REMOBILIZATION OF CU FROM MARINE PARTICULATE ORGANIC-MATTER AND FROM SEWAGE

The possible causes of enrichments of dissolved Cu in the bottom waters of Puget Sound were examined in a series of experiments designed to measure the release of Cu from surface marine organic suspended matter and from sewage-derived particles under ambient conditions. Decomposition of organic matter and ion-exchange controlled the release of about one-third of the Cu bound to large particles (> 53-mu-m). In contrast, no Cu was released from smaller particles (< 53-mu-m) suspended in natural seawater and only 5% of the Cu on small particles was released into artificial seawater with a low dissolved Cu concentration. Within 15 min of mixing primary effluent with natural seawater, 40% of the dissolved Cu was lost from solution by flocculation. Between 15 min and 4 days, 25% of the total effluent Cu was released back into solution. This release could have originated either from particulate Cu on the original sewage particles or from the flocculated Cu that was formed from dissolved Cu within the first 15 min. The release of Cu into the bottom waters of Puget Sound from settling marine organic matter was calculated to have been between 1 and 8-mu-g Cu m-2 day-1, which is comparable with the diffusion of Cu from sediments. In contrast, the release of sewage-derived Cu could have been as high as 725-mu-g Cu m-2 day-1 within 10 km of outfall.