| Summary: | 碩士 === 國立成功大學 === 環境工程學系 === 89 === Hydrogen peroxide (H2O2) is an important species in homogeneous and heterogeneous processes in the atmosphere as it is directly related to the HOx radical concentrations in the stratosphere and troposphere. Further, recent studies of the oxidation of sulfur dioxide (SO2) by H2O2 in solution have indicated that this process may be the dominant mechanism for the conversion of SO2 to H2SO4 in cloud, rain, and dew water where the typical pH is less than 5.5.
The purposes of this study are to investigate the measurements and analytical techniques of hydrogen peroxide and to compare the different between impingers and coil collectors. Fenton method was used in this study to analyze hydrogen peroxide in aqueous solution. The analytical method is based on the hydroxylation of benzoic acid by Fenton reagent [Fe(Ⅱ) and H2O2] to from the fluorescent product, hydroxybenzoic acid. Fluorescence intensity is enhanced by complexation with aluminum ion. The method detect limit is 0.69 ppb in solution, and the square of correlation coefficient of the calibration curve is above 0.999. In the laboratory experiment when the collective time over 20 minutes the collection efficiencies are above 99% with impinger and 96% with coil, respectively. However, it will be interfered by SO2 and O3 when apply to the field measurement.
In order to understand the interference due to SO2 and O3, this study carried out a series of experiments to investigate the situation of negative artifact of SO2 and the positive artifact of O3. The results showed that (1) SO2 depleted aqueous H2O2, (2) O3 enhanced H2O2 formation, (3) SO2 interference can be inhibited when the scrubbing solution contains 1.23mM HCHO, and (4) O3 can be removed by NO with 2.4 - 5.6 ppmv.
As the result of above, the pH 5.3 phosphate buffer solution and 1.23mM HCHO was used as scrubbing solution in this study, and we develop a new method to sampling and determination of hydrogen peroxide by following removal of ozone by gas-phase reaction with nitric oxide. Measurement of hydrogen peroxide in ambient
air were carried out at National Cheng Kung University, ShinYing and ShanHua during May 2001 and July 2001. The data indicate that ambient gas phase concentration of H2O2 varied from 0.41ppbv to 4.51ppbv and the maximum value occurred in the afternoon. In addition, H2O2 concentration is dependent on O3 and HCHO concentration。
|
|---|
