Modeling study of the impact of SO

Sulfate is a major component of PM2.5 in Japan, mainly produced from sulfur dioxide (SO2) oxidations. Volcanic activity is a significant source of SO2 alongside anthropogenic activities (fossil fuel combustion). This study focused on the PM2.5 pollution episode in the Kyushu region triggered by the Nishinoshima volcanic eruption in the summer of 2020. To simulate the episode, the CMAQ model was employed, incorporating a volcanic SO2 emission inventory (VolcCarn v202302). Three sensitivity simulations were conducted to assess the impact of SO2 injection height on PM2.5 concentrations. Although the WRF model accurately simulated meteorological conditions, the CMAQ model exhibited difficulty in matching observed PM2.5 levels in Fukuoka and Kagoshima in the higher SO2 injection cases (Case I and II), with the exception of the lowest injection height scenario (Case III) that closely matched observed PM2.5 concentrations. Furthermore, Case III indicated that the contribution of volcanic sources to PM2.5 concentrations in Fukuoka and Kagoshima was considerable, with over 90% of PM2.5 on peak days attributed to these sources. The study indicated that the Nishinoshima eruption was one of the primary contributors to the PM2.5 pollution episode in Kyushu and that the injection height had a significant impact on the model performance.