FY 1984

The influence of the pycnocline on the oceanic settling of manganese nodule mining waste

Ozturgut, E., and J.W. Lavelle

Mar. Environ. Res., 12, doi: 10.1016/0141-1136(84)90018-7, 127–142 (1984)

The likelihood that manganese nodule mining discharge (essentially deep-seabed clays and some nodule fragments) would reside on the pycnocline for a long period of time was investigated by introducing mining waste particles into a two-layer laboratory settling column illuminated by laser. The experiments were repeated with polystyrene particles of uniform shape and size to further study the effect of a density interface on settling. The results indicate that mining particulates do not have sufficiently low density to accumulate on the pycnocline although a density interface can temporarily concentrate settling particles. A review of related studies of accumulation of inorganic particles on density interfaces suggests that the available evidence for pycnocline accumulation of inorganic particles is slight. A measurement of the wet density spectra of any oceanic discharge is necessary to accurately assess the possibility of particles rafting on a density surface.