ABSTRACT

An analytical system to separate N₂O in the air was developed to measure the δ¹⁵N value and concentration of N₂O. The system was designed so that δ¹⁵N value and concentration of ca. 1 μmol N₂O from ca. 60 l air could be measured with the accuracy of ±0.2‰ and ±10 ppbv, respectively. Air samples were collected at three individual sites in Japan. The average values of δ¹⁵N and concentration of N₂O for 32 samples with the standard deviation were +8.1 ± 1.0‰ and 316 ± 14 ppbv, respectively. The diversity of the observed data was attributed to the change in the mixing ratio of air masses of different characteristics. A discussion was made on the global cycle of N₂O. Bacterial reduction of N₂O was proposed to be the major consuming process of N₂O on the Earths surface.