concentrated to less than 1 ml under a stream of nitrogen. The volume 

 of each fraction was adjusted to one ml with the appropriate solvent. 

 A 0.2 (Jl subsample was injected into a Varian 3700 flame ionization gas 

 chromatograph equipped with a 30 m glass WCOT column packed with SE-54 

 (Supelco) . Operating conditions were as follows: column temperature 

 programmed from 60 C to 260 C at 3 C/min with a 30 min hold at 260 C; 

 injection temperature: 250 C; detector temperature 250 C; carrier gas: 

 1 ml helium/min with a helium make-up gas of 29 ml/min. Results were 

 recorded on a Spectra-Physics model 4100 recording integrator. Hydro- 

 carbons labelled in Figure 9 were identified by comparison of retention 

 times to those of pure hydrocarbon standards. 



Sediment Chemistry 



Eh 



Duplicate sediment cores for Eh measurements were collected using 

 a plexiglass tube (30 cm x 25 mm ID) which had been split lengthwise 

 and taped together. Upon returning to the laboratory, one half of the 

 core liner was removed, and fresh sediment exposed 1 cm at a time by 

 slicing the core lengthwise with a spatula. Eh measurements were taken 

 by pressing a combination platinum electrode (Orion) into the freshly 

 exposed sediment surface. All Eh values are reported relative to the 

 normal H„ electrode. 



pH 



pH was determined using a VWR pH Master pH meter and glass com- 

 bination electrode. 



Interstitial Water 



Sediment porewater was obtained using the porewater squeezer of 

 Kalil (1974). After appropriate dilutions were made, sulfate was meas- 

 ured by the turbidometric method of Tabatabai (1974) and chloride was 

 measured by silver nitrate titration (Am. Pub. Health Assoc, 1976). 



Methane 



Dissolved methane was quantified by killing a 2 ml subcore in a 

 sealed vial by the addition of 0.5 ml of formalin and mixing on a vor- 

 tex mixer to strip the dissolved methane into the headspace. A gas 

 subsample was then analyzed by flame ionization gas chromatography as 

 described above. 



Radioisotopes, Chemicals, and Oils 



The following radioactive chemicals were used (radiochemical pur- 

 ity in parentheses): Na 2 S0 4 , 738^01/1^11016 (on 3/5/79), Na-[2- C]- 

 acetate, 44 mCi/mmole, and [ring-1- C]-toluene, 3.4-5.2 mCi/mmole (97- 



165 



