甲烷稳定同位素分析技术与标准物质的研究进展OA

Methane(CH4)is one of the important short-lived greenhouse gases affecting global climate change.Owing to its diverse emission sources,accurately identifying different methane sources and understanding the migration,transformation,and oxidation processes were of great significance for developing effective methane mitigation strategies.The stable isotopic composition of CH4 could preserve information on isotope fractionation occurring during different methane formation pathways,migration and transformation processes,and oxidation reactions.Among these isotopic characteristics,δ13 C and δD had become important indicators for methane source attribution and the study of methane cycling processes.This review presented a systematic assessment of recent advances in CH4 stable isotope analysis techniques and the corresponding reference materials.The analytical techniques covered low-temperature trapping-combustion conversion,gas chromatography-combustion-isotope ratio mass spectrometry(GC-C-IRMS),high-resolution isotope ratio mass spectrometry(HR-IRMS),tunable diode laser absorption spectroscopy(TDLAS),quantum cascade laser absorption spectroscopy(QCLAS),and cavity ring-down spectroscopy(CRDS).For each technique,the operational principle,analytical performance,and typical application scenarios were discussed.Different techniques exhibited distinct advantages and limitations due to differences in analytical principles,measurement procedures,and detection mechanisms.In general,mass spectrometry-based methods exhibited high measurement precision and reliable analytical performance,making them important approaches for high-precision CH4 isotope analysis in laboratory studies.However,these methods usually involved complicated sample preparation procedures and require expensive analytical instruments,which may limit their application in rapid measurements and field observations.In contrast,optical spectroscopic methods had the advantages of rapid response,convenient operation,and continuous online monitoring capability,making them suitable for in situ observations and dynamic monitoring of methane isotope variations in ambient air and other gas matrices.Nevertheless,the measurement accuracy of optical methods could be affected by gas matrix effects,spectral interferences,and calibration strategies.Reference materials were essential for ensuring the accuracy and comparability of CH4 isotope measurements.At present,δ13 C and δD values were mainly indirectly traceable to the Vienna Pee Dee Belemnite(VPDB)and Vienna Standard Mean Ocean Water-Standard Light Antarctic Precipitation(VSMOW-SLAP)reference scales.However,methane isotope reference gases that closely matched the composition and matrix of real samples are still lacking.Future research should focus on the development of CH4 isotope reference materials covering different concentration ranges and matrix conditions,together with the improvement of related metrological systems,to enhance the comparability of measurement results among different analytical platforms.