|Wardlaw, G.D., Nelson, R.K., Reddy, C.M., Valentine, D.L.,, |
Biodegradation preference for isomers of alkylated naphthalenes and benzothiophenes in marine sediment contaminated with crude oil. , Organic Geochemistry 42(6), 630-639. , 2011
Contamination of coastal marine sediments with polycyclic arom. hydrocarbons is pervasive, with major sources including anthropogenic activity and natural seepage. Biodegrdn. serves as a major hydrocarbon sink with evapn. and dissoln. responsible for the removal of low boiling range compds. and photo-oxidn. acting on many multi-substituted arom. compds. In this work, first-order rate consts. for aerobic biodegrdn. were quantified for naphthalene (N), benzothiophene (BT) and their alkylated congeners (1-4 carbon substituents (C1-C4)) in lab. expts. with oil laden marine sediments from a natural seep. Rate consts. were used as proxies for microbial preference, which follows the order: naphthalene > C1N > C2N > C1BT > C2BT > benzothiophene > C3BT > C3N > C4BT > C4N, with some overlap. The application of comprehensive two dimensional gas chromatog. further enabled sepn. and quantification of multiple structural isomers for C2N-C4N and C2BT-C4BT, with 7-12 isomers resolved for each C2N-C4N and 4-7 isomers resolved for each C2BT-C4BT. A strong isomeric biodegrdn. preference was noted within each of these compd. classes, with rate consts. varying as much as a factor of 2 for structural isomers of the same compd. class. Each isomer was consumed to a low, but non-zero concn., suggesting that their residual load in sediment may be proportional to the no. of structural isomers originally present, in addn. to the pattern and the no. of alkyl substitutions. The simultaneous first-order biodegrdn. rates obsd. for 52 arom. hydrocarbons resolved in this study, along with ref. compds. such as n-alkanes, lends support to the concept of broad scale metabolic specificity during aerobic biodegrdn. of petroleum.