WP3 Metals in the Environment: Chemistry and Fate Issues
254 Portland Ballroom
1:20 PM - 4:40 PM, Wednesday
() Silver(I) strong binding ligands in Ceriodaphnia food: a dilemma for acute-chronic Ag(I) toxicity correlation.
Bell, R1, Kramer, J1, Ernste, M1, Collins, P1, Naddy, R2, Gorsuch, J3, 1 McMaster University, Hamilton, Ontario, Canada2 ENSR International, Fort Collins, Colorado, USA3 Eastman Kodak Company, Rochester, New York, USA
ABSTRACT- Many aquatic organisms are acutely sensitive to Ag(I) in clean laboratory waters. In real-world natural waters, strong binding ligands in natural organic and inorganic matter (NOIM) result in amelioration of Ag(I) toxicity. When chronic Ag(I) toxicity experiments are undertaken, the organisms must be fed, and ligands present in the food must be taken into account. Food ligands differ from NOIM ligands in that they have not been so extensively oxidized. We have collected data on the kinetics of Ag(I) adsorption onto food particulates, and show that this is a combination of a fast surface adsorption followed by a slower diffusion of Ag(I) into the interiors of particulates. Chromium(II) reduction of NOIM and suspended food particles is known to release hydrogen sulfide, which can be quantitated by methylene blue formation. These give chromium(II) reducible sulfide (CRS) values, which may be used as a measure of Ag(I) strong binding capacities of food. Chronic (7 d) toxicity data from experiments with Ceriodaphnia, where the organisms are fed, give much greater LC50 values (less toxic) than acute (48 h) LC50 values. Concurrently measured CRS values illustrate the interaction of Ag(I) with food ligands and how these ligand concentrations change with Ag(I) concentrations, and time, during such experiments. Visible light, employed in acute and chronic toxicity tests, is shown to be a significant factor in changing CRS values.
Key words: toxicity, silver, Ceriodaphnia, food