From ether to acid: A plausible degradation pathway of glycerol dialkyl glycerol tetraethers

TitleFrom ether to acid: A plausible degradation pathway of glycerol dialkyl glycerol tetraethers
Publication TypeJournal Article
Year of Publication2016
AuthorsLiu X.L, Birgel D., Elling F.J, Sutton P.A, Lipp JS, Zhu R., Zhang C., Konneke M., Peckmann J., Rowland SJ, Summons RE, Hinrichs KU
JournalGeochimica Et Cosmochimica Acta
Date PublishedJun
ISBN Number0016-7037
Accession NumberWOS:000376168000010
KeywordsOil and Gas Degradation
AbstractGlycerol dialkyl glycerol tetraethers (GDGTs) are ubiquitous microbial lipids with extensive demonstrated and potential roles as paleoenvironmental proxies. Despite the great attention they receive, comparatively little is known regarding their diagenetic fate. Putative degradation products of GDGTs, identified as hydroxyl and carboxyl derivatives, were detected in lipid extracts of marine sediment, seep carbonate, hot spring sediment and cells of the marine thaumarchaeon Nitrosopumilus maritimus. The distribution of GDGT degradation products in environmental samples suggests that both biotic and abiotic processes act as sinks for GDGTs. More than a hundred newly recognized degradation products afford a view of the stepwise degradation of GDGT via (1) ether bond hydrolysis yielding hydroxyl isoprenoids, namely, GDGTol (glycerol dialkyl glycerol triether alcohol), GMGD (glycerol monobiphytanyl glycerol diether), GDD (glycerol dibiphytanol diether), GMM (glycerol monobiphytanol monoether) and bpdiol (biphytanic diol); (2) oxidation of isoprenoidal alcohols into corresponding carboxyl derivatives and (3) chain shortening to yield C-39 and smaller isoprenoids. This plausible GDGT degradation pathway from glycerol ethers to isoprenoidal fatty acids provides the link to commonly detected head-to-head linked long chain isoprenoidal hydrocarbons in petroleum and sediment samples. The problematic C-80 to C-82 tetraacids that cause naphthenate deposits in some oil production facilities can be generated from H-shaped glycerol monoalkyl glycerol tetraethers (GMGTs) following the same process, as indicated by the distribution of related derivatives in hydrothermally influenced sediments. (C) 2016 Elsevier Ltd. All rights reserved.