51 



England estuaries, but an order of magnitude lower than the Saco and 

 Great Bay estuaries, both of which are highly enriched with chromium due 

 to tannery operations (Armstrong et al. 3 1976; Mayer and Fink, 1980; 

 Lyons et al. s in press). 



Copper levels in Casco Bay are also elevated relative to the 

 non-industrialized estuaries and are comparable to the other impacted 

 sites with the exceptions of the Kennebec River estuary, Maine and 

 Branford Harbor, Connecticut. Long Island Sound is the only other site 

 from which nickel data are available and the mean value is much lower 

 than that of Casco Bay. 



The mean value of lead in Casco Bay sediments is higher than that 

 of the four non-industrialized sites and Long Island Sound, but 

 generally lower than the other industrialized estuaries. Mean zinc 

 concentration, on the other hand, is only exceeded by that reported for 

 Jeffreys Basin. 



These results show that trace metals are not distributed 

 homogenously in the Casco Bay region. Whereas a strong correlation 

 exists between metal concentrations and both mean grain size and organic 

 carbon concentrations, there is also a strong geographic pattern not 

 completely explained by these relationships or the location of 

 freshwater inputs. In general, high trace metal levels are found in the 

 Portland area, which includes the lower Fore River estuary, low levels 

 are found in scour channels, relatively low concentrations are 

 encountered at the offshore sites and moderate levels occur in the very 

 fine sediments of central and upper Casco Bay. In addition, four metals 

 exhibit a gradient down the lower Fore River estuary suggesting an 

 upstream addition. 



