The oxygen to carbon dioxide ratios observed in emissions from a wildfire in northern California

At Trinidad, California we observed elevated CO 2 concentrations and concomitant lowered O 2 levels coincident with forest fires 70 km distant (from 10/8/99 to 10/21/99). The precision of our O 2 data, ±1 µmol O 2 /mol dry air, revealed the reduction of atmospheric oxygen resulting from the combustion of biomass, and the stoichiometric ratios (−O 2 /CO 2 ) of the wildfire emissions. Estimates of daily −O 2 /CO 2 ratios were obtained by regression of CO 2 against corresponding O 2 data (R² 0.86 to 0.96). Daily −O 2 /CO 2 ratios changed from 1.15 to 1.41 on a particularly smoky day that coincided with elevated levels of CH 4 and increased CH 4 /CO 2 ratios. The change to a higher ratio during smoky conditions illustrates the association between changing emissions and −O 2 /CO 2 ratios, possibly due to changing wildfire dynamics.