Synergistic Effect of Soil Organic Matter and Nanoscale Zero-ValentIron on Biodechlorination

Nanoscale zero-valent iron (nZVI) provides apromising solution for organochlorine (OC)-contaminated soilremediation. However, the interactions among nZVI, soil organicmatter (SOM), and indigenous dechlorinating bacteria are intricate,which may result in unascertained effects on the reductivedegradation of OCs and merits specific investigation. Herein, weisolated an indigenous dehalogenation bacterium (Burkholderiaambifariastrain L3) from a paddy soil and further investigated thebiodechlorination of pentachlorophenol (PCP) with individual anda combination of SOM and nZVI. In comparison with individual-strain L3 treatment, the cotreatment with nZVI or SOM increasedthe removal efficiency of PCP from 34.4 to 44.3-54.2% after 15 daycultivation. More importantly, a synergistic effect of SOM and nZVIwas observed on the PCP removal by strain L3, and the PCP removal efficiency reached up to 75.3-84.5%. Other than thebiodegradation through ortho- and meta-substitution under the individual application of SOM or nZVI, PCP was furtherbiodegraded to 2,4,6-trichlorophenol (TCP) through para-substitution by the isolated bacteria with the cotreatment of SOM andnZVI. The main roles of the nZVI-SOM cotreatment in the biodegradation included the SOM-facilitated microbial proliferation,the nZVI-promoted microbial transformation of SOM, and the induced higher electron transport capacity of redox Fe-PCPbiocycling. Thesefindings provide a novel insight into the action of nZVI in environmental remediations.

Automated summary

Nanoscale zero-valent iron (nZVI) shows promise for remediating organochlorine-contaminated soil. However, the interactions between nZVI, soil organic matter (SOM), and dechlorinating bacteria are complex and may have uncertain effects on the degradation of organochlorines. This study investigates the biodechlorination of pentachlorophenol (PCP) with a specific bacterium (Burkholderia ambifaria strain L3) in the presence of nZVI and SOM. The results show that the cotreatment of nZVI and SOM enhances the PCP removal efficiency, with a synergistic effect observed. The nZVI-SOM cotreatment promotes microbial proliferation, microbial transformation of SOM, and higher electron transport capacity, leading to enhanced biodegradation. These findings provide valuable insights into the use of nZVI for environmental remediation.