The application of sterol biomarkers to the study of the sources of particulate organic matter in the Solo River system and and Serayu River,Java, Indonesia |
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Authors: | W Li J Dagaut A Saliot |
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Institution: | (1) Department of Oceanography, Xiamen University, Xiamen, 361005, People's Republic of China;(2) Laboratoire de Physique et Chimie Marines, Université Pierre et Marie Curie, UA CNRS 353,4 Place Jussieu, 75252 Paris Cedex 05, France |
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Abstract: | Sterols were analyzed in suspended particles collected in January 1991 in the Solo River system and in the Serayu River, Java,
Indonesia. Free sterols were extracted from particles larger than 0.7 μm and analyzed, after derivatization into their trimethylsilyl
esters, by GC and GC/MS. Concentrations of total sterols ranged from 438 to 7922 ng/1, or from 2.4 to 183.8 ng/mg of total
suspended matter, which varied from 3.3 to 400 and 471 mg/l, respectively in the Serayu River and at the downstream station
in the Solo River. POC concentrations also varied in a wide range, from 0.91 to 4.72 and 6.13% of TSM, respectively at the
above stations, and were associated with sterol/POC values ranging from 0.15 to 1.75 μg/mg. Eleven structures of C27, C28 and C29 sterols and associated stanols were identified. 28Δ3,22 was only found at downstream stations in the Solo River and in the Serayu River. This unique distribution, different from
that of other C27, C28 and C29 sterols, suggests a predominantly autochthonous origin for these compounds associated with an increased planktonic biosynthesis
near the estuary. Concentrations of 28Δ5, 29Δ5,22 and 29Δ5 showed similar spatial distributions and increased downstream, reflecting the significant accumulation of organic matter
originating from the vegetation of the various drainage basins.
Values of the autochthonous versus terrigenous sterol index, defined as 27Δ5/29Δ5,22 + 29Δ5 were in the 1.4–1.9 range at upstream stations, whereas at downstream stations lower values were found, 0.4–0.6, which also
corresponded to higher concentrations of TSM and lower POC values.
Insofar as the stanol/stenol values can be used to estimate the bacterial activity of oxic waters, simultaneous variations
of C27, and C29 stenol/stanol pairs suggest rather different bacterial degradation capacities of autochthonous versus allochthonous organic
matter. The wide differencies between the values of the stenol/stanol pairs observed in one of the main tributaries and in
downstream stations of the Solo River is evidence that allochthonous organic matter is much more resistant than autochthonous
matter. The low index value observed in the Serayu River indicates the highly refractory nature of both autochthonous and
allochthonous organic material. |
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Keywords: | sterol biomarkers particulate organic matter Indonesia |
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