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Marine pollution, ecotoxicology and sustainability
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A biotic ligand model for simultaneously modeling the bioaccumulation and toxicity of Cd-Zn mixtures in the clam Potamocorbula laevis
Monday 7th @ 1450-1510, Conference Room 7
Qiao-Guo Tan* , College of the Environment & Ecology, Xiamen University
Shun-Hua Lu, College of the Environment & Ecology, Xiamen University
Presenter Email: tanqg@xmu.edu.cn |
| Metal contaminants usually occur as a mixture in aquatic environments. However, it is still a challenge to assess the ecological risks of metal mixtures. The biotic ligand model (BLM) is a useful tool for predicting the bioavailability of metals. It can be used for simulating the effects of water chemistry on either metal bioaccumulation or metal toxicity, although usually separately in different studies. Therefore, even for the same combination of metal and organism, two different sets of BLM parameters would be generated, sharing the same symbols (e.g., KCuBL, KCaBL) but having different values. It has not been tested whether it is possible to obtain universal parameter values for both scenarios. Moreover, there are ongoing efforts to extend BLM for simulating the bioaccumulation and toxicity of metal mixtures, which raise the same question again. In this study, we tested the feasibility of using a single set of BLM parameters to explain both the bioaccumulation and toxicity of mixtures of cadmium (Cd) and zinc (Zn) in an estuarine clam Potamocorbula laevis. The assumptions of our mixture BLM include: (1) Cd2+ and Zn2+ are internalized through the same biotic ligands (i.e., transport sites); (2) Cd2+ and Zn2+ compete with each other during internalization; (3) Internalized Cd and Zn exert toxicity independently. Metal bioaccumulation were quantified using a stable isotope tracer technique; toxicity tests of the Cd-Zn mixtures were conducted in parallel. We found significant interactions between Cd and Zn in both the bioaccumulation experiments and the toxicity tests, consistent with the prediction of BLM. Analyzing the data under the framework of a toxicokinetic-toxicodynamic model using BLM as the toxicokinetic module, we obtained a set of parameter values that could well explain all of the bioaccumulation and toxicity data. The model can be further used to separately quantify the contribution of Cd and Zn to the overall toxicity of the mixture. Through this work, we demonstrated that a unified BLM could be developed to model the interaction between metals in their mixtures. |
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