Vapor-Phase Exchange of Perchloroethene between Soil and Plants

Abstract

Tree core concentrations of tetrachloroethylene (perchloroethene, PCE) at the Riverfront Superfund Site in New Haven, MO, were found to mimic the profile of soil phase concentrations. The observed soil-tree core relationship was stronger than that of groundwater PCE to tree core concentrations atthe same site. Earlier research has shown a direct, linear relationship between tree core and groundwater concentrations of chlorinated solvents and other organics. Laboratory-scale experiments were performed to elucidate this phenomenon, including determining partitioning coefficients of PCE between plant tissues and air and between plant tissues and water, measured to be 8.1 and 49 L/kg, respectively. The direct relationship of soil to tree core PCE concentrations was hypothesized to be caused by diffusion between tree roots and the soil vapor phase in the subsurface. The central findings of this research are discovering the importance of subsurface vapor-phase transfer for VOCs and uncovering a direct relationship between soil vapor-phase chlorinated solvents and uptake rates that impact contaminant translocation from the subsurface and transfer into the atmosphere.

Plant tissue analysis for explosive compounds in phytoremediation and phytoforensics

“…The method is particularly attractive for site with potential unexploded ordnance as the soil and groundwater need not be touched, because the plant uses the evapotranspiration to draw any compounds that are dissolved in the water phase or in the soil vapor. [16] This new approach requires the analytical methods providing the accurate concentration of contaminants detected in plant tissues for the concentration accuracy in site assessment.…”

Phytotechnologies – Preventing Exposures, Improving Public Health

“…Balouet and colleagues have investigated the use of plant sampling and environmental forensic applications (also referred to as “phytoforensics”), essentially using plants as biosensors for detecting contaminants in groundwater (Burken et al 2011). Researchers have also used plants to delineate subsurface contaminant plumes, both in the saturated and vadose subsurface horizons (Struckhoff et al 2005). The approach, which initially analyzed volatile compounds in plant tissue samples taken to the laboratory, has now advanced to in planta sampling approaches for more rapid and sensitive detection and delineation of subsurface pollutants and as indicators of subsurface degradation (Vroblesky et al .…”

“…Traditional approaches of subsurface sampling, such as extracting soil cores, require large equipment mobilization and energy inputs and the equipment can cause considerable damage to property. While phytoforensic approaches have certain limitations—namely the requirement that appropriate vegetation is present for sampling—the technology is most effective in shallow soil profiles where environmental contamination would have the greatest human exposure potential (Struckhoff et al 2005). …”

Numerical model for the uptake of groundwater contaminants by phreatophytes

“…Regression of field data at a solvent-contaminated site suggests that alternative models for plant uptake may be more appropriate and less constraining to simulate the contaminant fate in a phytoremediation system relative to the linear model [7]. In this case, regression analysis was performed between VOC transpiration concentration data collected from xylem in tree trunks and both soil and groundwater VOC concentration data to yield:…”