33 



Several stations within 100 m of WLIS "E", including the mound apex, had OSI 

 values of > +7. Median OSI values were +9, +7, and +4 for reference areas 2000W, 

 WLIS-REF, and 2000S, respectively. Median OSI values for the pooled reference areas had 

 major modes of +4 and +8 (median of +7) and were not statistically different from disposal 

 site OSI values (Mann-Whimey U-Test, p = 0.884). 



3.3 CTD and Dissolved Oxygen Sampling 



Depth gradients of temperature, salinity, and DO at the three reference areas and the 

 active disposal point are given in the Appendix. Surface salinity at each of the four sampling 

 locations was approximately 26 ppt, increasing slightly (0.5 ppt) with depth. A well-defined 

 thermocline at 5 - 10 meters water depth was present at each site. Surface temperatures of 

 18.5° C decreased to approximately 14° C within one meter of the bottom. 



Dissolved oxygen concentrations near the surface ranged from 9.5 to 11.0 mg-l' 

 (2000S and WLIS "E", respectively) (Table 3-1). DO levels decreased significantly in the 

 upper 5 - 10 m of the water column resulting in near-bottom concentrations which ranged 

 from 5.6 to 5.9 mg-l' (WUS-REF and WUS "E", respectively). Dissolved oxygen 

 concentrations, as determined by Winkler titration, were approximately 1.0 mg-l"' less than 

 DO concentrations measured by the CTD (Table 3-1). Near-surface DO levels (via Winkler 

 titration) ranged from 8.9 mg-l' to 10.4 mg-l' (2000S, WLIS-REF, and WLIS "E", 

 respectively), while near-bottom concentrations ranged from 5.0 to 5.2 mg-1'^ (WLIS-REF 

 and WLIS "E", respectively). 



3.4 Sediment Analysis 



Grain Size. The results of the sediment grain size analysis (Table 3-2) corresponded 

 well with the mapped distribution of sediment grain size as determined from REMOTS® 

 photos (Figure 3-7). The sediments at 2000W and WLIS-REF were dark grey clay/silts (>4 

 phi) with shell fragments present in sediment collected from 2000W. Sediments at 2000S 

 were predominantly dark gray fine and very fine sands (4-2 phi). The average TOC was 

 0.56 at 2000S, 0.96 at WLIS-REF, and 1.4 at 2000W. 



Metals. Cadmium (Cd), lead (Pb), and zinc (Zn) were detected at all three reference 

 areas (Table 3-3). Values for cadmium ranged from 0.18 to 1.20 ppm; lead 31 to 130 ppm; 

 and zinc 83 to 230 ppm. Replicate concentration values were within approximately one 

 standard deviation from the mean; however, the largest standard deviation in the 

 concentration of each of these metals was observed at the 2000S reference area (Table 3-3). 

 The average values for Pb and Zn were slightly higher at reference areas 2000W and 2000S 

 in comparison with WLIS-REF. Concentrations of Cd were fairly similar for the three 

 reference areas with average values ranging from 0.31 ppm to 0.53 ppm. 



Monitoring Cruise at the Western Long Island Sound Disposal Site, June 1991 



