REVIEW ON POTENTIAL ENGINEERING GEOLOGICAL ENVIRONMENT IMPACTS OF DEEP-SEA POLYMETALLIC NODULES MINING

Deep-sea polymetallic nodules are widely distributed on the global seabed,with abundant resources and great potential for exploitation. Since 1960 s,the mining methods of continuous chain-fighting,shuttle-type,pipe lifting and so on have been proposed around deep-sea polymetallic nodule mining. The exploitation of polymetallic nodules on the surface of seabed sediments would inevitably cause the disturbance of surface sediments,which would affect the chemical properties and marine biological activities of seawater. Many scholars have studied the resources and reserves of the nodules,the engineering geological conditions,mining technology and environmental impact of the deep-sea polymetallic nodules. Based on a large number of domestic and foreign literature,the research progress of the CC zone(the seabed area between the Clarion-Crippaton fault zone in the eastern Pacific Ocean) is collated. The following points are recognized for the potential engineering geological environmental impact of deep-sea polymetallic nodules mining by pipeline lifting: (1)During the process of nodule mining,the surface sediments are disturbed and resuspended,and the concentration of resuspended particles is the main reason affecting the chemical properties and biological activities of seawater; (2)The engineering geological properties of surface sediments in mining area are the key control factors of the ecological environment impact degree in the process of deep-sea polymetallic nodule mining,which determines the quality and spatial distribution characteristics of sediment resuspension during nodule mining; (3)At present,the environmental impact assessment of polymetallic nodule mining is mostly based on the qualitative assessment of the degree of impact on the biological community. There is no environmental impact assessment based on the changes of sediment engineering geological properties and the temporal and spatial distribution of resuspended sediment. The quantitative assessment system of environmental engineering geological impact of deep-sea polymetallic nodule mining in the future needs to be established.