Toxicity of Brass Particulate to Daphnia magna

摘要

The aquatic toxicity of a brass particulate was examined. Acute, 48-hour bioassays were performed using the water flea, Daphnia magna. Tests were conducted with uniform suspensions of uncoated brass particulate, brass particulate coated with a Teflon solution, silica, and titanium dioxide. The Teflon coating solution and the supernatant of the brass suspension (after settling of the brass) also were tested. The effective concentrations that would be lethal to 50% of a population were calculated for uncoated (20.9 micrograms/l) and coated (23.6 micrograms/l) brass particulate. The silica, titanium dioxide, and Teflon each had an EC50 of >1 gm/1. Chemical fate studies demonstrated that the brass dissociated to its ionic components of copper and zinc quickly at pH 2.0. At pH 5.0 and 6.5, the dissociation occurred too slowly to hypothesize that the observed toxicity was due to the presence of copper ions. The data suggested that the toxicity is due to filtration by the daphnids and subsequent ingestion. EC50 determinations for the brass are nearly identical with published EC50 values for copper salts.