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TitleStandardisation of Rock-Eval pyrolysis for the analysis of recent sediments and soils
AuthorCarrie, J C; Sanei, H S; Stern, G S
SourceOrganic Geochemistry vol. 46, 2012 p. 38-53,
Alt SeriesEarth Sciences Sector, Contribution Series 20110414
Mediapaper; on-line; digital
File formatpdf
Subjectspetroleum; hydrocarbon geochemistry; bulk samples; trace metals; pyrolysis; Rock-Eval 6 analysis; organic matter
Illustrationsdiagrams; tables; graphs; photomicrographs
ProgramEcosystems Risk Characterization, Environmental Geoscience
AbstractRock-Eval 6 Analysis, a well-established screening tool for petroleum geochemistry, is being increasingly used to characterize the varying species of organic matter (OM) in the bulk samples of recent aquatic sediments. This is particularly important due to recent scientific atten-tion on the role of OM in biogeochemical distribution of environmentally hazardous compounds (e.g., trace metals) in recent sediment archives. Rock-Eval's automated use, low sample volume requirements, and its high analytical accuracy and precision makes it an ideal tool for relatively rapid screening of OM in sediment cores. However, to date, there has been no broad-scale standardisation to determine what may be contributing to each signal (e.g., S1, S2, S3, RC). We have selected a wide variety of representative, pure biochemicals (proteins, lipids, carbohydrates and lignins) and biological standards (phytoplankton, copepods, tree bark and conifer needles) to better understand the Rock-Eval 6's measured organic matter parameters in the unconventional environmental samples. These data have been corroborated with organic petrographical and el-emental (CHNS/O) data. Our results show that small organic molecules (<500 daltons) are largely responsible for the release of S1 hydrocarbon peak while lipids and aquatic biological standards are contributing most in the S2 signal, and in particular the more labile 'S2a' signal. Furthermore, carbohydrates, lignins, and terrestrial plant standards are most responsible for the S3 signal. We also note that the S3 signals (CO/CO2 ratios: OICO, OICO2, and OIRE6) are the best discriminants for source of OM. Finally, step-wise pyrolysis of biological standards cou-pled with elemental analysis (CHNS/O) suggests that S2 and, to a lesser extent, S3 (S3CO and/or S3CO2), would be most responsible for metal-binding elements such as S and N, with implica-tions for element biogeochemical cycles.