Early diagenetic transformation of terpenoids from conifers in the aromatic hydrocarbon fraction: A long term, low temperature maturation experiment

Abstract An artificial maturation experiment at 80 °C was conducted for >5 years to investigate the early diagenetic transformations of organic matter (OM), mainly terpenoids, in conifers. The diagenetic products of aromatic hydrocarbons were determined in the earlier and later stages of maturation, namely, after >1 year and after ∼5.5 years. The OM in contemporary coniferous plants ( Cedrus deodara and Platycladus orientalis ) was also characterized for comparison. The results reveal that during the early diagenesis of OM from conifers, biological terpenoids were transformed into diagenetic aromatic terpenoids and common polycyclic aromatic hydrocarbons. Some polar terpenoids, such as dehydroabietate aldehydes and abietatetraenoic acid, were detected and identified. Information on these biological and evolutionary terpenoids may improve the understanding of their diagenetic pathways. The experimental data also show that the diagenesis of dehydrogenated and aromatic terpenoids and polycyclic aromatic hydrocarbons is affected by different experimental inorganic conditions. High salinity is favourable to diagenesis in aromatic fractions. Meanwhile, heavy metals such as lead and iron may delay and interrupt the transformation of terpenoids, respectively.