Abstract
The extreme salinity and high internal resistance of saline-alkali soil contaminated by petroleum hydrocarbons were two key limitations for using the bioelectrochemical remediation. In order to solve two problems, we simply rinsed soil, added carbon fiber to polluted soil. The charge output was enhanced by 110% with increase of the maximum current densities from 81 to 304 mA·m−2 while hydrocarbons degradation rate enhanced by 484%, especially the high molecular weight fractions (C28–C36 of n-alkanes and 4–6 rings of PAHs). These effects were possibly due to the selective enrichment of species belonged to δ-Proteobacteria (Proteobacteria), Flavobacteriia (Bacteroidetes) or Clostridia (Firmicutes), the activities of biological electron transfer and enzymes. As we know, oxygenase gene that directly decided the process of degradation, was surveyed for the first time in soil bioelectrochemical remediation system. The results confirmed that the bio-current stimulated the activities of naphthalene dioxygenase and xylene monooxygenase and thus the hydrocarbons degradation and the electricity generation. Given that electricity generation and the remediation performance are governed by multiple factors, understanding of microbial community and enzyme gene is crucial to promote the power yield and the bioelectrochemical remediation applicability.
Highlights
IntroductionPetroleum hydrocarbons contaminated saline-alkali soil is a common polluted environment because great oilfields always locate in coastal area
Salt-influenced soils represent around 40% of the world’s lands[16]
The accumulated charge output of 260 ± 51 C for CK was gained during 65 days, which was 23%, 64% and 110% lower than these of RS (320 ± 82 C), MC (427 ± 91 C), and RM (546 ± 43 C) respectively (Fig. 1b and Figure S1b)
Summary
Petroleum hydrocarbons contaminated saline-alkali soil is a common polluted environment because great oilfields always locate in coastal area. Qin et al found that the degradation rate of petroleum hydrocarbons increased by about 30% when the soil salinity decreased from 2.86% to 0.10%18. High internal resistance is a key limiting factor to performance of MFCs19–22, particular in soil/sediment due to the low electrical conductivity[23,24]. Our previous study found that U-type soil MFC with 7.4 Ω of internal resistance exhibited better performance of petroleum hydrocarbons degradation and power generation, compared to that with 42.6 Ω10. Two treatments including were conducted to enhance bioelectrochemical remediation of petroleum hydrocarbons contaminated saline-alkali soil. Comprehensive correlations were surveyed to further understand the interaction among these factors in the bioeletrochemical remediation system
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