HR: 16:30h
AN: A24B-03    [Abstracts]
TI: Photochemical Formation of Fe(II) in Aerosols Collected in Okinawa, Japan
AU: * Okada, K
EM: k058552@eve.u-ryukyu.ac.jp
AF: Graduate School of Engineering and Science, University of the Ryukyus, 1 Senbaru Nishihara-cho, Okinawa, 903-0213 Japan
AU: Kuroki, Y
EM: k058305@eve.u-ryukyu.ac.jp
AF: Graduate School of Engineering and Science, University of the Ryukyus, 1 Senbaru Nishihara-cho, Okinawa, 903-0213 Japan
AU: Nakama, Y
EM: k058313@eve.u-ryukyu.ac.jp
AF: Graduate School of Engineering and Science, University of the Ryukyus, 1 Senbaru Nishihara-cho, Okinawa, 903-0213 Japan
AU: Arakaki, T
EM: arakakit@sci.u-ryukyu.ac.jp
AF: Graduate School of Engineering and Science, University of the Ryukyus, 1 Senbaru Nishihara-cho, Okinawa, 903-0213 Japan
AU: Tanahara, A
EM: tanahara@lab.u-ryukyu.ac.jp
AF: Instrument Research Center, University of the Ryukyus, 1 Senbaru Nishihara-cho, Okinawa, 903-0213 Japan
AB: Particulate iron is transferred to the atmosphere by wind, volcanic activity, and anthropogenic activities. Iron concentrations are relatively high in aerosols. Since iron can undergo red-ox reactions, iron can change chemical compositions of aerosols. Some researchers reported that Fe(II) was produced by irradiation in suspended aerosol solutions. However, detailed mechanisms of Fe(II) formation are not clearly understood. We have studied Fe(II) photochemical formation in aqueous extracts of aerosol particles collected in Okinawa, Japan, using monochromatic irradiation system. We observed Fe(II) formation when the aerosol extracts were irradiated, and photoformed Fe(II) concentrations reached 80 to 100 percent of the total dissolved iron concentrations in the aerosol extracts. Initial rates of Fe(II) photoformation were very fast (ca. 20 microM/h). The results suggested that Fe(II) is photochemically formed within a short time while aerosols are floating in the atmosphere and aqueous-phase iron exists almost as Fe(II) in the aerosols. Quantum yield of Fe(II) photoformation at 313 nm in aerosol extracts was about 0.078 mole/einstein. Quantum yield values varied, depending on aerosol samples which were collected different time periods. It is suspected that iron speciation was different among the aerosol samples. Based on the relationship between quantum yields and wavelengths, we found that quantum yields were higher around 340 nm and decreased over 400 nm. Therefore it was suggested that photochemical formation of Fe(II) is strongly influenced by the substances that absorb light between 300 to 400 nm.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0317 Chemical kinetic and photochemical properties
DE: 0365 Troposphere: composition and chemistry
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005