Abstract
The aim of the study was to determine the efficacy of bioaugmentation in pyrene-contaminated soil based on microbial counts, colony development index (CD), ecophysiological diversity index (EP), soil enzyme activity, and an assay of residual pyrene levels in the soil. The soil samples were contaminated with pyrene doses of 100 and 1000 mg kg−1 DM soil. Two bacterial consortia were used in the study: P1 (Bacillus frigoritolerans Z2B-19, Bacillus simplex 2–134, and Bacillus thuringiensis ex4) and P2 (Bacillus pumilus Bp-11, Bacillus safensis L22, and Bacillus aerophilus KUDC1741). The following parameters were determined: counts of organotrophic bacteria, actinobacteria, and fungi; CD; EP; and the activity of soil enzymes. The pyrene degradation efficacy of the bioaugmentation was also established. Microbiological activity was influenced by the level of soil contamination with pyrene, the test time, and the type of consortium. Pyrene had a stimulatory effect on the microbial counts and was a diversifier of CD values, EP values, and enzyme activity levels in the soil. Bioaugmentation initially promoted the growth of microorganisms, but ultimately diminished the ecophysiological diversity and the activity of soil enzymes. The microorganisms used for bioaugmentation accelerated pyrene removal from the soil, by 24.6% and 16.4% in the case of P1 and P2 consortium, respectively. The use of bioaugmentation provides favorable conditions for the effective elimination of pyrene from soil. As the microbiological and biochemical properties of the soil were improved in the initial phase of the study, this method can be recommended for the bioremediation of pyrene-contaminated soils.
Highlights
Environmental pollution with polycyclic aromatic hydrocarbons (PAHs) is one of the major issues faced by the modern world
The counts of organotrophic bacteria and actinobacteria in the soil spiked with pyrene and amended with consortia were primarily determined by the pyrene dose, as reflected in the η2 percentages of the observed variability, which were 37.01% and 28.13% respectively (Fig. 2)
In the control series, at all test times, the mean organotrophic bacteria courts increased with the pyrene levels in the soil, unlike the counts of actinobacteria and fungi, which varied (Table 2)
Summary
Environmental pollution with polycyclic aromatic hydrocarbons (PAHs) is one of the major issues faced by the modern world. Toxicity, and carcinogenicity of PAHs, it is essential that their adverse impact is reduced by removing them from the environment. In view of the risks associated with PAHs, the US Environmental Protection Agency (US EPA) has designated 16 of them as priority pollutants targeted for elimination from the environment. Polycyclic aromatic hydrocarbons bioaccumulate in food chains and represent a threat to humans and animals (White 2002). Polycyclic aromatic hydrocarbons are comprised of two or more aromatic rings bonded in linear, angular, or cluster arrangements. They are grouped into two categories, based on the number of benzene rings: LMW
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