title: Response of Ceriodaphnia dubia to ionic silver: discrepancies among model predictions, measured concentrations and mortality.
abstract: Silver thiosulfate, often a waste product of photoprocessing, is less bioavailable or toxic to aquatic organisms than is ionic silver. We conducted duplicate 48-h Ceriodaphnia dubia tests in reconstituted laboratory water using treatments of 92.7 nM Ag+ with various concentrations of thiosulfate. Expected Ag+ concentrations were generated for thiosulfate treatment levels using MINEQL + chemical equilibrium modeling. Ag+ concentrations in treatments were determined using a novel silicon-based sensor. Based on predicted Ag+ and published 48-h LC50 values for C. dubia, we did not expect to observe adverse effects. Yet, 100% mortality was observed at low thiosulfate treatments, whereas > 85% and > 95% survival was observed at higher thiosulfate treatment levels, respectively. Our results indicate that biotic responses match the sensor-based Ag+ concentrations. However, there is a discrepancy between these empirical results and responses expected to occur with Ag+ concentrations as predicted by MINEQL + chemical modeling. By correlating silicon sensor data with toxicity results obtained from our laboratory, our work clearly relates a specific chemical form (Ag+) to toxicity results.
authors: Department of Chemistry, University of North Texas, Denton 76203, USA.
authors: Haiqing
authors: H
authors: Peng
authors: Bryan W
authors: BW
authors: Brooks
authors: Raymond
authors: R
authors: Chan
authors: Oliver
authors: O
authors: Chyan
authors: Thomas W
authors: TW
authors: La Point
mesh_terms: D000818:Animals; D001682:Biological Availability; D003445:Crustacea; D005544:Forecasting; D007477:Ions; D008956:Models, Chemical; D015203:Reproducibility of Results; D012834:Silver / Q000737:chemistry* / Q000493:pharmacokinetics / Q000633:toxicity*; D014873:Water Pollutants / Q000493:pharmacokinetics / Q000633:toxicity*
chemical_list: D007477:Ions; D014873:Water Pollutants; D012834:Silver