Time-Integrated Bioavailability Proxy for Actinides in a Contaminated Estuary.

Area of Science:

• Environmental chemistry
• Radiological protection
• Marine biology

Background:

• Actinides in aquatic biota pose radiological and biotoxicological risks to humans.
• Current concentration factor (CF) estimations show high variability, limiting accurate radiation dose modeling.
• Existing methods rely on spot samples, which may not reflect long-term bioavailable concentrations.

Purpose of the Study:

• To evaluate diffusive gradients in thin films (DGT) as a predictor for actinide bioaccumulation.
• To compare CFs derived from DGT-labile fractions versus bulk water samples.
• To assess the bioaccumulation of uranium, plutonium, and americium in the Esk Estuary.

Main Methods:

• Deployment of advanced DGT techniques to measure time-integrated labile actinide fractions.
• Cross-flow ultrafiltration of seawater to compare DGT-labile fraction with bulk concentration.
• Sequential elution of *Fucus vesiculosis* to determine radionuclide internalization and binding.

Main Results:

• Significant discrepancies were observed between CF values calculated using spot sampling and DGT measurements.
• DGT-based CFs suggest potential underestimation by traditional spot sampling methods.
• Uranium showed preferential internalization and strong intracellular binding in *Fucus vesiculosis*.

Conclusions:

• Time-integrated bioavailability proxies, such as DGT, provide a more accurate measure of actinide bioaccumulation.
• Revision of current CF values using bioavailability-based methods is recommended for improved risk assessment.
• Enhanced understanding of actinide bioavailability is crucial for public health protection through seafood consumption.