Effect of kinetics of complexation by humic acid on toxicity of copper to Ceriodaphnia dubia
Journal Article
·
· Environmental Toxicology and Chemistry
- Univ. of Delaware, Newark, DE (United States). Dept. of Civil and Environmental Engineering
The rate of reaction of trace metal ions is an important consideration when studying the chemistry of trace metals in natural waters. The application of speciation models to natural water systems requires knowledge of kinetics if reactions are slow. Most bioassay and toxicity tests conducted in static and flow-through systems have not taken reaction kinetics into account. Therefore, results from these studies may overestimate the toxicity in the receiving waters. In the present study, the kinetics of the interaction of Cu(II) with humic acid (HA) and its influence on the toxicity of copper to Ceriodaphnia dubia were investigated by both chemical kinetic studies using a copper ion selective electrode and bioassay tests using a continuous flow-through bioassay system. A two-ligand site, with fist-order rate constants, model gave a very good description of experimental kinetic data of the change of free Cu{sup 2+} concentration. Average k{sub 1} was 1.85/h and average k{sub 2} was 0.094/h. Bioassay tests indicated that different reaction times of copper with HA solution produced different toxic effects to organisms. The authors determined the hydrodynamic characteristics of the bioassay chambers to better describe the exposure of the organisms to free Cu{sup 2+}. The bioassays supported the free ion activity model that the bioavailability and therefore toxicity of copper was directly correlated to the free Cu{sup 2+} concentration rather than to the total copper concentration. It was further shown that conventional chemical kinetics can be used to predict the toxicity of copper in these bioassays. This study supports the importance of considering reaction kinetics when studying the chemistry of trace metals in natural waters.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 361934
- Journal Information:
- Environmental Toxicology and Chemistry, Journal Name: Environmental Toxicology and Chemistry Journal Issue: 5 Vol. 18; ISSN 0730-7268; ISSN ETOCDK
- Country of Publication:
- United States
- Language:
- English
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