Concentrations and isotope ratios of helium and other noble gases in the Earth’s atmosphere during 1978–2011

摘要: Abstract The evolution of the atmospheric noble gas composition during past few decades has hardly been studied because, in contrast to many other gases, systematic time-series measurements have not available. Based on theoretical considerations, isotope is assumed be stable time scales up about 10 6  yrs, with potential exception anthropogenic changes predicted for He concentration and 3 He/ 4 ratio. However, experimental assessments are controversial. To empirically test these assumptions predictions, we analysed samples Cape Grim Air Archive, a well-defined archive marine boundary layer air southern hemisphere. resulting series 20 Ne, 40 Ar, 86 Kr 136 Xe concentrations Ne/ 22 Ne Ar/ 36 Ar ratios 1978–2011 demonstrate stability this interval. data indicate decrease same interval at mean rate 0.23 – 0.30 ‰ per yr. This result consistent most model predictions ratio associated mining burning fossil fuels.