_^__^ 45 



WUS-REF consisted of 87% and 85% silt/clay, respectively. While the 1990 REMOTS® 

 results did not reveal such disparity among the reference areas (in terms of OSI values, RPD 

 depths, etc.), the 1991 data show that the implications of retaining the 2000S and WLIS-REF 

 reference areas (representing "ambient" sediment conditions) as comparison sites for the 

 WLIS Disposal Site could, in some instances, have a marked affect on the overall evaluation 

 of the disposal site. 



4.3 WLIS Reference Area Chemistry 



PAH concentrations at two of the reference stations, 2000W and WLIS-REF, appear 

 to be within ranges measured in Western Long Island Sound by the NS&T Program. 

 However, the relatively higher concentrations of PAHs at 2(XX)S of both LMW and HMW 

 PAHs make this station less suitable for use as a reference station. 



WLIS reference areas were analyzed for Cd and Zn by the NED laboratory in 1986 

 and 1987 (Table 4-1). The values for Cd in 1986 and 1987 were below the detection limit 

 and/or less than 3 ppm. Average values for 1991 were equal to or below 0.5 ppm (Table 3- 

 3). Average values for Zn were fairly similar for 1986, 1987, and 1991 at WLIS-REF 

 (Tables 3-3 and 4-1). Values of Zn were somewhat higher at 2000S in 1991 (138 ppm 

 versus 99 ppm in 1987) and lower at 2000W in 1991 (150 ppm versus 215 ppm in 1987). 



Sediment grain size and TOC are commonly correlated witb both metallic and organic 

 contaminants in sediments. Studies of both natural and polluted sediments have demonstrated 

 that higher concentrations of contaminants are usually associated with the fme-grained 

 fraction (silt/clay) of sediments (Forstner and Wittman 1983, Kennish 1992, Pequegnat et al. 

 1990). Particulate and colloidal organic matter, because of its fine grain size, surface 

 charges, high surface area to volume ratio, and microbial coatings, serve to adsorb or chelate 

 organic and metallic contaminants. Because of the regional variation of grain size and 

 organic content, all data are normalized (divided by a common constituent like grain size or 

 TOC) when comparing WLIS reference areas to regional Long Island Sound. 



PAH baseline information at the three WLIS reference areas was determined in 

 conjunction with grain size and TOC. The highest concentrations of both LMW and HMW 

 PAHs were found at 2000S; this station also contained the lowest concentration of TOC 

 (0.56%) and the lowest fine-grained fraction (42%). The sum of averaged HMW PAH 

 values at 2000S (3741 ppb) was over twice that at 2000W (1645 ppb), even though 2000W 

 had twice as much TOC (1.4%) and a higher clay and silt content (87%). The measured 

 PAH concentrations at WLIS-REF were intermediate between the other two stations (HMW 

 PAHs: 2835 ppb with a TOC content of 0.96% and 85% fine grains). The variability 

 (measured as one standard deviation; see Table 3-4) in PAH values between sample 

 replicates of the 2000S and WLIS-REF reference areas was greater than at 2000W. Such 

 between-sample variability is expected in dredged materials as they typically represent a 



Monitoring Cruise al the Western Long Island Sound Disposal Site, June 1991 



