Contaminant Gradients in Trees: Directional Tree Coring Reveals Boundaries of Soil and Soil-Gas Contamination with Potential Applications in Vapor Intrusion Assessment


Contaminated sites pose ecological and human-health risks through exposure to contaminated soil and groundwater. Whereas we can readily locate, monitor, and track contaminants in groundwater, it is harder to perform these tasks in the vadose zone. In this study, tree-core samples were collected at a Superfund site to determine if the sample-collection location around a particular tree could reveal the subsurface location, or direction, of soil and soil-gas contaminant plumes. Contaminant-centroid vectors were calculated from tree-core data to reveal contaminant distributions in directional tree samples at a higher resolution, and vectors were correlated with soil-gas characterization collected using conventional methods. Results clearly demonstrated that directional tree coring around tree trunks can indicate gradients in soil and soil-gas contaminant plumes, and the strength of the correlations were directly proportionate to the magnitude of tree-core concentration gradients (spearman's coefficient of -0.61 and -0.55 in soil and tree-core gradients, respectively). Linear regression indicates agreement between the concentration-centroid vectors is significantly affected by in planta and soil concentration gradients and when concentration centroids in soil are closer to trees. Given the existing link between soil-gas and vapor intrusion, this study also indicates that directional tree coring might be applicable in vapor intrusion assessment.


Mathematics and Statistics

Second Department

Civil, Architectural and Environmental Engineering

Research Center/Lab(s)

Center for High Performance Computing Research


This material is based upon work supported by the National Science Foundation under grant no. #1336877.

Keywords and Phrases

Contamination; Core samples; Forestry; Groundwater; Groundwater pollution; Health risks; Impurities; Soils; Trees (mathematics); Concentration gradients; Contaminant distributions; Contaminated sites; Contaminated soils; Conventional methods; Higher resolution; Human health risks; Soil concentrations; Soil pollution; Assessment method; Concentration (composition); Contaminated land; Pollutant; Public health; Superfund; Trees; Vadose zone; Humans; Linear regression analysis; Plume; Tree trunk; Vapor; Gases; Soil pollutants

International Standard Serial Number (ISSN)

0013-936X; 1520-5851

Document Type

Article - Journal

Document Version


File Type





© 2017 American Chemical Society (ACS), All rights reserved.

Publication Date

01 Nov 2017