Unveiling water quality and health risks from groundwater chemicals in Poyang Lake basin of China: a sophisticated analysis.

Background: Groundwater is a critical water resource in the Poyang Lake basin, especially given the increasing frequency of extreme drought events. However, comprehensive assessments of its chemical characteristics and associated health risks remain insufficient. This study aims to provide a comprehensive assessment of groundwater quality and associated health risks in the Poyang Lake basin, China. Methods: This study collected 670 groundwater samples from domestic and agricultural wells across the basin during the 2022 dry season. Hydrochemical parameters, including manganese (Mn), ammonia nitrogen (NH4+ ), iron (Fe3+), aluminum (Al3+), chemical oxygen demand (COD), fluoride (F-), and nitrate (NO3- ), were analyzed and compared against China's Class III groundwater quality standards. Spatial variations in water quality were evaluated using the Entropically Weighted Water Quality Index (EWQI). Non-carcinogenic health risks via ingestion and dermal contact pathways were quantified through deterministic risk assessment models, with uncertainty and probability analyzed via Monte Carlo simulations (10,000 iterations). Sensitivity analysis was conducted to identify dominant factors influencing risk outcomes, ensuring a robust probabilistic interpretation of health hazards. Results: The results unveils pronounced spatial variability across key hydrochemical parameters: pH ranges from 3.05 to 11.09, total dissolved solids (TDS) from 25.38 to 1,635.21 mg/L, Mn from below detection limits to 19.93 mg/L, COD from below detection limits to 8.57 mg/L, and TH from 9.47 to 905.78 mg/L. A notable proportion of samples breach the Class III groundwater quality standards, with 38% for Mn, 39% for COD, and 15% for NH4+ . The Piper diagram analysis categorizes the primary groundwater type as HCO3- -Ca, with a secondary Cl-Ca-Mg type. Through the EWQI assessment, while the overall water quality is deemed acceptable, we identify 56 sites with EWQI values indicative of poor to very poor quality, predominantly influenced by Mn and NH4+ . The irrigation risk assessment highlights extensive areas unsuitable for irrigation, particularly within the Ganjiang River basin. Health risk assessments utilizing a deterministic model reveal significant non-carcinogenic risks from F- and NO3- in groundwater, especially for children. However, our Monte Carlo simulation indicates that the probabilities of F- and NO3- posing non-carcinogenic health risks are virtually zero, suggesting that the deterministic assessment may have overestimated the health risks. This study provides critical insights into the groundwater quality and health risks in the Poyang Lake basin and underscores the necessity for targeted water management strategies to mitigate pollution sources and safeguard public health.