An assessment of correlations between chlorinated VOC concentrations in tree tissue and groundwater for phytoscreening applications

Abstract

The majority of prior phytoscreening applications have employed the method as a tool to qualitatively determine the presence of contamination in the subsurface. Although qualitative data is quite useful, this study explores the potential for using phytoscreening quantitatively. The existence of site-specific and non-site-specific (master) correlations between VOC concentrations in tree tissue and groundwater is investigated using data collected from several phytoscreening studies. The aggregated data comprise 100 measurements collected from 12 sites that span a wide range of site conditions. Significant site-specific correlations are observed between tetrachloroethene (PCE) and trichloroethene (TCE) concentrations measured for tree tissue and those measured in groundwater for three sites. A moderately significant correlation (r=0.56) exists for the entire aggregate data set. Parsing the data by groundwater depth produced a highly significant correlation (r=0.88) for sites with shallow (<4m) groundwater. Such a significant correlation for data collected by different investigators from multiple sites with a wide range of tree species and subsurface conditions indicates that groundwater concentration is the predominant factor mediating tree-tissue concentrations for these sites. This may be a result of trees likely directly tapping groundwater for these shallow groundwater conditions. This master correlation may provide reasonable order-of-magnitude estimates of VOC concentrations in groundwater for such sites, thereby allowing the use of phytoscreening in a more quantitative mode.

Phytoforensics: Trees as bioindicators of potential indoor exposure via vapor intrusion

“…Additionally, many of the groundwater samples were collected greater than 15 m bgs; therefore, trees in some areas might be taking up shallower, infiltrated groundwater from local recharge with smaller PCE concentrations from dilution than the samples at depth. A recent review of 12 sites in a previous study found that the coefficient of determination (R 2 ) between tree-core and groundwater concentrations increased from 0.56 to 0.88 when deeper (>4 m) groundwater was excluded [ 25 ], suggesting the poor correlation between tree and groundwater contamination at this site may be a result of both data sparsity and depth of groundwater.…”

Phytoscreening for Per- and Polyfluoroalkyl Substances at a Contaminated Site in Germany

“…Phytoscreening is primarily used to qualitatively determine spatially distributed groundwater contamination. Duncan and Brusseau indicated that that this method can reveal correlations between concentrations in tree tissues and groundwater. However, plant uptake is species-specific and depends upon many factors, such as the depth of the water table, evapotranspiration rates, season, and physicochemical properties of the contaminant …”

“…However, plant uptake is species-specific and depends upon many factors, such as the depth of the water table, evapotranspiration rates, season, and physicochemical properties of the contaminant. 33 Nonetheless, phytoscreenings have been successfully performed for various organic contaminants, including volatile organic compounds (VOCs), 33,34 aromatic hydrocarbons, 35 and inorganic contaminants, such as heavy metals. 36 Gobelius et al 37 demonstrated that certain plant species are suitable for both (i) the phytoscreening of PFAS and (ii) constantly removing the contaminants from soil and groundwater by harvesting leaves, commonly known as phytoremediation.…”

“…As such, there are clear benefits over traditional soil and groundwater investigations and sampling. 33 Moreover, within a short period of time, a great number of samples across large areas can be collected and analyzed. Phytoscreening is primarily used to qualitatively determine spatially distributed groundwater contamination.…”

“…Sampling tree cores and leaves is quick, simple, and cost-effective. As such, there are clear benefits over traditional soil and groundwater investigations and sampling . Moreover, within a short period of time, a great number of samples across large areas can be collected and analyzed.…”