As the most persistent aromatic compounds, the P and DBT compounds 

 (mainly C 2 , C 3 , and C 4 ) mark AMOCO CADIZ oil in tissue (oysters) and 

 sediments through mid-1980. The final (June 1981) sediment sampling 

 failed to reveal significant P and DBT levels in any of the stations. 

 The latest (1981) status of the oyster P and DBT levels is unknown. 

 However, through most of the data to be discussed, the P and DBT 

 compounds dominate the f 2 distribution. The ratios of C 2 P/C 2 DBT and 

 C3P/C3DBT, used by Overton et al. (1981) to differentiate oils, in this 

 spill remain in the 0.3-0.6 range. The use of this ratio is discussed 

 in the text. 



3.1.3 Residues in Tissues 



As stated, the P and DBT compounds are most readily associated 

 with oyster tissue samples in the two-year period following the spil- 

 lage. The branched alkanes (isoprenoids) also persist throughout this 

 period. 



3.1.4 Environmental Variability 



A major question in oil spill studies and for that matter environ- 

 mental studies in general is the question of patchiness of pollutant 

 distributions and the variability due to patchiness in chemical meas- 

 urements. To shed some light on this subject two sets of measurements 

 are available. Two principal investigators (Atlas and Ward) obtained 

 samples at the same time and location in several instances, Atlas 

 sampling the top 3-5 cm, Ward sampling an entire sediment core but 

 subdividing the top 0-5 cm section. The total hydrocarbon values 

 (Table 4) reveal wide disparities where contamination is very heavy 

 (pooling of oil in the lie Grande) but reasonable to excellent agree- 

 ment in most cases. (Note also that additional replicate analyses are 

 available for sediment samples in Section 3.2 as well). 



TABLE 4. Analysis of sampling variability. 



TOTAL HYDROCARBONS (f L + f 2 ) (ug/g) 



WARD (0-5 cm) 



1,100 

 700 



770 

 1,100 



290 

 1,100 



a Replicate samples. 



49 



