Low-temperature thermally enhanced bioremediation of polycyclic aromatic hydrocarbon-contaminated soil: Effects on fate, toxicity and bacterial communities

Remediation of polycyclic aromatic hydrocarbon (PAH)-contaminated soil using thermal desorption technology typically requires very high temperatures, necessitating coupled microbial treatment for energy and cost reduction. This study investigated the fate and toxicity of PAHs as well as the responses of microbial communities following thermal treatment within a low temperature range. The optimal temperature for PAH mineralization was 20-28 & DEG;C, within the growth range of most mesophilic microorganisms. By contrast, 50 & DEG;C treatment almost completely inhibited PAH mineralization but resulted in the greatest detoxification effect particularly for cardiotoxicity and nephrotoxicity. A potential increase in toxicity was observed at 28 & DEG;C. Co-metabolism and nonextractable residue formation may play an interdependent role in thermally enhanced bioremediation. Moreover, alterations in bacterial communities were strongly associated with PAH mineralization and zebrafish toxicity, revealing that soil microorganisms play a direct role in PAH mineralization and served as ecological receptors reflecting changes in toxicity. Network analysis revealed that Firmicutes formed specific ecological communities at high temperature, whereas Acidobacteria and Proteobacteria act as primary PAH degraders at moderate temperature. These findings will enable better integration of strategies for thermal and microbial treatments in soil remediation.

Automated summary

Thermal desorption technology is commonly used to remediate PAH-contaminated soil, but it requires high temperatures. This study found that low temperatures (20-28°C) were optimal for PAH mineralization, which is important for the growth of microorganisms. However, higher temperatures (50°C) inhibited PAH mineralization, but had the greatest detoxification effect. Bacterial communities were found to play a direct role in PAH mineralization and reflected changes in toxicity, highlighting the importance of microbial treatments in soil remediation.