ABSTRACT:

During mining manganese nodules, if the suspended tailings would be discharged into the ocean, the particle fluxes with enrichment in heavy metals (Mn, Co, Ni, Cu) would pollute the" ocean. In this paper, on the bases of analyzing the settling characterization of the tailings and the aggregate characterization of the particle fluxes, a three-dimensional model for the simulation of discharge of the tailings is suggested. At the same time, the simulation results are provided including the concentrations of suspended solids in different periods and in various water depths. With this method, the impacted region and time possibly can be estimated.

INTRODUCTION

Polymetallic nodules on deep ocean floor are a huge wealth for mankind, and its commercial interest is based on the fact that they contain economically attractive quantities of nickel, copper, cobalt, and manganese. Although deep-ocean mining does not seem to be feasible, at present, due to the metal market situation, this resources is considered viable alternative for metals in future. The deep ocean mining will pollute the ocean environment especially surface discharge including suspended tailings during mining of manganese nodules (Steffin et aI., 1979). The suspended tailing plume in the water column may have impacts on the near-surface biota.

THE CHARACTERISTICS· OF THE SUSPENDED TAILING PLUME

Composition of the suspended plume The manganese nodules are lifted into the mining vessel from the ocean floor by a slurry pump, the coarse particles in the water-mineral mixture will deposit in the vessel, and the time particles discharged back into the ocean because they cannot deposit due to their settling time. The fine particles are composed of two parts: the first is the sediments covering the nodules, the other is the powder of nodules because of collision, crushing, and friction (Yamazaki, et aI., 1991).

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