You are here:
USING SEDIMENT QUALITY GUIDELINES IN DREDGED MATERIAL ASSESSMENTS
Citation:
Berry, W J. USING SEDIMENT QUALITY GUIDELINES IN DREDGED MATERIAL ASSESSMENTS. Presented at ACE/EPA Dredged Material Management Seminar, Baltimore, MD, April 10-11, 2001.
Description:
Sediment quality guidelines (SQGs) are not formally included in the frameworks described in the Inland Testing manual and the Green Book because these frameworks are biologically based. The SQGs are often used informally, however, to help put the results of biological testing in context, e.g. to help establish if the mortality observed in a toxicity test was the result of toxic chemicals or of some other factor. Theoretically they could also be used to help identify the class of compounds responsible for observed mortality, which may influence decisions on disposal alternatives.
Before using any guideline it is important to know how the guideline was derived, and the proper use of the guidelines. Two major approaches exist for deriving sediment quality guidelines in sediments. Empirically-derived approaches evaluate the associations between measures of biological effects and measured dry weight concentrations of chemicals in sediments to derive numerical guidelines associated with certain frequencies of effects, e.g. ERMs, PELs, AETs. The equilibrium partitioning (EqP) approach uses insights into the sediment phases that control the bioavailability of mixtures of some nonionic organic compounds and of metals to assign a causal relationship between the toxicity of the compound in sediments and appropriately normalized concentrations, e.g. SEM-AVS, IWTUs. The empirically-derived approach is useful with typical harbor sediments, which contain mixtures of contaminants. However, in sediments where toxicity is the result of a few specific chemicals, empirically-derived approaches may be overprotective because these approaches do not account for bioavailability. In typical harbor sediments the EqP approach can determine if chemical concentrations in sediments should not be toxic, and can indicate sediments in which some classes of compounds are potentially the cause of observed toxicity, but cannot predict toxicity caused by other substances.
The two approaches answer fundamentally different questions: Is this sediment likely to be toxic? (empirically-derived) and Could these compounds cause toxicity in this sediment, at these concentrations? (EqP). Therefore, both the reasons for using a guideline and the strengths and limitations of the different approaches must be considered before an approach, or better yet a selected combination of approaches, is applied.