ANALYSIS OF METHANE CLUMPED ISOTOPES WITH 253 ULTRA

Methane has important environmental and resource implications as it is a widespread and profound representative of greenhouse gases while generating large amounts of energy. The sources of methane in different environments have important implications for estimating carbon cycle processes at global scales. The sources are generally classified as thermogenic, biogenic, and abiotic. Clumped isotopologues abundances of methane (¹³CH₃D and ¹²CH₂D₂) can improve the reliability of formation temperature reconstructions and even indications of kinetic isotopic effects, post-generation, and other processes. The combination of methane bulk isotopes (δ¹³C-CH₄ and δD-CH₄) and clumped isotopes (∆¹³CH₃D and ∆¹²CH₂D₂) provides new perspectives on source estimation, which is significant for studying the genesis of methane.

We report a commissioning dataset of methane clumped isotope measurement using High-Resolution Isotope Ratio Mass Spectrometry (Thermo Scientific 253 Ultra). Influences factors on the measurement process, such as temperature & humidity, slit quality, fragmentation rate, and bellow effect, are discussed separately, where we consider the impact of temperature & humidity and slit quality are not negligible. The calibration of the results was carried out using 500℃, 400℃, and 300℃ heated equilibrium gas experiments. The fitting results are comparable to the previous work. In addition, we reported an improved pretreatment system can purify the natural samples for ~15% concentration and verified its purification and fractionation with acceptable results. Natural Samples (e.g., natural gas and lake emission gas) clumped isotopes results exhibit typical thermogenic and biogenic characteristics here.