Biogeochemistry

Publications (full list below)

Featured publication

Methane formation driven by light and heat prior to the origin of life and beyond

L. Ernst, U. Barayeu, J. Hädeler, T.P. Dick, J. Klatt, F. Keppler, J.G. Rebelein (2023). Methane formation driven by light and heat prior to the origin of life. Nature Communications, 14, 4364, doi:10.1038/s41467-023-39917-0.

Methane is a potent greenhouse gas, which likely enabled the evolution of life by keeping the early Earth warm. Here, we demonstrate routes towards abiotic methane and ethane formation under early-earth conditions from methylated sulfur and nitrogen compounds with prebiotic origin. These compounds are demethylated in Fenton reactions governed by ferrous iron and reactive oxygen species (ROS) produced by light and heat in aqueous environments. After the emergence of life, this phenomenon would have greatly intensified in the anoxic Archean by providing methylated sulfur and nitrogen substrates. This ROS-driven Fenton chemistry can occur delocalized from serpentinization across Earth’s humid realm and thereby substantially differs from previously suggested methane formation routes that are spatially restricted. Here, we report that Fenton reactions driven by light and heat release methane and ethane and might have shaped the chemical evolution of the atmosphere prior to the origin of life and beyond.

Abiotic Methane Formation 2 2023

Reduced, methylated S-/N-compounds are formed abiotically in hydrothermal vents or transported to Earth by carbonaceous meteorites. Under anoxic conditions, H₂O₂ is formed by thermolysis and photolysis of water and [Fe(H₂O)₆]³⁺ complexes, reacting with dissolved ferrous iron (Fe²⁺) to hydroxyl radicals (∙OH) and [Fe^IV= O]²⁺ compounds that drive the oxidative demethylation of methylated S-/N-compounds, thereby facilitating CH₄ and C₂H₆ formation.

Full list

Peer reviewed papers - group members including former members are shown in bold

For book chapters and other manuscripts, please see bottom of page

2024

A. Wieland, P. Römer, F. Reinig, M. Torbenson, O. Urban, M. Greule, J. Čáslavský, N. Pernicová, M. Trnka, U. Büntgen, J. Esper, F. Keppler (2024). Multi-isotope study of tree ring cellulose and lignin methoxy groups identifying differences and age-related trends. Quaternary International. https://doi.org/10.1016/j.quaint.2024.02.004
F. Schmitt, A.K. Schmitt, C. Scholz, F. Keppler (2024). High index reflective glass beads in modern river sediments as a potential marker for the Anthropocene. Newsletters on Stratigraphy. DOI: 10.1127/nos/2024/0816
T. Cox, P. Laceby, M. Greule, F. Keppler, C. Alewell (2024). Using stable carbon isotopes of lignin derived methoxy groups to investigate the impact of historical land use change on sediment/particulate matter dynamics. Journal of Soils and Sediments. 1-24. https://doi.org/10.1007/s11368-024-03765-2

2023

M. Greule, P.M. Le, J. Meija, Z. Mester, F. Keppler (2023). Comparison of carbon isotope ratio measurements of the vanillin methoxy group by IRMS and ¹³C-qNMR. Journal of the American Society for Mass Spectrometry. doi:10.1021/jasms.3c00327.
S.E. Sapper, C.J. Jørgensen, M. Schroll, F. Keppler, J.R. Christiansen (2023). Methane emissions from subglacial meltwater of three alpine glaciers in Yukon, Canada. Arctic, Antarctic, and Alpine Research. 55, 2284456, doi:10.1080/15230430.2023.2284456.
J. Hädeler, G. Velmurugan, R. Lauer, R. Radhaman, F. Keppler, P. Comba (2023). Natural abiotic iron-oxido-mediated formation of C1 and C2 compounds from environmentally important natural methyl-substituted substrates. Journal of the American Chemical Society, 145, 24590-24602, doi:10.1021/jacs.3c06709.
M. Kanwischer, T. Klintzsch, O. Schmale (2023). Stable isotope approach to assess the production and consumption of methylphosphonate and its contribution to oxic methane formation in surface waters. Environmental Science & Technology, doi:10.1021/acs.est.3c04098.
D. Polag, F. Keppler (2023). Effect of immune responses on breath methane dynamics. Journal of Breath Research, 17, doi:10.1088/1752-7163/ace9f2.
M. Schroll, L. Liu, T. Einzmann, F. Keppler & H. P. Grossart (2023). Methane accumulation and its potential precursor compounds in the oxic surface water layer of two contrasting stratified lakes. Science of The Total Environment, 903, 166205, doi: 10.1016/j.scitotenv.2023.166205.
L. Ernst, U. Barayeu, J. Hädeler, T.P. Dick, J. Klatt, F. Keppler, J.G. Rebelein (2023). Methane formation driven by light and heat prior to the origin of life. Nature Communications, 14, 4364, doi:10.1038/s41467-023-39917-0.
F. Keppler, M. Boros, D. Polag (2023). Radical-driven methane formation in humans evidenced by exogenous isotope-labeled DMSO and methionine. Antioxidants, 12, 1381. https://doi.org/10.3390/antiox12071381.
F. Reinig, L. Wacker, O. Jöris, C. Oppenheimer, G. Guidobaldi, D. Nievergelt, F. Adolphi, P. Cherubini, S. Engels, J. Esper, F. Keppler, A. Land, C. Lane, H. Pfanz, S. Remmele, M. Sigl, A. Sookdeo, U. Büntgen (2023). Possible magmatic CO2 influence on Laacher See eruption date. Nature, 619, E3-E8, doi:10.1038/s41586-023-05966-0.
T. Klintzsch, H. Geisinger, A. Wieland, G. Langer, G. Nehrke, M. Bižić, M. Greule, K. Lenhart, C. Borsch, M. Greule, M. Schroll, F. Keppler (2023). Stable carbon isotope signature of methane released from phytoplankton. Geophysical Research Letters, 50, e2023GL103317, https://doi.org/10.1029/2023GL103317.
N. Schorndorf, N. Frank, S.M. Ritter, S. Warken, C. Scholz, F. Keppler, D. Scholz, J. Olguín, W. Stinnesbeck (2023). Mid- to late Holocene sea-level rise recorded in Hells Bells ²³⁴U/²³⁸U ratio and geochemical composition. Scientific Reports, 13, 10011, https://doi.org/10.1038/s41598-023-36777-y.
C. Hartmann, F. Keppler, M. Greule, R. Lauer, A. Horst (2023). Triple-element stable isotope analysis of chloromethane emitted by royal fern and degraded by club moss. Journal of Geophysical Research: Biogeosciences, 28, e2022JG007256, doi.org/10.1029/2022JG007256.
Q. Lu, X. Liu, L. Tan, K. Treydte, M. Greule, A. Wieland, J. Liu, L. Zhao, Y. Zhang, H. Kang, L. Zhang, X. Zeng, F. Keppler, Z. Chen, X. Xing (2023). The altitude-specific differences in tree-ring δ²H records of wood lignin methoxy in the Qinling Mountains, central China. Quaternary Science Reviews, 300, 107895, doi:10.1016/j.quascirev.2022.107895.

2022

P. Baur, P. Comba, L. R. Gahan, C. Scholz (2022). The ascidian Lissoclinum patella, the patellamides and copper. Australian Journal of Chemistry. doi:10.1071/CH22200.
K.M. Leberecht, S.M. Ritter, C.J. Lapp, L. Klose, J. Eschenröder, C. Scholz, C., S. Kühnel, W. Stinnesbeck, A. Kletzin, M. Isenbeck-Schröter, J. Gescher (2022). Microbially promoted calcite precipitation in the pelagic redoxcline: Elucidating the formation of the turbid layer. Geobiology, 20, 498-517.
T. Einzmann, M. Schroll, J.F. Kleint, M. Greule, F. Keppler (2022). Application of concentration and 2-dimensional stable isotope measurements of methane to constrain sources and sinks in a seasonally stratified freshwater lake. Frontiers in Environmental Sciences, 10:865862, doi:10.3389/fenvs.2022.865862.
Q. Lu, X. Liu, L. Tan, F. Keppler, K. Treydte, A. Wieland, L. Zhang, X. Shi, Y. Zhang, Y. Wang, X. Zeng, J. Liu, L. Zhao, G. Xu, X. Xing (2022). Tree-ring δ²H records of lignin methoxy indicate spring temperature changes since 20th century in the Qinling Mountains, China. Dendrochronologia, 76, 126020.
A. Wieland, M. Greule, P. Römer, J. Esper, F. Keppler (2022). Climate signals in stable carbon and hydrogen isotopes of lignin methoxy groups from southern German beech trees. Climate of the Past, 18, 1849-1866, doi:10.5194/cp-18-1849-2022.
F. Keppler, L. Ernst, D. Polag, J. Zhang, M. Boros (2022). ROS-driven cellular methane formation: potential implications for health sciences. Clinical and Translational Medicine, 12, e905, doi:10.1002/ctm2.905.
S., Hilt, H.-P. Grossart, D.F. McGinnis, F. Keppler (2022). Potential role of submerged macrophytes for oxic methane production in aquatic ecosystems. Limnology and Oceanography, doi:10.1002/lno.12095.
M. Schroll, K. Lenhart, S. Greiner, F. Keppler (2022). Making plant methane formation visible—Insights from application of ¹³C-labeled dimethyl sulfoxide. Plant-Environment Interactions, 3, 104–117, doi:10.1002/pei3.10076.
M. Jungmann, S.N. Vardag, F. Kutzner, F. Keppler, M. Schmidt, N. Aeschbach, U. Gerhard, S. Lautenbach, A. Siegmund, T. Goeschl, A. Butz (2022). Zooming in for Climate Action – Hyperlocal Greenhouse Gas Data for Mitigation Action? Climate Action, 1, 8, doi:10.1007/s44168-022-00007-4.

L. Ernst, B. Steinfeld, U. Barayeu, T. Klintzsch, M. Kurth, D. Grimm, T.P. Dick, J.G. Rebelein, I.B. Bischofs, F. Keppler (2022). Methane formation driven by reactive oxygen species across all living organisms. Nature, 603, 482–487, doi:10.1038/s41586-022-04511-9.
T.J. Porter, T. Anhäuser, J. Halfar, F. Keppler, A.Z. Csank, C.J. Williams (2022). Canadian Arctic Neogene temperatures reconstructed from hydrogen isotopes of lignin-methoxy groups of sub-fossil wood. Paleoceanography and Paleoclimatology, 37, e2021PA004345.

2021

F. Keppler (2021). A surprise from the deep. Science, 374, 821-822.
X. An, L. Liu, M. Schaefer, B. Yan, C. Scholz, S. Hillmer, K. Wang, Y. Luo, H. Ji, J, Gladkich, I. Herr (2021). Alpha-Lipoic Acid Prevents Side Effects of Therapeutic Nanosilver without Compromising Cytotoxicity in Experimental Pancreatic Cancer. Cancers, 13, 4770.
M. Greule, A. Wieland, F. Keppler (2021). Measurements and applications of δ²H values of wood lignin methoxy groups for palaeoclimatic studies. Quaternary Science Reviews, 268, 107107.
E. Kröber, S. Wende, S. Kanukollu, C. Buchen-Tschiskale, L. Besaury, F. Keppler, S. Vuilleumier, S. Kolb, F. Bringel (2021). ¹³C-chloromethane incubations provide evidence for novel bacterial chloromethane degraders in a living tree fern. Environmental Microbiology, 23, 4450-4465.
M. Muntau, M. Lebuhn, D. Polag, Y. Bajón-Fernández, K. Koch (2021). Effects of CO₂ enrichment on the anaerobic digestion of sewage sludge in continuously operated fermenters. Bioresource Technology, 332, doi.org/10.1016/j.biortech.2021.125147.
J.F. Kleint, Y. Wellach, M. Schroll, F. Keppler, M. Isenbeck-Schröter (2021). The impact of seasonal sulfate-methane transition zones on methane cycling in a sulfate-enriched freshwater environment. Limnology and Oceanography, 66, 2290–2308.
K.A. Jakob, S.L. Ho, A.N. Meckler, J. Pross, J. Fiebig, F. Keppler, O. Friedrich (2021). Stable Biological Production in the Eastern Equatorial Pacific across the Plio-Pleistocene Transition (~3.35–2.0 Ma). Paleoceanography and Paleoclimatology, 36, e2020PA003965.
D. Müller, C.N. Stirn, M.V. Maier (2021) Arsenic Removal from Highly Contaminated Groundwater by Iron Electrocoagulation—Investigation of Process Parameters and Iron Dosage Calculation. Water 13, 687.

2020

Y. Sun, A. K. Schmitt, T. Häger, M. Schneider, L. Pappalardo, M. Russo (2020). Natural blue zircon from Vesuvius. Mineralogy and Petrology, 1-16.
T. Klintzsch, G. Langer, A. Wieland, H. Geisinger, K. Lenhart, G. Nehrke, F. Keppler (2020). Effects of temperature and light on methane production from widespread marine algae. Journal of Geophysical Research: Biogeosciences, 125, e2020JG005793. doi.org/10.1029/2020JG005793.
M. Schroll, F. Keppler, M. Greule, C. Eckart, H. Zorn, K. Lenhart (2020). The stable carbon isotope signature of methane produced by saprotrophic fungi. Biogeosciences, 17, 3891-3901.
Q. Lu, X. Liu, T. Anhäuser, F. Keppler, Y. Wang, X. Zeng, Q. Zhang, L. Zhang, K. Wang, Y. Zhang (2020). Tree-ring lignin proxies in Larix gmelinii forest growing in a permafrost area of northeastern China: temporal variation and potential for climate reconstructions. Ecological Indicators, 118, 106750.
A. Hou, A. Bahr, J. Raddatz, S. Voigt, M. Greule, A.L. Albuquerque, C.M. Chiessi, O. Friedrich (2020). Insolation and Greenhouse Gas Forcing of the South American Monsoon System Across Three Glacial-Interglacial Cycles. Geophys. Res. Lett., 47, e2020GL087948.
Y. Wang, X. Liu, T. Anhäuser, Q. Lu, X. Zeng, Q. Zhang, K. Wang, L. Zhang, Y. Zhang, F. Keppler (2020). Temperature signal recorded in δ2H and δ13C of wood lignin methoxyl groups from a permafrost forest in northeastern China. Science of the Total Environment, 727, 138558.
F. Keppler, A.N. Röhling, N. Jaeger, M. Schroll, S.C. Hartmann, M. Greule (2020). Sources and sinks of chloromethane in a salt marsh ecosystem: constraints from concentration and stable isotope measurements of laboratory incubation experiments. Environmental Science: Processes & Impact, DOI: 10.1039/C9EM00540D.

T. Anhäuser, B. Sehls, W. Thomas, C. Hartl, M. Greule, D. Scholz, J. Esper, F. Keppler (2020). Tree-ring δ²H values from lignin methoxyl groups indicate sensitivity to European-scale temperature changes. Palaeogeography, Palaeoclimatology, Palaeoecology, 546, 109665.
F. Keppler, J.D. Barnes, A. Horst, E. Bahlmann,J. Luo, T. Nadalig, M. Greule,S.C. Hartmann, S. Vuilleumier (2020). Chlorine isotope fractionation of the major chloromethane sinks in the environment. Environmental Science & Technology, 54, 1634-1645.
J.F. Hartmann, M. Günthel, T. Klintzsch, G. Kirillin, H.-P. Grossart, F. Keppler, M. Isenbeck-Schröter (2020). High Spatio-Temporal Dynamics of Production and Emission of Methane in Oxic Surface Water. Environmental Science & Technology, 54, 1451-1463.
M. Greule, H. Moossen, M.K. Lloyd, H. Geilmann, W.A. Brand, J.M. Eiler, H. Qi, F. Keppler (2020). Three wood isotopic reference materials for δ²H and δ¹³C measurements of plant methoxy groups. Chemical Geology, 533, 119428.
M. Bižić, T. Klintzsch, D. Ionescu, M. Y. Hindiyeh, M. Günthel, A. M. Muro-Pastor, W. Eckert, T. Urich, F. Keppler, H.-P. Grossart (2020). Aquatic and terrestrial cyanobacteria produce methane. Science Advances, 6, eaax5343.

2019

J. Lippold, F.Pöppelmeier, F. Süfke, M. Gutjahr, T.J. Goepfert, P. Blaser, O. Friedrich, J.M. Link, L. Wacker, S. Rheinberger, S.L. Jaccard (2019). Constraining the Atlantic Meridional Overturning Circulation during the Holocene. Geophysical Research Letters, 46, 11338-11346.
M. Boros, F. Keppler (2019). Methane Production and Bioactivity-A Link to Oxido-Reductive Stress. Frontiers in Physiology, 10:1244.
O.A. Kern, A. Koutsodendris, B. Mächtle, K. Christanis, G. Schukraft, C. Scholz, U. Kotthoff, J. Pross (2019). XRF core scanning yields reliable semiquantitative data on the elemental composition of highly organic-rich sediments: Evidence from the Füramoos peat bog (Southern Germany). Science of The Total Environment, 697, 134110.
M.V. Maier, Y. Wolter, D. Zentler, C. Scholz, C. N. Stirn, M. Isenbeck-Schröter (2019). Phosphate Induced Arsenic Mobilization as a Potentially Effective In-Situ Remediation Technique—Preliminary Column Tests. Water, 11, 2364.
T. Sattler, M. Sörgel, J. Wittmer, E. Bourtsoukidis, T. Krause, E. Atlas, S. Benk, S. Bleicher, K. Kamilli, J. Ofner, R. Kopetzky, A. Held, W.-U. Palm, J. Williams, C. Zetzsch, H.-F. Schöler (2019). Natural Formation of Chloro- and Bromoacetone in Salt Lakes of Western Australia. Atmosphere, 10, 663.
T. Klintzsch, G. Langer, G. Nehrke, A. Wieland, K. Lenhart, F. Keppler (2019). Methane production by three widespread marine phytoplankton species: release rates, precursor compounds, and relevance for the environment. Biogeosciences, 16, 4129-4144.
D. Polag, F. Keppler (2019). Global methane emissions from the human body: past, present and future. Atmospheric Environment, 214, 116823.
J. Liu, S.C. Hartmann, F. Keppler, D.Y.F. Lai, (2019). Simultaneous abiotic production of greenhouse gases (CO2, CH4, and N2O) in subtropical soils. Journal of Geophysical Research: Biogeosciences, 124. https://doi.org/10.1029/2019JG005154.
A.S. Wilde, H.L. Frandsen, A. Fromberg, J. Smedsgaard, M. Greule (2019). Isotopic characterization of vanillin ex glucose by GC-IRMS - New challenge for natural vanilla flavour authentication? Food Control, 106, 106735.
F. Bringel, L. Besaury, P. Amato, E. Kröber, S. Kolb, F. Keppler, S. Vuilleumier, T. Nadalig (2019). Methylotrophs and methylotroph populations for chloromethane degradation. Current Issues in Molecular Biology, 33, 149-172.
S.M. Ritter, M. Isenbeck-Schröter, C. Scholz, F. Keppler, J. Gescher, L. Klose, N. Schorndorf, J.A. Olguín, A. González-González, W. Stinnesbeck. (2019). Subaqueous speleothems (Hells Bells) formed by the interplay of pelagic redoxcline biogeochemistry and specific hydraulic conditions in the El Zapote sinkhole, Yucatán Peninsula, Mexico. Biogeosciences, 16, 2285-2305.
E. Bahlmann, F. Keppler, J. Wittmer, M. Greule, H.F. Schöler, R. Seifert, C. Zetzsch (2019). Evidence for a major missing source in the global chloromethane budget from stable carbon isotopes. Atmospheric Chemistry and Physics, 19, 1703-1719.
M. Greule, H. Moossen, H. Geilmann, W.A. Brand, F. Keppler (2019). Methyl sulfates as methoxyl isotopic reference materials for δ13C and δ2H measurements. Rapid Communication in Mass Spectrometry, 33, 343-350.
K. Lenhart, T. Behrendt, S. Greiner, J. Steinkamp, R. Well, A. Giesemann, F. Keppler (2019). Nitrous oxide effluxes from plants as a potentially important source to the atmosphere. New Phytologist, 221, 1398-1408.

2018

T. Anhäuser, B. Hook, J. Halfar , M. Greule, F. Keppler (2018). Earliest Eocene cold period and polar amplification - Insights from δ2H values of lignin methoxyl groups of mummified wood. Palaeogeography, Palaeoclimatology, Palaeoecology, 505, 326-336.
K. A. Jakob, J. Pross, C. Scholz, J. Fiebig, O. Friedrich (2018), Thermocline state change in the eastern equatorial Pacific during the late Pliocene/early Pleistocene intensification of Northern Hemisphere glaciation. Climate of the Past, 14, 1079-1095.
P. Comba, D. Faltermeier, S. Gieger, F. Keppler, H.F. Schöler, M. Schroll (2018). Iron catalyzed demethylation of acetic acid. Journal of Coordination Chemistry, 71:11-13, 1704-1714.
N. Jaeger, L. Besaury, A.N. Röhling, F. Koch, A.-M. Delort, C. Gasc, M. Greule, S. Kolb, T. Nadalig, P. Peyret, S. Vuilleumier, P. Amato, F. Bringel, F. Keppler (2018). Chloromethane formation and degradation in the fern phyllosphere. Science of the Total Environment, 634, 1278-1287.
J.F. Hartmann, T. Gentz, A. Schiller, M. Greule, H.-P. Grossart, D. Ionescu, F. Keppler, K. Martinez-Cruz, A. Sepulveda-Jauregui, M. Isenbeck-Schröter (2018). A fast and sensitive method for the continuous in-situ determination of dissolved methane and its δ13C-isotope ratio in surface waters. Limnology and Oceanography, 16, 273-285.
F. Keppler, E. Bahlmann, M. Greule, H.F. Schöler, J. Wittmer, C. Zetzsch (2018). Mass spectrometric measurement of hydrogen isotope fractionation for the reactions of chloromethane with OH and Cl. Atmospheric Chemistry and Physics, 18, 6625–6635.
T. May, D. Polag, F. Keppler, M. Greule, L. Müller, H. König (2018). Methane oxidation in industrial biogas plants – insights in a novel methanotrophic environment evidenced by pmoA gene analyses and stable isotope labelling studies. Journal of Biotechnology, 270, 77-84.
D. Schulze-Makuch, D. Wagner, S.P. Kounaves, K. Mangelsdorf, K.G. Devine, J.-P. de Vera, P. Schmitt-Kopplin, H.-P. Grossart, V. Parro, M. Kaupenjohann, A. Galy, B. Schneider, A. Airo, J. Frösler, A.F. Davila, F.L. Arens, L. Cáceres, F.S. Cornejo, D. Carrizo, L. Dartnell, J. DiRuggiero, M. Flury, L. Ganzert, M.O. Gessner, P. Grathwohl, L. Guan, J. Heinz, M. Hess, F. Keppler , D. Maus, C.P. McKay, R.U. Meckenstock, W. Montgomery, E.A. Oberlin, A.J. Probst, J. Saenz, T. Sattler, J. Schirmack, M.A. Sephton, M. Schloter, J. Uhl, B. Valenzuela, G. Vertergaard, L. Wörmer, P. Zamorano (2018). A transitory habitat for microorganisms in the hyperarid Atacama Desert. PNAS, 115, 2670-2675.
N. Jaeger, L. Besaury, E. Kröber, A.-M. Delort, M. Greule, K. Lenhart, T. Nadalig, S. Vuilleumier, P. Amato, S. Kolb, F. Bringel, F. Keppler (2018). New insights into chloromethane degradation in soils gained using a combined microbial and two-dimensional stable isotope approach. Journal of Environmental Quality, 47, 254-262.
J. Esper, S. Holzkämper, U. Büntgen, B. Schöne, F. Keppler , C. Hartl-Meier, S. St.George, D.F.C. Riechelmann, K. Treydte (2018). Site-specific climatic signals in stable isotope records from Swedish pine forests. Trees, 32, 855-869.
D. Polag, F. Keppler (2018). Long-term monitoring of breath methane. Science of the Total Environment, 624, 69-77.

2017

D.G. Mulat, F. Mosbæk, A.J. Ward, D. Polag, M. Greule, F. Keppler, J. Nielsen, A. Feilberg (2017). Exogenous addition of H₂ for an in situ biogas upgrading through biological reduction of carbon dioxide into methane. Waste Management, 68, 146-156.
D. Riechelmann, M. Greule, R.T.W. Siegwolf, T. Anhäuser, J. Esper, F. Keppler (2017). Warm season precipitation signal in δ²H of wood lignin methoxyl groups from high elevation larch trees in Switzerland. Rapid Communication in Mass Spectrometry, 31, 1589-1598.
K. Benzing, P. Comba, B. Martin, B. Pokrandt, F. Keppler (2017). Nonheme iron-oxo-catalyzed methane formation from methyl-thioethers: Scope, mechanism and relevance for natural systems. Chemistry - A European Journal, 23, 10465 – 10472.
F. Keppler, J. Fischer, T. Sattler, D. Polag, N. Jaeger, H. F. Schöler, M. Greule (2017). Chloromethane emissions in human breath. Science of the Total Environment, 605, 405-410.
C. Mayer, U. Schreiber, O. Schmitz, P. Rosendahl, A. Bronja, M. Greule, F. Keppler, I. Mulder, T. Sattler, H.F. Schöler (2017). Organic compounds in fluid inclusions of Archean quartz - archives of prebiotic chemistry on early Earth. PlosOne, 12, e0177570.
K. Geisler, M. Greule, U. Schäfer, J. Hans, T. Geisler, L. Meier, F. Keppler, G. Krammer (2017). Vanilla authenticity control by DNA barcoding and isotope data aggregation. Flavour and Fragrance Journal, 32, 228-237.
J. Hepp, R. Zech, K. Rozanski, M. Tuthorn, B. Glaser, M. Greule, F. Keppler, Y. Huang, W. Zech, M. Zech (2017). Late Quaternary relative humidity changes from Mt. Kilimanjaro, based on a biomarker-isotope paleohygrometer. Quaternary International, 438, Part B, 116-130.
T. Anhäuser, M. Greule, F. Keppler (2017) Stable hydrogen isotope values of lignin methoxyl groups of four tree species across Germany and their implication for temperature reconstruction Science of The Total Environment, 579, 263-271.
T. Anhäuser, M. Greule, D. Polag , G.J. Bowen, F. Keppler (2017) Mean annual temperatures of mid-latitude regions derived from δ²H values of wood lignin methoxyl groups and its implications for paleoclimate studies. Science of The Total Environment, 574, 1276-1282.

2016

K.A. Kamilli, J. Ofner, T. Krause, T. Sattler, P. Schmitt-Kopplin, E. Eitenberger, G. Friedbacher, B. Lendl, H. Lohninger, H.F. Schöler, A. Held (2016) How salt lakes affect atmospheric new particle formation: A case study in Western Australia. Science of The Total Environment, 573, 985-995.
J. Hepp, M. Rabus, T. Anhäuser, T. Bromm , C. Laforsch, F. Sirocko, B. Glaser, M. Zech (2016) A sugar biomarker proxy for assessing terrestrial versus aquatic sedimentary input. Organic Geochemistry, 98, 98-104.
K. Lenhart, T. Klintzsch, G. Langer, G. Nehrke, M. Bunge, S. Schnell, F. Keppler (2016) Evidence for methane production by the marine algae Emiliania huxleyi, Biogeosciences. 13, 3163-3174.
F. Keppler, A. Schiller, R. Ehehalt, M. Greule, J. Hartmann, D. Polag (2016) Stable isotope and high precision concentration measurements confirm that all humans produce and exhale methane. J. Breath Res. 10, 16003.
D. Riechelmann, M. Greule, K.S. Treydte, J. Esper and F. Keppler (2016) Climate signals in δ13C of wood lignin methoxyl groups from high elevation larch trees. Palaeogeogr. Palaeoclimatol. Palaeoecol. 445, 60–71.

2015

D. Polag, T. May, L. Müller, H. König, F. Jacobi, S. Laukenmann, F. Keppler (2015). Online monitoring of stable carbon isotopes of methane in anaerobic digestion as a new tool for early warning of process instability. Bioresource Technology, 197, 161-170.
K. Lenhart, B. Weber, W. Elbert, J. Steinkamp, T. Clough, P. Crutzen, U. Pöschl, F. Keppler (2015). Nitrous oxide and methane emissions from cryptogamic covers. Global Change Biology, 21(10), 3889-3900.
T. May, M. Koch-Singenstreua, J. Ebling, R. Stantscheff, L. Müller, F. Jacobi, D. Polag, F. Keppler, H. König (2015). Design and application of a synthetic DNA standard for real-time PCR analysis of microbial communities in a biogas digester. Applied Microbiology and Biotechnology, 99(16), 6855-6863.
C. McRoberts, F. Keppler, D.B. Harper, J.T.G. Hamilton (2015). Seasonal changes in chlorine and methoxyl content of leaves of deciduous trees and their impact on release of chloromethane and methanol at elevated temperatures. Environmental Chemistry, 12(4), 426-437.
M. Greule, A. Mosandl, J.T.G. Hamilton, F. Keppler (2015). Comment on: “Authenticity and Traceability of Vanilla Flavors by Analysis of Stable Isotopes of Carbon and Hydrogen”. Journal of Agricultural and Food Chemistry, 63, 5305–5306.
M. Mischel, J. Esper, F. Keppler, M. Greule, W. Werner (2015). δ²H, δ¹³C and δ¹⁸O from whole wood, α-cellulose and lignin methoxyl groups in Pinus sylvestris: a multi-parameter approach. Isotopes in Environmental and Health Studies , 51(4), 553-568.
K. Lenhart, F. Althoff, M. Greule, F. Keppler (2015) Technical Note: Methionine, a precursor of methane in living plants. Biogeosciences 12, 1907-1914.

T. Anhäuser, M. Greule, M. Zech, Kalbitz, K., C. McRoberts, F. Keppler (2015) Stable hydrogen and carbon isotope ratios of methoxyl groups during plant litter degradation. Isotopes in Environmental and Health Studies 51, 143-154.
M. Greule, A. Rossmann, H.-L. Schmidt, A. Mosandl and F. Keppler (2015) A Stable Isotope Approach to Assessing Water Loss in Fruits and Vegetables during Storage. J. Agric. Food Chem., 63, 1974-1981. Available at: http://pubs.acs.org/doi/abs/10.1021/jf505192p.

2014

T. Nadalig, M. Greule, Francoise Bringel, F. Keppler, S. Vuilleumier (2014). Probing the diversity of chloromethane-degrading bacteria by comparative genomics and isotopic fractionation. Frontiers in Microbiology, 5, 523.
F. Keppler, D.B. Harper, M. Greule, U. Ott, T. Sattler, H.F. Schöler, J.T.G. Hamilton (2014). Chloromethane release from carbonaceous meteorite affords new insight into Mars lander findings. Scientific Reports, 4, 7010.
T. Anhäuser, F. Sirocko, M. Greule, J. Esper, F. Keppler (2014). D/H ratios of methoxyl groups of the sedimentary organic matter of Lake Holzmaar (Eifel, Germany): a potential palaeoclimate/-hydrology proxy. Geochimica et Cosmochimica Acta, 142, 39-52.
F. Althoff, K. Benzing, P. Comba.,C. McRoberts, D.R. Boyd, S. Greiner, F. Keppler (2014). Abiotic methanogenesis from organosulfur compounds under ambient conditions. Nature Communications, 5, 4205.
D. Polag, O. Leiß, F. Keppler (2014). Age dependent breath methane in the German population. Science of the Total Environment, 481, 582-587.
D. Polag, L.C. Krapf, S. Laukenmann, H. Heuwinkel, J. Lelieveld, F. Keppler (2014). Stable carbon isotopes of methane for real-time process monitoring in anaerobic digesters. Engineering in Life Sciences, 4, 153-160.
A. Horst, H. Holmstrand, P. Andersson, B.F. Thornton, A. Wishkerman, F. Keppler, Ö. Gustafsson (2014). Stable bromine isotopic composition of methyl bromide released from plant matter. Geochimica et Cosmochimica Acta, 125, 186-195.

2013

T. Nadalig, M. Greule, Francoise Bringel, S. Vuilleumier, F. Keppler (2013). Hydrogen and carbon isotope fractionation during degradation of chloromethane by methylotrophic bacteria. MicrobiologyOpen, 2(6), 893-900.
D. Polag, S. Laukenmann, H. Heuwinkel, M. Greule, F. Keppler (2013). Evidence of anaerobic syntrophic acetate oxidation in biogas batch reactors using stable carbon isotopes labelling experiments. Isotopes in Environmental and Health Studies, 49, 365-77.
O. Wuerfel, M. Greule, F. Keppler, M.A. Jochmann, T.C. Schmidt (2013). Position Specific Isotope Analysis of the Methyl Group Carbon in Methylcobalamin for the Investigation of Biomethylation Processes. Analytical and Bioanalytical Chemistry, 405, 2833-2841.
Y. Gori, R. Wehrens, M. Greule, F. Keppler, L. Ziller, N. La Porta, F. Camin (2013). C, H and O stable isotope ratios of whole wood, cellulose and lignin methoxyl groups of Picea abies as climatic proxy. Rapid Communication in Mass Spectrometry, 27, 265-275.

2012

M. Greule, S.G. Huber, F. Keppler (2012). Stable hydrogen-isotope analysis of methyl chloride emitted from halophytic plants. Atmospheric Environment, 62, 584-592.
K. Lenhart, M. Bunge, S.Rathering, T. Neu, I. Schüttman, M. Greule, C. Kammann, S. Schnell, C. Müller, H. Zorn, F. Keppler (2012). Evidence for methane production by saprotrophic fungi. Nature Communications, 3, 1046.
F. Keppler, I. Vigano, A. McLeod, U. Ott, M. Früchtl, T. Röckmann (2012). Ultraviolet-radiation-induced methane emissions from meteorites and the Martian atmosphere. Nature, 486, 93-96.
M. Hurkuck, F. Althoff, H. Jungkunst, A. Jugold, F. Keppler (2012). Release of methane from aerobic soil: an indication of a novel chemical natural process? Chemosphere, 86, 684-689.
L. Derendorp, A. Wishkerman, F. Keppler, C. McRoberts, R. Holzinger, T. Röckmann (2012). Methyl chloride emissions from halophyte leaf litter: dependence on temperature and chlorine content. Chemosphere, 87, 483-489.

2011

M. Greule, F. Keppler (2011). Stable isotope determination of ester and ether methyl moieties in plant methoxyl groups. Isotopes in Environmental and Health Studies, 47, 470-482.
Z.-P. Wang, F. Keppler, M. Greule, J.T.G. Hamilton (2011). Non-microbial methane emissions from fresh leaves: effects of physical wounding and anoxia. Atmospheric Environment 45, 4915-4921.
L. Derendorp, R. Holzinger, A. Wishkerman, F. Keppler, T. Röckmann (2011). Methyl chloride and C2–C5 hydrocarbon emissions from dry leaf litter and their dependence on temperature. Atmospheric Environment, 45, 3112-3119.
A. Wishkerman, S. Greiner, M. Ghyczy, M. Boros, T. Rausch, K. Lenhart, F. Keppler (2011). Enhanced formation of methane in plant cell cultures by inhibition of cytochrome c oxidase. Plant Cell & Environment, 34, 457–464.

2010

S. Laukenmann, D. Polag, H. Heuwinkel, M. Greule, A. Gronauer, J. Lelieveld, F. Keppler (2010). Identification of methanogenic pathways in anaerobic digesters using stable carbon isotopes. Engineering in Life Sciences, 10, 509–514.
M. Greule, L. D. Tumino, T. Kronewald, U. Hener, J. Schleucher, A. Mosandl, F. Keppler (2010). Improved rapid authentication of vanillin using δ13C and δ2H values. European Food Research Technology, 231, 933–941.
T. Röckmann, C.X. Gómez Álvarez, S. Walter, C. van der Veen, A.G. Wollny, S. Gunthe, G. Helas, U. Pöschl, F. Keppler, M. Greule, W.A. Brand (2010). The isotopic composition of H2 from biomass burning - dependency on combustion efficiency, moisture content and dD of local precipitation. Journal of Geophysical Research, 115, D17308.
F. Keppler, S. Laukenmann, J. Rinne, H. Heuwinkel, M. Greule, M. Whiticar, J. Lelieveld (2010). Measurements of 13C/12C Methane from Anaerobic Digesters: Comparison of Optical Spectrometry with Continuous-Flow Isotope Ratio Mass Spectrometry. Environmental Science & Technology, 44, 5067-5073.
F. Althoff, A. Jugold, F. Keppler (2010). Methane Formation by Oxidation of Ascorbic Acid using Iron Minerals and Hydrogen Peroxide. Chemosphere, 80, 286-292.
I. Vigano, R. Holzinger, T. Röckmann, F. Keppler, M. Greule, W.A. Brand, H. Geilmann (2010). Water drives the deuterium content of the methane emitted from plants. Geochimica et Cosmochimica Acta, 74, 3865–3873.

2009

F. Keppler, M. Boros, C. Frankenberg, J. Lelieveld, A. McLeod, A.M. Pirttilä, T. Röckmann, J.-P. Schnitzler (2009). Methane formation in aerobic environments. Environmental Chemistry, 6, 459-465.
I. Vigano, R. Holzinger, T. Röckmann, A. van Dijk, F. Keppler, M. Greule, W.A. Brand, H. Geilmann, J. van Dongen (2009). The stable isotope signature of methane emitted from plant material under UV irradiation. Atmospheric Environment, 43, 5637-5646.
N. Yassaa, A. Wishkerman, F. Keppler, J. Williams (2009) Fast determination of methyl chloride and methyl bromide emissions from plant matter and soil samples using HS-SPME and GC-MS. Environmental Chemistry, 6, 311-318.
M. Greule, A. Mosandl, J.T.G. Hamilton, F. Keppler (2009). A simple rapid method to precisely determine 13C/12C ratios of plant methoxyl groups. Rapid Communication in Mass Spectrometry, 23, 1710-1714.
L. Weissflog, N.F. Elanskii, K. Kotte, F. Keppler, A. Pfennigsdorff, K. Lange E. Putz, L.V. Lisitzina (2009). Late permian changes in conditions of the atmosphere and environments caused by halogenated gases. Doklady Earth Sciences, 425, 291-295.

2008

F. Keppler, J.T.G. Hamilton (2008). Tracing the geographical origin of early potato tubers using stable hydrogen isotope ratios of methoxyl groups. Isotopes in Environmental and Health Studies, 44, 337-347.
M. Greule, A. Mosandl, J.T.G. Hamilton, F. Keppler (2008). A rapid and precise method for determination of D/H ratios of plant methoxyl groups Rapid Communication in Mass Spectrometry, 22, 3983-3988.
A. Wishkerman, S. Gebhardt, C.W. McRoberts, J.T.G. Hamilton, J. Williams, F. Keppler (2008). Abiotic methyl bromide formation from vegetation and its strong dependence on temperature Environmental Science & Technology, 42, 6837-6842.
I. Vigano, R. Holzinger, H. van Weelden, F. Keppler, A. McLeod, T. Röckmann (2008). Effect of UV radiation and temperature on the emission of methane from plant biomass and structural components. Biogeosciences, 5, 937-947.
F. Keppler, J.T.G. Hamilton, C.W. McRoberts, I. Vigano, M. Braß, T. Röckmann (2008). Methoxyl groups of plant pectin as a precursor compound for atmospheric methane: evidence from deuterium labelling studies. New Phytologist, 178, 808-814.
S. Draxler, F. Keppler (2008). Ansätze zur regionalen Quantifizierung von Methan aus Pflanzen. UWSF – Z Umweltchem Ökotox, 20(1) 75-79.

2007

G. Rösing, F. Keppler (2007). Production of biogas. PCT Int. Appl., WO 2006-EP7504, 32 pp.
F. Keppler, D.B. Harper, R.M. Kalin, W. Meier-Augenstein, N. Farmer, S. Davis, H.-L. Schmidt, D.M. Brown, J.T.G Hamilton (2007). D/H ratios of lignin methoxyl groups as a paleoclimate proxy and constraint of the geographical origin of woods. New Phytologist, 176, 600-609.

2006

F. Keppler, R. Borchers, J.T.G. Hamilton, G. Kilian, J. Pracht, H. F. Schöler, (2006). De-novo formation of chloroethyne in soil. Environmental Science & Technology 40, 130-134.
F. Keppler, J.T.G. Hamilton, M. Brass, T. Röckmann (2006). Methane emissions from terrestrial plants under aerobic conditions. Nature, 439, 187-191.
S. Houweling, T. Röckmann, I. Aben, F. Keppler, M. Krol, J.-F. Meirink, E. J. Dlugokencky, C. Frankenberg (2006). Atmospheric constraints on global emissions of methane from plants. Geophysical Research Letters, 33, L15821.

2005

F. Keppler, T. Röckmann, R.M. Moore, D.B. Harper, J.T.G. Hamilton (2005). New insight into the atmospheric chloromethane budget gained using stable carbon isotope ratios. Atmospheric Chemistry and Physics 5, 2403-2411.

2004

F. Keppler, R.M. Kalin, D.B. Harper, W.C. McRoberts, J.T.G. Hamilton (2004). Carbon isotope anomaly in the major plant C₁ pool and its global biogeochemical implications. Biogeosciences 1, 123-131.
H. Biester, F. Keppler, A. Putschew, A. Martinez-Cortizas, M. Petri (2004). Halogen retention, organohalogens and the role of organic matter decomposition on halogen enrichment in two Chilean peat bogs. Environmental Science & Technology 38, 1984-1991.
F. Keppler, H. Biester, A. Putschew, P. J. Silk, H.F. Schöler, G. Müller (2004). Organoiodine formation during humification in peatlands: a key process in terrestrial iodine cycling. Environmental Chemistry Letters 1, 219-223.

2003

J.T.G. Hamilton, W.C. McRoberts, F. Keppler, R.M. Kalin, D.B. Harper (2003). Chloride methylation by plant pectin: an efficient environmentally significant process. Science 301, 206-209.
F. Keppler and H. Biester (2003). Peatlands: a major sink of naturally formed organic chlorine. Chemosphere 52, 451-453.
H. F. Schöler, F. Keppler, I. J, Fahimi, V. W. Niedan (2003). Fluxes of trichloroacetic acid between atmosphere, biota, soil and groundwater. Chemosphere 52, 339-354.
I. Fahimi, F. Keppler, H.F. Schöler (2003). Formation of chlorinated acetic acids from soil, humic acid and phenolic moieties. Chemosphere 52, 513-520.
H.F. Schöler and F. Keppler (2003). Abiotic formation of organohalogens in the terrestrial environment. Chimia, 57(1/2), 33-34.
F. Keppler, R. Borchers, P. Elsner, I. Fahimi, J. Pracht, H. F. Schöler (2003). Formation of volatile iodinated organic compounds in soil – results from laboratory studies. Chemosphere 52, 477-483.
A. Putschew, F. Keppler, M. Jekel (2003). Differentiation of the halogen content of peat samples using ion chromatography after combustion (TX/TOX-IC). Analytical and Bioanalytical Chemistry, 375, 781-785.
V.W. Niedan, F. Keppler, B. Ahlsdorf, H.F. Schöler (2003). Anthropogenically induced de-novo formation of organochlorines. Biogeochemistry 62, 277-287.

2002 - 1998

F. Keppler, R. Borchers, J. Pracht, S. Rheinberger, H. F. Schöler (2002). Natural formation of vinyl chloride in the terrestrial environment. Environmental Science & Technology 36, 2479-2483.
J. Pracht, J. Boenigk, M. Isenbeck-Schröter, F. Keppler, H.F. Schöler (2001). Abiotic Fe(III) induced mineralization of phenolic substances. Chemosphere 44, 613-619.
F. Keppler, R. Eiden, V.W. Niedan, J. Pracht, H.F. Schöler (2000). Halocarbons as degradation products of organic matter by natural oxidation processes. Nature 403, 298-301.
V.W. Niedan, F. Keppler, B. Ahlsdorf, H.F. Schöler (1998). Bildung von Organohalogenen in einer kommunalen Kläranlage. Vom Wasser 91, 175-184.

Book chapters / other manuscripts

T. Kirchhoff, F. Keppler, T. Meier, J. Lorenzen, T. Granzow (2023). Umweltwissenschaften. In: Umwelt interdisziplinär. Grundlagen – Konzepte – Handlungsfelder. Hrsg. T. Meier, F. Keppler, U. Mager, U. Platt, F. Reents. Universitätsbibliothek Heidelberg, 1-42. http://www.ub.uni-heidelberg.de/archiv/32129
T. Meier, F. Keppler, U. Mager, U. Platt, F. Reents (2023). Vorwort. In: Umwelt interdisziplinär. Grundlagen – Konzepte – Handlungsfelder. Hrsg. T. Meier, F. Keppler, U. Mager, U. Platt, F. Reents. Universitätsbibliothek Heidelberg, 1-42. http://www.ub.uni-heidelberg.de/archiv/31076
O. Schlaudt, O. Bubenzer, H. Gebhardt, F. Keppler, Jacqueline Lorenzen, Friederike Reents (2022). Antropozän. In: Umwelt interdisziplinär. Grundlagen – Konzepte – Handlungsfelder. Hrsg. T. Meier, F. Keppler, U. Mager, U. Platt, F. Reents. Universitätsbibliothek Heidelberg, 1-42. http://www.ub.uni-heidelberg.de/archiv/31286.
F. Keppler, A Schmitt, M Trieloff (2022). Geowissenschaften. In: Umwelt interdisziplinär. Grundlagen – Konzepte – Handlungsfelder. Hrsg. T. Meier, F. Keppler, U. Mager, U. Platt, F. Reents. Universitätsbibliothek Heidelberg, 1-22. http://www.ub.uni-heidelberg.de/archiv/31077
O. Bubenzer, H. Gebhard, F. Keppler (2019). Der Mensch als Geologische Kraft - Das Zeitalter des Anthropozäns.
Ruperto Carola, Research Magazine Heidelberg University, Ausgabe 15/2019, 24-33.
F. Bringel, L. Besaury, P. Amato, E. Kröber, S. Kolb, F. Keppler, S. Vuilleumier, T. Nadalig (2019). Methylotrophs and methylotroph populations for chloromethane degradation.
In Methylotrophs and Methylotroph Communities, Ed : L. Chistoserdova, Caister Academic Press, Chap. 8, 149-172.
M. Boros, F. Keppler (2018). The Production and Signaling of Methane.
In: Gasotransmitters, Metallobiology Series No 12. Ed. R. Wang, The Royal Society of Chemistry, UK, 192-234.
K. Lenhart, F. Keppler (2013). Pilze – eine neu entdeckte Methanquelle.
MPG Jahrbuch, 1-7.
I. Vigano, F. Keppler, T. Röckmann (2011). Aerobic methane production: Mechanism and isotope studies.
In: Advances in Environmental Research. Volume 14. Eds. J.A. Daniels, Nova Publisher, 209-234.
A. McLeod, F. Keppler (2010). Methane from vegetation.
In: Methane and Climate Change. Eds. D. Reay, P. Smith, A. van Amstel, Earthscan Ltd, London, UK, 74-96.
F. Keppler, T. Röckmann (2007). Methan, Pflanzen und Klima.
Spektrum der Wissenschaft, 68-73.
F. Keppler, T. Röckmann (2007). Methan, Pflanzen und Klima.
MPG Jahrbuch, 287-291.
F. Keppler, T. Röckmann (2007). Methane, Plants and climate change.
Scientific American, 296(2), 52-57.
H. Biester, A. Martinez-Cortizas, F. Keppler (2006). Occurrence and fate of halogens in mires.
In: Peatlands: Evolution and Records of Environmental and Climatic changes. Eds. Martini, P., Martinez-Cortizas, A. Chesworth, W., Elsevier Series Development in Earth Surface Processes 9, Elsevier, 449-465.
H.F. Schöler, F. Keppler (2005). Abiotic formation of organohalogens in the terrestrial environment.
In: Volatile chlorinated hydrocarbons: Occurrence, fate and impact. Ed.: R. Zellner. GDCh-Monographie 34, 14-23.
H. F. Schöler, F. Keppler (2003). Abiotic formation of organohalogens during early diagenetic processes.
In: The Handbook of Environmental Chemistry Vol.3, Part P. Natural production of organohalogen compounds. Eds.: O. Hutzinger, G.W. Gribble. Springer Verlag, Heidelberg, 63-84.
F. Keppler, H.F. Schöler (2002). Report on the Second International Conference on 'Naturally Produced Organohalogens' (Heidelberg, Germany, September 30 to October 3, 2001).
Environmental Science and Pollution Research 9(2) 154.
F. Keppler, H.F. Schöler (2002). Natürliche Ozonkiller aus dem Boden.
Ruperto Carola, Forschungsmagazin der Universität Heidelberg (Nr.2/2002) 20-24.

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Latest Revision: 2024-03-27