3.2.1 Horizontal Characterization 



To test for between station differences in PAH concentration and composition, 

 images collected at three stations (Shooters Dock, Site 2 [A], State Pier [B], and Sassafras 

 Point [D]) were spectrally analyzed. Results are presented by station and excitation band 

 in Figures 3 and 4, respectively. In Figure 3, the three stations show that the 365 nm 

 excitation wavelength generated the largest fluorescence intensities, exceeding by a factor 

 of 3 to 4 those contributed by other wavelengths. 



A comparison across stations at the same excitation wavelength is shown in Figure 4. 

 Two notable features in the data are the peak at 314 nm excitation/400 emission band (B) at 

 Shooters, and the higher emission for the Shooters or Sassafras Point samples relative to the 

 State Pier sample at 299, 314, and 365 nm (A,B,D). Higher fluorescence returns for 

 Shooters/Sassafras vs. State Pier is probably related to total PAH concentration in the 

 sediment; the State Pier station is generally lower in Total PAH and constituent analytes 

 than the other two locations based on 1992 analyses of PAH concentrations (Table 1). An 

 alternative explanation is the presence of dissolved humic or chlorophyll/phaeophytin 

 substances which exhibit a broad fluorescence emission peak centered between 420 and 

 460 nm. The discrimination between the two potential fluorescing agents will require 

 further characterization. The 314 excitation/400 emission peak (B) may be explained by 

 high pyrene in the sediment (13 ppm) (Table 1), as this compound has peak emission at 398 

 nm (Rudnick and Chen 1998), although a similar pyrene peak was not observed for the 

 laboratory PAH mix discussed in Section 3.1. 



3.2.2 Vertical Characterization 



To test for within-station difference in PAH concentration and composition, four 

 Regions of Interest (ROI) were selected for each of the three stations (Shooters Dock 2, 

 State Pier, and Sassafras Point) as indicated by open circles in the RGB images of 

 Figure 5. Possible variation may be due to the history of sediment deposition and/or 

 localized biomrbation. The ROI locations were selected to maximize area while avoiding 

 image edges. These ROIs have the same size (pixel population) and spatial orientation. 

 The ROIs are designated in the results below as Middle Left (ML), Middle Right (MR), 

 Bottom Left (BL), and Bottom Right (BR). An additional two ROIs were selected for 

 Shooters Dock, Site 2 to characterize the water column immediately above the sediment. 

 These ROIs were designated as Top Left (TL) and Top Right (TR). 



Spectral analysis of each ROI allowed for an inter-comparison of each site and also 

 allowed for spectral comparison of ROIs containing just water and/or just sediment. An 

 analysis was performed on the six ROIs at Shooters Dock, Site 2, to compare the two ROIs 

 located entirely in the water column with the sediment signals (Figure 5A). Results are 

 shown in Figure 6. The purpose of this analysis was to determine how fluorescence 

 returns in the water column (a shade was used to cover the camera prism's optical window 



