328 



Figure 1. An hypothetical sediment criteria matrix. Lowercase 

 letters represent the sediment criteria for a particular set of 

 sediment and water quality conditions. Arrows indicate increasing 

 trends. 



and for the lack of knowledge regarding the effects of mixtures. 



In summary, the concept of sediment quality criteria is broad enough 

 to encompass a combination of single-chemical criteria (such as those 

 developed by the Equilibrium Partitioning approach or the Apparent 

 Effects Threshold), toxicity bioassays, and in-situ measurements of benthic 

 health. SingJe-chemicaJ numbers by themselves will not meet the "sensitive 

 species" or margin of safety" criteria. Toxicity bioassays should be able to 

 define chrome effects and sublethal endpoints. Due to gaps in the 

 understanding of sediment chemistry and bioavailablity, sediment quality 

 criteria must incorporate this full suite of tests to be accurate and 

 protective. Thus, a site could be declared clean only if it successfully passes 

 all biological and chemical testing. 



