2019 Volume 54 Issue 3 Pages 85-95
Long-term trends from FY1998 to FY2012 were analyzed using the component concentrations of gas–aerosols in Fukuoka Prefecture. These data were then compared to those of wet depositions. The average concentrations of nss-SO42-, T-NO3 (=NO3-+HNO3), NH4+, and nss-Ca2+in the gas–aerosols were 64.2 nmol/m3, 74.7 nmol/m3, 108 nmol/m3, and 15.6 nmol/m3, respectively, and showed high concentrations in spring, as well as the photochemical oxidants (Ox). Comparing the annual variation (three-year moving average) of the component concentrations in the gas–aerosols with those of the wet depositions, both nss-SO42- and T-NO3 showed upward trends after FY2000, then began those of the wet depositions to decrease after a peak in approximately FY2007. The T-NO3/nss-SO42- equivalent ratio in the gas–aerosols gradually decreased after FY2000 but switched to an upward trend after approximately FY2008. Conversely, the NO3-/nss-SO42- equivalent ratio in the wet depositions showed a tendency to increase year by year. The NH4+concentration in the gas–aerosols and wet depositions showed the same trend as nss-SO42-. The nss-Ca2+reflected the influence of yellow sand, particularly in the wet depositions.
It is considered that the effect of the transport of pollutants from East Asia to northern Kyushu is decreasing because nss-SO42-, T-NO3 (NO3-) and nss-Ca2+in both the gas–aerosols and wet depositions have exhibited a slightly downward trend since approximately FY2008.
