Diurnal Variations of the Oxidized Nitrogen Distribution during Photochemical Smog Episodes at an Osaka Urban Site

Abstract

This paper describes the results of a field study of atmospheric nitrogenous pollutants conducted at an Osaka urban site during selected July 1986 photochemical episodes. The one-hour averaged maxima were 21 ppb for PAN, 31 ppb for CH₃ONO₂, 17 ppb for HNO₃, 17μg.m^-3 for NO₃^-, and 125 ppb for Oxidant. Diurnal patterns of PAN and HNO₃ were closely related to Oxidant. But NO₃^- peaked previously to those. CH₃ONO₂ concentrations were high frequency during the forenoon, and low during the afternoon. Hourly variations of oxidized nitrogen distribution, Fn= ([PAN] + [HNO₃] + [NO₃^-])/([NO] + [NO₂] + [PAN] + [HNO₃] + [NO₃-]), tracked to that of Oxidant nearly exactly. And the maximum hourly value of Fn was 0.49 and its values exceeding 0.30 were common during midday. The values of Fn increased by 0-0.20 compared to those not in cluded CH₃ONO₂. On a nitrogen basis, the PAN contribution averaged between 0 and 73% and HNO₃ averaged between 13 and 84%. PAN was more abundant than inorganic nitrates at photochemical smoggy hours.