Yuan Hezhong, Li Qiang, Kukkadapu Ravi K, Liu Enfeng, Yu Jianghua, Fang Hao, Li Hui, Jaisi Deb P
School of Environmental Science and Engineering, Nanjing University of Information Science & Technology, Nanjing, Jiangsu 210044, PR China; Department of Plant and Soil Sciences, University of Delaware, Newark, DE 19716, United States.
Department of Plant and Soil Sciences, University of Delaware, Newark, DE 19716, United States.
Sci Total Environ. 2019 Aug 1;676:823-833. doi: 10.1016/j.scitotenv.2019.04.322. Epub 2019 Apr 23.
Biotic and abiotic pathways for the transformation of phosphorus (P) in the sediment of Taihu Lake, a eutrophic shallow freshwater lake in southeastern China, were studied using the oxygen isotope ratios of phosphate (δO) along with sediment chemistry, X-ray diffraction, and Fe-Mössbauer spectroscopic methods. The results showed that δO values of sediment P pools significantly deviated from equilibrium and thus allowed distinguishing potential P sources or pathways of transformation. Isotope values of authigenic P being lighter than equilibrium suggests the re-mineralization of organic matter and subsequent precipitation of apatite as the major pathway of formation of authigenic P. The δO values of the Al-bound P pool (18.9-23.5‰) and ferric Fe-bound P (16.79-19.86‰) could indicate potential terrestrial sources, but the latter being closer to equilibrium values implies partial overprinting of potential source signature, most likely due to reductive dissolution and release of P and followed by partial biological cycling before re-sorption/re-precipitation with newly formed ferric Fe minerals. Oxic/anoxic oscillation and dissolution/re-precipitation reactions and expected isotope excursion are corroborated by sediment chemistry and Mössbauer spectroscopic results. These findings provide improved insights for better understanding the origin and biogeochemical cycling of P associated with eutrophication in shallow freshwater lakes.
利用磷酸盐的氧同位素比值（δO）结合沉积物化学、X射线衍射和Fe-穆斯堡尔光谱方法，研究了中国东南部富营养化浅水湖泊太湖沉积物中磷（P）转化的生物和非生物途径。结果表明，沉积物磷库的δO值显著偏离平衡态，因此能够区分潜在的磷源或转化途径。自生磷的同位素值比平衡态轻，这表明有机质的再矿化以及随后磷灰石的沉淀是自生磷形成的主要途径。铝结合磷库的δO值（18.9-23.5‰）和铁结合磷（16.79-19.86‰）可能指示潜在的陆源，但后者更接近平衡值，这意味着潜在源特征存在部分叠加，最有可能是由于磷的还原溶解和释放，随后在与新形成的铁矿物再吸附/再沉淀之前发生了部分生物循环。沉积物化学和穆斯堡尔光谱结果证实了氧化/缺氧振荡以及溶解/再沉淀反应和预期的同位素偏移。这些发现为更好地理解浅水湖泊中与富营养化相关的磷的来源和生物地球化学循环提供了更深入的见解。
