Assessment of the danger of the release of deep hydrogen sulfide from the Black Sea to the surface

Abstract

The relevance of this study is due to the fact that the Black Sea is the largest body of water with a hydrogen sulfide zone. The proven reserves of hydrogen sulfide in the water column of the Black Sea amount to five billion tons. In terms of volume, this corresponds to 3.5 trillion cubic meters. At the same time, a mixture of hydrogen sulfide with air is explosive starting with a concentration of hydrogen sulfide in the air of 50 g/ m3. In addition, hydrogen sulfide is toxic, since it is a nerve gas, deadly already at 1 g/ m3. It is of interest to assess the possibility of the release of hydrogen sulfide waters of the sea to the surface with their subsequent degassing, as well as the consequences of increasing the concentration of hydrogen sulfide in surface waters and in the air for coastal areas. The distribution of hydrogen sulfide in the Black Sea is well studied. Especially a lot of measurement data was obtained for the top layer at a depth of 1000 m. Data on the concentration of hydrogen sulfide at depths from 1000 m to 2000 m is significantly less for technical reasons. The maximum concentration of hydrogen sulfide in the sea is reached at depths above 1500 m. A numerical assessment of the consequences of the release of deep waters to the surface has been obtained. It is shown that the concentration of hydrogen sulfide in the air will not exceed 1 g/m3, which is almost two orders of magnitude less than the explosive concentration. The balance estimates of oxygen and hydrogen sulfide fluxes in the Black Sea are considered in connection with forecasts of a rise in the boundary of the hydrogen sulfide zone. It is shown that the rise of the boundary is a consequence of the imbalance of these flows, however, the amount of net hydrogen sulfide production cannot be estimated accurately enough. With an accuracy of estimates of the fluxes themselves of 20-30%, the resulting increase in the amount of hydrogen sulfide per year is a statistically insignificant amount. The release of hydrogen sulfide to the surface in the foreseeable future is possible if the stratification of waters is disrupted by mechanical intervention.