Phosphorus Buildup and Release Risk Associated with Agricultural Intensification in the Estuarine Sediments of Chaohu Lake Valley, Eastern China

摘要

Phosphorus (P) accumulation and the risk of P release were studied in the estuarine sediments of the Chaohu Lake Valley in Eastern China. Rapid agricultural intensification has occurred in this area since the 1980s, resulting in the extensive use of phosphate fertilizers. This extensive use of phosphate has affected P processes throughout the valley and resulted in the total phosphorus (TP) contents in the substrates and surface sediments increasing from 374 to 537 mg/kg, on average. Of all the forms of P evaluated in this study, residual P (Res-P) was present at the highest levels and accounted for 19.8-74.0% of the TP. Conversely, the lowest contents were observed for KCl-extracted P (KC1-P), which accounted for only 0.602% of the TP. Additionally, aluminum/iron-bound P (NaOH-Pi), which accounted for 16.0-53.1% of the TP, was an important factor that caused the TP to increase due to long-term P fertilization. However, calcium-bound P (Ca-P) was maintained at a relatively stable level. Furthermore, the degree of P saturation (DPS) and the P-induced lake eutrophication risk index (ERI) were investigated to determine the risk of release of P from the sediments. The average DPS and ERI values were found to range from 3.92-21.4% and from 12.6-33.6%, respectively. These results suggest that almost half of the estuarine sediments posed a potential risk of eutrophication. Moreover, these findings indicate that estuarine sediments that have been enriched with P are likely the sources of P that lead to the formation of algal blooms in Chaohu Lake.