Study on the Release Patterns of Chemical Oxygen Demand from Sediments in Typical Eutrophic Shallow Lakes on Plateaus

Lake eutrophication and water quality deterioration are increasingly jeopardizing both ecological integrity and human health. As a typical eutrophic shallow lake on plateaus, Yilong Lake currently faces the primary issue of excessive CODCr levels. Through systematic sampling and analysis, as well as static release of CODCr from sediment experiments, we have categorized the release process of CODCr and identified factors that are highly correlated with COD by using RDA and random forest analyses. The aim is to investigate the release patterns of CODCr in Yilong Lake, explore the primary factors influencing CODCr, and understand the causes of water quality pollution in the lake. The principal findings of this study are as follows: the static release of CODCr from sediment experiments was conducted to estimate the CODCr release flux from the sediments of Yilong Lake using Fick’s first law, and the release process was divided into three stages: initial release, intermediate adsorption, and late equilibrium. The RDA results indicate that SedpH and SedTP are positively correlated with both CODCr and CODMn; CODMn is statistically most closely related to SedAP; and CODCr exhibits the strongest synergy with SedpH. The random forest model output demonstrates that BOD5 is the factor most highly correlated with CODCr, followed by SedAP. The results of the submerged plant humic degradation experiments show that the organic matter released during the humic degradation process of submerged plants has a significant impact on CODCr in water bodies, and that algal activity also affects CODCr. These findings provide a scientific basis for environmental protection and pollution control in Yilong Lake and similar lakes.