Am. Ferreira et al., Formation of mid-chain alkane keto-ols by post-depositional oxidation of mid-chain diols in Mediterranean sapropels, ORG GEOCHEM, 32(2), 2001, pp. 271-276
A high resolution (1-3 cm sediment intervals) organic geochemical study was
carried out on the upper 50-60 cm of three box-cores (including the S1 sap
ropel) from eastern Mediterranean Sea sediments. The C-org, Ba/Al and Mn/Al
depth profiles were used to define the oxidised and unoxidised part of the
S1 sapropel. Post-depositional oxidation affected ca. 50% of the original
sapropel in all three cores, resulting in a significant drop in C-org. C-30
long-chain 1,15-diol and keto-ols in the extracts of these sediments were
quantified by GC:MS. The vertical variation of these biomarkers in the thre
e cores showed a common depth profile. The C-30 long-chain 1,15-diol occurs
almost exclusively in the unoxidised sapropel. The corresponding C-30 long
-chain keto-ol follows this depth profile, although the keto-ol concentrati
ons in the unoxidised sapropel are much lower than the diol concentrations.
However, the [keto-ol]/{[keto-ol] + [diol]} ratio shows a significant incr
ease at the base of the oxidised sapropel. This suggests that the long-chai
n diol was transformed upon post-depositional oxidation into the chemically
related long-chain keto-ol, and that this keto-ol was subsequently further
oxidised. These findings indicate that long-chain keto-ols, which have no
reported biological source but occur ubiquitously in marine sediments, may
be formed by oxidation of long-chain diols, both in the water column and in
the sediment. (C) 2001 Elsevier Science Ltd. All rights reserved.