31 



Table 3-1 



Dissolved Oxygen Concentrations (mg T 1 ) 

 at NLON and Reference Stations, July 1990 



Station 



Surface 1 



Bottom 2 



NLON-REF 



7.6 



8.3 



NE-REF 



8.6 



8.3 



W-REF 



8.4 



8.3 



NL-85 



8.4 



8.3 



NL-TR (Center) 



7.7 



8.3 



NL-TR (West) 



8.1 



- 



NL-TR (South) 



8.4 



- 



NL-TR (East) 



8.1 



- 



NL-TR (North) 



7.9 



- 



Measured with YSI oxygen meter 

 2 Measured by Winkler titration 



recorded in the same area during the July- August 1988 survey. Surface oxygen 

 measurements made with a YSI dissolved oxygen meter were slightly more variable but 

 nearly identical to bottom oxygen concentrations. Surface values for all profiles ranged from 

 7.6 to 8.4 mgT 1 , with an average concentration of 8.1 mg-1" 1 (s = 0.3 mgT 1 ; Table 3-1). 



Plots of depth gradients in temperature, salinity, and density (sigma-t) are given in the 

 Appendix. CTD profiles at both the disposal site and the reference stations showed only a 

 slightly stratified water column, with a broad pycnocline existing between 4 to 10 m deep. 

 Mean bottom temperature of all profiles was 16.09° C (s = 0.12° C), which was slightly 

 cooler and less variable than the mean surface temperature of 17.32° C (s = 0.40° C; Table 

 3-2). Concomitant with the small thermal gradient, salinity and sigma-t did not change 

 greatly over the depth of the water column. For all parameters, surface waters were slightly 

 more variable than bottom waters, and surface-to-bottom gradients were small (Table 3-2, 

 and see Appendix). 



Monitoring Cruise at the New London Disposal Site, June- July 1990 



