Observation of the Diurnal Variation of Gaseous H2O2 in Los Angeles Air Using a Cryogenic Collection Method
Titel:
Observation of the Diurnal Variation of Gaseous H2O2 in Los Angeles Air Using a Cryogenic Collection Method
Auteur:
Sakugawa, H. Kaplan, I. R.
Verschenen in:
Aerosol science and technology
Paginering:
Jaargang 12 (1990) nr. 1 pagina's 77-85
Jaar:
1990
Inhoud:
During the Carbonaceous Species Method Comparison Study at Glendora, CA in August 11-21, 1986, gaseous H2O2 in the air was collected by a cold trap method using dry ice-acetone as a cooling reagent. Sampling time of the H2O2 was every 4 hours during the day and 8 hours from 11 p.m. through 7 a.m. (PST). Gaseous H2O2 was also collected simultaneously at Duarte and Westwood during the comparison study. After H2O2 entrapment from air, H2O2 concentration in the defrosted sample was measured by a fluorescence technique. The observed range of gaseous H2O2 was 0.08-1.02 (n = 23), 0.10-0.86 (n = 23), and 0.09-0.34 ppb (n= 10) at Glendora, Duarte, and Westwood, respectively. The highest values in H2O2 content was found during midday when O3 content was maximum and NOx content was minimum at all the sites studied. On the other hand, lowest values in H2O2 content were observed in the evening through early morning. H2O2 concentration was always higher at Glendora than at Duarte and Westwood during midday. This regional variation of gaseous H2O2 closely correlated with O3 distribution in the Los Angeles Basin. Meteorological data suggest that the transport of atmospheric pollutants in the Basin by sea breeze during daytime from coastal and central to inland areas when the inversion height is low, may be an important process for the generation of H2O2, as well as O3. The H2O2 concentration measured by the UCLA method at Glendora is sometimes significantly lower than concentrations measured by aqueous stripping methods, but is similar to values measured by a spectroscopic method.
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