Particle settling characteristics and environmental impacts of deep-sea mining sediment plumes

Plumes generated during the collection of deep-sea polymetallic nodules have raised significant concerns. The settling characteristics of particles in the plume directly determine the diffusion range of the plume. This study utilized deep-sea sediments to prepare the deep-sea sediment plumes. The study identified three distinct stages of turbidity variation over time: rapid decrease (stage I), slow decrease (stage II), and stable (stage III). Additionally, the researchers proposed a functional model to describe the overall turbidity variation. The study also found significant stratification in the distribution of particles based on size. The settling velocities of various type particles were calculated, and it was found that the particle size distribution was primarily determined by the settling velocity. As a result, the variations of turbidity were caused by the different settling motions. These findings allowed for a description of the settling process of particles in the plume. The impact of the plume generation and particles settling on the water quality was initially explored. The contents of total dissolved solids, chemical oxygen demand, total organic carbon, and ultraviolet absorptive value in the water increased when the plume was generated, and as the particles settled, these contents slowly decreased.