Quantification of toluene phytoextraction rates and microbial biodegradation functional profiles at a fractured bedrock phytoremediation site

Michael BenIsrael; Philipp Wanner; Jeremy Fernandes; Joel G Burken; Ramon Aravena; Beth L Parker; Elizabeth A Haack; David T Tsao; Kari E Dunfield

doi:10.1016/j.scitotenv.2019.135890

Quantification of toluene phytoextraction rates and microbial biodegradation functional profiles at a fractured bedrock phytoremediation site

Sci Total Environ. 2020 Mar 10:707:135890. doi: 10.1016/j.scitotenv.2019.135890. Epub 2019 Dec 5.

Authors

Michael BenIsrael¹, Philipp Wanner², Jeremy Fernandes², Joel G Burken³, Ramon Aravena⁴, Beth L Parker², Elizabeth A Haack⁵, David T Tsao⁶, Kari E Dunfield⁷

Affiliations

¹ School of Environmental Sciences, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada.
² G(360) Institute for Groundwater Research, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada.
³ Civil, Architectural and Environmental Engineering, Missouri University of Science and Technology, 1401 N. Pine St., Rolla, MO 65409-0030, USA.
⁴ Department of Earth and Environmental Sciences, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada.
⁵ EcoMetrix Inc., 6800 Campobello Road, Mississauga, ON L5N 2L8, Canada.
⁶ BP Corporation North America Inc., 150 W Warrenville Road #605-2E, Naperville, IL 60563, USA.
⁷ School of Environmental Sciences, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada. Electronic address: dunfield@uoguelph.ca.

PMID: 31865073
DOI: 10.1016/j.scitotenv.2019.135890

Abstract

This field study evaluated the efficacy of a mature hybrid poplar phytoremediation system for the remediation of toluene in a fractured bedrock aquifer site. Phytoextraction activity of the trees and the ecology and biodegradation potential of root-colonizing bacteria that ultimately influence how much toluene is transported from the roots and phytoextracted to the aboveground point of measurement were explored. Peak-season toluene mass removal rates ranging from 313 to 743 μg/day were quantified using passive in planta contaminant sampling techniques and continuous heat dissipation transpiration measurements in tree stems. Root bacterial microbiome structure and biodegradation potential were evaluated via high-throughput sequencing and predictive metagenomic functional modelling of bacterial 16S rRNA genes in roots. Poplar roots were colonized mostly by Proteobacteria, Actinobacteria, and Bacteroidetes. Distinct, more uniform communities were observed in roots associated with trees planted in the toluene source area compared to other areas, with differences apparent at lower taxonomic levels. Significant enrichment of Streptomyces in roots was observed in the source area, implicating that genus as a potentially important poplar endophyte at toluene-impacted sites. Moreover, significantly greater aerobic toluene biodegradation capacity was predicted in these roots compared to other areas using taxonomic functional modelling. Together with passive sampling, the molecular results provided supporting evidence of biodegradation activity in the source area and contextualized the detected phytoextraction patterns. These results support the application of phytoremediation systems for aromatic hydrocarbons in environments with complex geology and demonstrate field-validated monitoring techniques to assess phytoextraction and biodegradation in these systems.

Keywords: BTEX hydrocarbons; Endophyte; Molecular biological tools; Root microbiome; Site monitoring; Site remediation.

MeSH terms

Biodegradation, Environmental*
Groundwater
RNA, Ribosomal, 16S
Toluene
Water Pollutants, Chemical

Substances

RNA, Ribosomal, 16S
Water Pollutants, Chemical
Toluene