Tracking alterations of alkyl side chains of N1 species in heavy crude oil after anaerobic biodegradation with negative-ion electrospray ionization coupled with high-field Fourier transform ion cyclotron resonance mass spectrometry.

Abstract

Heteroatomic compounds are relatively abundant and believed to be bio-resistant in heavy crude oils. However, few studies have focused on the biodegradation of these heteroatomic compounds. Heteroatoms, especially N1 species, in a blank crude oil and in three treated oils co-incubated with anaerobic sulfate-reducing bacteria, nitrate-reducing bacteria and fermentative consortia cultures were detected using negative-ion electrospray ionization coupled with high-field Fourier transform ion cyclotron resonance mass spectrometry. The relative abundance of N1 species in the three treated oils decreased, while the relative abundance of O2 species increased. Remarkably, the relative abundances of N1 species with low carbon number increased and those with higher carbon number decreased. These results revealed that the anaerobic biodegradations of heavy crude oil occurred. With direct evidences, the degradations of alkyl side chains of N1 species by the anaerobic microbes could be deduced.