Impacts of Airborne Pollutants on Soil Fauna

The impacts of airborne pollutants have been studied in only a few groups of soil animals, notably protozoans, nematodes, potworms, earthworms, mites, and collembolans. Pollutants in the form of acid depositions, which contain SO4²⁻, NOx, H⁺, heavy metals, and some organic compounds, are not homogeneously distributed on the landscape. Deposition patterns depend mainly on landscape configuration and plant cover. Airborne pollutants affect soil animals both directly and indirectly. Direct toxic effects are associated with uptake of free acidic water from the environment by some soil animals and with consumption of polluted food by others. Indirect effects are mediated primarily through disappearance or reduction of the food resources (microflora and microfauna) of soil animals, changes in organic matter content, and modification of microclimate. In the field, changes in competition among species are probably important factors that influence the soil animal community structure as well as the reactions of individual species to soil acidification or liming. The overall effect is a depauperation of soil with an attendant reduction in the rate of organic matter decomposition. We have provided five hypotheses, using soil fauna as indicators, to allow for quick evaluation of environmental changes caused by airborne pollutants.