4:30 PM - 4:45 PM
[AAS07-19] Two-year continuous observation of gaseous ammonia at Nagasaki in western Japan: Impacts of long-range transport, local sources, and volcanic activities
Keywords:Ammonia, Field observation, Laser spectroscopy, Long-range transport, Volcano, Nitrogen cycle
Gaseous ammonia (NH3) plays crucial roles in the atmosphere by neutralizing acidic compositions and leading secondary aerosol formation, and also acts as a key component in the nitrogen cycles of the Earth. Therefore, detailed understandings of behaviors and sources of NH3 are critically important for evaluating influence of acidic pollutants to atmospheric environment and human health. However, previous observations of NH3 have mainly conducted based on offline chemical analyses after collecting NH3 on filter pack or denuder tube, and reports on long-term continuous observation of NH3 are still very limited.
In this study, continuous observation of NH3 were conducted for more than two years from 2019 to 2021 using laser spectroscopic technique. By comparing the observed temporal variations of NH3 with meteorological data and gas- and particle-phase compositions, potential factors determining NH3 concentrations in different seasons have been analyzed. As results, high concentration events exceeding 10 ppbv were observed especially in late spring and autumn and with precipitations but NH3 concentrations were not positively correlated with particle-phase ammonium, suggesting the important contributions of local sources in Nagasaki in these seasons. From winter to early spring, increases in NH3 concentrations were often observed during the long-range transport events of air pollutants (e.g., sulfate, nitrate) from Asian continent, implying that gaseous NH3 are transported with particle-phase ammonium. In summer, whereas high concentration events were rarely observed, suppression of NH3 concentrations were observed when airmasses were considered to be affected by volcanic plumes containing sulfur dioxide (SO2) from southern Japan.
In this study, continuous observation of NH3 were conducted for more than two years from 2019 to 2021 using laser spectroscopic technique. By comparing the observed temporal variations of NH3 with meteorological data and gas- and particle-phase compositions, potential factors determining NH3 concentrations in different seasons have been analyzed. As results, high concentration events exceeding 10 ppbv were observed especially in late spring and autumn and with precipitations but NH3 concentrations were not positively correlated with particle-phase ammonium, suggesting the important contributions of local sources in Nagasaki in these seasons. From winter to early spring, increases in NH3 concentrations were often observed during the long-range transport events of air pollutants (e.g., sulfate, nitrate) from Asian continent, implying that gaseous NH3 are transported with particle-phase ammonium. In summer, whereas high concentration events were rarely observed, suppression of NH3 concentrations were observed when airmasses were considered to be affected by volcanic plumes containing sulfur dioxide (SO2) from southern Japan.