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National Institute of Environmental Health Sciences

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Your Environment. Your Health.

Final Progress Reports: University of Iowa: Phytoremediation to Degrade Airborne PCB Congeners from Soil and Groundwater Sources

Superfund Research Program

Phytoremediation to Degrade Airborne PCB Congeners from Soil and Groundwater Sources

Project Leader: Jerald L. Schnoor
Grant Number: P42ES013661
Funding Period: 2006-2020
View this project in the NIH Research Portfolio Online Reporting Tools (RePORT)

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Final Progress Reports

Year:   2019  2014  2009 

The goal of this project is to provide engineering research (non-biomedical) to determine whether plants can be used for the in situ bioremediation of PCB congeners from airborne sources. Plants can uptake PCB congeners from soil and groundwater, as well as from air directly. Together with the plants, microbes in the rhizosphere of plants can break-down PCBs to less toxic products depending on the metabolites produced. In 2014, researchers continued to identify novel metabolites within plant tissues and to elucidate their reaction pathways (e.g., chiral PCB metabolites). Using metagenomics, researchers have identified the dominate groups of bacteria and individual species in a sediment core contaminated with PCBs. By mining 16S rDNA databases, researchers revealed that a large proportion of 'no blast' sequences belong to an uncultured Thiobacillus sp. that was previously detected at various contaminated sites and which may play a role in PCB natural attenuation. Results from microcosm experiments showed that the combined use of phytoremediation and bioaugmentation with Burkholderia xenovorans LB400 could be an efficient and sustainable strategy to remediate PCB contaminated soil.

Highlights:

  1. Reactivity of chiral PCB metabolites in plants. Poplar plants can enantioselectively uptake and biotransform chiral 5-OH-PCB95, but not chiral 5-OH-PCB91. This has important implications for which chiral metabolites are recalcitrant in the environment and which are ultimately degraded.
  2. Metagenomic Analysis of the Bacterial Community in a PCB-Contaminated Sediment Core. Using 16S rDNA metagenomic pyrosequencing, researchers obtained detailed profiles of the bacterial community structure in a sediment core from a PCB-contaminated site which showed that the dominant bacterial groups in all core sections were taxa containing known PCB-degraders: Firmicutes, Proteobacteria, Bacteroidetes, and Actinobacteria. Interestingly, a strong correlation was also detected between PCBs and unidentified 16S rDNA ('no blast'), suggesting the presence of unknown bacterial species involved in the PCB metabolism. Mining further 16S rDNA databases revealed that a large proportion of 'no blast' sequences belong to an uncultured Thiobacillus sp. that was previously detected at various contaminated sites and may play a role in PCB natural attenuation.
  3. Bioaugmentation with LB400. Results from microcosm experiments show that combined use of phytoremediation and bioaugmentation with Burkholderia xenovorans LB400 could be an efficient and sustainable strategy to remediate PCB contaminated soil.

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