256 



'Entries are for the 1991 sampling year except for sites 1760 and 1777 where 1990 samples were also taken. The totals 

 for the individual years (1990,1991) arc shown within the parentheses. 



Other Sampling. Water, plankton (mesh size > 80^.), and sediment were sampled by 

 personnel from UMD in October of 1991 (JI5 sites for water, 4 sites for plankton, and 10 sites 

 for sediment) and again in June 1992 (11 sites for water, 11 sites for plankton, and 1 site for 

 sediment) using the methods described in Glass et al. (1990) and Sorensen etal. (1990). 



Analytical Methods 



Mercury (total) measurement methods utilized cold vapor atomic absorption spectrometry 

 (CVAA) approved by the USEPA (1983) with modifications for standardizing operating 

 procedures and screening reagents for lowest levels of Hg content to reduce the blank value. 

 General details for analysis and quality assurance are published in Glass et al. (1990) and 

 Sorensen et al. (1990). Specific details regarding fish analysis are given in Olson et al. 

 (1975) Mercury concentrations in fish are expressed in terms of wet tissue weight while 

 those for plankton and sediment are in terms of dry sample weight. 



Fish ages were detennined by personnel from the FDLIR by counting annular growth rings 

 on scales. In some cases ages were reported as greater thans (e.g. 5+ yr), and were treated as 

 the next highest half-year ages for all analyses in this report (e.g. 5+ yr = 5.5 yr). 



