_l<tiStl!,i;S A M) DISCUSSION 

 ^u•aw.•ltl■r .iiul SuHpt'iuled Matter. 



TrKj metal concentrations found in the dissolved and particulate phases of 

 seav.;ater samples taken durinj'. 1983 are reported in Tables 5a and 5b, and for 

 comparison purposes, the comparable data from 1982 are reproduced in Table 5c. 



A comparison of 1982 and 1983 levels of dissolved metals shows close 

 agreement. As expected from earlier work (Waslenchuk, 1982), quarry and plume 

 waters are usually slightly enriched witli dissolved Cu. Dissolved zinc 

 enrichments are sometimes seen, but as in earlier observations there is less 

 consistency tlian for copper. Cooling water is not evidently an enriched source 

 of the other metals. This would be anticipated since the condenser tubes are 

 essentially Cu-Ni alloys. Zn m,'iy be provided by sacrificial Zn blocks used for 

 corrosion protection, and by Cu-Ni-Zn alloy pipes in auxiliary systems. 



The particulate copper load associated with cooling waters is somewhat 

 elevated above Long Island Sound waters near the discharge plume, as found in 

 earlier studies, but this is not the case for other metals. As before (1982), 

 particulate copper levels are about 1/10 the dissolved load, zinc is more 

 evenly distributed between the two phases, whereas iron, chromium, and lead are 

 everywhere preferentially partitioned to the particulates. 



Mol luscs . 



Metal concentrations found in oysters in 1982 are presented in Table 6, 

 and Lhose found in mussels are presented in Table 7. Tn general, the levels of 

 chromium, copper, and zinc in oysters from Giant's Neck, Fox Island, and White 

 Point were spatially uniform for each sampling date. There is no indication of 

 excess metal burdens in oysters that grew near the cooling water outfall. 



All metal levels in oysters from the quarry exposure cages and the 

 natural population were about 1.5 or more times higher than levels in oysters 

 from other cages outside the quarry, probably reflecting slight long-term 

 enrichment of the dissolved metals in quarry waters. 



A comparison of bivalve metal levels reported for the 1982 program, 

 covering 1980, 1981, and 1982 results, showed that overall levels of Cu and Zn 

 had been constant. The 1983 values are similar again. However, the 1982 

 reported values of iron and chromium were up to 5 times higher than earlier 

 ones; no apparent reason was offered other than the suggestion that the 

 differences might be due to dissimilar instrumentation (an atomic fluorescent 

 spec trophotometric (AFS) technique was first used in the 1982 study). 

 Subsequent to the 1982 report it was determined that previous investigators had 

 depurated the shellfish samples prior to analysis, and that our inclusion of 

 gut contents might explain the higher iron and chromium concentrations. On one 

 occasion (May/83), therefore, we depurated two groups of mussels from Giant's 

 Neck for comparison with the three groups from that location that were handled 

 in the usual manner (ie. not depurated). Although the two depurated groups had 

 quite different metal loads, they were less than those of the non-depurated 

 groups: for iron, non-depurated groups averaged 700 ppm , depurated group #1 had 

 330 ppm, depurated group #2 had 53 ppm; for chromium, non-depurated samples 

 averaged 14.5 ppm, whereas the two depurated samples had 9.3 and 1.5 ppm. 

 Hence at least part of the differences amongst results of the past few years 

 can reasonably be attributed to this differing methodology. 



