| Nitrous oxide (N{dollar}sb2{dollar}O), which plays an important role in both greenhouse warming and in stratospheric ozone depletion, is increasing by about 0.2 ppb per year. The sources of this compound are poorly quantified. Sulfur hexafluoride (SF{dollar}sb6),{dollar} an entirely anthropogenic compound, is per molecule the strongest greenhouse gas known, and it too is increasing in the atmosphere.; For this research project, a gas chromatography/electron capture detection (GC/ECD) system was built to measure N{dollar}sb2{dollar}O and SF{dollar}sb6{dollar} from the Cooperative Air Sampling Network of NOAA/CMDL--over 40 globally dispersed sites at which weekly air samples are collected in glass flasks. This GC system analyzes a 10mL air sample for N{dollar}sb2{dollar}O at {dollar}sim{dollar}0.1% precision and for SF{dollar}sb6{dollar} at {dollar}sim{dollar}1.0% precision. In the long-term, these network data will be used to help us estimate N{dollar}sb2{dollar} sources on a regional level. The SF{dollar}sb6{dollar} data will help us to quantify variations in interhemispheric mixing, and to characterize the history of the air masses being sampled at our network sites.; Thus far, about six months of data have been collected from a subset of network sites. The flask data are consistent with data from other NOAA sampling programs. As expected, N{dollar}sb2{dollar}O levels appear relatively well mixed globally, except for a 1 ppb interhemispheric gradient and elevated mixing ratios at some continental sites. For SF{dollar}sb6,{dollar} a quadratic growth rate of 6.5% yr{dollar}sp{lcub}-1{rcub}{dollar} was determined from archived air samples, and an interhemispheric difference of 0.27 ppt was calculated from latitudinal profiles. Using these profiles in a two-box model, a 1996 emission rate of 5.9 Gg SF{dollar}sb6{dollar} yr{dollar}sp{lcub}-1{rcub}{dollar} and an interhemispheric exchange time of 1.3 years were derived.; N{dollar}sb2{dollar}O and SF{dollar}sb6{dollar} were also measured on two research cruises, providing high resolution latitudinal profiles over both the Atlantic and Pacific oceans. The measurements of N{dollar}sb2{dollar}O, in the atmosphere and surface water, are combined with data from previous cruises to estimate the global ocean-to-atmosphere flux of N{dollar}sb2{dollar}O (1 to 4 Tg N yr{dollar}sp{lcub}-1{rcub},{dollar} using four different air-sea exchange models). SF{dollar}sb6{dollar} was examined for its use as a tracer of the oceanic physical processes that affect our air-sea flux calculations. |
