OBSERVATION OF THE DIURNAL-VARIATION OF GASEOUS H2O2 IN LOS-ANGELES AIR USING A CRYOGENIC COLLECTION METHOD

During the Carbonaceous Species Method Comparison Study at Glendora, CA in August 11–21, 1986, gaseous H2O2in the air was collected by a cold trap method using dry ice-acetone as a cooling reagent. Sampling time of the H2O2was every 4 hours during the day and 8 hours from 11 p.m. through 7 a.m. (PST). Gaseous H2O2was also collected simultaneously at Duarte and Westwood during the comparison study. After H2O2entrapment from air, H2O2concentration in the defrosted sample was measured by a fluorescence technique. The observed range of gaseous H2O2was 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 H2O2content was found during midday when O3content was maximum and NOxcontent was minimum at all the sites studied. On the other hand, lowest values in H2O2content were observed in the evening through early morning. H2O2concentration was always higher at Glendora than at Duarte and Westwood during midday. This regional variation of gaseous H2O2closely correlated with O3distribution 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 H2O2concentration 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. © 1990 Elsevier Science Publishing Co., Inc.