Le Fan, Ruan Xiaohong, Wei Zhao, Wu Kedi, Wei Haizhen, Liu Congqiang
Department of HydroSciences, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China; MOE Key Laboratory of Surficial Geochemistry, Nanjing University, Nanjing 210023, China.
Department of HydroSciences, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China; MOE Key Laboratory of Surficial Geochemistry, Nanjing University, Nanjing 210023, China.
Sci Total Environ. 2024 Nov 1;949:175022. doi: 10.1016/j.scitotenv.2024.175022. Epub 2024 Jul 24.
The biogeochemical cycling of phosphorus (P) in river-lake systems presents significant challenges in tracing P sources, highlighting the importance of effective traceability approaches for formulating targeted management measures to mitigate lake eutrophication. In this study, we used the oxygen isotope of phosphate (δO) as a tracer in the river-lake systems, establishing a tracing pathway from potential end-members, through inflow rivers, and eventually to the lake. Taking Dianshan Lake and its main inflow rivers as the study area, we measured δO values of potential end-members, including domestic sewage treatment plant effluents, industrial effluents from phosphorus-related enterprises (printing and dyeing, electroplating, plastics, etc.), and farmland soils. Notably, the industrial effluent signatures ranged from 13.1 ‰ to 21.0 ‰ with an average of 16.8 ‰ ± 3.2 ‰, enriching the δO threshold database. Using the MixSIAR model, it was found that phosphorus in the Jishuigang River primarily originated from agricultural non-point sources and domestic sewage in the dry season, while the Qiandengpu River, with a higher proportion of urban area, had a greater influence from domestic sewage and industrial effluents. Moreover, significant differences were observed between δO values at the lake entrances of the inflow rivers (13.7 ‰ ± 1.0 ‰) and in acid-soluble phosphate of the lake sediments (9.9 ‰ ± 1.0 ‰). Isotopic tracing revealed that phosphorus in the lake originated from both external inputs (80.6 %) and internal release (19.4 %) in the dry season. Alongside pollutant flux calculations based on the hydrological conditions and water quality of the inflow rivers, our findings indicated that phosphorus in Dianshan Lake was mainly attributed to agricultural non-point sources, domestic sewage and sediment release in the dry season. This study provided novel insights into the identification of pollution sources in the river-lake systems, with broad implications for pollution control and environmental protection.
河湖系统中磷（P）的生物地球化学循环在追踪磷源方面面临重大挑战，这凸显了有效溯源方法对于制定针对性管理措施以减轻湖泊富营养化的重要性。在本研究中，我们将磷酸盐的氧同位素（δO）用作河湖系统中的示踪剂，建立了一条从潜在端元、经入流河流最终到湖泊的追踪路径。以淀山湖及其主要入流河流为研究区域，我们测量了潜在端元的δO值，包括生活污水处理厂出水、磷相关企业（印染、电镀、塑料等）的工业废水以及农田土壤。值得注意的是，工业废水的δO值范围为13.1‰至21.0‰，平均为16.8‰±3.2‰，丰富了δO阈值数据库。使用MixSIAR模型发现，在旱季，急水港河中的磷主要源于农业面源和生活污水，而城镇区域占比更高的千灯浦河受生活污水和工业废水的影响更大。此外，入流河流的湖泊入口处的δO值（13.7‰±1.0‰）与湖泊沉积物酸溶性磷中的δO值（9.9‰±1.0‰）之间存在显著差异。同位素示踪表明，旱季湖泊中的磷来自外部输入（80.6%）和内部释放（19.4%）。结合基于入流河流水文条件和水质的污染物通量计算，我们的研究结果表明，淀山湖中的磷在旱季主要归因于农业面源、生活污水和沉积物释放。本研究为河湖系统污染源的识别提供了新见解，对污染控制和环境保护具有广泛意义。
