Sediment phosphate release flux under hydraulic disturbances in the shallow lake of Chaohu, China

Abstract

Quantifying the effect of hydraulic disturbances on sediment phosphate release is a key issue in the water quality assessment of lakes, especially for the shallow lakes which are susceptible to winds and waves. Here, we sampled the original sediment columns from 12 positions in the eastern, central, and western areas of the Chaohu Lake, a representative shallow lake in China, and observed phosphate release under three levels of hydraulic disturbances in the laboratory. When the disturbance was weak and the surface sediment of bottom mud moved individually (the Individual Motion Mode), sediment phosphate release rate was insigni cant (0.24 mg/m 2 /d). When the disturbance was medium and only a small percentage (<16%) of surface sediment started to move (the Small Motion Mode), phosphate release rate sharply increased to 4.81 mg/m 2 /d. When the disturbance was further strengthened and most (≥16%) of the surface sediment moved (the General Motion Mode), phosphate release rate was more than doubled (10.23 mg/m 2 /d). With the increase of hydraulic disturbance intensity, the variation range of phosphate release also became wider. Spatial distribution showed that the release rate varies the most in the western area, followed by the eastern and the central areas. By extrapolating the experimental results to the real scale, we found the phosphate release uxes would probably fall within a wide range between 203.43 kg/d to 7311.01kg/d under different levels of hydrodynamic disturbances with considerably affects phosphate release from shallow lakes. This study also has implications for the pollutant management in other shallow lakes.

Distribution Patterns of Sediment Organic Carbon Stocks in Shallow Lakes and the Significance for Sustainable Lake Management: Chaohu Lake in Eastern China as a Case Study

“…Chaohu Lake is one of the five major freshwater lakes in China. In recent years, due to natural and anthropogenic factors, eutrophication of the lake is serious, and the accumulation of SOC has intensified, which has seriously constrained the sustainable development of the socio-economy in the basin [20,21]. At present, SOC research mainly focuses on the water body or the lakeside green belt in Chaohu Lake; however, the prominent characteristic of the eco-environment is that there are open water, shallow groundwater, and strong surface runoff activities near it [22].…”