Identifying sources and cycling of phosphorus in the sediment of a shallow freshwater lake in China using phosphate oxygen isotopes

Hezhong Yuan; Qiang Li; Ravi K Kukkadapu; Enfeng Liu; Jianghua Yu; Hao Fang; Hui Li; Deb P Jaisi

doi:10.1016/j.scitotenv.2019.04.322

Identifying sources and cycling of phosphorus in the sediment of a shallow freshwater lake in China using phosphate oxygen isotopes

Sci Total Environ. 2019 Aug 1:676:823-833. doi: 10.1016/j.scitotenv.2019.04.322. Epub 2019 Apr 23.

Authors

Hezhong Yuan¹, Qiang Li², Ravi K Kukkadapu³, Enfeng Liu⁴, Jianghua Yu⁵, Hao Fang⁵, Hui Li², Deb P Jaisi⁶

Affiliations

¹ 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.
² Department of Plant and Soil Sciences, University of Delaware, Newark, DE 19716, United States.
³ Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA 99354, United States.
⁴ College of Geography and Environment, Shandong Normal University, Ji'nan, Shandong 250359, PR China.
⁵ School of Environmental Science and Engineering, Nanjing University of Information Science & Technology, Nanjing, Jiangsu 210044, PR China.
⁶ Department of Plant and Soil Sciences, University of Delaware, Newark, DE 19716, United States. Electronic address: jaisi@udel.edu.

PMID: 31076206
DOI: 10.1016/j.scitotenv.2019.04.322

Abstract

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 (δ¹⁸O_P) along with sediment chemistry, X-ray diffraction, and ⁵⁷Fe-Mössbauer spectroscopic methods. The results showed that δ¹⁸O_P 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 δ¹⁸O_P 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.

Keywords: (57)Fe-Mössbauer spectroscopy; Phosphate oxygen isotopes; Phosphorus; Sediment; Sources and cycling.