Phytoforensic tools: directional uptake of chlorinated solvents

Trees have been used to locate contaminated soil and groundwater, augmenting traditional methods, such as well drilling, that are time-consuming and expensive. In the past decade, plant sampling has gained acceptance as a reliable method for site screening. In this new field of phytoforensics, research efforts focus on developing quicker, more accurate and more informative sampling and analysis methods for measuring contaminant concentrations in trees. These phytoforensic tools are a novel approach to site assessments, potentially reducing cost while more effectively locating contaminated groundwater. This thesis evolved from field data suggesting azimuthal concentrations in tree trunks may reflect the corresponding azimuthal concentrations in the groundwater below the tree. In the lab, large diameter trees were subjected to concentration gradients in the groundwater and analyzed for contaminants and evidence of directional uptake. Upon analysis, concentrations were approximately five times higher on the side of the tree near the highly contaminated groundwater. The conservation of azimuthal PCE and TCE gradients was observed at all levels up the tree. This indicates that advective transport in the xylem exceeds radial or circumferential diffusion of PCE and TCE. Several field sites showed similar data, where concentrations in the tree matched groundwater concentrations in an azimuthal pattern. In practice, each tree sampled directionally can provide compass-like information, pointing investigators towards the most concentrated region of the plume --Abstract, page iv