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

Abstract

环保疏浚的决策研究主要涉及“是否疏浚”、“疏浚多少”、“如何疏浚”、“能否疏浚”等问题，关系到工程是否立项、资金投入、工艺选择和疏浚效果等.本文首先简要回顾了50年来环保疏浚研究和发展历史，系统总结了国内外在针对湖泊富营养化、潜在生态风险以及湖泛污染控制方面开展环保疏浚的研究进展，分析了疏浚决策理念的差异和需要完善的问题.然后就疏浚工程量设计，分析了湖泊环保疏浚区域的选定和疏浚面积的确定方法和实例，围绕环保疏浚深度的确定，介绍和分析了视觉分层法、拐点法、背景值法、标准偏差倍数法、频度控制法、生态风险指数法、分层释放法和吸附解析法等方法及其优缺点.接着总结了应用不同工艺疏浚过程中产生的底泥扩散、泄漏和残留原因及影响方面的研究成果，提出了疏浚决策对疏浚工艺的选用要求.最后从重视疏浚后环境效果的过程回溯、悬浮态颗粒物影响以及实质性融入生态风险理念等方面，对湖泊环保疏浚决策的研究进行了展望.本文认为，湖泊的疏浚效果未达到预期多与忽视决策研究有关.决策上的主观性和任意性，不仅可能造成资金的浪费，还容易造成生态环境效益的损害.湖泊的环保疏浚不可能一劳永逸，也不是每个污染的湖泊都需要或可以采用疏浚方式来改善水环境，即使达到了环保疏浚的必要性研究和工程量设计水平，仍需要外源的有效控制和高精度、低扩散、低泄漏的疏浚工艺作为保证.;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.