RELATION TO TOTAL ORGANIC CARBON 



Both the saturates and the PAH compounds are strongly associated with 

 total organic carbon (TOC) in the sediments. While the absolute concentration 

 of total hydrocarbons ranges from 0.2 to 20 ppm and of PAH compounds ranges 

 from about 0.01 to 1.0 ppm, the respective ratios to TOC are relatively 

 constant, suggesting a well -mixed geochemical area. Saturated hydrocarbons of 

 a terrigenous plant wax origin dominate the overall assemblage and covary 

 strongly with TOC and the clay content of the sediment (THC = 0.96 (TOC) + 

 .29; r=.88). PAH also covaries strongly with TOC (PAH = 2.2 (TOC) - 0.027; 

 r=.93). The PAH distributions are similar to those originating in the 

 combustion of fossil fuels, with distributions dominated by the higher 

 molecular weight (i.e., 4- and 5-ring compounds) rather than petroleum-sourced 

 PAH. PAH also covaries strongly with terrigenous plant material (r=.93) and 

 is considered to be either sourced onshore and distributed with the plant wax 

 residues or is introduced via aerial transport and is mixed and distributed 

 with other fine-grained material. The PAH/TOC ratios are very similar to 

 those found in sediments from other geographical areas well removed from the 

 North Atlantic outer continental margin. 



IMPLICATIONS FOR FATE OF POLLUTANTS 



The distributions of hydrocarbons in the shelf and slope areas have 

 important implications for predictions of the fate of pollutants which may 

 originate through outer continental shelf development. Sedimented 

 hydrocarbons associated with fine-grained sediments will be redistributed from 

 their point of origin rapidly (weeks to months) and will be transported to 

 depositional areas which include canyon heads, deeper slope areas, and shelf 

 basins such as the "mud patch." In particular, canyon heads are likely sites 

 for the accumulation of total and PAH hydrocarbons. Although much of the 

 present data suggests that introduced pollutants will be deposited in canyon 

 heads and transported down the canyons, hydrocarbon data from muddy lobes 

 found on the shelf near the heads of Oceanographer and Lydonia Canyons suggest 

 a canyon source for this mud. Present data are thereby also consistent with 



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