Quantification of lignin oxidation products as vegetation biomarkers in speleothems and cave drip water
<p>Here we present a sensitive method to analyze lignin oxidation products (LOPs) in speleothems and cave drip water to provide a new tool for paleo-vegetation reconstruction. Speleothems are valuable climate archives. However, compared to other terrestrial climate archives, such as lake s...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-10-01
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| Series: | Biogeosciences |
| Online Access: | https://www.biogeosciences.net/15/5831/2018/bg-15-5831-2018.pdf |
| Summary: | <p>Here we present a sensitive method to analyze lignin oxidation products
(LOPs) in speleothems and cave drip water to provide a new tool for
paleo-vegetation reconstruction. Speleothems are valuable climate archives.
However, compared to other terrestrial climate archives, such as lake
sediments, speleothems contain very little organic matter. Therefore, very
few studies on organic biomarkers in speleothems are available. Our new
sensitive method allows us to use LOPs as vegetation biomarkers in speleothems.</p><p>Our method consists of acid digestion of the speleothem sample followed by
solid-phase extraction (SPE) of the organic matter. The extracted polymeric
lignin is degraded in a microwave-assisted alkaline CuO oxidation step to
yield monomeric LOPs. The LOPs are extracted via SPE and finally analyzed via
ultrahigh-performance liquid chromatography (UHPLC) coupled to electrospray
ionization (ESI) and high-resolution Orbitrap mass spectrometry (HRMS). The
method was applied to stalagmite samples with a sample size of 3–5 g and
cave drip water samples with a sample size of 100–200 mL from the
Herbstlabyrinth-Advent Cave in Germany. In addition, fresh plant samples,
soil water, and powdered lignin samples were analyzed for comparison. The
concentration of the sum of eight LOPs (Σ8) was in the range of
20–84 ng g<sup>−1</sup> for the stalagmite samples and
230–440 ng L<sup>−1</sup> for the cave drip water samples. The limits of
quantification for the individual LOPs ranged from 0.3–8.2 ng per
sample or 1.5–41.0 ng mL<sup>−1</sup> of the final sample solution.</p><p>Our method represents a new and powerful analytical tool for paleo-vegetation
studies and has great potential to identify the pathways of lignin
incorporation into speleothems.</p> |
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| ISSN: | 1726-4170 1726-4189 |