Removal of Ozone by Soil

Abstract

Simultaneous measurements of the vertical profiles of horizontal wind, temperature, and ozone concentration above a bare, freshly cultivated fine sandy loam were obtained on 12 occasions during a 4-day period in July when ozone concentrations ranged from 8 to 26 X 10 z molecules (mol) -3 (1X 101~ tool cm =3 ---4 ppb = 8/~g m-3). The decrease in ozone near the soil surface clearly indicated that the soil was removing ozone from the atmosphere. The rate of ozone removal varied from 3 to 12 )< 10~z mol cm -2 sec -~. The flux into the soil varied with the concentration of ozone in the air, and indicated a resistance of about 2 sec cm -z to ozone removal bythe soil and the 2.5-cm air layer immediately above the soil. The rapid removal of ozone by soil in a ventilated chamber suggested a small resistance in the soil alone. A sample of soil containing 14% moisture had a resistance of 0.37 sec cm-ito ozone removal, which was 0.23 sec cm -1 greater than that of activated charcoal, a strong adsorbing agent. Compaction and additional soil moisture increased the resistance to ozone removal, whereas autoclaving decreased the resistance. Additional Index Words: resistance to ozone removal.Q --(Ca -Cb)/ra -b.[ 1 ]Since ra -bcombines the resistances of both the boundary layer and the soil itself, its magnitude can be reduced 1Contribution from the

Field measurement of small ozone fluxes to snow, wet bare soil, and lake water

“…For example, Aldaz (1969) recommends a value of deposition velocity (vertical flux divided by concentration at a specified height) of 0.02 cm s-l over snow and 0.04 cm s-l over water. These estimates are about an order of magnitude smaller than values found above vegetation in the daytime and over bare soil not saturated with water (Regener, 1957;Regener and Aldaz, 1969;Aldaz, 1969;Galbally, 1971;Turner et al, 1973;Wesely et al, 1978;Garland and Derwent, 1979;Leuning et al, 1979). Galbally and Allison (1972) report fluxes over snow equivalent to deposition velocities that range from 1.7 to -3.3 cm s-l , depending on the condition of the snow surface.…”

“…Hence, snow appears to have a characteristic surface resistance of about 34 s cm-', whether thawing or not, but might be less for very fresh snow. , about one third that for snow, but a factor of 10 greater than that likely for much drier soil (Turner et al, 1973).…”

“…For example, reactions at the wet inner leaf surfaces of vegetation result in an effective canopy surface resistance of l-4 s cm-' when stomata are open (Wesely eta/., 1978;Leuning et al, 1979). Slightly moist soil has a surface resistance on the order of only 1 s cm-', but the resistance increases strongly with soil moisture content (Turner et al, 1973). Apparently, the amount and nature of water at the surface strongly affect the resistance to ozone removal from the atmosphere.…”

Global emissions and natural processes for removal of gaseous pollutants

“…There is evidence though that 0 3 is removed by the oceans to some extent (Aldaz, 1969). Ozone is also absorbed by vegetation (Hill, 1971;Hill and Littlefield, 1969;Rich et al, 1970), and soil (Junge, 1962;Kroening and Ney, 1962;Aldaz, 1969;Turner et al, 1973). Aldaz (1969) has shown that soil and vegetation probably represent a major sink for this gas.…”

Acid Rain and Ozone Influence Mycorrhizal Infection in Tree Seedlings

“…Ozone does not penetrate the soil surface 18 and consequently, must influence mycorrhizae by altering plant metabolism. The soluble carbohydrates of roots are generally considered a major factor in mycorrhizal infection 19 and, thus, any effect of O3 on the availability of root sugars would be of importance to the carbohydrate metabolism of the associated fungi.…”