Characteristics of soill air 1. The level of CO2 in soil is about eight times higher than the normal atmospheric level 2. The O2 level in soil air is slightly lower than it is in atmospheric air 3. Soil air usually is much higher in water vapor than is the atmosphere Also, under waterlogged conditions, the concentrations of gases such as methane(CH4) and ydrogen sulf ide(h2s)are notably higher in soil airCharacteristics of soil air 1．The level of CO2 in soil is about eight times higher than the normal atmospheric level. 2．The O2 level in soil air is slightly lower than it is in atmospheric air. 3．Soil air usually is much higher in water vapor than is the atmosphere. 4 ． Also, under waterlogged conditions, the concentrations of gases such as methane（CH4）and hydrogen sulfide (H2S) are notably higher in soil air