Identification of environmentally significant halomethanes using stable isotope techniques

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Although it has recently become more evident that terrestrial ecosystems play an important role in production, consumption and emission of volatile halogenated compounds, they are still very poorly characterized. A potentially powerful tool in the investigation of the lifecycle of halomethanes is the use of stable isotope ratios (13C/12C, 2H/1H). Variations in the carbon isotope composition (13C values) of compounds, produced and destroyed in the global carbon cycle, are often used successfully to investigate biogeochemical cycles and global source-sink relationships, as well as the underlying mechanisms. The objective of the proposed research activities as part of the DFG research unit HALOPROC is to further explore the formation of environmentally-relevant halomethanes such as chloromethane, bromomethane, iodomethane, chloroform and bromoform; and to study their biogeochemical cycles utilising a stable isotope approach. Stable isotope values of volatile halogenated compounds will be measured from a series of samples collected in semi -arid areas of South Russia. Laboratory investigations of several environmental parameters influencing the emissions of halocarbons will be conducted. Furthermore, a series of laboratory experiments with varying degrees of complexity will be conducted to gain more information about the underlying mechanisms involved in halocarbon formation.