Bioelectric field accelerates the conversion of carbon and nitrogen in soil bioelectrochemical systems

Soil bioelectrochemical systems (BESs) utilize indigenous microorganisms to generate biocurrent/electric fields that stimulate the degradation of organic pollutants, exhibiting great potential in the removal of petroleum hydrocarbons from soils. In this study, a horizontal bioelectric field was constructed to investigate the conversion of carbon and nitrogen in a soil BES. After 182 days, the degradation rates of total petroleum hydrocarbons, alkanes, and aromatics were promoted by 52 %, 38% and 136%, respectively. Meanwhile, the bioelectric field accelerated NH₄⁺-N production near the cathode, whereas NH₄⁺-N consumption near the anode indicated that the bioelectric field promoted the cathode-dominated ammoniation process and the anode-dominated denitrification process. Additionally, a distinctive microbial community was formed under the bioelectric field, and the improved degradation on the cathode and the anode relied on special functional bacteria (typically, cathode, Alcanivorax; anode, Marinobacter). The dramatic enrichment in anodic denitrifying bacteria, including Pontibacillus, Sediminimonas, Georgenia, etc., explained the enhanced denitrification process under the bioelectric field. This study simultaneously clarified the carbon and nitrogen conversion processes and corresponding bacterial community occurring under the bioelectric field for the first time, helping to form regulation strategies in the practical application of soil BESs and providing a new perspective for removing petroleum hydrocarbons from soils.