Composition of phosphorus in wetland soils determined by SMT and solution 31P-NMR analyses
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In Eastern China, wetlands are common in the lower reaches of catchments or in coastal zones. Wetlands are at risk from eutrophication because of the large quantities of phosphorus (P) they receive from rivers. They are also decreasing in size. In this contribution, we present information about the composition of P in wetland soils, obtained using the Standards, Measurements, and Testing (SMT) protocol and 31P-nuclear magnetic resonance (NMR) spectroscopy. Average P concentrations varied in the different wetland soils and, in four of the five wetlands sampled, exceeded 500 mg∙kg−1. HCl-inorganic P (Pi) was the main Pi fraction in wetland soils. The percentage contribution of Pi (89.7 %) to total P was the highest in the Yangtze River estuary wetland. Six P components were detected by 31P-NMR analysis. Mono-P was the main organic P (Po) in wetland soils. Orthophosphate (Ortho-P) was positively and negatively related to NaOH-Pi (R 2 = 0.957, p < 0.001) and HCl-Pi (R 2 = −0.689, p < 0.001), respectively. Orthophosphate monoesters (Mono-P) were positively related to Po (R 2 = 0.617, p < 0.001) and ortho-P (R 2 = 0.624, p < 0.001), respectively. The main Po component was Mono-P, and it may be mineralized to ortho-P under the frequently changing redox conditions in wetland soils. The information from this study will support the development of robust scientific and effective policy for P management in wetlands.
KeywordsWetland P-NMR SMT Phosphorus Organic phosphorus Soil
This work was supported by the National Natural Science Foundation of China (Grant No. 21507146) and the special fund from the State Key Joint Laboratory of Environment Simulation and Pollution Control (Research Center for Eco-environmental Sciences, Chinese Academy of Sciences) (15Z01ESPCR). We thank Dr. Jingxin Yang and Dr. Xiaogang Niu for 31P-NMR analysis (Beijing Nuclear Magnetic Resonance Center). We also thank Xunhong Kong, Shou Yuan, Bozhen Zhang, and Jianlin Bi for collecting the samples.
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