56 



of PAH in the base sample of MQR6 was consistent with the visual interpretation of the 

 recovery of basement material. 



PAH concentrations in MQR core samples were compared with previously measured 

 PAH data. The average value of pyrene of 2 ppm was lower than the recently measured 

 average value in New Bedford Harbor sediments (3.5 ppm; Pruell et al. 1990), and higher 

 than the average measured at the surface of the Mud Dump Site in New York (0.98 ppm; 

 Charles and Muramoto 1991). 



Because of the lack of historical organic contaminant data, a "contaminant stratigraphy" 

 of the MQR cores cannot be assembled. However, the PAH data do indicate that much of the 

 entire dredged material mound at MQR has relatively high PAH concentrations, and discrete 

 intervals of very high PCB concentrations. Because of the estimated thicknesses of New 

 Haven sediment, the cores should consist of at least one meter of New Haven material. 

 Organic data suggest two alternative conclusions: (1) PAH concentrations are indicative of the 

 original concentrations of New Haven Harbor capping material at the time of disposal, or (2) 

 PAHs have remobilized from the capped materials and infiltrated the capping material. 



Two points are important to note in order to draw the most reasonable conclusion. 

 Although PAHs are readily adsorbed onto particulate matter, biodegradation and oxidation 

 may occur in the sediment column (e.g., Kennish 1992). There is no current evidence, 

 however, to support the organic contaminant flux scenario, and in previous CLIS cores, 

 capping material remained relatively low in contaminant constituents (SAIC 1994). Secondly, 

 the samples with high PAH and PCB concentrations lie in the Mill and Quinnipiac River 

 fields, as defined by metals ratios. Considering that both the Mill and the Quinnipiac Rivers 

 eventually flow into New Haven Harbor, it is not inconceivable that the final capping material 

 dredged from New Haven Harbor was obtained from the upper reaches influenced by Mill and 

 Quinnipiac River input. Thus, the first conclusion is also the most plausible. 



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



