SORPTION OF GASEOUS ATMOSPHERIC POLLUTANTS BY SOILS

Abstract

Gas chromatographic studies showed that soils have the capacity to sorb substantial amounts of sulfur dioxide, hydrogen sulfide, and methyl mercaptan and small amounts of carbon monoxide, ethylene, and acetylene. Sulfur dioxide was sorbed more rapidly than H2S or CH3SH, and all three sulfur gases were sorbed much more rapidly than CO, C2H4, or C2H2. When expressed as mg of gas sorbed/g of soil, the capacities of air-dry samples of the soils studied for sorption of sulfur gases ranged from 1.1 to 15.3 for SO2, from 15.4 to 65.2 for H2S, and from 2.4 to 32.1 for CH3SH. The corresponding capacities of moist (50 percent WHC) samples ranged from 9.3 to 66.8 for SO2, from 11.0 to 62.5 for H2S, and from 2.2 to 21.4 for CH3SH. The rates of sorption of these gases and the amounts of gas sorbed were not significantly correlated with soil pH, organic-matter content, or clay content. Experiments with steam-sterilized soils indicated that soil microorganisms are responsible for the sorption of CO, C2H4, and C2H2 by moist soils, but play little, if any, part in the sorption of SO2, H2S, and CH3SH. Evolution of CO was detected from moist (50 percent WHC) samples of several of the soils studied, and this evolution was promoted by steam sterilization of these soils. The work reported indicates that soil is an important natural sink for gaseous atmospheric pollutants and may prove valuable for purification of industrial emissions heavily polluted by sulfur gases.