Compound-specific hydrogen isotope ratios of sedimentary n-alkanes [Elektronische Ressource] : a new palaeoclimate proxy / von Dirk Sachse

Informations

• Publié par: friedrich-schiller-universitat_jena
• Publié le: 01 janvier 2005
• Nombre de lectures: 21
• Poids de l'ouvrage: 5 Mo

Extrait

Compound-specific hydrogen isotope ratios of
sedimentary n-alkanes: a new palaeoclimate proxy


Dissertation
Zur Erlangung des akademischen Grades doctor rerum naturalium
(Dr. rer. nat.)













vorgelegt dem Rat der Chemisch-Geowissenschaftlichen Fakultät der Friedrich-Schiller-
Universität Jena
von Diplom-Geologe Dirk Sachse
Geboren am 24.09.1974 in Halle/Saale





















Gutachter:
1. PD Dr. Gerd Gleixner (Max-Planck Institut für Biogeochemie Jena)
2. Prof. Reinhard Gaupp (Friedrich-Schiller Universität Jena)
3. Prof. John M. Hayes (Woods Hole Oceanographic Institution, Massachustetts, U.S.A.)
Datum der öffentlichen Verteidigung: 29. Juni 2005
Index

INDEX.............................................................................................................................................................................3
1. INTRODUCTION.................................................................................................................................................5
1.1. OBJECTIVES......................................................................................................................................................7
1.2. THESIS ORGANISATION ...................................................................................................................................7
2. METHODS/STRATEGIES.................................................................................................................................9
2.1. SAMPLE SITES AND FIELD SAMPLING.............................................................................................................9
182.2. ANALYSIS OF WATER SAMPLES FOR δ O AND δD .......................................................................................12
2.3. SAMPLE PREPARATION, BIOMARKER IDENTIFICATION AND QUANTIFICATION............................................12
2.4. GAS CHROMATOGRAPHY TEMPERATURE CONVERSION ISOTOPE RATIO MONITORING MASS
SPECTROMETRY (GC-TC-IRMS) FOR ANALYSIS OF δD ON THE N-ALKANES .......................................................13
2.5. CALCULATION OF THE ISOTOPIC FRACTIONATION ε.....................................................................................14
3. HYDROGEN ISOTOPE RATIOS OF LACUSTRINE SEDIMENTARY N-ALKANES RECORD
MODERN CLIMATE VARIABILITY...................................................................................................................15
3.1. INTRODUCTION ..............................................................................................................................................15
3.2. RESULTS AND DISCUSSION............................................................................................................................16
3.2.1. n-alkane concentrations ..........................................................................................................................16
183.2.3. δD and δ O values of water....................................................................................................................17
3.2.4. δD values of the n-alkanes .......................................................................................................................19
3.2.4.1. δD values of the even carbon numbered short-chain n-alkanes (n-C , n-C , n-C , n-C , n-C ) and n-C 12 14 16 18 20 13
and n-C ............................................................................................................................................................................ 20 15
3.2.4.2. δD values of the n-C , n-C , n-C , n-C alkanes.............................................................................22 17 19 21 23
3.2.4.3. δD values of the even carbon numbered medium to long-chain n-alkanes (n-C , n-C , n-C , n-22 24 26
C , n-C ) ............................................................................................................................................................24 28 30
3.2.4.4. δD values of the odd carbon numbered long-chain n-alkanes (n-C to n-C ) ................................25 25 31
3.3. CONCLUSIONS................................................................................................................................................26
4. COMPOUND-SPECIFIC δD VALUES OF N-ALKANES FROM TERRESTRIAL PLANTS
ALONG A CLIMATIC GRADIENT – IMPLICATIONS FOR THE SEDIMENTARY BIOMARKER
RECORD ......................................................................................................................................................................30
4.1. INTRODUCTION ..............................................................................................................................................30
4.2. RESULTS AND DISCUSSION............................................................................................................................31
4.2.1. n-alkane concentrations of biomass ....................................................................................................31
4.2.2. δD values of n-alkanes .............................................................................................................................34
4.2.2. Hydrogen isotope fractionation between source water and biomass n-alkanes ..............................37
4.2.3. Comparison with sedimentary n-alkane distributions and δD values...............................................39
4.3. CONCLUSIONS................................................................................................................................................42
135. SEASONAL VARIATIONS IN DECIDUOUS TREE LEAF WAX N-ALKANE δD AND δ C
VALUES: IMPLICATIONS FOR THEIR USE AS A PALAEOCLIMATE PROXY ...................................44
5.1. INTRODUCTION ..............................................................................................................................................44
5.2. MATERIALS AND METHODS ..........................................................................................................................45
5.2.1. Study site and sample collection ..............................................................................................................45
5.2.2. Meteorological measurements at the Hainich site .................................................................................46
5.2.3. Modelling leaf water isotopic enrichment...............................................................................................46
5.3. RESULTS.........................................................................................................................................................48
5.3.1. n-alkane concentrations ...........................................................................................................................48
135.3.2. n-alkane δD and δ C values ...................................................................................................................50
5.4. DISCUSSION....................................................................................................................................................52
5.4.1. Seasonal variations in n-alkane concentration.......................................................................................52
135.4.2. Seasonal variations in n-alkane δD and δ C values for Maple leaves................................................52
135.4.3. Seasonal variations in n-alkane δD and δ C values for Beech leaves - Comparison of modelled leaf
water enrichment with n-alkane δD values .......................................................................................................54
5.4.4. Implications for the use of n-alkane δD values as a palaeoclimate proxy ...........................................60
6. CONCLUDING REMARKS.............................................................................................................................61
7. SUMMARY..........................................................................................................................................................66
8. ZUSAMMENFASSUNG....................................................................................................................................68
ACKNOWLEDGEMENTS .......................................................................................................................................71
9. REFERENCES ....................................................................................................................................................73

Introduction
1. Introduction

The reconstruction of past climate variability can provide valuable information on the causes,
timing and magnitude of climate change. Since direct observational evidence for climatic
changes is available only for the past 100 years, so-called palaeoclimate proxies (e.g. isotope
ratios, pollen data, palaeontology, sedimentological methods etc.) can provide us with a better
understanding of natural climate variability and it’s forcing mechanisms. Analysis of ice-cores
from the polar regions and sediments have provided valuable information on the natural climate
variability throughout the geological time. The obtained da