Graphical Abstract

Umezawa, T., S. J. Andrews, and T. Saito, 2020: A cryogen-free automated measurement system of stable carbon isotope ratio of atmospheric methane. J. Meteor. Soc. Japan, 98, 115-127. Abstract with highlights

Plain Language Summary: Methane (CH4) plays an important role in climate change and atmospheric chemistry. The stable carbon isotope ratio of atmospheric methane (δ13C-CH4) is useful for separating contributions of different CH4 source types. We set up a new measurement system for δ13C-CH4, optimized for the automated analysis of air samples. The system is operated with no use of cryogens (e.g., liquid nitrogen) and attained reproducibility sufficient to analyze atmospheric variations (~0.1‰). Automated continuous measurements of ambient air characterized imprint of local methane sources well. Future measurement operation will provide a large number of atmospheric δ13C-CH4 data.