14 



acceptance range is 56-121%). Since four out of five pesticide recoveries were within 

 control limits, the endrin results indicate no laboratory extraction problem. 



Precision was measured as a relative percent difference between the spike and spike 

 duplicate results. The relative percent difference for all QC samples was within laboratory 

 control limits, indicating acceptable sample precision. 



2.4 CTD and Dissolved Oxygen Sampling 



A Seacat Model SBE 19-01 CTD was used to obtain vertical profiles of temperature, 

 salinity, and dissolved oxygen at the center of each reference area and the WLIS "F" 

 REMOTS® sampling grid. Prior to the survey the oxygen probe on the CTD was calibrated 

 using a 2-point procedure with saturated water and a zero oxygen solution. The conductivity 

 and temperature sensors were factory calibrated and checked with standard seawater and a 

 mercury thermometer. A laptop computer with Seabird instrumentation software was used to 

 communicate with the CTD via an RS-232 serial interface. During deployment, the SBE 19- 

 01 was set to record data at 2-second intervals. All profile data were archived on diskettes. 



To verify the CTD dissolved oxygen measurements, near-surface and near-bottom 

 (within 1 m) water samples were analyzed for DO using a modification of the standard 

 Winkler titration method (Strickland and Parsons 1972; Parsons et al. 1984). Water samples 

 were collected by Niskin bottle. Immediately following collection, a 300 ml aliquot was 

 drawn from the bottle and preserved. All preserved water samples were titrated within eight 

 hours of the time of collection. 



2.5 Benthic Habitat and Sediment Toxicity Assessment at Selected Stations 



The 1991 WLIS "A" and "D" stations (WLIS "A," Station E400W; WLIS "D," 

 stations D200N, D300S, D100S, and D100W) that had exhibited unusually dark (highly 

 reduced) subsurface sediments were reoccupied during the 1992 survey. REMOTS® 

 sediment-profile photography and sediment toxicity were used to provide data for the 

 assessment of current habitat conditions. Triplicate REMOTS® photographs were taken at 

 each station for comparison with the photographs from the 1991 REMOTS® survey. 



Sediment toxicity samples were collected with a Van Veen grab on July 30, 1992. 

 One 4-liter sediment sample was composited from several sediment grab samples taken at 

 Station E400W. A second 4-liter sediment sample was collected by compositing samples 

 taken from each of the WLIS "D" stations. A third 4-liter sample was collected from the 

 2000W reference area. Samples were placed in iced coolers for delivery to the SAIC 

 Environmental Testing Center (ETC), Narragansett, Rhode Island. Samples were 

 refrigerated at the ETC until initiation of the testing procedures. A 10-day bioassay using 

 the amphipod Ampelisca abdita determined toxicity of the sediment samples. Toxicity of the 



Monitoring Cruise at the Western Long Island Sound Disposal Site, July 1992 



