Details
| Originalsprache | Englisch |
|---|---|
| Seiten (von - bis) | 4917-4928 |
| Seitenumfang | 12 |
| Fachzeitschrift | Geochimica et cosmochimica acta |
| Jahrgang | 75 |
| Ausgabenummer | 17 |
| Publikationsstatus | Veröffentlicht - 1 Sept. 2011 |
Abstract
During the last decade, compound-specific hydrogen isotope analysis of plant leaf-wax and sedimentary n-alkyl lipids has become a promising tool for paleohydrological reconstructions. However, with the exception of several previous studies, there is a lack of knowledge regarding possible effects of early diagenesis on the δD values of n-alkanes. We therefore investigated the n-alkane patterns and δD values of long-chain n-alkanes from three different C3 higher plant species (Acer pseudoplatanus L., Fagus sylvatica L. and Sorbus aucuparia L.) that have been degraded in a field leaf litterbag experiment for 27. months.We found that after an initial increase of long-chain n-alkane masses (up to ~50%), decomposition took place with mean turnover times of 11.7months. Intermittently, the masses of mid-chain n-alkanes increased significantly during periods of highest total mass losses. Furthermore, initially high odd-over-even predominances (OEP) declined and long-chain n-alkane ratios like n-C31/C27 and n-C31/C29 started to converge to the value of 1. While bulk leaf litter became systematically D-enriched especially during summer seasons (by ~8‰ on average over 27months), the δD values of long-chain n-alkanes reveal no systematic overall shifts, but seasonal variations of up to 25‰ (Fagus, n-C27, average ~13‰).Although a partly contribution by leaf-wax n-alkanes by throughfall cannot be excluded, these findings suggest that a microbial n-alkane pool sensitive to seasonal variations of soil water δD rapidly builds up. We propose a conceptual model based on an isotope mass balance calculation that accounts for the decomposition of plant-derived n-alkanes and the build-up of microbial n-alkanes. Model results are in good agreement with measured n-alkane δD results. Since microbial 'contamination' is not necessarily discernible from n-alkane concentration patterns alone, care may have to be taken not to over-interpret δD values of sedimentary n-alkanes. Furthermore, since leaf-water is generally D-enriched compared to soil and lake waters, soil and water microbial n-alkane pools may help explain why soil and sediment n-alkanes are D-depleted compared to leaves.
ASJC Scopus Sachgebiete
- Erdkunde und Planetologie (insg.)
- Geochemie und Petrologie
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in: Geochimica et cosmochimica acta, Jahrgang 75, Nr. 17, 01.09.2011, S. 4917-4928.
Publikation: Beitrag in Fachzeitschrift › Artikel › Forschung › Peer-Review
}
TY - JOUR
T1 - Effect of leaf litter degradation and seasonality on D/H isotope ratios of n-alkane biomarkers
AU - Zech, Michael
AU - Pedentchouk, Nikolai
AU - Buggle, Björn
AU - Leiber, Katharina
AU - Kalbitz, Karsten
AU - Marković, Slobodan B.
AU - Glaser, Bruno
N1 - Copyright: Copyright 2011 Elsevier B.V., All rights reserved.
PY - 2011/9/1
Y1 - 2011/9/1
N2 - During the last decade, compound-specific hydrogen isotope analysis of plant leaf-wax and sedimentary n-alkyl lipids has become a promising tool for paleohydrological reconstructions. However, with the exception of several previous studies, there is a lack of knowledge regarding possible effects of early diagenesis on the δD values of n-alkanes. We therefore investigated the n-alkane patterns and δD values of long-chain n-alkanes from three different C3 higher plant species (Acer pseudoplatanus L., Fagus sylvatica L. and Sorbus aucuparia L.) that have been degraded in a field leaf litterbag experiment for 27. months.We found that after an initial increase of long-chain n-alkane masses (up to ~50%), decomposition took place with mean turnover times of 11.7months. Intermittently, the masses of mid-chain n-alkanes increased significantly during periods of highest total mass losses. Furthermore, initially high odd-over-even predominances (OEP) declined and long-chain n-alkane ratios like n-C31/C27 and n-C31/C29 started to converge to the value of 1. While bulk leaf litter became systematically D-enriched especially during summer seasons (by ~8‰ on average over 27months), the δD values of long-chain n-alkanes reveal no systematic overall shifts, but seasonal variations of up to 25‰ (Fagus, n-C27, average ~13‰).Although a partly contribution by leaf-wax n-alkanes by throughfall cannot be excluded, these findings suggest that a microbial n-alkane pool sensitive to seasonal variations of soil water δD rapidly builds up. We propose a conceptual model based on an isotope mass balance calculation that accounts for the decomposition of plant-derived n-alkanes and the build-up of microbial n-alkanes. Model results are in good agreement with measured n-alkane δD results. Since microbial 'contamination' is not necessarily discernible from n-alkane concentration patterns alone, care may have to be taken not to over-interpret δD values of sedimentary n-alkanes. Furthermore, since leaf-water is generally D-enriched compared to soil and lake waters, soil and water microbial n-alkane pools may help explain why soil and sediment n-alkanes are D-depleted compared to leaves.
AB - During the last decade, compound-specific hydrogen isotope analysis of plant leaf-wax and sedimentary n-alkyl lipids has become a promising tool for paleohydrological reconstructions. However, with the exception of several previous studies, there is a lack of knowledge regarding possible effects of early diagenesis on the δD values of n-alkanes. We therefore investigated the n-alkane patterns and δD values of long-chain n-alkanes from three different C3 higher plant species (Acer pseudoplatanus L., Fagus sylvatica L. and Sorbus aucuparia L.) that have been degraded in a field leaf litterbag experiment for 27. months.We found that after an initial increase of long-chain n-alkane masses (up to ~50%), decomposition took place with mean turnover times of 11.7months. Intermittently, the masses of mid-chain n-alkanes increased significantly during periods of highest total mass losses. Furthermore, initially high odd-over-even predominances (OEP) declined and long-chain n-alkane ratios like n-C31/C27 and n-C31/C29 started to converge to the value of 1. While bulk leaf litter became systematically D-enriched especially during summer seasons (by ~8‰ on average over 27months), the δD values of long-chain n-alkanes reveal no systematic overall shifts, but seasonal variations of up to 25‰ (Fagus, n-C27, average ~13‰).Although a partly contribution by leaf-wax n-alkanes by throughfall cannot be excluded, these findings suggest that a microbial n-alkane pool sensitive to seasonal variations of soil water δD rapidly builds up. We propose a conceptual model based on an isotope mass balance calculation that accounts for the decomposition of plant-derived n-alkanes and the build-up of microbial n-alkanes. Model results are in good agreement with measured n-alkane δD results. Since microbial 'contamination' is not necessarily discernible from n-alkane concentration patterns alone, care may have to be taken not to over-interpret δD values of sedimentary n-alkanes. Furthermore, since leaf-water is generally D-enriched compared to soil and lake waters, soil and water microbial n-alkane pools may help explain why soil and sediment n-alkanes are D-depleted compared to leaves.
UR - http://www.scopus.com/inward/record.url?scp=79961170323&partnerID=8YFLogxK
U2 - 10.1016/j.gca.2011.06.006
DO - 10.1016/j.gca.2011.06.006
M3 - Article
AN - SCOPUS:79961170323
VL - 75
SP - 4917
EP - 4928
JO - Geochimica et cosmochimica acta
JF - Geochimica et cosmochimica acta
SN - 0016-7037
IS - 17
ER -