In this Mage proposal, the PIs propose to determine the hydrocarbon and hydrocarbon composition of air samples collected during the ASTEX/MAGE campaign. Proposed measurements include approximately 25 chlorocarbon compounds containing one or two carbon atoms and 50 or more hydrocarbons ranging in molecular weight from methane to the terpenes (C4 - C10). The overall objective is to provide information for the construction and testing of detailed photochemical models to examine the chemical cycles controlling each of the measured species and of the unmeasured reactive free radicals such as OH and Cl. The Pis propose to set up a remote laboratory in Miami, Florida where gas chromatographic analyses of grab samples obtained from aircraft will be conducted. (Note: this is a change from the originally proposed remote site of Santa Maria; see new work statement and budget sheets.) In this MAGE proposal the PIs plan to determine the hydrocarbon and halocarbon composition of air samples collected during the ASTEX/MAGE campaign. With knowledge of these concentrations, detailed photochemical models can be constructed and tested for the chemical cycles controlling each of the measured species, and also of the unmeasured reactive free radicals such as HO and Cl. Specifically, the measurements will provide data (or upper limits) on the concentrations of approximately 25 chlorocarbon compounds containing one or two carbon atoms and numerous hydrocarbons. In particular, the chlorofluorocarbon compounds and carbon tetrachloride are very long-lived (>50 years) in the atmosphere and are entirely anthropogenic. These compounds are excellent markers for air contaminated by recent injections from urban or industrial areas. Shorter-lived chlorocarbons are also excellent markers of anthropogenic activity, and the correlations among such species are useful for distinguishing between air masses mixed from multiple urban sources and homogeneous air masses subjected to different HO radical exposures. Additionally, several alkanes appear to have their primary origin in anthropogenic activities, and on occasion furnish through multiple correlations enough information to identify particular source regions.
