52 



Metal ratios were compared by normalizing both Cd and Zn data to Cu, resulting in 

 relatively discrete fields for each of the MQR source areas (Figure 4-7, A). Cd/Cu and 

 Zn/Cu Black Rock Harbor metal ratios were minimized and concentrated in a field due to 

 high Cu concentrations. Quinnipiac and Mill River sediments were separated because of the 

 relatively higher Cd concentration of Quinnipiac sediments. New Haven sediments fell in a 

 field between Mill River and Quinnipiac sediments, as predicted according to the discussion 

 above (Figure 4-7, A). 



All of the MQR core samples fell within a field dominated by New Haven and Mill 

 River sediments (Figure 4-7, B). Considering trace metal concentrations alone, the results 

 indicated that no samples representative of remnant Black Rock Harbor sediments were taken 

 from the MQR cores. If any Black Rock Harbor material was sampled, it was either not 

 representative of average Black Rock Harbor material, or in such a thin layer that it was 

 diluted by sediment originating from somewhere else. These results also suggested that most 

 of the MQR core samples could be remnant New Haven Harbor capping material. These 

 results do not exclude the possibility that unmeasured contaminants (e.g., PAHs) contributed 

 to the biological disturbance. 



4.3 Organic Contamination of MQR Sediments 



Core descriptions and grain size data were available for all six cores recovered. 

 These data indicated that only MQR1 and MQR6 recovered potential ambient material. PAH 

 results from MQR6-E were consistent with this conclusion as the base sample decreases to 

 low PAH levels relative to the sample above (Figures 3-8 and 3-9). Interpreting organic 

 contaminant results from the MQR mound was hampered by the paucity of historical data. 

 Analytical methods have been modified, and detection limits improved, over the past ten 

 years. Due to the lack of historical organic data, MQR core samples were compared with 

 the more recent CLIS coring results. 



Two PAH compounds were plotted against each other from the four CLIS mounds 

 (Figure 4-8). These results indicated that most of the MQR samples have PAH 

 concentrations comparable to sediments classified as remnant Black Rock and Stamford 

 Harbor, except for MQR-3F and MQR-5E. These two samples had exponentially higher 

 PAH concentrations relative to the rest of the samples (Figure 4-8). MQR-5E was also the 

 sample with the excessively high PCB value (31 ppm). 



Most significantly, all of the MQR PAH concentrations were higher than the majority 

 of samples classified as capping material in the other CLIS mounds. Plotting pyrene at the 

 same scale in the three cored capped mounds, concentrations approached zero in the top 50- 

 100 cm of STNH-N and CS-2, while the average of the MQR pyrene concentrations was 

 approximately 2 ppm in the same depth interval of MQR cores (Figure 4-9). The decrease 



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



