It must be emphasized that this is the amount in the entire vertical column of air, with the vast majority being at high levels (five kilometers or more), so its effect on surface conditions is minimal. In addition, with increasing distance from the volcano and a longer stay in the atmosphere of SO2 it gradually mixes with other components of the air, and the concentration thus decreases significantly, especially at lower levels. Current measurements show that sulfur dioxide concentrations are very low throughout the Czech Republic, almost nowhere exceeding 25 micrograms per cubic meter. Presence of SO2 at altitude, however, it can manifest itself in a certain slight turbidity of the sky if it is not covered with clouds.
Acid rain can come
While gaseous sulfur dioxide is very difficult to reach the earth’s surface from higher levels, in liquid form this is already possible to some extent. This is because sulfur dioxide in the air can react with water vapor and lead to the formation of sulfuric acid. And it can then become part of raindrops, which fall to the earth’s surface during precipitation, creating so-called acid rain.
However, at present, the acid rains thus caused will have only a very slightly reduced pH, i.e. they will be only very weakly acidic. Some of the sulfur dioxide is located in levels higher than those at which clouds and precipitation normally occur at this time of year. Thus, it is certainly not possible to expect such an intensity of acid in rains as we used to have in the Czech Republic before the desulphurisation of thermal coal-fired power plants in the 1980s. Moreover, of course, this is only a short-term matter. With the change of flow over Central Europe, the concentration of SO2 at higher levels above the Czech Republic, it will fall significantly again in the coming days and the possibility of acid rain will disappear.