Seasonal variation of atmospheric ammonia and particulate ammonium concentrations in the urban atmosphere of yokohama over a 5-year period

Abstract

Measurements of ammonia and particulate ammonium were made in the daytime (1200–1500) at a urban site in Yokohama during the 5-year period, 1982–1986. Diurnal NH 3 concentrations showed a distinct seasonal trend with a maximum in summer. The diurnal monthly average concentrations were above 10 ppb during the late spring and summer months, while the concentrations during the winter months were between 1 and 5 ppb. The seasonal variation was found to be very similar to that of the average air temperature and showed a periodic pattern over 1 year. A good correlation was observed between diurnal NH 3 concentrations and average air temperatures during the 5-year period. The annual mean concentrations were in the range of 6.6–7.6 ppb with only a minor deviation. The diurnal monthly average concentrations of particulate NH 4 + were between 1 and 4 μg m −3 and no significant seasonal variations were seen. As a short-term study, simultaneous measurements of NH 3, HNO 3 and particulate NO 3 − were made. The diurnal mean concentrations of NH 3 and HNO 3 were 7.6 and 0.8 ppb, respectively. The concentration of particulate NO 3 − ranged from 0.3 to 6μg −3. Both HNO 3 and particulate NO 3 − concentrations were relatively low and constant. Thus, NH 3 and HNO 3 levels did not agree with the concentrations predicted from the NH 4NO 3 equilibrium constant.