Short-term variability of atmospheric helium revealed through a cryo-enrichment method

Abstract. Tropospheric helium variations are tightly linked to CO2 due the co-emission of He and from natural-gas burning. Recently, Birner et al. (2022a) showed that global consumption natural gas has measurably increased content atmosphere. Like CO2, is also predicted exhibit complex spatial temporal variability on shorter timescales, but measurements these short-term lacking. Here, we present development an improved delivery purification system for semi-continuous mass spectrometric measurement atmospheric He-to-nitrogen ratio (He/N2). The method replaces chemical getter used previously by (2021, 2022a) preconcentrate in air stream with a cryogenic trap which can be more simply regenerated heating improves precision 22 per meg (i.e., 0.022 ‰) 10 min (1σ). Using this “cryo-enrichment” method, measured He/N2 ratios ambient at La Jolla (California, USA) over 5 weeks 2022. During period, was strongly correlated concentrations, as expected anthropogenic emissions, diurnal cycle 450–500 (max–min) caused sea–land breeze pattern local winds, modulates influence pollution sources.