UC Irvine

Measurements of atmospheric N//2O concentrations in and around Ann Arbor, Michigan, between August 1976 and September 1977 yielded 329. 5 ppb (parts per billion) (mole fraction in whole air samples) as the average with a standard deviation of 3. 3 ppb. No seasonal or overall trend is discernible. Small, marginally significant diurnal variations of N//2O concentrations in the lowest 0. 5 m of atmosphere can be seen in our data. Gas collectors applied to soils near our laboratory provided evidence that soils can consume atmospheric N//2O under some conditions. Soils were seen to be N//2O sources more often than sinks. Stronger source activity was evident in compost piles. Exhaust samples taken from several conventional vehicles showed less than ambient N//2O concentrations, while catalytic converter equipped autos produce N//2O. Samples of steaming volcanic vent air from Hawaii indicate that volcanoes are probably a source of atmospheric N//2O, although emissions at the Sulphur Bank contain much less than ambient values of N//2O. All measurements were made by electron capture-gas chromatography; techniques and equipment are described.