Effects of electrokinetic operation mode on removal of polycyclic aromatic hydrocarbons (PAHs), and the indigenous fungal community in PAH-contaminated soil

Abstract

Electrokinetic remediation is an emerging physical remediation technology for the removal of heavy metals and organic chemicals from contaminated soil. We set up a soil chamber (24 × 12 × 8 cm) with two stainless steel electrodes (12 × 0.5 cm), and a constant voltage gradient of 1.0 v cm⁻¹ or 2.0 v cm⁻¹ was applied to study the effects of unidirectional and altered directional electric field operation modes on the moisture content and pH, the removal rate of PAHs, and the abundance and diversity of indigenous fungi in a PAH-contaminated soil at the Benxi Iron and Steel Group Corporation (N41°17′24.4″, E123°43′05.8″), Liaoning Province, Northeast China. Electrokinetic remediation increased the PAH removal rate, but had less effect on soil moisture content and pH, in comparison with the control. In the 1 v cm⁻¹ altered directional operation, in particular, the PAH removal rate by the end of the experiment (on day 23) had increased from 5.2% of the control to 13.84% and 13.69% at distances of 4 and 20 cm from the anode, respectively, and to 18.97% in the middle region of the soil chamber. On day 23, the indigenous fungal 18S rRNA gene copy numbers and community diversity were significantly higher in a voltage gradient of 1 v cm⁻¹ than in a voltage gradient 2 v cm⁻¹. An altered directional operation was more conducive to the fungal community's uniform distribution than was a unidirectional operation of the electric field. We found the major PAH-degrading fungi Fusarium oxysporum and Rhizophlyctis rosea to be present under EK remediation. We suggest that a 1 v cm⁻¹ altered directional operation could be an appropriate electrokinetic operation mode for PAH removal, and the maintenance of abundance and diversity of the indigenous fungal community.

Keywords:

• electrokinetic remediation
• electric field
• fungi
• electric intensity
• PAHs

Acknowledgments

This work was supported in part by the Knowledge Innovation Project Key Direction Project Sub-project of the Chinese Academy of Sciences (No. KZCX2-EW-407), the National High Technology Research and Development Program (863) of China (No. 2012AA100603), and the National Science Foundation of China (Nos. 41271336 and 41271336).