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.
J. L. Wilson et al., "Contaminant Gradients in Trees: Directional Tree Coring Reveals Boundaries of Soil and Soil-Gas Contamination with Potential Applications in Vapor Intrusion Assessment," Environmental Science and Technology, vol. 51, no. 24, pp. 14055-14064, American Chemical Society (ACS), Nov 2017.
The definitive version is available at https://doi.org/10.1021/acs.est.7b03466
Mathematics and Statistics
Civil, Architectural and Environmental Engineering
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)
Article - Journal
© 2017 American Chemical Society (ACS), All rights reserved.
01 Nov 2017