24 



with metal and organic concentrations (e.g., NOAA 1991). Consequently, MBDS organics 

 data were normalized and compared with the same regional Massachusetts sites (CAGH, 

 SAL, QUI, and DBCI; Figure 1-1). Data over several years were averaged from each of 

 these sites and divided by the TOC concentration (Table 4-3). 



After normalizing pesticide concentrations to TOC, the DDE concentration of Station 

 18-17 falls within the ranges of other values measured at MBDS. In general, DDE 

 concentrations are similar to those measured at the NS&T sites. This factor, and the lack of 

 any spatial distribution of DDE concentrations, indicates that the detections of DDE at 

 MBDS are representative of background concentrations in Massachusetts Bay. 



SAL and QUI are reported to have "high" concentrations (greater than one standard 

 deviation from the national mean) of total LMW and HMW PAHs, and total DDT pesticides 

 (NOAA 1991). CAGH also is reported to have "high" concentrations of total HMW PAHs, 

 and actually has higher concentrations in individual HMW PAHs than the other regional 

 Massachusetts sites examined here (Table 4-3). 



About one-third of the MBDS stations were below detection for all PAHs measured, 

 and only two LMW PAH compounds and eight HMW compounds were detected in any 

 sample. Both reference areas were below detection in all PAHs except for an estimated 

 value of pyrene at FG-23. 



Many of the detected and estimated concentrations of individual PAHs in MBDS 

 sediment were in the same range or higher than those measured at all of the NS&T sites used 

 in the comparison (Table 4-3). A degree of uncertainty exists in comparing the MBDS 

 estimated PAH concentrations, which are below the MDL and estimated from the 

 chromatograms. This uncertainty is compounded by the different methods used by NS&T. 



All of the PAHs detected (not estimated) at Station 12-3 were above the MDL and 

 higher than all of the NS&T sites, which indicates clearly that the sediment near this station 

 is anomalously high in HMW PAHs relative to both the NS&T stations and the national 

 average. The distribution of HMW PAHs at MBDS indicates that the highest values are 

 concentrated in the far western edge of MBDS, and are influenced by historical disposal of 

 dredged and perhaps other waste materials (Figure 4-2). HMW PAHs were detected at many 

 MBDS stations, including those near the current disposal buoy, in concentrations similar to 

 coastal measurements made in the NS&T program (Table 4-3). HMW PAHs have long 

 residence times in the aquatic environment, even relative to LMW PAHs, and are generally 

 derived from fossil fuel combustion (Kennish 1992). It is currently thought that pyrogenic 

 PAHs (HMW) are more tightly bound to particles than petroleum source (LMW) PAHs 

 (McGroddy et al. 1992). 



Chemical Analyses of Sediment Sampling at the Massachusetts Bay Disposal Site, June 1989 



