Assessment of light chestnut soil phytotoxicity after crude oil pollution and the use of biologics-petrodestructors

Light chestnut soil has specific structural organization and chemical composition, suggesting the features of its negative effects on plants (phytotoxicity) in various pollutants, in particular crude oil. The article aimed to consider and discuss results of model experiments with artificial contamination of light chestnut soil with oil and attempts of its purification using modern biological products based on associations of hydrocarbon-oxidizing bacteria (oil degraders). One used infrared spectrometry to determine the content of petroleum products in the soil, and conductometry to measure soil pH. To analyze soil phytotoxicity we used the test system based on germination of Raphanus sativus seeds. It has been shown for Multibac Active and DOP-UNI to remove effectively over 50% of crude oil from soil in 15 days, the higher its initial concentration. This process is accompanied by a decrease in the pH of the soil to 4.55-4.94. Spontaneous utilization of oil is 7.5% at high oil concentrations of in the soil, and it is no more than 4% at low concentrations. Biological products have moderate phytotoxicity, and oil has significant one. Comparing two biologics, we show that Multibac Active has a comparatively higher phytotoxicity, it reduces laboratory germination of seeds by 12%, and DOP-UNI reduced laboratory germination by only 4%. Crude oil reduces germination at a concentration of 2.0 g/kg by 56%, and at a concentration of 4.0 g/kg, it completely suppresses germination of R. sativus seeds. The use of biological products for the purpose of soil purification from oil pollution enhances its phytotoxic properties. These results and findings are of practical importance for the development and optimization of technologies and strategies for bioremediation of soils contaminated with oil and petroleum products.