2020 Fiscal Year Annual Research Report
Understanding chemical exposure in sediment contact tests for improved effect extrapolation from laboratory to field
| Project/Area Number |
20F20753
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| Research Institution | National Institute for Environmental Studies |
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Principal Investigator |
遠藤 智司 国立研究開発法人国立環境研究所, 環境リスク・健康研究センター, 主任研究員 (30748934)
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| Co-Investigator(Kenkyū-buntansha) |
FISCHER FABIAN 国立研究開発法人国立環境研究所, 環境リスク・健康研究センター, 外国人特別研究員
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| Project Period (FY) |
2020-07-29 – 2022-03-31
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| Keywords | Chemical fate / Bioavailability / Bioaccumulation / Diffusion / Passive dosing / Toxicity |
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| Outline of Annual Research Achievements |
To understand the chemical exposure in the laboratory sediment toxicity tests, a mechanistic model was established that accounts for diffusion, sorption, dilution, and colloid-facilitated transport. The model successfully reproduced experimental concentration data, demonstrated the applicability domain of the standard test setup and enabled to propose possible changes for optimization of test conditions. The model showed that the chemical exposure concentrations in the sediment toxicity tests depend on the space and time, and that the spaciotemporal behavior strongly depends on the chemical’s sorption properties. In addition, the passive dosing method in water tests using polymer meshes was developed and optimized regarding the suitability of different polymers and mesh sizes, loading procedures, and pre-incubation periods. Toxicity tests with a set of chemicals with varying properties proved the robustness, repeatability, and applicability of the method. As a next step, the mesh-based passive dosing method was applied to measure the bioaccumulation of chemicals while varying the chemical uptake by food and dissolved organic carbon from sediment. Internal organism concentrations were measured over time by solvent extraction yielding uptake rates.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
As originally planned, the mathematical model was developed, and a manuscript was written that will be submitted to an international scientific journal in the upcoming weeks. The final experiments of the passive dosing method are currently being carried out and a publication is in preparation. The setup of the bioaccumulation experiments was successfully tested.
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| Strategy for Future Research Activity |
The standard sediment contact test will be further evaluated and optimized based on the previous findings, possibly adjusting the sediment composition and dosing, the water refreshment procedure, and/or the addition of a passive dosing reservoir. Exposure concentrations will be measured for validation, targeting steady-state concentrations that deviate by <20% in space (pore and overlying water) and throughout the test duration. More sophisticated bioaccumulation experiments are under way with different food sources, dissolved organic carbon originating from artificial sediment, and sediment particles. The data will form the basis to develop a kinetic bioaccumulation model to analyze the relevance of different uptake routes for chemicals with varying hydrophobicity in different test systems (water-only and sediment tests). Finally, the bioaccumulation model will be linked to the chemical fate model to comprehensively understand chemical exposure in the test system.
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