Emissions of methyl chloroform (CH3CCl3) from biomass burning and the tropospheric methyl chloroform budget

The only known sources of atmospheric methyl chloroform are industrial prod uction and biomass burning. With the phase-out of industrial methyl chlorof orm production the atmospheric burden of methyl chloroform is rapidly decli ning. Consequently the potential importance of nonindustrial sources is inc reasing. Up to now only one experimental investigation of methyl chloroform emissions from biomass burning has been published. Here laboratory studies of methyl chloroform emission from wood burning are presented. The emissio n ratios relative to carbon dioxide and carbon monoxide are 12.7 +/- 2.6 x 10(-8) and 15.6 +/- 3.3 x 10(-7), respectively. Although based on a limited number of measurements, they strongly suggest that methyl chloroform emiss ions from biomass burning are at the lower end of previous estimates. The i mpact of these emissions on the chemistry of the atmosphere will be margina l. However, reliable knowledge of the biomass burning source strength will be essential for a detailed analysis of the trend of atmospheric methyl chl oroform concentrations.