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Hydrogen sulﬁde concentration in a cavity under snow cover

Osamu M

ATSUBAYA Akita University

Abstract

At a snowed area, a cavity is often formed under the snow cover by water flow. If the flowing water dissolves hydrogen sulfide, concentration of hydrogen sulfide in air in the cavity rises, because of degassing of hydrogen sulfide from the water. If a person stands on snow surface upper such a cavity and if ceiling of the cavity collapses under his foot, he breathes hydrogen sulfide and meet with a quite serious accident. Hydrogen sulfide concentration in such a cavity was estimated based on extrapolation of hydrogen sulfide solubility from+atmospheric pressure to much lower pressure by application of the Henry’s law. If hydrogen sulfide concentration of flowing water is in a range of/+/ppm, for instance at+/, the hydrogen sulfide concentration in the cavity reaches a range of+,***

-,***ppm at equilibrium. Such concentration is high enough to kill persons. Time duration till the equilibrium was estimated by a model of continuous water flow as the fol- lowing. A constant volume of water is taken into the cavity at a content time interval, and hydrogen sulfide concentration of the water is equilibrated with the air in the cavity, and then the water is taken out the cavity at the same time at the next take-in of constant volume water. The time duration for the equilibration depends on the ratio of the cavity volume and the water volume taken into for a definite time duration, which corresponds the rate of continuous water flow. If the volume of cavity is+**times of the volume of water taken for+hour, for example, after-days concentration in the cavity reaches about 3*ῌof the equilibrium concentration.

Key words : Hydrogen sulﬁde, Cavity under snow, Degassing, Gas accident

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