24_ 



3.0 RESULTS 



3.1 Sediment Core Descriptions 



Cores were photographed and described in the field notebook. After the cruise, core 

 descriptions were transcribed and redrawn for interpretation (Figures 3-1, 3-2, and 3-3). The 

 most commonly described lithology was "black silty clayey mud" which was present in the 

 top 1-1.5 meters of every core. Discrete sandy intervals, often in thin layers, were present 

 in all of the cores. Organic remnants (plant fragments) and small clasts (shells, pebbles) 

 were also present in discrete intervals in all of the cores. Material which closely resembled 

 ambient Central Long Island Sound sediment (olive grey-green with burrows) was described 

 at the base of MQR1 and MQR6 (Figures 3-1 and 3-3). The implications of the recovery of 

 ambient material is discussed below (Section 4.1). A strong hydrocarbon smell and spots of 

 oil sheen were noted in the descriptions for all of the cores except MQR1 . 



3.2 Grain Size Results 



Samples from all six MQR cores were analyzed for grain size (Table 3-1). 

 Generally, silt was the dominant grain size, followed by clay, and then by sand. Silt content 

 ranged from 21.9 to 87.8%, clay from 9.3 to 44.9%, and sand from 2.5 to 61.9% (Table 3- 

 1). Sand constituted < 10% of more than half of the samples (18 out of 33). However, 

 several samples contained relatively high sand content (>50%), generally deeper in the cores 

 (Figure 3-4). 



3.3 Chemistry Results 



Samples from four of the six MQR cores were analyzed for pesticides/PCBs, metals, 

 and PAHs. All of the surface samples collected in December 1991 were analyzed for 

 volatile organics. 



3.3.1 Pesticide/PCB Results 



Total PCBs were detected in every sample, with concentrations ranging from 0.012 to 

 2.2 ppm, except for one high value (31 ppm) in sample MQR5-E (Table 3-2; Figure 3-5). 

 The very high detection of 31 ppm was confirmed by the laboratory. Samples taken from 

 the upper meter of all of the cores had generally the lowest total PCB concentrations 

 (<0.35 ppm; Figure 3-5). The lowest total PCBs value, however, was measured in the 

 deepest sample of MQR-6 (0.013 ppm). 



The PCB results from MQR were compared with the NERBC sediment classification 

 (Table 1-2), and samples collected previously through the DAMOS Program. All but two 

 sample results were lower than the NERBC highly contaminated category ( > 1 ppm; NERBC 



Sediment Core Chemistry Data Summary from the MQR Mound, August and December 1991 



