Organic Phosphorus Mineralization Dominates the Release of Internal Phosphorus in a Macrophyte-Dominated Eutrophication Lake

• Published in: Frontiers in environmental science Vol. 9
• Main Authors: Yu, Wei, Yang, Haiquan, Chen, Jingan, Liao, Peng, Chen, Quan, Yang, Yongqiong, Liu, Yong
• Format: Journal Article
• Language: English
• Published: Frontiers Media S.A 14.01.2022
• Subjects: 31P NMR; bioavailability; eutrophication; Lake Caohai; organic phosphorus; sediment
• ISSN: 2296-665X; 2296-665X
• DOI: 10.3389/fenvs.2021.812834

Macrophyte-dominated eutrophication (MDE) lakes have attracted wide attention due to the high phosphorus (P) loading in sediments that poses a wide spread risk for P release and pollution management. However, because of the superior productivity characteristics, the role of organic P mineralization in sediments in the internal P loading of MDE lake is still under debate. This study investigated the release dynamic of P in the sediments of Lake Caohai, a MDE lake in southwest of China, using a combination of the modified Huffer sequential extraction method, 31 P nuclear magnetic resonance spectroscopy (NMR), and composite diffusive gradient in thin films (DGT) technology. Results showed that the apparent P diffusion flux at the sediment-water interface was remarkably high, with a mean value of 0.37 mg m −2  d −1 . The phosphate ester organophosphorus components (i.e., Mono-P and Diester-P) continuously deposited and degraded in the sediments maintained the high productivity of the lake, and the mineralization process plays a critical role in the release of internal P. Although the content of inorganic P in sediment is relatively high (accounting for approximately 60% of total P), the reductive mechanism based on P-containing iron oxide/hydroxide has a low contribution to the internal P loading, as was indicated by the low release rate of P-combination iron-manganese (Fe-Mn)/iron-aluminum (Fe-Al) (BD-P and NaOH-P) and the insignificant positive correlations between DGT-labile P and DGT-labile Fe in the sediment cores. Additionally, organic P in sediments could transfer to P-combination Fe-Al/Fe-Mn. However, in severely expropriated environments, the enrichment of P-combination Fe-Al/Fe-Mn in surface sediments inhibited the mineralization of monophosphate to some degree. Taken together, this study emphasized the impact of sediment organic P loading on the release of internal P in lake, highlighting that organic P is also the valuable objects for avoiding eutrophication of MDE lakes.