A comprehensive hydrocarbon database was obtained at 6 sites in the Atlanta metropolitan area during the Bummer of 1990. amples were collected in stainless steel canisters and analyzed for 54 hydrocarbon species plus total non-methane organic compounds (TNMOC). he contributions of the major sources of TNMOC at each of the 6 sites were estimated through a procedure called Chemical MASS Balance (CMB) receptor modeling. patial variability of the source contributions is discussed. esults of the CMB analysis for one of the sites are compared with the emission inventory for Atlanta using several different approaches. he inventory highway mobile source estimate tends to be smaller than the minimum ambient data-derived highway mobile source estimate, and the inventory area plus point source estimate tends to be larger than the maximum ambient data-derived estimate for the data set examined. owever, these source estimates are interdependent to some extent. imitations of these comparisons are discussed.