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
Chemical concentrations
Chemical protection
Chemical toxicity
Chronic exposure
Conversion methods
Ecological risk assessment
Environmental conditions
Freshwater ecosystem
Nuclear application
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
Risk management
Toxicity
Transuranium elements
Uranium
Water pollution
Water quality
Ecosystems
radioisotope
uranium
benchmarking
bioavailability
ecotoxicology
environmental risk
freshwater ecosystem
pollution exposure
probability
radiation exposure
radionuclide
risk assessment
toxicity test
water quality
article
concentration (parameters)
ecotoxicity
environmental protection
freshwater environment
long term exposure
radiation dose
species differentiation
Ecosystem
Environmental Exposure
Fresh Water
Models
Theoretical
Probability
Risk Assessment
Time Factors
Water Pollutants
Radioactive