环保绞吸船清淤作业过程对湖泊水环境的影响

Research on the impact of eco-friendly cutter suction dredger’s sediment removal operation on lake water environment

有效控制和减轻环保清淤施工过程对周边水体的影响,是减少二次污染和加强工程质量控制的关键措施。以长荡湖环保清淤四期工程中实施清淤作业的环保绞吸船为研究对象,通过现场监测和模拟实验,探究了环保绞吸船在水下施工过程中对周边水体水质的时空影响。结果表明,绞吸船作业对周边水体的总悬浮颗粒物(TSS)质量浓度影响最为显著,其影响范围约为50 m。通过模拟绞吸船施工后的底泥沉降过程,发现在停止扰动4 h后,上覆水中总氮(TN)、总磷(TP)和TSS分别下降至初始值的20%、7%和5%。底泥再悬浮扰动停止8 h后,绞吸船施工对周边水体影响基本消除。比较绞吸船作业前后柱状底泥中污染物质量分数的变化,清淤前后0~20 cm表层底泥中TN、TP、有机质(OM)和镉(Cd)等4种污染物的去除率分别为70%、73%、72%和85%。建议根据实际工况条件合理调整绞吸船施工扩散距离限制阈值;对于浅水湖泊应重点关注风浪和绞吸船施工影响叠加对于敏感水体的潜在不利影响。该研究结果可为类似湖泊环保清淤工程设计提供参考。

Effectively controlling and mitigating the impact of environmental dredging construction on surrounding water bodies is a key measure to reduce secondary pollution and enhance quality control of the project.This study focuses on the eco-friendly cutter suction dredger employed in the fourth phase of the environmental dredging project at Changdang Lake.Through on-site monitoring and simulation experiments,we investigated the spatiotemporal impact of the eco-friendly cutter suction dredger on the water quality of the surrounding water bodies during underwater operations.The results showed that the most significant impact of the dredger’s operation on the surrounding water was on the concentration of total suspended solids(TSS),affecting an area of approximately 50 meters.By simulating the sediment settlement process after dredger construction,it was found that 4 hours after the disturbance ceased,the concentrations of total nitrogen(TN),total phosphorus(TP),and TSS in the overlying water decreased to 20%,7%,and 5%of their initial values,respectively.8 hours after the cessation of resuspension disturbance,the impact dredger construction on surrounding water was essentially eliminated.By comparing the pollutant content in columnar sediments before and after dredger operation,the removal rates of TN,TP,organic matter(OM),and cadmium(Cd)in the 0-20 cm surface sediment were 70%,73%,72%,and 85%,respectively.It is recommended that the diffusion distance limit of the dredger’s construction should be adjusted based on actual working conditions.For shallow water lakes,special attention should be paid to the potential adverse effects of wind,waves,and dredger construction on sensitive water.