32 巻 (2017) 1 号 p. 4-13
Chemical compositions and particle number densities of atmospheric aerosols were measured continuously in the coastal area of Seto Inland Sea during the spring of 2015. The mean concentrations of NH4+, NO3-, and water soluble organic nitrogen (ONws) were 1.6, 0.85, and 0.28 μg N m-3, respectively in total sampling mode. NO3- existed in both fine and coarse modes, while NH4+ and ONws existed primarily in fine mode. On the days of normal atmospheric conditions, the amount of ONws contributing to the total nitrogen was about 14% N in both fine and coarse sampling modes. This ratio was equivalent to the amount of NO3- content in fine mode and NH4+ in coarse mode. On the days with polluted atmospheric conditions, the amount of ONws contributing to total nitrogen was about 9.3% N in fine mode and about 5.0% N in coarse mode. This ratio was equivalent to the contributions of NO3- in fine mode and NH4+ in coarse mode. Dry deposition fluxes of particulate NH4+, NO3-, and ONWS in the area were 280, 660, and 83 μg N m-2 day-1, respectively. The flux of NO3- was more effective than any other nitrogen compounds, since the deposition rate depends upon a size distribution. The dry deposition of ONws accounted for about 8.1% of the total nitrogen dry deposition. Thus, ONWS cannot be ignored when considering the nitrogen budget and cycles in this area.