Properties of nitrate, sulfate and ammonium in typical polluted atmospheric aerosols (PM10) in Beijing

To gain an understanding of the characteristics of nitrate, sulfate and ammonium in the urban atmosphere of Beijing, an experiment was conducted in October 2004, using a method involving the rapid collection of particles and analysis using an ion chromatography system. The study shows that the mean concentration of water soluble ions (WSI) increased during heavily polluted weather, and this change in the concentration of pollutants was related to the meteorological background. The concentration of nitrate, sulfate and ammonium increased 7.9, 4.1 and 5.4 times, respectively, during heavily polluted periods. The concentration of nitrate increased most among the WSI in PM10. The diurnal variations of nitrate, sulfate and ammonium in more polluted periods were different from those in less polluted periods. The highest concentration of nitrate (NO3−), sulfate (SO42−), and ammonium (NH4+) appeared at 19:00 during more polluted periods. In contrast, the highest concentrations of these compounds occurred at noon during less polluted periods. A correlation analysis showed that NO3−, SO42−, NH4+, nitrogen oxides (NOx) and sulfur dioxide (SO2) had significant positive correlations in more polluted periods. The transformation ratio from SO2 and NOx to SO42− and NO3− was higher in more polluted than that in less polluted periods.