Identification, fluxes and stable isotope composition of halocarbons released from halogen rich semi-arid environments
Final Report Abstract
This project was part of the HALOPROC DFG Research Unit that investigated natural halogenation processes in the environment. The overall aims of the research groups SP Keppler/Williams were to further explore the formation of atmospherically-relevant halocarbons including chloromethane and bromomethane, and to study their biogeochemical cycles, in particular in semi-arid areas. Generally, we followed the project according to the research plan and most work packages were addressed successfully. Most of our results have been published in peer-reviewed journals. Furthermore we have developed new measurement methods/techniques, i.e. a new soil chamber system with volatile organic compound measurements has been constructed and validated; a new fast GC-MS system has been built, certified and flown; and halogenated emissions from soil have been performed by GC-MS and PTR-ToF-MS. In addition a new idea emerged during the project which led to the successful development of a total chlorine reactivity measurement system. The following are the most notable achievements from the research groups of SP Keppler/ Williams: Release of chloromethane and short chained hydrocarbons emissions from halophyte leaf litter and its dependence on temperature and chloride content has been investigated. - Stable hydrogen-isotope values of methyl chloride emitted from halophytic plants were determined. - Chlorine and methoxyl content of tree leaves were measured and their impact on release of chloromethane and methanol at elevated temperatures was studied. - Hydrogen and carbon isotope fractionation during degradation of chloromethane by methylotrophic bacteria has been determined. - A fast GC-MS system (measurement cycle 2-3 minutes), has been successfully developed for quantification of organohalogen compounds. The instrument was certified for the German research aircraft HALO and it was flown between 10-15 km in the monsoon outflow of continental India. The trace gases chloromethane, dichloromethane, chloroform and tetrachloromethane were measured on these flights giving insights into the quantities of such species convected to the upper troposphere. - A dataset of chloromethane and bromomethane has been taken from saline soils as a function of temperature. Collaborative work between the Keppler and Williams group has revealed that both a biotic and abiotic mechanisms are responsible for these emissions. - While scanning soil emission from the new constructed cuvette system it was noted that although no chlorine containing compounds could be detected by PTR-ToF-MS, dimethyl sulfide could be detected at surprisingly high levels in rainforest soil corroborating field studies. This was therefore reported in a combined paper. - A new measurement system for measuring total chlorine reactivity has been developed and deployed for the first time. Finally, our project opened up new research avenues that might have implications for the search of life on extra-terrestrial environments. Next to our investigations of chloromethane release from soils we studied potential CH3Cl release from extraterrestrial matter such as carbonaceous meteorites. Based on our results we suggested that the stable carbon and hydrogen isotope signatures of CH3Cl could potentially be utilized to determine the origin of CH3Cl detected on Mars by distinguishing between terrestrial contamination, meteoritic infall and indigenous Martian sources. Thus for future planetary missions CH3Cl could be an important target compound for constraining the origin of any organics found.
Publications
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(2011): Methyl chloride and C2-C5 hydrocarbon emissions from dry leaf litter and their dependence on temperature. Atmospheric Environment, 45, 3112-3119
Derendorp, L., Holzinger, R., Wishkerman, A., Keppler, F., Röckmann, T.
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(2012): Methyl chloride emissions from halophyte leaf litter: Dependence on temperature and chloride content. Chemosphere, 87, 483-489
Derendorp, L., Wishkerman, A., Keppler, F., McRoberts, W.C., Holzinger, R., Röckmann, T.
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(2012): Stable hydrogen-isotope analysis of methyl chloride emitted from halophytic plants. Atmospheric Environment , 62, 584-592
Greule, M., Huber, S.G., Keppler, F.
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(2013): Hydrogen and carbon isotope fractionation during degradation of chloromethane by methylotrophic bacteria. MicrobiologyOpen, 2, 893-900
Nadalig, T., Greule, M., Bringel, F., Vuilleumier, S., Keppler, F.
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(2014): Abiotic methanogenesis from organosulfur compounds under ambient conditions. Nature Communications, 5, 4205
Althoff, F., Benzing, K., Comba, P., McRoberts, W.C., Boyd, D.R., Greiner, S., Keppler, F.
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(2014): Characterisation of NO production and consumption: new insights by an improved laboratory dynamic chamber technique. Biogeosciences, 11, 5463-5492
Behrendt, T., Veres, P. R., Ashuri, F. Song, G., Flanz, M., Mamtimin, B., Bruse, B., Williams, J. Meixner, F. X.
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(2014): Chloromethane release from carbonaceous meteorite affords new insight into Mars lander findings. Scientific Reports, 4, 7010
Keppler, F., Harper, D.B., Greule, M., Ott, U., Sattler, T., Schöler, H.F., Hamilton, J.T.G.
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(2014): Probing the diversity of chloromethane-degrading bacteria by comparative genomics and isotopic fractionation. Frontiers in Microbiology, 5, 523
Nadalig, T., Greule, M., Bringel, F., Keppler, F., Vuilleumier, S.
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(2015): Dimethyl sulfide in the Amazon rain forest. Global Biogeochemical Cycles, 29
Jardine, K., Yañez-Serrano, A.M., Williams, J., Kunert, N., Jardine, A., Taylor, T., Abrell, L., Artaxo, P., Guenther, A., Hewitt, C..N., House, E., Florentino, A.P., Manzi, A., Higuchi, N., Kesselmeier, J., Behrendt, T., Veres, P.R., Derstroff, B., Fuentes, J.D., Martin, S.T., Andreae, M.O.
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(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, 426-437
McRoberts, W.C., Keppler, F., Harper, D.B., Hamilton, J.T.G.
