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 +3  +  +/   +3  ,  ,+ Hydrogen sulﬁde concentration ina cavity under snow cover
Osamu MATSUBAYA
Akita UniversityAbstract
At a snowed area, a cavity is often formed under the snow cover by water ﬂow. If theﬂowing water dissolves hydrogen sulﬁde, concentration of hydrogen sulﬁde in air in thecavity 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 sulﬁdeconcentration in such a cavity was estimated based on extrapolation of hydrogen sulﬁdesolubility from + atmospheric pressure to much lower pressure by application of the Henry’slaw. If hydrogen sulﬁde concentration of ﬂowing water is in a range of /+/ ppm, forinstance 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 following. 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 constantvolume 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 ofwater taken for + hour, for example, after - days concentration in the cavity reaches about
3*ῌ of the equilibrium concentration.
Key words : Hydrogen sulﬁde, Cavity under snow, Degassing, Gas accident

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Fig. , Hydrogen sulﬁde concentration in air equilibrated
with water dissolving hydrogen sulﬁde in a range of
ppm concentration.
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8Fig. - A model of degassing from continuous water ﬂow in a cavity, regarding as
stepwise take-in and out of a constant volume water at a constant time interval.
Va and Vw are volumes of the cavity and of the water taken in and out, respectively. C* and C are hydrogen sulﬁde concentrations of the water taken in andout, respectively. P is partial pressure of hydrogen sulﬁde in the cavity.
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Fig. . An example of the estimation about time variationof hydrogen sulﬁde concentration in a cavity. The ratio of the cavity volume and the volume of water taken
in and out is +**, the time interval is + hour, the hydrogen sulﬁde concentration of water taken in is +* ppm,
and the temperature is +/».
.
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