Research progress and prospect of environmental dredging decision-making of lake sediment

Abstract

The decision-making strategy on environmental dredging mainly involves "whether to dredge or not", "how much to dredge", "how to dredge" and "can we dredge", which are related to issues such as the project approval, capital investment, process selection and dredging effect. This paper at first briefly reviews the research and development history of environmental dredging in the past 50 years, systematically summarizes the research progress on the necessity of environmental dredging in the aspects of lake eutrophication, potential ecological risk, and black bloom pollution control at home and abroad, and illustrates the differences of decision-making concepts in answering whether to dredge or not and the problems that need to be improved. Then, on the design of dredging volume, the paper analyzes the principles, methods and examples of the selection of environmental dredging zone and the determination of dredging area. Among the determination of dredging depth, eight methods are introduced and evaluated, including visual method, inflection point method, background value method, multiple standard deviation method, frequency control method, ecological risk index method, layered release method, and adsorption/desorption method. Thirdly, the research results on the reasons and influences of sediment diffusion, leakage and residue in the process of dredging with different dredging processes are summarized, and the selection requirements of dredging technology for dredging decision-making are put forward. Finally, the prospect of environmental dredging decision-making for lakes is put forward from the aspects of paying attention to the process backtracking of environmental effects after dredging, the impact of suspended particulate matter and the substantial integration of ecological risk concept. It is considered that the dredging effect of some lakes has not reached the expected level, which is mainly related to the neglect of decision-making research. The subjectivity and arbitrariness of decision-making may not only cause waste of funds, but also damage the ecological and environmental benefits. The authors point out that dredging is not a environmental protection project could be done once and for all, and not every polluted lake needs or can be dredged to improve the water environment. Even if it reaches the level of necessity research and engineering quantity design of environmental dredging, it still needs the effective control of external sources and the proper dredging technology with high precision, low diffusion and less leakage.