Decadal time series of tropospheric abundance of N2O isotopomers and isotopologues in the Northern Hemisphere obtained by the long‐term observation at Hateruma Island, Japan

摘要: [1] Decadal time series and short-term temporal variations in mixing ratio of atmospheric nitrous oxide (N2O) abundance its isotopomers (14N15N16O 15N14N16O) isotopologue (14N14N18O) relative to 14N14N16O have been observed for the first Northern Hemisphere at Hateruma Island (HAT), Japan during 1999–2010 by monthly air sampling. Results show that bulk nitrogen isotope δ15Nbulk decreased rate −0.023 ± 0.006‰ yr−1, although N2O increased about 0.7 nmol mol−1 yr−1 (ppb yr−1) period. Isotope budget calculation with trend supports earlier estimates showing isotopically light sources such as agriculture industry contribute increase N2O. However, decrease is slightly smaller magnitude than rates obtained virtually 20th century from firn polar regions surface Southern (Tasmania Antarctica), which suggests greater contribution 15 N-enriched recent years or extra-polar Hemisphere. In contrast, oxygen (δ18O) intramolecular 15N site preference (SP, difference between ratios central terminal atoms) showed no significant trends, contrary previous reports. seasonal variation exists δ15Nbulk, δ18O, SP HAT past decade within limits our sampling frequency analytical precision.