The effect of biodegradation on crude oil bulk and molecular composition

Abstract

A laboratory simulation of an oil spill was used to monitor the effect of microbial alteration on crude oil molecular, bulk and carbon isotopic compositions. The rate of microbial alteration of alkanes decreased with increasing carbon number. Straight-chain alkanes were more rapidly removed than branched (isoprenoid) hydrocarbons though ultimately even the isoprenoids were degraded. Aromatic compounds were also altered. Isomer specific degradation was observed within a given aromatic alkylation (i.e. methylphenanthrenes). The most stable properties, under the given conditions, were carbon isotopic composition, Ni/V ratios, total scanning fluorescence spectra, and various molecular distributions. Aromatics with two or more rings and more than a two carbon substitution, triterpanes and steranes were relatively stable. Mono- and tri-aromatized steranes were substantially altered. These stable chemical properties or fingerprints are suggested as unique and sensitive indicators that can be used to determine the source of microbially altered hydrocarbons in the environment.