and convenient definition of "high" 

 concentrations as those whose logarith- 

 mic value is more than the mean plus 

 one standard deviation of the logarithms 

 for all concentrations. In practice, be- 

 cause we are dealing with normal distri- 

 butions, about 1 7% of all the concentra- 

 tions for each chemical will fall into the 

 "high" category. ForcadmiumandtPCB, 

 for example, the "high" concentrations 

 correspond to 1 .3 ^ig/g (dry) and 200 

 ng/g, respectively, as shown in Figure 1 . 

 For those and the rest of the chemicals 

 being used in this report, the "high" 

 concentrations are listed in Table 2. 



Table 2. Concentrations in sediment 

 that are defined as "high" for 

 NS& T sites. Concentrations 

 are in units of[ig/g (dry) for 

 trace metals and ng/g (dry) 

 for groups of organic 

 compounds. 



That definition of "high" in a listing of all 

 the NS&T sites can be used to indicate 

 which ones have sediments with "high" 

 concentrations of each chemical. The 

 Appendix lists, in clockwise geographic 

 sequence from Maine to Hawaii, all sites 

 sampled in 1984 through 1989. It also 

 indicates which chemicals, if any, had 

 concentrations in the "high" range. That 

 information is displayed graphically in 

 Figure 2 where NS&T sites are shown 

 on a map of the U.S. 



On a national scale, particularly for sites 

 with three or more high concentrations, 

 it is clear that contamination is associ- 

 ated with urbanized areas of the North- 

 east states; near San Diego, Los Ange- 

 les, and Seattle on the West Coast; and, 

 except at a few sites, relatively rare in 

 the Southeast and along the Gulf of 

 Mexico Coast. The association of higher 

 levels of sediment contamination with 

 highly populated areas is not a surpris- 

 ing result. Nevertheless, it is important 

 to note that these results come from 

 sites that are considered to be "repre- 

 sentative." 



However, some NS&T sites may not be 

 representative. One could doubt that 

 the NS&T site in the Elizabeth River, VA, 

 is typical of the southern end of Chesap- 

 eake Bay, because no chemicals are at 

 high concentrations in sediments at other 

 sites in that area. Sediments from sites 

 near Los Angeles, the one off Palos 

 Verdes and one in Santa Monica Bay, 

 were taken within about a mile of the 

 ends of discharge pipes from major 

 sewage treatment plants. In those cases 

 concentrations are very high, but other 

 sites in the area, away from major dis- 

 charges, also have sediments with high 

 concentrations. The high concentrations 

 in St. Andrews Bay, FL, were unex- 



