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

At Trinidad, California we observed elevated CO2concentrations and concomitant lowered O2levels coincident with forest fires 70 km distant (from 10/8/99 to 10/21/99). The precision of our O2data, ±1 µmol O2/mol dry air, revealed the reduction of atmospheric oxygen resulting from the combustion of biomass, and the stoichiometric ratios (−O2/CO2) of the wildfire emissions. Estimates of daily −O2/CO2ratios were obtained by regression of CO2against corresponding O2data (R² 0.86 to 0.96). Daily −O2/CO2ratios changed from 1.15 to 1.41 on a particularly smoky day that coincided with elevated levels of CH4and increased CH4/CO2ratios. The change to a higher ratio during smoky conditions illustrates the association between changing emissions and −O2/CO2ratios, possibly due to changing wildfire dynamics.