Sorption of Nitrogen Dioxide by Calcareous Soils

Abstract The NO 2 sorption capacity and rate of calcareous soils, a calcic soil, and a granular limestone were measured at room temperature by passing air or nitrogen gas containing NO 2 through them. In dry air (humidity < 5%), NO 2 sorption reached an equilibrium value within 2.5 min. In moist air (humidity > 95%), NO 2 sorption increased to as much as 10‐fold that in dry air and approximately equaled the acid‐titratable basicity of calcareous soils. The sorption rate was proportional to the unreacted fraction of the capacity with sorption rate constants ranging from 0.015 to 0.03 min ‐1 at a NO 2 concentration of 0.5% volume. At a concentration of 0.1%, the sorption rate was slower but the capacity remained unchanged. Sorption of NO 2 was similar when either air or a nitrogen carrier was used.