14 

 99%) from New England Nuclear; n-[l- C] -hexadecane , 54 mCi/mmole (97- 



99%), [1(4, 5, 8)- C] -naphthalene, 5 mCi/mmole (97-98%), [U- C]-ben- 



zene, 101 mCi/mmole (98-59%), [7, 10- C]-benzo(a]pyrene, 60.7 mCi/m 



mole, (99%), and [methyl- C]-toluene, 30 mCi/mmole (96-99%) from Awer- 



sham Corp.; n-[l- C] -heptadecane , 16 mCi/mmole (>99%), and [1- C]- 



heptadecene, 18.5 mCi/mmole (97%) from ICN. 



AMOCO CADIZ mousse was obtained from the NOAA National Analytical 

 Facility and was collected at Ploumanach on April 30, 1978 (44 days 

 after the spill). Light Arabian crude oil (SX//0308) was obtained from 

 Exxon Corp., Baytown, Texas. The crude oil was weathered by evapora- 

 tion at 25 C for 8 and 48 h. All oil samples were stored at 4 C until 

 used. 



RESULTS 



Physical-Chemical Comparison of Sites 



Beach cores consisted of medium grained sand, while estuary and 

 marsh cores consisted of fine grained silt and clay. It was possible 

 to determine Eh profile for muddy sediments (Fig. 3). In all sediments 



Eh (mv) 

 + IOO + 200 +300 -100 



SALT MARSH MUDFLATS 



+ 100 +200 +300 



- 1 - -£r-' ' 



/ 



\ 



« V AW 



A 



AI 



/ 



/ 



\ 



ABER MUDFLATS 



Figure 3. Eh profiles in muddy sediments. Bars indicate the range of 

 measurements on duplicate cores. pH increased with depth 

 from 7.5 to 8.2 in He Grande, from 6.7 to 7.2 in Aber lldut, 

 from 5.9 to 7.5 in Aber Wrac'h and from 7.0 to 8.1 in the lie 

 Grande oiled site. 



conditions became more reducing with depth. The steepest Eh profile 

 was observed in the He Grande oil site where a brown layer approxi- 

 mately 2 mm thick covered black sediment. Marsh mudflat sediments 



166 



