LOSS OF UNBURNED-FUEL HYDROCARBONS FROM COMBUSTION AEROSOLS DURING ATMOSPHERIC TRANSPORT

Urban, coal-fired power plant, coastal, and marine aerosols were compa red in terms of pyrogenic (PHC) and unburned-fuel (FHC) hydrocarbon co ntributions. It was observed that the relative content of FHC decrease d from near combustion source to remote samples. Artificially irradiat ed and aerated combustion aerosols also exhibited selective loss of FH C along with photoreactive compounds. Furthermore, different correlati on to soot content has been obtained for the two fractions in marine a erosols. We suggest that PHC and FHC present a decoupled association t o soot Whereas soot-compound interactions protect PHC from major trans formations, FHC occur more exposed to vapor/particle partitioning. Thi s is consistent with the decoupled size distribution of the two fracti ons in aged aerosols: PHC mostly occur in small (soot-rich) particles whereas FHC distribute onto all sizes. Our findings are relevant to so urce reconciliation modeling and aerosol chemistry.