| Carbon monoxide (CO), one of the most important prevalent trace gases in the troposphere, controls the oxidizing capacity of the atmosphere. In this project, whole air samples were collected quarterly (March, June, September and December) in the remote Pacific basin during 1995--2001. Each season, samples were collected over a wide global latitudinal range (710 N to 47°S). The whole air samples were returned to the laboratory and analyzed for a suite of gases, including CO.; CO analysis consisted of gas chromatographic separation of air constituents on a Molecular Sieve 5A column and subsequent reduction of CO to methane on a nickel catalyst. The reduced CO was then detected on a flame ionization detector. Quantified standards were analyzed in a similar manner and used to assign mixing ratios to the whole air samples. The quantified whole air samples were then analyzed using a 1-dimensional 16-box model of the atmosphere. The box model divided the surface of the earth into 16 latitudinal bands of equal surface area.; Between 1995 to 2001, the yearly mean for the northern hemisphere (NH) was roughly twice as large as the yearly mean of the southern hemisphere (SH). The greatest latitudinal gradient between the NH and the SH was found in March and the smallest gradient was found in September. This was consistent with the seasonal variation of OH.; The global growth rate of CO has been reported as decreasing in the early 1990's. In this research study, it was found that CO is decreasing by 1.4 +/- 0.2 ppbv CO year-1 globally, 2.1 +/- 0.3 ppbv CO year-1 in the NH and 0.7 +/- 0.2 ppbv CO year-1 in the SH. Mixing ratios from samples collected on the California coast were removed from the data as they gave enhanced background levels of CO due to local contamination. The hemispheric growth trends were driven by enhanced northern latitude CO mixing ratio in 1998 due to abnormally high boreal forest biomass burning in Canada, and in southern equatorial latitudes by biomass burning in Indonesia during late 1997 and early 1998. |
