Sediment-Associated Contaminants
Issues Concerning Reliable Assessment & Regulation

Many Sediment Quality Guidelines & Criteria Approaches
Unreliable for Evaluation & Management

Some Key Issues in Evaluating & Regulating
Sediment-Associated Contaminants:
See Our Publications on These Issues:
  • Aquatic sediments tend to accumulate potential pollutants
    - e.g., heavy metals, larger organics, nutrients
  • Sediment-associated potential pollutants exist in a variety of chemical forms
    - only small portion are toxic/available in sediment or when re-suspended in water
    - cannot reliably distinguish availability based on chemical concentration analyses
    - no relationship between total concentration of potential pollutant in sediment and its impact on water quality or sediment organisms
    - “Co-occurrence”-based (e.g., “Long & Morgan”-type) target/trigger concentrations for sediment quality assessment not technically valid and not reliable even for "screening"
    - Inclusion of sediment chemical concentrations in "weight-of-evidence" assessment renders results unreliable
    - Heavy metals & larger organics present in sediment are often not the cause of observed toxicity
    -- Toxicity often caused by ammonia or low-DO associated with algal growth
    -- "Remediating" heavy metals & larger organics in sediment would not remediate the toxicity
  • Important to identify sediments of concern based on impacts (e.g., toxicity, body burden of edible organisms), NOT on concentration of a chemical or group of chemicals in sediment
  • To reliably assess & manage sediments of concern, conduct site-specific evaluations interpreted in non-numeric BPJ weight-of-evidence format
    - TIEs to determine toxicity & sources of toxity
    - Organism-based bioavailability studies focused on edible organisms
    - Not valid or reliable to regulate chemicals in sediments with chemical-concentration-based criteria/standards/guidelines

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