Developing process-based kinetic models, such as the toxicokinetic-toxicodynamic (TKTD) model, is critical yet challenging for accurately predicting the bioaccumulation and toxicity of metals in sediments. The primary obstacle lies in precisely quantifying the rates of metal uptake and elimination in organisms during sediment exposure. Conventional isotope tracing techniques are limited by their inefficacy in sedimentary environments, which hampers their utility for tracing metal fluxes. To address this, we designed a novel stable isotope tracing approach that bypasses these limitations. Rather than labeling sediment particles, we pre-labeled the clams Ruditapes philippinarum with stable isotopes and exposed them to metal-contaminated sediments. This approach allows us to distinguish between the processes governing metal dynamics within the organism. Specifically, the loss of labeled isotopes reflects metal efflux, while the accumulation of unlabeled isotopes indicates both metal uptake and efflux. The mortality of clams was linked to the net internalized metal concentrations relative to their tolerance thresholds. By integrating these observations into a TKTD model, we derived reliable kinetic rate constants that enable accurate prediction of metal bioaccumulation and toxicity in contaminated sediments. This novel technique not only improves the precision of bioaccumulation predictions but also enhances the ecological risk assessment of metal-contaminated sediments, providing a more robust basis for environmental management and decision-making.
 

Sediment contamination,risk assessment,bioaccumulation,process-based model,toxicity