The Improving Conditions for the Aerobic Bacteria Performing the Degradation of Obsolete Pesticides in Polluted Soils

Abstract

Currently, in the territory of Kyrgyzstan, 50 storage facilities of obsolete pesticides exist; they store about 5000 tons of these hazardous chemicals. The storage conditions have become unusable for a long time. They pose a serious threat to the people living there, livestock, and the environment. The main purpose of this research was the use of selected bacteria with cytochrome P450 genes for the bioremediation of polluted soils around the burial sites in model soil experiments. In the first trial of biodegradation experiments, one contaminated soil was used without any changes in chemical contents, and in the second, the physical and chemical contents of the soil were improved to maintain the bioremediation conditions. The soils in both variants were treated 3 times (ie, once a month) with suspensions of a single culture or a blend of active bacteria (1 × 108 cells/mL) selected from in vitro biodegradation experiments. Two control units without the addition of the bacteria culture were also run. The quantification of targeted persistent organic pollutants (POPs) before and after biodegradation was performed by capillary gas chromatography (GC) coupled to a mass spectrometer. In 6 months, obsolete pesticides such as dieldrin, α-endosulfan, β-endosulfan, and 4-heptachlor-epox pure were able to degrade almost completely, up to 98% to 99.0%, by the blend of bacteria and the single culture of bacteria. Endrin aldehyde showed more resistance as the blend of bacteria was able to degrade it to 59.77%. To improve the aerobic degradation for elimination of pesticides from contaminated soils, it is necessary to create optimal agrotechnical and agrochemical conditions.