Gas‐chromatographic measurements of the atmospheric oxygen/nitrogen ratio at Hateruma Island and Cape Ochi‐ishi, Japan

The O 2 /N 2 ratios were determined of air samples collected at Hateruma Island (lat 24°3′N, long 123°49′E) from July 1997 to December 2001, and at Cape Ochi‐ishi (lat 43°10′N, long 145°30′E) from December 1998 to December 2001. The O 2 /N 2 ratios, based on gas‐chromatographic analysis, clearly showed decreasing trends and seasonal variations, increasing in spring and summer, and decreasing in autumn and winter. The amplitudes of the seasonal O 2 /N 2 cycles for Ochi‐ishi were twice as large as those for Hateruma. The average rates of decrease were 18.4 ± 1.4 per meg yr −1 over a 4‐year period (1998–2001) for Hateruma, and 19.2 ± 1.6 per meg yr −1 over a 3‐year period (1999–2001) for Ochi‐ishi.