risks.The results indicated that the dominant anions and cations in the groundwater were HCO3-and Ca2+,respectively.The groundwater was generally weakly alkaline and slightly hard,with chemical constituent concentrations following the sequence:low-flow period>normal-flow period>high-flow period.The hydrochemical type across the basin was consistent,classified entirely as HCO3-Ca.Groundwater hydrochemistry in the Pingjiang Underground River Basin was primarily governed by rock weathering processes,particularly of carbonate and silicate rock,while also being notably influenced by anthropogenic activities.This influence was evidenced by elevated nitrate(NO3-)concentrations attributable to agricultural practices.Health risk assessment revealed that during the normal-flow and low-flow periods,64％and 79％of groundwater samples,respectively,exceeded the natural threshold for NO3-(3 mg·L-1)for adults,corresponding to a low-risk level(Hazard Index,0.09<RHI<0.30).For children,the proportions were 64％and 86％during the same periods,exceeding the same threshold and reaching a lower threshold for risk(0.06<RHI<0.20),indicating potential low-level non-carcinogenic health risks,particularly for younger populations.The spatial patterns of groundwater quality degradation aligned closely with the distribution of NO3--related health risks,showing a stepwise increase from northwest to southeast and consistently higher risk levels for children compared to adults.These findings provide valuable insights for the sustainable use and protection management of groundwater resources in the Pingjiang Underground River Basin and analogous karst regions.