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.