Alkanol and sterol degradation in a sediment core from the continental slope off southwestern Taiwan

Abstract

A sediment core (ca. 36 cm in length and sectioned at 4 cm intervals) collected from the anoxic continental slope off southwestern Taiwan has been analyzed for alkanols and sterols in the extractable and bound forms to understand their degradation in this reducing environment during diagenesis. Generally speaking, the two compound classes (both extractable and bound) degrade faster in the upper core and slower in the lower core; however, extractable phytol degrades sharply from sections 1 to 2 and gradually from section 2 down. The calculated apparent rate constants (y −1) for the extractable phytol, Σn-alkanols, and Σsterols are respectively 0.015, 0.011, and 0.010; and those for the bound phytol, Σn-alkanols, and Σsterols are respectively 0.011, 0.007 and 0.007.The bound form is slightly less reactive than the extractable form.These constants are at least one order of magnitude lower than those reported for two shallow coastal marine sediments--Cape Lookout Bight and Peru, but are similar to or slightly lower than those reported for the anoxic Black Sea deep basin. The interesting result can be attributed to anoxicity which plays the most important role during lipid degradation in the sediment.