Distribution Characteristics and Environmental Risks of Persistent and Mobile Organic Compounds (PMOCs) in Groundwater of a Typical Recharge Area, North China

Persistent and mobile organic compounds (PMOCs) are a class of emerging contaminants with high environmental persistence and mobility, posing significant risks to aquatic ecosystems and public health. The Hutuo River in Shijiazhuang is a typical ecological water recharge area, where the inflow of reclaimed water from wastewater treatment plants along the river can facilitate the infiltration of PMOCs into the groundwater system. To investigate the distribution, sources, and environmental risks of PMOCs in groundwater during the recharge process, surface water and groundwater samples were collected annually from 2023 to 2025 and analyzed using hydrochemical analysis, principal component analysis (PCA), and self-organizing maps (SOM). The results showed that all ten PMOCs, including tri-(2-chloroisopropyl)phosphate (TCPP), adamantan-1-amine (AMANT), benzyltrimethylam monium (BETMA), caprolactam (CAP), p-toluenesulfonamide (PTSA), acesulfame(K) (ACE), saccharine (SAC), trifluoromethanesulfonic acid (TFMSA), bisphenol S (BPS), (sodium) methyl sulfate (MS), were detected in groundwater during the recharge period, with total concentrations and detection frequencies both exhibiting a declining trend. Notably, AMANT, PTSA, and MS showed the highest maximum concentrations (2616.70, 5503.60 and 1427.41 ng/L, respectively). Meanwhile, TCPP, AMANT, CAP, and MS were the most frequently detected compounds, with the detection rates exceeding 93%. The distribution of PMOCs exhibited a strong correlation between surface water and groundwater. Groundwater hydrochemical types varied with PMOC pollution levels, with high concentrations samples clustering within Na⁺-Cl⁻ enriched zones on the Piper diagram. PCA revealed a significant correlation among Na⁺, Cl^-, and ∑PMOCs, which was further corroborated by SOM analysis. These findings indicated that reclaimed water inflows from the Zhengding and Gaocheng sections were the key anthropogenic source governing the distribution of PMOCs. During the continuous recharge process, certain PMOCs (e.g., AMANT and MS) showed accumulation trends in groundwater within areas influenced by reclaimed water, highlighting the ecological risks of long-term exposure. Therefore, it is recommended to strengthen the integrated monitoring and pollution control of PMOCs across reclaimed water, surface water, and groundwater to ensure water quality safety.