Change in soil ion content and soil water-holding capacity during electro-bioremediation of petroleum contaminated saline soil

Abstract

This study investigated changes in soil ion content and soil water-holding capacity during electro-bioremediation (EK-Bio) of petroleum contaminated saline soil (ion content of 3.92 g/kg). The results indicated that the soil ions surrounded the electrodes with increasing time, thus changing the soil water-holding capacity. According to the Van Genuchten model fitting results, the soil residual water content (θr) increased with the soil ion content, which represented a capacity decrease of the soil water supply. At the end of the EK-Bio experiment, the θr values in the soil near (site A) and far from (site B) the electrodes were 19.1 % and 12.1 %, where the soil ion content was 7.92 g/kg and 0.55 g/kg, respectively. The ion aggregation process significantly impacted the growth of soil microbial. The bacteria numbers decreased when the soil ion content was high (7.41 g/kg, site A) and low (0.84 g/kg, site B) after 70 days of treatment. The applied electric field significantly enhanced the bioremediation efficiency. However, the biodegradation promotion effect was the weakest at site A. The synergistic effect between the applied electric field and degrading bacteria was delayed.

Keywords: Electro-bioremediation; Microbial numbers; Soil ion; Soil water-holding capacity; Total petroleum hydrocarbons.