Improving the degradation of benzo[a]pyrene and soil biodegradability by enhanced ozonation with mechanical agitation

Abstract

Gas-phase ozone (O3) can easily diffuse into soil aggregates and effectively degrade hydrocarbon compounds. However, gas channels in soil impede remediation efficiency. This study developed an enhanced ozonation by applying mechanical agitation (100 and 150 rpm) compared with conventional ozonation (0 rpm), to improve degradation of benzo[a]pyrene (BaP) and soil biodegradability. During ozonation process, O3 consumption, BaP removal, soil carbon balance, and intermediates of BaP were investigated. Results showed that the enhanced ozonation disturbed gas channels and improved utilization of O3. At 90 min, more than 90% of the initial BaP (67.86 mg/kg) was degraded at 100 rpm, while it was 83.61% at conventional ozonation. Enhanced ozonation rapidly oxidized soil organic carbon (SOC), Acetone-n-hexane-extractable organic carbon (AeOC), residual organic carbon (ROC) and BaP into dissolved organic carbon (DOC), which increase of DOC was 31.97% higher than conventional ozonation. Enhanced ozonation accelerated decomposition of BaP to more biodegradable and lower molecular weight intermediates at short time mainly by increasing direct ozonation, which was conducive to the subsequent biodegradation. This work provides an enhanced ozonation to improve the degradation efficiency of BaP in soil by destroying gas channels and enhancing the utilization efficiency of O3 and direct ozonation.