ABSTRACT

Mining technology of manganese nodules has been developed these twenty years bysever.al countries and groups. The impacts due to nodule mining activity on the ocean environment, however, are not clear because of lack of information about the discharged materials from nodule mining system and their impact on the environment Environmental impacts are induced, at the sea floor and the surface. The burial impact on the benthos by resedimentation of deep-sea sediments, which are discharged from nodule collector at the seafloor, is considered as a serious impact on the environment. The amounts of discharged sediments from a commercial stage collector are estimated based on the results of sediment intake tests. Surface impacts are caused by surface plume created by discharged bottom water and solids. The volume of cold and nutrient rich water discharged from a mining vessel into surface environment are calculated based on the results of module lifting tests and the production rate of a commercial module mining system. The amounts and the size distribution of the discharged solids, consisting of lifted sediment sand fine abraded nodule., are also calculated.

INTRODUCTION

Deep-sea manganese modules, which have been Found in large quantities at the Clarion-Clipperton Area, have been focused as potential resources for CU, Ni, Co, and Mn in the 21st century. Since mini.ng technology of manganese nodules has been developed these twenty years by several countries and groups, the profitability of module industrial venture has been expected accurately (Fl ipse, 1983; Johnson and Otto,1986; Herrouinet al., 1989). On the other hand, less information about the impacts to the environment caused by nodule mining has been accumulated until now. The DOMES (Deep Ocean Mining Environmental Study) Project, which was carried out by the U. S., Federal Government from 1975 to 1980, was the on ly one systematic study.

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