Interlaboratory comparison of delta C-13 and delta D measurements of atmospheric CH4 for combined use of data sets from different laboratories

摘要

We report results from a worldwide interlaboratory comparison of samples among laboratories that measure (or measured) stable carbon and hydrogen isotope ratios of atmospheric CH4 (delta C-13-CH4 and delta D-CH4). The offsets among the laboratories are larger than the measurement reproducibility of individual laboratories. To disentangle plausible measurement offsets, we evaluated and critically assessed a large number of intercomparison results, some of which have been documented previously in the literature. The results indicate significant offsets of delta C-13-CH4 and delta D-CH4 measurements among data sets reported from different laboratories; the differences among laboratories at modern atmospheric CH4 level spread over ranges of 0.5% for delta C-13-CH4 and 13% for delta D-CH4. The intercomparison results summarized in this study may be of help in future attempts to harmonize delta C-13-CH4 and delta D-CH4 data sets from