| Details: |
Methane (CH4) is a significant greenhouse gas with a global warming potential 28 times greater than carbon dioxide (CO2) over a 100-year period. It originates from both natural sources, such as wetlands and geological seepage, and anthropogenic activities, including agriculture and fossil fuel use. The isotopic composition of CH4, particularly the ratios of carbon-13 to carbon-12 (δ13C-CH4) and deuterium to hydrogen (δD-CH4), provides insights into its sources and sinks. Each CH4 source has a distinct isotopic signature influenced by the substrates and formation conditions. Removal processes, primarily oxidation by hydroxyl radicals (OH), chlorine (Cl), and soil microbes, also affect the isotopic composition of atmospheric CH4. The global isotopic composition of atmospheric CH4 reflects the combined signatures of its sources, adjusted for removal processes. Variations in isotopic composition can indicate changes in source mix, removal rates, or imbalances between sources and sinks. This isotopic balance helps constrain the global CH4 budget and track changes in source contributions over time. However, uncertainties arise due to spatial and temporal variability in isotopic signatures, complicating the assignment of representative values to different sources. Despite these challenges, isotopic measurements remain crucial for studying the global CH4 cycle. Recent studies have identified shifts in global CH4 sources over recent decades, with significant implications for climate change and air quality. Clumped isotopologues, such as 13CDH3 and 12CD2H2, offer additional constraints on CH4 sources, though their measurement poses technical challenges. Advances in high-resolution isotope-ratio mass spectrometry have improved the ability to resolve these small mass differences, enhancing the study of CH4 clumped isotopes and their role in the environment. |