Ecotoxicological assessment of soil using the Bacillus pumilus contact test

We estimated the toxicity of soils artificially contaminated with metals and a pesticide using the Bacillus pumilus dehydrogenase activity (DHase) inhibition test. We found a masking effect of organic matter while testing the toxicity of soil samples with low content of toxicants. To avoid this effect, uncontaminated soil should be used as a control; in its absence, we recommend using a “substitute” control. We developed a method to estimate the “substitute” control by multiplying the quotient (So), which depends on organic matter content (Corg) of the soil sample, by the activity of the test culture determined in the presence of water (Arelw). This method does not require uncontaminated soil controls and can be extended to use with other test organisms that are sensitive to Corg.

Research highlights► We estimated the toxicity of soils artificially contaminated with metals and a pesticide using the Bacillus pumilus dehydrogenase activity (DHase) inhibition test. ► We found a masking effect of organic matter while testing the toxicity of soil samples with low content of toxicants. ► To avoid this effect, uncontaminated soil should be used as a control; in its absence, we recommend using a “substitute” control. ► We developed a method to estimate the “substitute” control by multiplying the quotient (So), which depends on organic matter content (Corg) of the soil sample, by the activity of the test culture determined in the presence of water (Arelw). ► This method does not require uncontaminated soil controls and can be extended to use with other test organisms that are sensitive to Corg.