Biochar carrying hydrocarbon decomposers promotes degradation during the early stage of bioremediation

Abstract

Abstract. Oil pollution is one of the most serious current environmental problems. In this study, four strategies of bioremediation of oil polluted soil were tested in the laboratory over a period of 84 days: (A) aeration and moistening; (B) amendment with 1 % biochar (w/w) in combination with A; amendment with 1 % biochar with immobilized Pseudomonas aeruginosa (C) or Actinetobacter radioresistens (D) in combination with A. All strategies used resulted in a decrease of the hydrocarbon content, while biochar addition (B, C, D strategies) led to acceleration of decomposition in the beginning. Microbial biomass and respiration rate increased significantly at the start of bioremediation. For microbial biomass, moistening and aeration were the main factors of the changes observed, while for respiration, the main factors were biochar and the introduction of microbes. All four remediation strategies altered bacterial community structure and phytotoxicity. Illumina MiSeq method revealed 391 unique OTUs belonging to 40 bacterial phyla and a domination of Proteobacteria in all investigated soil samples. The lowest alpha-diversity was observed in the samples with introduced bacteria on the first day of remediation. Metric multidimensional scaling demonstrated that in the beginning and at the end, microbial community structures were more similar than those on the 28th day of remediation. Strategies A and B decreased phytotoxicity of remediated soil in 2.5–3.1 times as compared with untreated soil. C and D strategies led to additional decrease of phytotoxicity in 2.1–3.2 times.