concentrations of certain contaminants in surface sediments. These 
biological problems can result from both historical and ongoing sources. 
Study of the geographic extent of biological problems produced by the 
present levels of toxic chemicals is still underway. 
A number of tests have been used to assess adverse biological effects 
associated with sediment contamination in Puget Sound (Figure 3). 
Laboratory tests include acute lethal and sublethal bioassays to measure 
sediment toxicity (e.g., Rhepoxinius abronius amphipod mortality and 
oyster larvae abnormality). Direct field measurements include the numbers 
and kinds of organisms living in the sediments (infauna), levels of 
chemicals in fish and other organisms (bioaccumulation), and the 
prevalence of abnormalities (lesions) in fish livers. 
Definitive cause-effect data relating the individual and collective 
effects of chemicals to a wide range of biological effects are largely 
unavailable. As an interim measure, sediment criteria based on empirical 
associations between sediment chemistry and biological conditions of 
sediments were developed in Puget Sound for PSDDA, the Puget Sound Estuary 
Program (PSEP), and the Commencement Bay Nearshore/Tideflats Superfund 
Investigation (Tetra Tech 1985, 1986b). Matched chemical and biological 
data collected for the same sediment samples (or strictly comparable 
samples) are now available for 200 sampling stations in Puget Sound. 
Although not all biological indicators were measured for every sample, 
this data set covers 11 different urban and nonurban areas of Puget Sound 
(Figure 4). Additional theoretical and empirical studies have been 
conducted for U.S. EPA at the national level (Battelle 1986) and applied 
to Puget Sound (Tetra Tech 1986b). 
In a recent comparison of four independent field and laboratory 
approaches to relating bulk sediment chemistry to biological effects 
(Chapman et al. 1987), sediment criteria for three common contaminants 
yielded comparable values ranging from (dry weight sediment): lead, 
50-300 ppm; PAH, 2-12 ppm; PCB 0.06-0.13 ppm. These values include 
concentrations at or below which biological effects have been shown to be 
minimal and the lowest concentrations at which biological effects have 
been shown to occur. Data used in each approach derived either 
exclusively or in part from Puget Sound. 
Identification of contaminated sediments that produce adverse 
biological effects is only one step in the process of solving 
environmental problems. Recent efforts in Puget Sound have begun to focus 
on eliminating problem sediments through a combination of source control 
and sediment remedial action. A kinetic model is being developed to 
assess the proper mix of source control and oftentimes expensive sediment 
remedial action. This model predicts decreases in surface sediment 
concentrations over time associated with different source control actions. 
The model also considers sediment mixing and the residence time of 
contaminants in the biologically active surface sediments. Hence, the 
model can be used to predict what actions are necessary to obtain 
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