Phytoscreening with SPME: Variability Analysis

Abstract

Phytoscreening has been demonstrated at a variety of sites over the past 15 years as a low-impact, sustainable tool in delineation of shallow groundwater contaminated with chlorinated solvents. Collection of tree cores is rapid and straightforward, but low concentrations in tree tissues requires sensitive analytics. Solid-phase microextraction (SPME) is amenable to the complex matrix while allowing for solvent-less extraction. Accurate quantification requires the absence of competitive sorption, examined here both in laboratory experiments and through comprehensive examination of field data. Analysis of approximately 2,000 trees at numerous field sites also allowed testing of the tree genus and diameter effects on measured tree contaminant concentrations. Collectively, while these variables were found to significantly affect site-adjusted perchloroethylene (PCE) concentrations, the explanatory power of these effects was small (adjusted R² = 0.031). 90th quantile chemical concentrations in trees were significantly reduced by increasing Henry's constant and increasing hydrophobicity. Analysis of replicate tree core data showed no correlation between replicate relative standard deviation (RSD) and wood type or tree diameter, with an overall median RSD of 30%. Collectively, these findings indicate SPME is an appropriate technique for sampling and analyzing chlorinated solvents in wood and that phytoscreening is robust against changes in tree type and diameter.

Keywords::

• chlorinated solvents
• phytoforensics
• phytoremediation
• tree-coring

Acknowledgments

This field work was sponsored by a number of industrial, governmental and industrial partners. Much of the European work was funded through ADEME by the project “Pollution Investigation by Trees” including support from collaborators Chris Balouet and Michelle Chalot. Investigations at many sites in Canada were funded by the Ontario Ministry of the Environment (MOE Best in Science Program, Project #7824) and sampling assistance was provided by The University Consortium for Field Focused Groundwater Contamination Research Program (University of Guelph, ON, Canada). Other field site partners include John Schumacher and Jordan Wilson of USGS, Foth Environmental, The Dow Chemical Company, U.S. EPA, URS, and DuPont. The authors also thank the Missouri S&T Environmental Research Center for analytical assistance and V.A. Samaranayake for statistical guidance. Matt Limmer was supported through a Graduate Research Fellowship by the National Science Foundation.