Considerations of particle transformations and their effects on particulate waste transport

Kee Muschenheim (Canada)

ABSTRACT

Techniques recently developed for the study of particulate waste dispersion from offshore oil and gas drilling platforms may have applicability to the study of environmental impacts from aquaculture. The BOSS (Benthic Organic Seston Sampler) device samples water and suspended particulates at several heights between 0.05 and 0.5 m above the seabed, within the Benthic Boundary Layer (BBL). Offshore studies have shown that both natural and man-made particulate matter concentrations within the BBL are extremely variable and may be several orders of magnitude higher than in the water column. Often, discharged fine inorganic material is complexed with naturally occurring seston to produce large aggregates that settle at a much faster rate than the inorganic fines would by themselves. This results in transient accumulations of material that would otherwise have been completely dispersed. The coordinated use of direct sampling in the BBL with high-resolution imaging and image analysis techniques yields information on the in situ flocculated particle size distribution, as well as the composition of the flocs, which is necessary for any attempts at modelling the transport and dispersion of the particulate wastes.