HR: 1400h
AN: A23A-11    [Abstracts]
TI: Development of a new Method for Determination of Atmospheric Halogen Atom Concentrations
AU: * Tackett, P J
EM: ptackett@purdue.edu
AF: Purdue University Department of Chemistry, 560 Oval Drive, West Lafayette, IN 47907, United States
AU: Shepson, P B
EM: pshepson@purdue.edu
AF: Purdue University Department of Chemistry, 560 Oval Drive, West Lafayette, IN 47907, United States
AB: A flowtube reactor has been developed for the quantitative determination of atmospheric halogen atom concentrations. The technique operates by drawing atmospheric halogen atoms (Cl, Br, I) into a 20 mm diameter quartz flowtube, in which they quickly react with an introduced alkene (trifluoropropene) and NO to produce a halogenated ketone that is detected by gas chromatography with electron capture detection (GC-ECD). This method allows for the "direct" determination of atmospheric halogen atom concentrations, which have so far only been determined by indirect methods, e.g. as inferred from hydrocarbon decay rates. The fluorinated alkene reagent is utilized to increase the final product's ECD sensitivity as well as provide a compound not found in the environment (i.e. very low blanks), leading to greater overall instrument sensitivity. A solid-sorbent sample preconcentrator is used following reaction in the flow tube to increase the sample volume and allow detection of the halogenated ketone product at concentrations in the ppq and ppt range. The halogen monoxide radicals (XO) can also be determined by conversion to X via reaction with NO at the inlet. The resulting halogen atom concentration measurements allow for the greater understanding of halogen atom photochemistry in the lower troposphere. Here we show results from laboratory tests and system calibrations.
DE: 0365 Troposphere: composition and chemistry
DE: 0394 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: 2007 Joint Assembly