This project seeks to evaluate the relative importance of the various sources of atmospheric formaldehyde, formic acid and acetic acid at remote continental locations within the US from the isotopic composition of collected samples. At chosen locations: (a) The carbon isotopic composition of atmospheric formaldehyde will be determined and compared to the compositions of the principal sources at those sites - methane and natural non-methane hydrocarbons. The relative contributions of these sources to the carbon flux through formaldehyde to carbon monoxide should thus be evaluated. (b) The carbon isotopic compositions of formic acid and non-formic light mono-carboxylic acids will be determined and compared to each other, to formaldehyde and to other major organic emissions, both anthropogenic and natural, to deduce likely source contributions. Specifically the project will refine existing collection and work-up techniques, determine the 13C and 14C content of the three atmospheric species, estimate the 13C content of local plant emissions, and determine the relative anthropogenic influence.
