3.0 RESULTS 



3.1. Laboratory Studies 



Laboratory investigations with anthracene in water and sediment were performed to 

 evaluate the spectral sensitivity of the UV-R system to PAH concentration. Typical spectra 

 of clean 'reference' sediment from Central Long Island Sound for four excitation 

 wavelengths show corrected fluorescence intensity ranges from 10-80 units (Figure 2A). 

 Measured anthracene concentration for this sediment was < 1 ppm. In contrast, the spectra 

 obtained when 1000 ppm anthracene is added to seawater (0 to 1200 units; Figure 2B) or 

 sediment (0 to 1100 units; Figure 2C) show a characteristic anthracene signature (note 

 change in intensity scale). The 365 nm excitation band (1100-1150 ADU) exhibits a 

 strong peak at 420 nm, (i.e., dropping sharply for higher and lower excitation 

 wavelengths) and a secondary peak at 450 nm. Little difference in the anthracene spectra 

 is observed whether the carrier matrix is water or sediment. 



The spectral signature of a PAH mixture containing approximately 500 ppm 

 anthracene, benzo(a)pyrene and pyrene in sediment is more complex (Figure 2D). The 

 latter two PAHs are known to have peaks at 420 nm as well as broader peaks in the 450- 

 500 nm range. The peak for anthracene at 420 nm is retained, although apparently 

 augmented by fluorescence at this wavelength from either benzo(a)pyrene and pyrene. 

 These data illustrate the need for a spectral PAH library so as to permit the deconvolution 

 (i.e., spectral unfolding) of the PAH mix spectra into its component parts. 



3.2 Field Data 



Preliminary analysis of the RGB images taken at the locations shown in Figure 1 

 indicated that only three of the locations had sufficient camera penetration to produce data 

 for analysis. These locations included Shooters Dock site 2 (A), State Pier (C), and 

 Sassafras Point (E), (Figure 1). 



Data images from the above locations were inspected to characterize both between 

 and within-station differences in PAH distributions. Between station characterizations were 

 conducted to address horizontal gradients of PAH distribution which might be correlated 

 with known PAH gradients in the Providence River. Within-station analyses focused on 

 investigation of PAH vertical distribution in the sediment column, particularly the existence 

 of potential "hot spot" areas which might be caused by aggregations of PAH particulates 

 (e.g., coal tar) or bioturbation patterns. Horizontal and vertical spatial analyses are 

 presented separately below. 



