The authors have made field measurements of methane fluxes from rice paddies, fresh water lakes, and saltwater marshes to infer estimates of the size of these sources of atmospheric methane. The rice-paddy measurements, the first of their kind, show that the principal means of methane escape is through the plants themselves as opposed to transport across the water-air interface via bubbles or molecular diffusion. Nitrogen-fertilized plants release much more methane than unfertilized plants but even these measured rates are only one fourth as large as those inferred early by Koyama and on which all global extrapolations have been based to date. They also compare their measured methane fluxes from lakes and marshes to similar earlier data and find that extant data and flux-measurement methods are insufficient for reliable global extrapolations.

To allow increased understanding of the global budget of atmospheric methane, individual methane sources require investigation. We have measured methane emissions from a California rice paddy during the entire 1982 growing season. A very strong seasonal dependence was observed. -from Authors

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.