hydrocarbons, we obtained sediment cores at several locations in coastal areas 

 of the western North Atlantic (8). At Station P Pb-210, geochronology 

 measurements were obtained (7). These measurements and the measurements 

 of Pu-239/240 and Cs-137 at this same location by others (4) allowed us to 

 estimate sedimentation rates. We then measured hydrocarbon concentrations in 

 several core sections at Station P. We also applied quantitative GC-MF analyses 

 to measure phenanthrene and Cj and C2 phenanthrenes. The results of these 

 measurements, as reported in (8), are given in Table 6-3. It is clear that circa 

 1900 concentrations of hydrocarbons constituting the unresolved complex 

 mixture increased, as did the concentrations of phenanthrenes. The ratios of 

 the Ci and C^ phenanthrenes are not those found in spilled oil. Instead, the 

 ratios indicate that these aromatic hydrocarbons are from pyrolytic sources 

 (13, 20). Our hypothesis is that these hydrocarbons are primarily from direct 

 and remobilized urban air hydrocarbons (8). We have determined that there is a 

 trend of decreasing concentrations of UCM hydrocarbons with increasing depth 

 in a core at another station in Buzzards Bay (8), and a station in the Gulf of 

 Maine (Figure 6-2). 



Furthermore, similar results have been reported for Lake Washington, 

 Seattle, Washington sediments (16). A much more detailed analysis of the 

 aromatic hydrocarbons in three sections of another core from Station P, 



Table 6-3. Hydrocarbons and Chlorinated Hydrocarbons 

 in Station P Core Sections 



Section Average Time UCM^ Phenanthrenes 



of Deposition (mq/q) (ng/g) 



Cq C^ C2 



0-1 cm 74 NA^ 44 38 



1-2 cm 105 34 27 28 



8-1 2 cm 1940 44 NA 31 29 



20-24 cm 1900 12 15 11 10 



54-58 cm 1790 5.2 3.7 2.9 2.8 



58-62 cm 1780 6.2 NA NA NA 



^Mixture of alkanes and cycloalkanes — indicates petroleum hydrocarbons. 

 NA — not analyzed. 



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