Der Fe(III)-Reduktionstest - ein einfaches Verfahren zur Abschätzung der Wirkung von Umweltchemikalien auf die mikrobielle Aktivität in Böden

The Fe(III)-reduction test - a simple procedure to determine the effects of environmental chemicals on the microbial activity in soils A new simple microorganism test is described. The test is based on the fact that the degree of microbial reduction in waterlogged soils is influenced by the addition of different amounts of toxic chemicals. The microbial activity under reducing conditions can be measured by the degree of the microbial reduction of easily reducable Fe(III)-oxides (ferrihydrites) to soluble Fe²⁺-ions. The influence of different test parameters, the reproducibility and limitations of the proposed test are described. Toxicity indices of the investigated chemicals are derived graphically from the resulting dose effect curves. Values are determined for those concentrations which cause no (Non Effect Level, NEL) and a 50%-inhibition (ED₅₀) of the microbial activity in soil samples. By representing some results for 2,4-D, 2,4,5-T, LAS, Cd and Hg the scope of the test is described. First results show that the effective toxicity of chemicals is strongly influenced by the adsorption capacity of the soils. Furthermore the relation of toxic substances to nutrients in the soil solution causing competition or antagonistic and synergistic effects during uptake and also within the organisms can substantially influence the toxicity of chemicals.