A Slow-Release Reduction Material of Escherichia Sp. F1 Coupled with Micron Iron Powder Achieves the Remediation of Trichloroethylene-Contaminated Soil

Abstract

Trichloroethylene (TCE) is a common organic pollutant found in soil. The oxide passivation layer covering the surface of micron iron powder prevents the release of its reducing components, resulting in ineffective reduction and purification of TCE in soil. A slow-release reduction material "Escherichia sp. F1-micron iron powder" was constructed to enhance TCE degradation in soil. A new iron-reducing bacterium Escherichia sp. F1 was isolated from soil contaminated with chlorinated hydrocarbon, the reduction rate of Fe(III) was 38.7% within 15 days, showing sustained iron reduction ability. Genome sequencing revealed that the strain contained 53 functional iron reduction and 2 dehalogenation genes. Single-factor experiments indicated that the optimal conditions for TCE degradation in soil using the coupling material were as follows: the glucose concentration was 40 mmol/kg, the soil water content was 50%, and the bacterial inoculum was 1% (v:w). Under these optimal degradation conditions, the coupled material reached 86.86% degradation of TCE in soil within 28 days. Further analysis using x-ray photoelectron spectroscopy of micron iron powder, soil Fe(II) concentration, and soil physiochemical properties demonstrated that the addition of strain F1 to soil could destroy the passivation layer of iron oxide on the surface of micron iron powder, promoted the exposure of its reaction sites and internal reducing active components, realized in situ self-actuated activation of passivated micron iron powder, thus improving the removal rate and achieving complete dechlorination of TCE in soil. Soil microbial high-throughput sequencing revealed that strain F1 addition regulated the soil bacterial community, leading to the significant enrichment of Escherichia-Shigella related to iron-reducing function. This promotion facilitated the degradation of TCE in soil by coupling materials. The functional material plays an important role in the realization of low-cost green treatment and risk control of chlorinated organic pollutants-contaminated sites.

Keywords: soil, trichloroethylene, iron-reducing bacterium, micron iron powder, remediation