Estimates of environmental loading from copper alloy materials

Metal release rates were measured from four different copper alloy-based materials used by the aquaculture industry: copper sheet machined into a diamond mesh, copper alloy mesh (CAM), silicon bronze welded wire mesh, and copper sheeting, and compared with conventional nylon aquaculture net treated with a cuprous oxide antifouling (AF) coating. Release rates were measured in situ in San Diego Bay using a Navy-developed Dome enclosure system at nine different time points over one year. As expected, copper was the predominant metal released, followed by zinc and nickel, which were fractional components of the materials tested. Release rates followed a temporal trend similar to those observed with copper AF coatings applied to vessel hulls: an initial spike in copper release was followed by a decline to an asymptotic low. Leachate toxicity was consistent with prior studies and was directly related to the metal concentrations, indicating the alloys tested had no additional toxicity above pure metals.