Geogenic and anthropogenic impacts on phosphorus enrichment in groundwater around China’s largest freshwater lake

• Published in: Journal of hydrology (Amsterdam) 2024-05, Vol.635, p.131154, Article 131154
• Main Authors: Ke, Xianzhong, Tao, Yanqiu, Zhang, Xinxin, Liu, Guangning, Zhang, Yanpeng, Deng, Yamin, Li, Qinghua
• Format: Article
• Language: English
• Subjects: biodegradation; China; detection limit; dissolved organic matter; freshwater lakes; Geogenic; Groundwater; human health; hydrochemistry; methane production; optical properties; Phosphorus; Poyang Lake Basin; Stable isotopes; total dissolved phosphorus
• ISSN: 0022-1694
• DOI: 10.1016/j.jhydrol.2024.131154

[Display omitted] •We firstly study P cycle in groundwater around China’s largest freshwater lake.•Highest groundwater TDP concentrations up to 2.52 mg/L were found in Jiangbei Plain.•The origins of high TDP groundwater includes geogenic and anthropogenic controls.•The geological evolutionary histories affected the formation of high TDP groundwater. High phosphorus (P) groundwater poses a serious threat to the ecological environment and human health because it can be exposed through groundwater-surface water interactions or extraction projects. An investigation was conducted at China’s largest freshwater lake (Poyang Lake) regarding the total dissolved phosphorus (TDP) concentration in groundwater as well as the geogenic and anthropogenic controls on the formation of high TDP groundwater. TDP concentrations in the groundwater of the Poyang Lake Plain (PLP) ranged from 0.01 to 1.29 mg/L, with 19.5 % of samples exceeding 0.4 mg/L (i.e., referred as high TDP groundwater); in the groundwater of the Jiangbei Plain (JBP), the TDP concentrations ranged from below detection limit (BDL) to 2.52 mg/L, with 47.9 % of samples exceeding 0.4 mg/L. Stable isotope analysis (δ18O-H2O and δ15N-NH4+) combined with groundwater chemistry analysis revealed the formation of high TDP groundwater in the PLP is mainly influenced by anthropogenic activities, while in the JBP is mainly affected by geogenic factors. Further, stable carbon isotope (δ13C-DIC) and optical characterization of dissolved organic matter (DOM) were employed to determine possible geochemical processes associated with groundwater P enrichment in the JBP. The responsible geochemical processes were found to include the biodegradation of more recalcitrant aromatic organic matter (OM) accompanied by methanogenesis, coupled with active reductive dissolution of Fe(III) (oxyhydr)oxides. Moreover, over geologic time scales the main body of Poyang Lake gradually migrated southward and affected the thickness of the overlying aquitard, subsequently controlling the source and occurrence of P in the groundwater in the two areas around Poyang Lake. To our knowledge, this is the first study to report TDP concentrations and evaluate the P cycle in the groundwater system around the largest freshwater lake in China.