A probabilistic assessment of the chemical and radiological risks of chronic exposure to uranium in freshwater ecosystems
Résumé
Uranium (U) presents a unique challenge for ecological risk assessments (ERA) because it induces both chemical and radiological toxicity, and the relative importance of these two toxicities differs among the various U source terms (i.e., natural, enriched, depleted). We present a method for the conversion between chemical concentrations (μg L -1) and radiological dose rates (μGy h -1) for a defined set of reference organisms, and apply this conversion method to previously derived chemical and radiological benchmarks to determine the extent to which these benchmarks ensure radiological and chemical protection, respectively, for U in freshwater ecosystems. Results show that the percentage of species radiologically protected by the chemical benchmark decreases with increasing degrees of U enrichment and with increasing periods of radioactive decay. In contrast, the freshwater ecosystem is almost never chemically protected by the radiological benchmark, regardless of the source term or decay period considered, confirming that the risks to the environment from uranium's chemical toxicity generally outweigh those of its radiological toxicity. These results are relevant to developing water quality criteria that protect freshwater ecosystems from the various risks associated with the nuclear applications of U exploitation, and highlight the need for (1) further research on the speciation, bioavailability, and toxicity of U-series radionuclides under different environmental conditions, and (2) the adoption of both chemical and radiological benchmarks for coherent ERAs to be conducted in U-contaminated freshwater ecosystems. © 2009 American Chemical Society.
Mots clés
- environmental protection
- Models
- Fresh Water
- Environmental Exposure
- Ecosystem
- species differentiation
- radiation dose
- long term exposure
- freshwater environment
- Theoretical
- ecotoxicity
- concentration (parameters)
- article
- water quality
- toxicity test
- risk assessment
- radionuclide
- radiation exposure
- Probability
- Risk Assessment
- Time Factors
- Water Pollutants
- Radioactive
- Freshwater ecosystem
- Environmental conditions
- Ecological risk assessment
- Conversion methods
- Chronic exposure
- Chemical toxicity
- Chemical protection
- Chemical concentrations
- Risk management
- Probabilistic assessments
- Radioactive decay
- Radiological dose
- Radiological risks
- Relative importance
- Source terms
- U-series
- Water quality criteria
- Benchmarking
- Biochemistry
- Chemical speciation
- Radioactivity
- Radioisotopes
- Radiology
- Risk assessment
- Nuclear application
- Toxicity
- Transuranium elements
- Uranium
- Water pollution
- Water quality
- Ecosystems
- radioisotope
- uranium
- benchmarking
- bioavailability
- ecotoxicology
- environmental risk
- freshwater ecosystem
- pollution exposure
- probability