Characteristics of phosphorus components in the sediments of main rivers into the Bohai Sea

Abstract

Phosphorus (P) is an essential nutrient for aquatic organisms; however, excessive P inflow to freshwater ecosystems can induce eutrophication. P concentrations in the rivers around the Bohai Sea have been amplified by fertilizer and sewage inputs associated with the development of industry and agriculture. Yet, knowledge of the characteristics of P is lacking at the main rivers which were inflow into the Bohai Sea. We determined the distribution and speciation of P in rivers inflow into the Bohai Sea using the Standards, Measurements and Testing method (SMT) and solution phosphorus nuclear magnetic resonance (31P-NMR). The results indicate that P pollution in the river surface sediments was serious. The total P content in the rivers sediment was between 87.28 to 2610.43mgkg−1, and the main component was Ca-P, which accounted for 34.75%–93.69%; the content of easy released P (Fe/Al/Mn-P) was less than that of HCl-P. Six P species, including two inorganic P species (orthophosphate and pyrophosphate) and four organic P (OP) components (phosphonates, orthophosphate monoesters, phospholipids and DNA-P) were detected in the NaOH-EDTA extracts by 31P-NMR. The main content orthophosphate was between 18.35 to 1681.31mgkg−1, and the orthophosphate monoester as a main kind of components of the OP, represented 0–31.39% of the TP. Because the heavy pollution heavily polluted zones in the Haihe basin includes the Luan River, the Yongdingxin River, and the Ziya River, the content of TP, OP and ortho-P in their sediments were relatively high. To be our knowledge, this is the first systematic study for the characteristics of P components in the rivers which were inflow into the Bohai River, and this study will support nutrition management and eutrophication risk control.