Soil ice content measurement using a heat pulse probe method

Liu, G. and Si, B. C. 2011. Soil ice content measurement using a heat pulse probe method. Can. J. Soil Sci. 91: 235–246. Measuring the volume-based ice content (θi) and thermal conductivity (k) of frozen soil is important for modeling energy and water balance of the earth's surface. The objective of this study was to examine whether a heat pulse probe (HPP) method can be used to measure soil ice content. To minimize ice melting, a heat pulse of duration of 60 s and strength of q′≈25 W m−1was used for a HPP in frozen sands at various temperatures (T). For a 60-s heating duration, we compared the infinite line source (ILS) solution and finite line source solution with the solution of finite sample size and finite line source through simulations. The simulation suggested that a 60-s heating duration for ILS can be used for long heater probes in infinite media, or short probes in finite size samples in containers made of thermally insulating materials. In this study, sands were packed in small containers with heat pulse probes and a 60-s heating duration, and ILS were used for ice content estimation. Our results suggest that the HPP method has limited use in frozen soil. For sands with a mean grain size of 0.41 mm and 2.13 mm, there were good agreements between the HPP measured and gravimetric θivalues at temperature below −22°C and −18°C, respectively. However, above these temperatures, ice melting was significant and would lead to overestimation of θi. The higher the initial temperature, the larger the overestimation of θi.