SYMPOSIA PAPER Published: 24 December 2013

Importance of Soil Moisture for In Situ Gas Surveying and Plume Assessment


To establish responsible values for finding subsurface groundwater or other volatile containment plumes, one must take into account the native pore size structure and current pore water (soil moisture) available. That can change gas/pore access routes and speeds from the source to the surface. Pore constriction caused by variable soil-moisture levels can alter flow and migration paths. Therefore, the assumed concentration topology findings will map differently as it affects gas egress from the plume source to the surface through surrounding soil/rock lithology. It is then necessary to normalize sampled values to account for these possible changes in subsurface soil-moisture conditions as they directly affect transfer rates and direction of volatiles. The pore-water availability throughout the lithological profile will be the most important restrictive variable element other than the native pore structures. Knowing and monitoring soil moisture over the sampling period will be crucial to determine both a normalized gas sample volume and their accumulated mass over time. If not accounted for, soil moisture created variable pore sizing can create biased topology concentrations and as a result offset location findings and/or migration patterns where unadjusted standard grid sampling or single-point techniques were used.

Author Information

Skaling, Whitney
Soilmoisture Equipment Corp., Goleta, CA, US
Farsad, Ali
Soilmoisture Equipment Corp., Goleta, CA, US
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Developed by Committee: G18
Pages: 92–112
DOI: 10.1520/STP157020130037
ISBN-EB: 978-0-8031-7586-0
ISBN-13: 978-0-8031-7585-3