HR: 1340h
AN: A33B-1200    [Abstracts]
TI: Determination of Bimolecular Rate Constants for Reactions of Hydroxyl Radical with Large Organic Compounds in Atmospheric Water Drops
AU: * Nakajima, H
EM: k068555@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: Anastasio, C
EM: canastasio@ucdavis.edu
AF: Department of Land, Air and Water Resources, University of California, 1 Shields Ave., Davis, CA 95616-8627, United States
AB: The hydroxyl radical (OH) is a potent oxidant in the aquatic environment. The lifetimes of many organic compounds are determined by reactions with hydroxyl radicals, and the lifetime of OH is often determined by reactions with organic compounds. Many studies have determined bimolecular rate constants for reactions between hydroxyl radical and relatively small inorganic and organic compounds, but only a few studies have determined rate constants for the reactions of OH with very large organic molecules such as atmospheric humic- like substances (HULIS). We are working to develop a competition kinetics technique to determine effective bimolecular rate constants with HULIS and other molecules. In this technique, we illuminate aqueous solutions containing three components: (1) the organic compound of interest, (2) benzoic acid (BA) as a competitive scavenger of OH, and (3) hydrogen peroxide as a source of OH. By changing the BA concentrations while maintaining the concentration of the organic compound, we can determine the lifetime of OH in the system in the absence of BA. We then use this lifetime to determine the bimolecular rate constant for the reaction of OH with the organic compound. Preliminary results, using organic compounds whose rate constants have been previously reported, indicate that the technique gives good results. We will report on these verification tests as well as on studies of rate constants of OH with humic substances as a function of pH.
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: 2007 Fall Meeting