Recognition of the Sources of Isoprenoid Alkanes in Recent Environments

Abstract

Alkanes are ubiquitous components of contemporary aquatic and terrestrial environments and derive from natural and/or pollutant sources. In many cases, a detailed consideration of the structure and stereochemistry of individual components is necessary to distinguish the sources of these components. High resolution gas chromatography and computerised gas chromatography-mass spectrometry allow determination of the structures, including stereochemistry, of certain widely-distributed alkanes in recent sediments. Three examples of such compounds have been chosen to illustrate the principles by which these structural determinations permit assignment to particular sources: (i) pristane (2,6,10,14-tetramethylpentadecane) from a lacustrine sediment is shown to derive from a mixed source (biological and pollutant); (ii) 17βH-hopane in the same sediment appears to derive from reduction of hop-22 (29)-ene, an abundant alkene of Microcystis aeruginosa, present in the lake; (iii) 17α(H)-homohopane in a sphagnum peat arises mainly as a result of bacterial decay of Sphagnum cuspidatum.