Determination of vadose zone water content using gas-phase partitioning tracers combined with time-lapse electrical conductivity measurements
EMSL Project ID
47846
Abstract
Water content is an important indicator of contaminant distribution and plays a governing role in contaminant transport within the vadose zone. Understanding the water content distribution is critical for both remediation and contaminant flux monitoring in unsaturated environments. In this work we propose to further develop method we've recently demonstrated capable of remotely determining water content levels using gas phase partitioning tracers and time-lapse bulk electrical conductivity measurements. Results have demonstrated the capability to accurately monitor gas breakthrough curves along the length of a column according to the corresponding electrical conductivity response, and to adequately determine gas partitioning coefficients, leading to accurate water content estimates for the tested conditions. So far, the new method has only been tested for a limited water content range on clean, well-characterized sand under controlled laboratory conditions in the EMSL.This Science Theme proposal builds on the recent demonstration work. The main objective is to increase our understanding of the physical and chemical processes associated with the novel combination method by: (1) determination of the range in moisture contents than be accurately obtained under unsaturated conditions, (2) testing the validity of the method for systems with variable water contents, (3) investigation of the applicability of the method for natural sediments, and (4) demonstration of its feasibility for heterogeneous, multidimensional systems.
This work is motivated by the need to develop effective characterization and monitoring techniques for contaminated deep vadose zone environments, and might ultimately lead toward uniquely characterized and monitored water content levels at the field scale and in three-dimensions using electrical resistivity tomography. The proposed work is necessary to bridge the gap from the recently completed proof-of-principle experiments and analysis to application at a larger scale. The proposal addresses the Geochemistry/Biogeochemistry and Subsurface Science call for intermediate scale flow and reactive transport studies with geochemical relevance to vadose zone subsurface environments. We request experimental support from the EMSL to complement our theoretical development efforts geared towards understanding the partitioning tracer geochemistry in natural unsaturated sediments and implementation of the reactive transport into the STOMP simulator. In that respect, the experimental data sets will be used to test the theory and validate the modified simulator.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2013-10-01
End Date
2015-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Co-Investigator(s)
Team Members