Information on Source Organisms and Early Degradation Through Complete Analysis of Acid Moieties in Surficial Marine Sediments in Areas Close to Main River Mouthes (Lena, Changjiang)

Abstract

The soluble fraction of Recent marine sediments has been extensively studied to derive information on the nature of source organisms, the relative contribution of terrestrial and marine inputs and the diagenetic changes underwent by lipids. Among the examined lipids, acids are often used since some of these compounds are specific of a type of microorganism. In sediments, acids can occur as extractible compounds, termed free acids or be covalently linked to the insoluble macromolecular network and are then termed bound acids. The release of such bound acids requires the use of chemical treatments such as hydrolyses. In almost all previous studies, only the acids released by a classical saponification using KOH were examined. More recently, saponification with KOH and a phase transfer catalyst (PTC) was shown to improve the release of OH-labile fatty acids from soils and kerogens (Amblbs et al., t993). The OH--labile acids released by both saponifications corresponds to ester-linked moieties. However, some linkages, including amide and ether functions, are not cleaved upon saponification. In fact, it was observed that acid hydrolysis on previously saponified sediments can afford large amounts of acids, termed H+-labile acids (Goossens et al., 1989). It was also noted that some acids cannot be released by strong acid or base hydrolyses but these tightly bound acids can only be released upon pyrolysis (Kawamura and Ishiwatari, 1984; Largeau et al., 1986).