High Time-Resolution Monitoring of Free-Tropospheric Sulfur Dioxide and Nitric Acid at the Summit of Mt. Fuji, Japan

This is the first paper that describes the atmospheric sulfur dioxide (SO2) and nitric acid (HNO3) monitored with a good time-resolution at the summit (3776 m a.s.l.), which is located in the free troposphere, and southeastern foot (1284 m a.s.l.) of Mt. Fuji. Japan. During the summer of 2012, two analytical systems consisting mainly of a parallel-plate wet denuder and ion chromatograph operated simultaneously at both the sampling sites. All the samples collected at both the sampling sites contained detectable levels of sulfate from gas-phase SO2 while the nitrate from gas-phase HNO3 was detectable in 97.8% of air samples at the southeastern foot and 88.4% at the summit. The average concentrations of SO2 and HNO3 were, respectively, 0.061 ± 0.071 and 0.031 ± 0.020 ppbv at the summit (n = 672), and 0.347 ± 0.425 and 0.146 ± 0.070 ppbv at the southeastern foot (n = 1344) of Mt. Fuji. Both the acidic gases at the southeastern foot and the HNO3 at the summit showed a diurnal pattern with daytime maxima and nighttime minima. Meanwhile, the SO2 at the summit did not show a distinct shift, which indicates the SO2 concentrations at the summit would be principally controlled by the advection of air parcel in the free troposphere.