HR: 0830h
AN: A11F-0046    [PDF]
TI: Hydroxyl Radical Formation in Solutions of Fe(III) and Hydrogen Peroxide - Impact of Freezing and Thawing Process
AU: * Arakaki, T
EM: arakakit@sci.u-ryukyu.ac.jp
AF: University of the Ryukyus, 1 Senbaru, Nishihara-cho, Okinawa, 903-0213 Japan
AU: Kinjo, M
EM: rocko116@hotmail.com
AF: University of the Ryukyus, 1 Senbaru, Nishihara-cho, Okinawa, 903-0213 Japan
AU: Shiroma, K
EM: alwayskayo@hotmail.com
AF: University of the Ryukyus, 1 Senbaru, Nishihara-cho, Okinawa, 903-0213 Japan
AU: Shibata, M
EM: brushroad9@infoseek.jp
AF: Japan Science and Technology Corporation, The Center for Forest Decline Studies, Faculty of Integrated Arts and Sciences, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima, Hiroshima, 739-8521 Japan
AU: Miyake, T
EM: tmiyake@chikyu.ac.jp
AF: Research Institute for Humanity and Nature (RIHN), 335 Takashima-cho, Marutamachi-dori Kawaramachi nishi-iru, Kamigyo-ku, Kyoto, 602-0878 Japan
AU: Hirakawa, T
EM: hirakawa@mail.towakagaku.co.jp
AF: Towa Kagaku Co., Ltd., 6-5 Naka-ku Funairimachi, Hiroshima, Hiroshima, 730-0841 Japan
AU: Sakugawa, H
EM: hsakuga@hiroshima-u.ac.jp
AF: Graduate School of Biosphere Sciences, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima, Hiroshima, 739-8521 Japan
AB: Hydroxyl radical formation was studied by detecting concentration of formate in solutions of hydrated formaldehyde, HOOH, and Fe(III) or Cu(II). Oxidation of hydrated formaldehyde by OH radical is known to form formate. Formate formation increased by about 4 times when the solution underwent freezing and thawing. Although the reaction mechanisms are not clearly understood, we believe that the concentration effect of freezing enhanced the catalytic reactions between HOOH and Fe(III) or Cu(II) and the reduction of transition metals, i.e., Fe(III) to Fe(II) and Cu(II) to Cu(I). The concentration effect also enhanced reactions between Fe(II) and HOOH or Cu(I) and HOOH, which generated OH radical (freeze-Fenton reaction). Study of the effects of pH showed that formate formation was the highest at pH = 4.0, indicating that the speciation of Fe(III) affected the formation of formate. Concentration-dependent experiments demonstrated that Fe is probably the limiting agent under typical atmospheric conditions. Our results suggested that the freezing process could be an important source of hydroxyl radical in high cloud, winter fog, rime ice and freezing acidic rain, and more importantly, a potentially additional oxidation mechanism in the atmosphere.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0317 Chemical kinetic and photochemical properties
DE: 0322 Constituent sources and sinks
DE: 0365 Troposphere--composition and chemistry
DE: 0399 General or miscellaneous
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting