CLARK and FINLEY: UPTAKE AND LOSS OF PETROLEUM HYDROCARBONS 



oil-water mixture, as distinct from our nonagitat- 

 ed surface oil slick under tidal conditions, they also 

 showed rapid uptake. Anderson (1973) found up- 

 take of No. 2 fuel oil to be greatest in the first 24 h 

 with lower uptake at longer periods. By com- 

 parison, he found uptake in clams, Rangia cunea- 

 ta, reached a maximum in 72 h, and greater con- 

 centrations in the clam tissue were reached than 

 for oysters. Aromatic hydrocarbons showed a 

 greater uptake in the moUusk tissue than satu- 

 rated forms. 



Stegeman and Teal (1973), using a flow-through 

 exposure system, showed that oysters initially 

 took up a No. 2 fuel oil-water mixture in direct 

 relation to the hydrocarbon concentration in the 

 water up to at least 450iWg/liter, above which they 

 remained closed. They also found an enrichment in 

 aromatic fractions compared to the saturated 

 fraction, and under long-term exposure (49 days) 

 the latter fraction showed a progressive decrease 

 in amount with increasing length of exposure. 



Under our conditions the No. 5 fuel oil-exposed 

 specimens took up less w-paraffin hydrocarbons 

 than the No. 2 fuel oil-exposed mussels, and the 

 former also lost them faster. Both sets of 

 specimens had depurated their residual hydrocar- 

 bons by 75% within 1 week, but the No. 2 fuel 

 oil-exposed mussels still contained detectable 

 amounts at the end of 35 days. Lee, Sauerheber, 

 and Benson (1972) found that mussels would 

 discharge over 90% of the incorporated mineral oil 

 after several days, a result they confirmed with 

 labelled w-heptadecane. 



Anderson (1973) found that oysters lost 94% of 

 the saturated hydrocarbon uptake but only 82% of 

 their aromatics after 13 days when exposed to a 

 No. 2 fuel oil; after 52 days no residual pollutant 

 hydrocarbons were detected at the 0.5-ppm. level 

 (wet weight). Exposure to South Louisiana crude 

 oil showed detectable but low levels of saturates 

 but no detectable aromatics after 27 days depura- 

 tion. Stegeman and Teal (1973) also found a rapid 

 loss of hydrocarbons from oysters exposed to No. 2 

 fuel oil-water mixture, but a persistent portion (34 

 ppm. wet weight above background) remained. 



These preliminary experiments did not provide 

 results as to the mechanisms or pathways of pe- 

 troleum hydrocarbon uptake by the contaminated 

 mussels. The mechanisms of uptake and transport 

 of pollutant hydrocarbons from the environment 

 into organisms may have a very important effect 

 on the degree to which the subsequent depuration 

 is reversible. For instance, hydrocarbons trans- 



ported across gill membranes in solution or as 

 emulsified droplets enter the bloodstream of fishes 

 very rapidly and can be rapidly depleted on 

 removal of the pollutant (Roubal 1974). On the 

 other hand, hydrocarbons in food sources are 

 resorbed at a different site, which, for the basking 

 shark occurs in the spiral valve where they are 

 transferred to the liver and remain highly persis- 

 tent (Blumer 1967). 



The residual paraffin hydrocarbon patterns 

 showed a strikingly similar pattern to the aged 

 pollutant, yet the organisms appeared healthy and 

 had no visible contamination or oily odor. Lee, 

 Sauerheber, and Benson (1972) indicated that 

 gas-liquid chromatograms of mineral oil in mus- 

 sels were like the original mineral oil except for 

 some loss of the short-chain paraffin hydrocarbons. 

 Blumer et al.(1970) used gas chromatograms of 

 oysters and scallops contaminated by a No. 2 fuel 

 oil to show that the patterns had the same general 

 features as the chromatogram of the fuel oil. 



Anderson (1973) found an %-paraffin hydrocar- 

 bon pattern in clams similar to the high-aromatic 

 No. 2 fuel oil; however, the maximum hydrocarbon 

 in the clam (n-Cn'. approximately 1.6 times more 

 than n-Cie and 1.9 times n-Cig ) was one carbon 

 number higher than the pollutant maximum [n- 

 Ci6 : 1.1-1.2 times the adjacent paraffins). 

 Stegeman and Teal (1973) showed gas chroma- 

 tograms of contaminated oysters having a patter'n 

 similar to the pollutant and a maximum n-paraf- 

 fin concentration of C is or C 



18' 



'19- 



Our presentation of petroleum hydrocarbon up- 

 take as evidenced by w-paraffin analyses is not a 

 complete picture of petroleum contamination 

 since it reflects only a portion of the total 

 hydrocarbons and non-hydrocarbons in the oil. Al- 

 so, the various hydrocarbon components of the pe- 

 troleum are not necessarily available to the or- 

 ganisms in the water in the same proportion as 

 they exist in the original petroleum. Vaughan 

 (1973) reported an enrichment of methyl- 

 naphthalenes compared to w-C 12.20 paraffins of 15:1 

 in oysters exposed to a South Louisiana crude oil 

 (50/ig/ml) in a seven-day bioassay experiment and 

 an enrichment in the water extracts of about 3:1. 

 Further, the w-paraffin content of petroleum 

 pollutants in shellfish is often depleted with time 

 relative to that of the source (Stegeman and Teal 

 1973). Therefore, while our values for pollutant 

 uptake based on w-paraffin hydrocarbon analyses 

 yield conservative estimates, they demonstrate 

 that these experimentally simple methods can be 



513 



