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

Project-Specific Links

Final Progress Reports

Year:   2019  2014  2009 

In 2019, the research team made several new findings:

1. PCB 91 can be selectively uptaken and metabolized based on the differential chirality of its isomers in liver tissues of mice. Previously, the researchers showed that similar enantioselectivity could be demonstrated in transport through plant tissues of poplar. Thus, the researchers continue to advance understanding of the “green liver model” for plant uptake and metabolism of toxic chlorinated organic contaminants and the analogous processes in mammalian tissues.
2. Toxicity testing conducted with the model plant, Arabidopsis thaliana, has revealed that OH-PCBs are more toxic than parent PCBs and that different OH-PCB isomers exhibit different levels of toxicity. Whole-genome expression analyses were conducted to compare the effects of 2,5-DCB and three of its OH-isomers on Arabidopsis plants. The higher toxicity of OH-PCBs is related to their inability to induce xenobiotic response genes (XRGs): e.g., cytochrome P-450 monooxygenases, glutathione S-transferases. The higher toxicity of OH-PCBs is also related to the inhibition of brassinosteroid synthesis. Two molecular mechanisms of regulation of XRGs are under investigation: MicroRNAs and DNA (cytosine) methylation.
3. Project researchers have evidence of dechlorination of PCBs with sediment material collected previously from Altavista Virginia, site E2. Material from the original microcosms was transferred to anaerobic media (RAMM), and fed electron donor (e.g., lactate and other volatile fatty acids) and PCBs as electron acceptor (50 ppm Aroclor 1248). Dehalococcoides 16S rRNA gene abundance was monitored periodically. The researchers observed apparent growth of Dehalococcoides within the first two months of incubation, followed by a similar magnitude decrease over the following two months.
4. Uptake, translocation, and metabolism of toxic organic chemicals are important processes in plants, such as poplar, and in some food plants like pumpkin, rice and soybean. In 2019, project researchers showed how plant enzymatic systems detoxify halogenated organic chemicals including chlorinated paraffins, brominated bisphenols, PCBs and pesticides, and improved the modeling and prediction of bioconcentration factors of these chemicals on plant root systems.