1 1.3.3 Surface Sediments 



Initially 15 sediment samples covering the entire region were 

 analyzed by glass capillary gas chromatography and several subjected to 

 GC/MS analysis for detailed aromatic hydrocarbon determinations. Al- 

 though several different suites of hydrocarbons were observed in the 

 extracts (see Fig. 11.9 and 11.10), no petrogenic inputs were observed 

 that related to the spilled Tsesis oil. The UCM was a prominent feature 

 in most of the chromatogranis . The UCM material is generally ascribed to 

 anthropogenic inputs from several possible sources, including urban 

 particulates (Hauser and Pattison, 1972) and weathered petroleum from 

 storm runoff, municipal sewage, and chronic oil spills (Van Vleet and 

 Quinn, 1978; Boehm and Quinn, 197S; Famngton et al., 1978) and is 

 observed in most silt/clay surface sediment in the region (Rudling, 

 197b) . The dominant feature other than the UCM, in the GC traces, was 

 the terrigenous n-alkanes n-C , n-C , n-C 0Q , n-C,,,, and their dom- 

 inance over their even carbon number neighbors, yielding CPI values from 

 2.5 to 5.4 (Table 11.7). 



The absence of significant quantities of petrogenic hydrocarbons in 

 the surface sediment (0 cm to 2 cm) was puzzling. It was hypothesized 

 that the gravity corer used in the initial sampling might, on impact, 

 blow away the fine floe layer, just on the sediment water interface, 

 where newly deposited material resides. Also the depth of the sediment 

 sampled (2 cm) might cause background levels of hydrocarbons (50 pg/g to 

 1,000 pg/g, Table 11.7) to obscure smaller quantities of petrogenic 

 hydrocarbons (see also section 6.4.1). 



A careful resampling was performed at Station 20 with a wide-bore 

 corer which presumably disturbed the surface layer less. In addition, 

 two sections, the cm to 0.5 cm and 0.5 cm to 1.0 cm layers, were 

 obtained for analysis. Again, the analytical results indicate no petro- 

 leum in the sediment, with the possible exception of one 0.5 to 1.0 cm 

 section, which indicates an input of lower boiling n-alkanes to the 

 terrigenous assemblage (Fig. 11.9a). If this is Tsesis -related hydro- 

 carbon material, then it has been significantly altered. 



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