산화 퇴적토 내 카드뮴의 독성 평가 기법 개선: 철 산화물 형성에 따른 생물학적 이용성 변화 반영

초록

Accurate evaluation of sediment toxicity remains challenging due to complex interactions among sediment geochemistry,contaminant partitioning, and bioavailability. Conventional sediment quality guidelines classify sediments based on bulkcontaminant concentrations, often overlooking bioavailability and yielding low predictive accuracy near threshold levels. Likewise, equilibrium partitioning models mainly consider organic carbon and acid volatile sulfides, limiting theirapplicability under oxidizing conditions where iron oxides dominate metal binding. This study developed a predictiveframework for cadmium (Cd) toxicity assessment in freshwater sediments by incorporating multiple sorption phases andbioavailability metrics. A mechanistic model for the sediment–water distribution coefficient (Kd) of Cd was establishedusing pH, total organic carbon (TOC), and amorphous/crystalline iron oxides. Windermere Humic Aqueous Model 7simulations and adsorption experiments showed that Kd varied over three orders of magnitude across pH ranges, withamorphous iron oxides exhibiting the strongest affinity at alkaline pH (˃7.5). Application to 21 field sediments yieldedpredictions within one order of magnitude of measured Kd values. Predicted Kd values were further used to estimateporewater Cd concentrations and derive Interstitial Water Toxic Units. Comparison with Hyalella azteca bioassaysincreased classification accuracy from 43 to 76%. This bioavailability-based framework improves sediment toxicityprediction under oxidizing conditions where previous models are inadequate.

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