Soil Dielectric, Temperature, and Heat Capacity Data from Ontario Agricultural Soils Undergoing Phase Transitions in a Laboratory Setting

The aim of this research project is to develop an in-situ method to measure hydrological processes in frozen soils through the characterization of coaxial impedance dielectric reflectometry probe response to soil freeze-thaw events. This data set is collected for the project titled Transformative sensor Technologies and Smart Watershed (TTWS), which is a Pillar 3 project under the Global Water Futures Program funded by Canada First Research Excellence Fund.

We conducted an experiment to characterize the response of Steven’s HydraProbe (HP), a coaxial impedance dielectric reflectometry probe, to phase state transitions of soil moisture using coincident measurements from heat pulse probes (HPP). Soil samples were collected in the from the University of Guelph’s Elora Research Station (sandy loam; collected late Fall 2017) as well as private farms in Cambridge (loamy sand; collected late Fall 2017) and Dunnville (clay loam; collected during a mid-winter thaw in 2018), all in Ontario. Ten undisturbed mesocosms were extracted from each site in Polyvinyl chloride (PVC) cylinders measuring 12 cm in height and 10 cm in diameter. The holders were only filled to a depth of 10 cm. Each PVC sample holder was machined to accommodate a horizontally placed HP at a depth of 2.5 cm into the soil profile (4.5 cm below the top of the holder). This was complimented by the orthogonal insertion of two heat pulse probes, placed horizontally and diametrically opposed, covering the vertical span of the HP’s sensing volume. The temperature and permittivity (ⲉ) were measured using HPs while two HPPs captured the apparent heat capacity at 24-minute intervals. The collected samples were placed in insulated cardboard boxes and filled with sand to laterally insulate the mesocosms and mimic a freezing front. The soil samples were subjected to temperature transitions from +10 °C to -10 °C and vice versa at ~24-hour intervals. Each mesocosm had different soil moisture content levels, either from collection, addition of distilled water, or removal of water by oven drying. One mesocosms of each soil type was oven dried at 105 °C for 48 hours to serve as a control.

Pardo, R., & Berg, A. (2019). Soil Dielectric, Temperature, and Heat Capacity Data from Ontario Agricultural Soils Undergoing Phase Transitions in a Laboratory Setting. Waterloo, Canada: Canadian Cryospheric Information Network (CCIN). (Unpublished Data).

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