The environmental impact of mercury released from the volcanic activity of Sakurajima

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1. In order to elucidate vertical fluxes of the mercury, hourly variations of atmospheric mercury at 3m and 12m heights were investigated every two hours for three days. It was found that atmospheric mercury concentration in the daytime was higher than that in the nighttime: mercury concentration of 3m height (Hg_<3m>) ranged 1.65-17.92 ng m^<-3> (5.96±3.47 ng m^<-3>) in the daytime and 1.50-12.81 ng m^<-3> (4.20±2.33 ng m^<-3>) in the nighttime, and that of 12m height (Hg_<12m>) ranged 1.24-29.38 ng m^<-3> (4.74±3.61 ng m^<-3>) and 1.38-14.82 ng m^<-3> (4.50±2.85 ng m^<-3>), respectively. The variations of mercury concentration from day to night were observed through the year, showing the temperature dependency. Hg_<3m> is higher than Hg_<12m> in the daytime and Hg_<12m> is higher than Hg_<3m> in the nighttime, since the daytime-nighttime variation of Hg_<3m> was considerably larger than that of Hg_<12m>. Those observations suggest that mercury is emitted from soil surface with the ri … More se of temperature in daytime and deposits with the fall of temperature in nighttime.2. In order to elucidate the process of mercury uptake by plant from natural environment, total mercury contents in leaves, stems and roots of Solidato altissima L were determined. Mercury content in stems was considerably lower than that in leaves and roots. A positive correlation with mercury content in soil was observed in roots. The leaves at lower part of the plant tend to have higher concentration of mercury than the upper part. However, the mercury content of the leaves was independent of that in soil. These observations suggested that the mercury taken from soil into roots was not distributed to the whole plant bodies and the mercury in leaves might mainly be coming from ambient air.3. Vertical variation of mercury in sediment of Kagoshima Bay was investigated. Sediment near submarine fumaroles included higher concentration of mercury. Moreover, considerably higher content of mercury bind with organic matter was observed in the sediment. Less