Determination of acidic sulfate aerosols in urban atmospheres in Erfurt (F.R.G.) and Sokolov (Former C.S.S.R.)

Acidic sulfate aerosols were sampled from the atmosphere with the Harvard Impactor-Honeycomb Denuder System. This sampler incorporates a citric-acid-coated denuder to remove NH3 and an impactor with a 50% size cutoff of 2.5 μm (da). Fine particles were collected on a Teflon filter. The sampling (24 h) lasted from December 1990 until June 1992. The sampling sites were in Erfurt and Sokolov, two eastern European cities with high SO2 concentrations. At the same time approximately 230 asthmatic children and adults were followed by daily peak flow measurements and symptom diaries. Despite the high SO2 pollution with daily averages of 62 μg m−3 and peaks of nearly 500 jug m−3, the mean SO4−2 concentration for Erfurt, 9.8 μg m−3, and that for Sokolov, 8.9 μg m−3, were moderate. In addition, the average H+ concentration over the entire period was low in Erfurt (0.3 μg m−3, H+ as H2SO4) as well as in Sokolov (0.4 μg m−3). H+ concentrations tended, however, to be higher during the cold winter months and the hot summer months. In Sokolov, there were three episodes in the winter when measurements exceeded 3.5 μg m−3. The measurements suggest that the environmental conditions in Erfurt and Sokolov produce a low SO2 oxidation rate and have a high H2SO4 neutralization potential. Daily PM10 concentrations (59.90 μg m−3 in Erfurt and 53.8 μg m−3 in Sokolov) were in the same range for both cities with higher values in winter. Of note was the decrease of all pollutants during the period of observation.