Distribution of ion contents and microorganisms during the electro-bioremediation of petroleum-contaminated saline soil

This study investigated the distribution of ion contents and microorganisms during the electro-bioremediation (EK-Bio) of petroleum-contaminated saline soil. The results showed that soil ions tend to accumulate around the electrodes, and the concentration was correlated with the distance from the electrodes. The average soil ion content was 7.92g/kg around the electrodes (site A) and 0.55g/kg at the furthest distance from the electrodes (site B) after 112days of treatment, while the initial average content was 3.92g/kg. Smooth linear (R-2 = 0.98) loss of soil ions was observed at site C, which was closer to the electrodes than site B, and had a final average soil ion content of 1.96g/kg. The dehydrogenase activity was much higher in EK-Bio test soil than in the Bio test soil after 28days of treatment, and followed the order: site C > site B > site A. However, the soil dehydrogenase activity dropped continuously when the soil ion reached very high and low concentrations at sites A and B. The soil microbial community varied in sample sites that had different ion contents, and the soil microbial diversity followed the order: site C > site B > site A. The applied electric field clearly enhanced the biodegradation efficiency for soil petroleum contaminants. However, the biodegradation promotion effects were weakening in soils where the ion contents were extremely high and low (sites A and B). These results can provide useful information for EK-Bioremediation of organic-contaminated saline soil.