HR: 17:10h
AN: A22G-05    [PDF]
TI: Development of a Chemiluminescence Method for Gas-Phase HO$_{2}$ Detection
AU: * Zheng, J
EM: juzheng@ic.sunysb .edu
AF: State University of New York at Stony Brook, Marine Sciences Research Center Stony Brook University, Stony Brook, NY 11794-5000 United States
AU: Lloyd, J
EM: LloydJ@oldwestbury.edu
AF: State University of New York at Old Westbury, Chemistry Department PO Box 210, Old Westbury, NY 11568 United States
AU: Springston, S
EM: srs@bnl.gov
AF: Brookhaven National Laboratory, Atmospheric Sciences Division Building 815E, Upton, NY 11973 United States
AB: Hydroperoxyl Radical (HO$_{2}$) is a highly reactive intermediate species that participates in photochemical processes in the troposphere. Accurate measurement of HO$_{2}$ will facilitate the verification of the ozone production mechanism used by the atmospheric chemistry community. HO$_{2}$ is also the major source of H$_{2}$O$_{2}$, which is responsible for the oxidation of SO$_{2}$ in droplets. Here, we describe a new HO$_{2}$ detection method based on flow injection analysis (FIA) with a chemiluminescence detector. Gas-phase HO$_{2}$ is first scrubbed into a pH 9 borax buffer solution, then injected into a chemiluminescence detector, where HO$_{2}$ and its conjugate base O$_{2}$$^{-}$ react with MCLA, a synthetic analog of the luciferin from the crustacean Cypridina, to emit light at 465 nm. This technique shows high sensitivity (DL = 0.1 nM in liquid phase or 1 pptv in gas phase) and selectivity for the HO$_{2}$ / O$_{2}$$^{-}$ system. A unique feature of our technique is the calibration with a radiolytic method that uses a $^{60}$Co gamma ray source to quantitatively produce stable aqueous HO$_{2}$ / O$_{2}$$^{-}$ standards. This calibration method is highly reproducible, producing an instrument response that varies less than 5% from day to day. We tested our instrument in the meteorology field at Brookhaven National Laboratory (BNL), which is considered a clean remote rural site with background ozone levels about 30 ppbv. On July 17, 2003, a clear sunny day, with a steady NW wind, HO$_{2}$ started to build up after sunrise and reached a maximum of 9 pptv at about 3 pm local time, approximately two hours after the maximum solar intensity. Our technique has the advantages of simplicity, low cost and ease of operation. It is especially suitable for field measurements, where space and energy resources are usually limited.
DE: 0365 Troposphere--composition and chemistry
DE: 0394 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting