Conditions for a partial summation of SO₂ and NO₂ hazardous effect in gas emission regulations

Abstract

In order to provide environmental safety, the concentrations of SO₂ and SO₂ in the surface layer of atmospheric air should not exceed corresponding one-time values accepted for maximum permissible concentrations (MPCs). The only document that provides a normative calculation of hazardous substance dispersion in the atmospheric air up to the present time is presented by regulations OND-86. It has established that, in taking into account the summation (unidirectionality) of hazardous action of substances (including SO₂ and NO₂ gases), the sum of their relative concentrations should not exceed unity. A novel standard GN 2.1.6.2326-08 stipulates that “nitrogen dioxide and sulfur dioxide have a partial summation of action; therefore the sum of their relative concentrations should not exceed 1.6.” This paper is devoted to analyzing the calculation of the summation of action for SO₂ and NO₂ gases and proving that the condition established in GN 2.1.6.2326-08 is not quite correct. According to the condition required by standard GN 2.1.6.2326-08, it turns out that, for some combinations of concentrations, the hazardous effect of gases is not added together, but one gas compensates an effect of the other, which contradicts the points of OND-86. For example, at SO₂ and NO₂ concentrations amounting to 0.6 and 0.04, respectively, the condition required by standard GN 2.1.6.2326-08 is satisfied, although the concentration of SO₂ exceeds a normatively fixed value of MPC = 0.5. The graphical analysis of a concentration region for SO₂ and NO₂ gases clearly shows the areas where the condition required by standard GN 2.1.6.2326-08 is satisfied, but the environmental safety according to OND-86 is not provided. Recommendations are proposed for the correction of requirements established by standard GN 2.1.6.2326-08.