HR: 1340h
AN: A53C-0908    [Abstracts]
TI: Behavior of the Hydroxyl and Hydroperoxy Radicals in a Smog Chamber Study
AU: * Ren, X
EM: ren@essc.psu.edu
AF: Department of Meteorology, Pennsylvania State University, 503 Walker Building, University Park, PA 16802 United States
AU: Mao, J
EM: jzm145@psu.edu
AF: Department of Meteorology, Pennsylvania State University, 503 Walker Building, University Park, PA 16802 United States
AU: Kang, E
EM: euk111@psu.edu
AF: Department of Meteorology, Pennsylvania State University, 503 Walker Building, University Park, PA 16802 United States
AU: Metcalf, A R
EM: arm199@psu.edu
AF: Department of Meteorology, Pennsylvania State University, 503 Walker Building, University Park, PA 16802 United States
AU: Mitchell, M
EM: mjm613@psu.edu
AF: Department of Meteorology, Pennsylvania State University, 503 Walker Building, University Park, PA 16802 United States
AU: Lesher, R L
EM: lesher@essc.psu.edu
AF: Department of Meteorology, Pennsylvania State University, 503 Walker Building, University Park, PA 16802 United States
AU: Shirley, T
EM: trs161@psu.edu
AF: Department of Meteorology, Pennsylvania State University, 503 Walker Building, University Park, PA 16802 United States
AU: Brune, W H
EM: brune@essc.psu.edu
AF: Department of Meteorology, Pennsylvania State University, 503 Walker Building, University Park, PA 16802 United States
AU: Carter, W P
EM: carter@cert.ucr.edu
AF: Center for Environmental Research and Technology, University of California at Riverside, CE-CERT, University of California, Riverside, CA 92521 United States
AU: Tonnesen, G
EM: tonnesen@mail.cert.ucr.edu
AF: Center for Environmental Research and Technology, University of California at Riverside, CE-CERT, University of California, Riverside, CA 92521 United States
AU: Chien, C
EM: chien@cert.ucr.edu
AF: Center for Environmental Research and Technology, University of California at Riverside, CE-CERT, University of California, Riverside, CA 92521 United States
AU: Fitz, D
EM: dfitz@cert.ucr.edu
AF: Center for Environmental Research and Technology, University of California at Riverside, CE-CERT, University of California, Riverside, CA 92521 United States
AU: Malkina, I
EM: irina@cert.ucr.edu
AF: Center for Environmental Research and Technology, University of California at Riverside, CE-CERT, University of California, Riverside, CA 92521 United States
AU: Sauer, C
AF: Center for Environmental Research and Technology, University of California at Riverside, CE-CERT, University of California, Riverside, CA 92521 United States
AU: Bumiller, K
EM: bumiller@cert.ucr.edu
AF: Center for Environmental Research and Technology, University of California at Riverside, CE-CERT, University of California, Riverside, CA 92521 United States
AU: Bufalino, C
EM: cbufalin@cert.ucr.edu
AF: Center for Environmental Research and Technology, University of California at Riverside, CE-CERT, University of California, Riverside, CA 92521 United States
AB: The hydroxyl radical (OH) and the hydroperoxyl radical (HO$_{2}$), together called HO$_{x}$, are significant reactants in the production of pollutants such as ozone and fine particles in real and simulated environments. The concentrations of OH and HO$_{2}$ and the OH reactivity were measured as part of a smog chamber study to assess the sensitivity of ozone on volatile organic compounds (VOC) and nitrogen oxides (NO$_{x}$). The experiments were carried out in the EPA next-generation smog chamber at University of California, Riverside, CA in September and October 2003. A matrix of chamber experiments were performed at graduated levels of VOC and NO$_{x}$ designed of replicate the range of VOC and NO$_{x}$ concentrations typically found in urban and rural environments. The OH and HO$_{2}$ radicals were measured by laser-induced fluorescence (LIF) in addition to the standard chamber measurements of O$_{3}$, VOCs, NO, NO$_{2}$, HNO$_{3}$, HCHO and H$_{2}$O$_{2}$. Box models with four different photochemical mechanisms were used to calculate the simulated concentrations of OH, HO$_{2}$ and other species for each chamber experiment. The model simulations were compared with the measurements in the smog chamber. While OH and HO$_{2}$ generally show the expected behavior, three interesting observations emerge. First, modeled HO$_{2}$ concentrations were generally lower than the observations, which was consistent with the underestimation of observed H$_{2}$O$_{2}$ and O$_{3}$. Second, OH budget analysis show that additional OH sources are required to balance the observed OH sinks. Third, simultaneous observations of dark OH and HO$_{2}$ after the light was turned off suggest the presence of unidentified dark HO$_{x}$ sources. The evidence supporting these observations will be discussed.
DE: 0317 Chemical kinetic and photochemical properties
DE: 0345 Pollution--urban and regional (0305)
DE: 0365 Troposphere--composition and chemistry
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting