As can be seen in Tables 11.3 and 11.4, levels of individual hydro- 

 carbon compounds initially as high a UO fJg/g decrease rapidly to the 3 

 |jg/g to 10 pg/g level in December and to the 0.1 (Jg/g level in October 

 of 1978. It is interesting to note that one of the baseline or pre- 

 spill samples (station G) contains significant quantities of substituted 

 phenanthrenes as well as the organo-sulphur compounds, the dibenzothio- 

 phenes. These are probably the residual aromatics from previous pollu- 

 tion events. The other baseline sample from station D also exhibits 

 small quantities of substituted aromatics (see Fig. 11.3a) as well. 

 After one year (October 30, 1978) it is apparent that pre-spill levels 

 are being approached, although the detailed aromatic composition does 

 not mirror the pre-spill composition; i.e., one year after the spill 

 mussels still contain substituted naphthalenes whereas the pre-spill 

 samples contained none. 



As was the case for the aliphatic uptake patterns, the aromatic 

 uptake profiles reveal temporal changes. On an absolute basis all 

 aromatic components appear to have decreased substantially during the 

 first month of post-spill depuration (Tables 11.2 and 11.4). On a 

 comparative basis consider Fig. 11.4. Samples obtained after the first 

 two weeks, post-spill, exhibit a slightly altered aromatic composition 

 vis-a-vis the spilled oil. Soon thereafter the biphenyl and fluorene 

 compounds decrease to non-detectable levels (May 1978) in the tissues 

 and remain so until biphenyl reappears in tissues and, with the naph- 

 thalenes, assumes a prominent comparative importance one year after the 

 spill. It should be noted that Fig. 11.4 presents the data on a com- 

 parative basis with the absolute sum of the total components in Fig. 

 11.4 decreasing throughout the year from 165.4 (Jg/g to 0.7 M8/S- During 

 the year there appears to be a greater comparative loss of the naphtha- 

 lenes, fluorene, and biphenyl, the lower boiling compounds, in addition 

 to the parent organo-sulphur compound dibenzothiophene . The substituted 

 dibenzothiophenes and substituted phenanthrenes are less readily depurated 

 on a comparative basis. 



The aromatic hydrocarbon gas chromatograms also reveal a series of 

 substituted trimethylbenzene (TMB) compounds that are relatively long- 



236 



