Detection and indication of 1,3,4-C27–29 triol in the sediment of northern South China Sea

After the detection of the 1,20,21-C_(29) long-chain triol in some sediments and freshwater pteridophytes, in this study, a new homologous long-chain triol, 1,3,4-C_(27-29), is detected for the first time in the Site4 B core sediment in the northern South China Sea. The hydroxyl location and length of the carbon chain of this newly discovered triol differ from those of 1,20,21-C_(29) triol. The test results of its molecular distribution and individual carbon isotope reveal that 1,3,4-C_(29) triol has a good correlation with n-C_(26-30) even carbon-numbered long-chain fatty alcohols, with R~2(n=68) values of 0.905, 0.929 and 0.903, respectively, and its carbon isotope composition, at –32.3‰±1.9‰, is similar to that of n-C_(26-30), at –29.13‰±0.87‰, –32.98‰±1.28‰, and –32.98‰±1.28‰. 1,3,4-C_(29) triol from the Site4 B core sediment and terrigenous long-chain fatty alcohol(n-C_(26-34)) show highly consistent distribution trends in the entire section; thus, the former could serve as a proxy indicator of the terrigenous input. Considering that the 1,20,21-C_(29) triol in previous research belongs to Azolla, which are fresh water pteridophytes, the 1,3,4-C_(27-29) triol identified in this study might have similar biogenetic derivation. Thus, determination of its biogenic area and growing environment could provide potential organic geochemical evidence supporting the terrigenous input and source in the northern South China Sea.