Phosphorus occurrence and release potential at the sediment-water interface in lakes in cold-arid regions

Abstract

In recent years, climate change has led to frequent eutrophication of lakes in cold-arid regions. To explore the potential release of P in sediments in cold-arid regions and its impact on eutrophication, we investigated P in Hulun Lake and Ulanor Wetland, lakes typical of cold-arid regions of China. Using continuous extraction of P and gradient diffusion film technology (DGT), the characteristics of P in the overlying water and sediments of Hulun Lake and Ulanor Wetland were analyzed. Bioavailability and the potential for release of P in sediments were evaluated. Mean concentrations of total P (TP) in the overlying water of Hulun Lake and Ulanor Wetland were 0.21 and 0.27 mg/L, respectively, mainly in particulate form. These concentrations fall into Class V for surface water, indicating inferior quality. The sediments of Hulun Lake and Ulanor Wetland mainly contain calcium-bound P and residual P, which together accounted for 68.7% and 67.0% of total P, respectively. The mean concentrations of bioavailable P (CDGT-P) in the sediments of Hulun Lake and Ulanor Lake were 0.04 and 0.01 mg/L, respectively, lower than those of Taihu Lake and Dianchi Lake, indicating low bioavailability of P in sediments. The concentration of inorganic P in the interstitial water of the surface sediments in Hulun Lake and Ulanor Wetland was higher than that in overlying water, indicating that there was a risk of P release from sediments. However, the recharge capacity of P from sediments was limited.