There is increasing support for the use of a best professional judgment, non-numeric, triad weight of evidence approach for evaluating aquatic sediment quality. This approach is based on an integrated use of sediment toxicity/source of bioaccumulatable chemicals, organism assemblages and chemical information to determine the potential for constituents in sediments to be adverse to the beneficial uses of the waterbody in which the sediments are located. This triad approach is a far more reliable approach for evaluating whether a chemical constituent(s) associated with a sediment is adverse to sediment/water quality than a chemical-specific numeric sediment quality guideline. Significant problems occur, however, with the use of this approach by some in incorporating chemical information into the triad. The use of total concentrations of constituents and/or the exceedance of a co-occurrence-based so-called ‘sediment quality guideline’ is technically invalid. Such an approach can distort the triad sediment quality evaluation because it incorporates information into the triad that is not related to the impact of the chemicals on aquatic-life-related beneficial uses. The chemical information that should be used in a triad evaluation includes the chemical forms and concentrations of the constituents of concern in the sediments that can be toxic to aquatic life or that can lead to bioaccumulation in higher-trophic-level organisms that are a threat to these organisms or those who use aquatic life as food. Sediment TIE information and information about the cause of toxicity or the amount of a bioaccumulatable chemical in a bioavailable form in the sediments should be used as a chemical component of a triad.
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