Extraction and identification of volatile organic substances (VOS) from Scottish peat cores

The degradation of organic matter in peat bogs is complex and not yet well understood. Recent investigations of the trace gases CO2 and CH4 focussed on the impact of these greenhouse gases on global warming. However, there have to be metabolic intermediates between complex organic structures (i.e., humic acids) and gaseous end products (CH4, CO2 N-2, NOx and H2S) other than water-soluble substances (i.e., aromatic acids, amino acids, fatty acids). Deoxygenation during microbial decomposition of plant material also produces anoxic conditions that favor the formation of kinetically stable hydrocarbons. In this study, volatile organic substances (VOS) in peat bogs were investigated using two techniques: purge-and-trap and closed-loop stripping. Coupled gas chromatography-mass spectroscopy analysis revealed mainly branched hydrocarbons (C8H18) in concentrations up to 260 nM in peat pore-water. Additionally, alkylated benzenes were found in concentrations of up to 464 nM, in the peat pore-water, and up to 23 pptv in the headspace of peat cores. However, one-third of all the compounds in the complex VOS-fraction extracted from the peat system remain to be identified, especially those substances containing oxygen. (C) 2000 Elsevier Science Ltd. All rights reserved.