Some characteristics of oxidant occurrence in the atmosphere of belgrade

Abstract

Oxidant occurrence in the atmosphere of Belgrade was investigated during the warm periods of the years 1981 and 1982. Air samples were taken daily (04–20 h) at the Aerological Observatory, Zeleno Brdo and Meteorological Station, Vračar in the periods June–September 1981 and May–September 1982. Episodic measurements were occasionally performed. Oxidant concentrations were determined by the alkaline spectrophotometric iodometric method. Measurements of direct and global u.v.-radiations at 320 nm were performed simultaneously at the Aerological Observatory. Radiosounding was carried out at this observatory every 6 h. In addition, hourly values of meteorological parameters in the surface layer were measured at both sites throughout the period. In characteristic episodes micrometeorological measurements were performed at 40 points in the city. Extra-high oxidant concentrations were found at both sites in the period June–August, 1981. In the same period of 1982 the oxidant concentrations dropped to the permitted level. However, short episodes with extra-high concentrations at one of the sampling sites appeared in September of both observed years. The episodes of June 1981 and 16 September 1982 in particular were analysed to illustrate the conditions which favour photochemical smog occurrence in Belgrade. It is shown that a chaotic arrangement of sources of precursors presents an inherent danger of oxidant occurrence in situations with stable, calm and warm weather.