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Title: Laboratory and Field Measurements of SoilBulk Electrical Conductivity Using Time Domain Reflectometry
Authors: American Geophysical Union, Fall Meeting 2013
Contributors: 國立臺灣海洋大學:應用地球科學研究所
Date: 2013-12
Issue Date: 2017-01-19T07:06:17Z
Publisher: American Geophysical Union, Fall Meeting 2013
Abstract: Abstract: As the increasing of contamination in soil and groundwater, there is a demand for fast, accurate, and cost-effective techniques for contaminated site investigation. Time domain reflectometry (TDR) is a nondestructive geophysical method that allows, in real time, simultaneous estimation of both the dielectric constant and the bulk soil electrical conductivity (EC). On such bases, TDR is a technique that could potentially be adapted for continuous monitoring of solute contaminants in soil and water. The objective of this study is to assess the performance of TDR for estimating the EC and the solute concentration through the laboratory experiments and then applied it to a field of mercury contamination in the sediments. Measurement of EC using TDR is based on the attenuation of the applied voltage as it traverses the medium of interest. Once the geometric constant of the probe can be determined and the mismatch of the TDR instrument can be corrected during the experimental setup, EC can easily be accurately evaluated through a single TDR measurement on the considered sample. The results obtained from the laboratory experiments showed the good agreement between the TDR measurement and conductivity meter, and the linear relationship between EC and solute concentration is also validated. Given a specific concentration of solution, the decrease of EC with the decrease of water content followed Archie's law. Experiments with releasing a pulse and continuous potassium nitrate solutions into a soil column were conducted to demonstrate the TDR capability of real time monitoring. The results showed that the breakthrough curve (BC) can be accurately and clearly delineated by the TDR measurement. In this study, the TDR application was also extended to a contaminated site in southern Taiwan. The mercury contaminated sediments were deposited at the bottom of saline lakes and the TDR probes were modified to overcome the measurement under the water. The field work showed that the spatial distribution of relative-high mercury concentrations could be identified by TDR. Although the absolute mercury concentration is still undetermined, but the feasibility of using TDR as a reference tool for contaminant site investigation and self-assessment of remediation was successfully demonstrated.
Appears in Collections:[Institute of Applied Geosciences] Lecture & Seminar

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