Fate of CuO-derived lignin oxidation products during plant combustion: Application to the evaluation of char input to soil organic matter

Abstract. 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. 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−1 for the stalagmite samples and 230–440 ng L−1 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−1 of the final sample solution. 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.

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Quantification of lignin oxidation products as vegetation biomarkers in speleothems and cave drip water

10.5194/bg-2018-253 ◽

2018 ◽

Author(s):

Inken Heidke ◽

Denis Scholz ◽

Thorsten Hoffmann

Keyword(s):

Organic Matter ◽

Sample Size ◽

Water Samples ◽

Solid Phase ◽

Oxidation Products ◽

Drip Water ◽

Cave Drip Water ◽

Lignin Oxidation ◽

The Individual ◽

Sensitive Method

Abstract. Here we present a sensitive method to analyse 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 to use LOPs as vegetation biomarkers in speleothems. 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 analysed via ultrahigh-performance liquid chromatography (UHPLC) coupled to electrospray ionisation (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 analysed for comparison. The concentration of the sum of eight LOPs (Σ8) was in the range of 20–84 ng g−1 for the stalagmite samples and 230–440 ng L−1 for the cave drip water samples. The limits of quantification for the individual LOPs ranged from 0.3–8.2 ng per sample. 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.

Download Full-text