Abstract
The summer observational campaign of gaseous elemental mercury (GEM) in the ambient air was performed at the top of Mt. Fuji (3776 m a.s.l.), which is located in the free troposphere, from July 14 to 20 and August 22 to 25, 2014, to clarify the background concentration of GEM and the influence of the long-range transport from East Asia to Japan. We also observed GEM at the southeastern foot of Mt. Fuji (1284 m a.s.l.), Shinjuku (urban site), and Kazo (suburban site). The mean GEM concentration in the daytime was 10.1±7.70 ng/m3 (n=19) at the foot of Mt. Fuji, 3.67±0.744 ng/m3 (n=9) at the top of Mt. Fuji, 2.53±0.895 ng/m3 (n=8) in Shinjuku, and 2.50±0.245 ng/m3 (n=5) in Kazo in the order of decreasing concentration. On the other hand, there were little differences in the GEM concentration in the nighttime between sites, namely 2.58±0.360 ng/m3 (n=11) in Shinjuku, 2.38±0.521 ng/m3 (n=9) at the top of Mt. Fuji, 2.37±0.281 ng/m3 (n=6) in Kazo, and 2.13±1.88 ng/m3 (n=14) at the foot of Mt. Fuji. The GEM concentration clearly showed a day-night variation both at the top and the foot of Mt. Fuji. At the foot of Mt. Fuji, it increased in the daytime along with the air temperature, indicating its evaporation from the local surface soil. The backward trajectory analysis showed that the frequencies of the air mass transported from the Asian continent to the top of Mt. Fuji was higher in July than in August, suggesting that the GEM concentration was strongly affected by the pathway of the air mass at the top of Mt. Fuji.
