资源环境科技发展态势分析平台

We analyzed long-term fine-and coarse-mode synergetic observations of nitrate and related aerosols (SO42-, NO3-, NH4+, Na+, Ca2+) at Fukuoka (33.52 degrees N, 130.47 degrees E) from August 2014 to October 2015. A Goddard Earth Observing System chemical transport model (GEOS-Chem) including dust and sea salt acid uptake processes was used to assess the observed seasonal variation and the impact of long-range transport (LRT) from the Asian continent. For fine aerosols (fSO(4)(2), fNO(3)(-), and fNH(4)(+)), numerical results explained the seasonal changes, and a sensitivity analysis excluding Japanese domestic emissions clarified the LRT fraction at Fukuoka (85% for fSO(4)(2), 47% for fNO(3)(-), 73% for fNH(4)(+)). Observational data confirmed that coarse NO3- (cNO(3)(-)) made up the largest proportion (i. e., 40-55 %) of the total nitrate (defined as the sum of fNO(3)(-), cNO(3)(-), and HNO3) during the winter, while HNO3 gas constituted approximately 40% of the total nitrate in summer and fNO(3)(-) peaked during the winter. Large-scale dust-nitrate (mainly cNO(3)(-)) outflow from China to Fukuoka was confirmed during all dust events that occurred between January and June. The modeled cNO(3)(-) was in good agreement with observations between July and November (mainly coming from sea salt NO3-). During the winter, however, the model underestimated cNO(3)(-) levels compared to the observed levels. The reason for this underestimation was examined statistically using multiple regression analysis (MRA). We used cNa C, nss-cCa(2+) C, and cNH(4)(+) as independent variables to describe the observed cNO(3)(-) levels; these variables were considered representative of sea salt cNO(3)(-), dust cNO(3)(-), and cNO(3)(-) accompanied by cNH(4)(+)), respectively. The MRA results explained the observed seasonal changes in dust cNO(3)(-) and indicated that the dust-acid uptake scheme reproduced the observed dust-nitrate levels even in winter. The annual average contributions of each component were 43% (sea salt cNO(3)(-)), 19% (dust cNO(3)(-)), and 38% (cNH(4)(+) term). The MRA dust-cNO(3)(-) component had a high value during the dust season, and the sea salt component made a large contribution throughout the year. During the winter, cNH(4)(+) term made a large contribution. The model did not include aerosol microphysical processes (such as condensation and coagulation between the fine anthropogenic aerosols NO3- and SO42- and coarse particles), and our results suggest that inclusion of aerosol microphysical processes is critical when studying observed cNO(3)(-) formation, especially in winter.