The Petrophysical Relationship between the Dielectric Permittivity and Water Content of Peat Soil Moisture Measurements

摘要

Understanding the water content patterns of soil is important in agriculture, ecosystems, and in terms of the quality of the soil, especially in peat soil. To determine the water content of peat soil, an appropriate site-specific petrophysical relationship is needed. Although a few petrophysical relationships have been established, such as the Topp equation, which is commonly used by researchers to determine the water content, the signal tends to deviate when applied in organic soils. Hence, this study aims to determine a mathematical model for the site-specific petrophysical relationship between the dielectric permittivity and the soil moisture of peat soil. Samples of peat soil were taken for laboratory measurement. A two-dimensional adjusted parallel plate capacitor was designed and fabricated for determination of the dielectric permittivity. The oven drying process was conducted for estimation of the water content. A model fitting of the relationship between the dielectric permittivity and water content was proposed, and the results indicate that a two-dimensional adjustable soil cylindrical capacitor can be used to construct a good relationship between the dielectric permittivity and the water content. Hence this appropriate site specific petrophysical relationship can be used by the GPR to determine the water content of the peat soil. Linear and polynomial models were adjusted for the peat soil in respect of the dielectric permittivity and water content. Through verifying this site-specific petrophysical relationship using GPR with a frequency of 250MHz, the adjusted linear and polynomial models provide sufficient accuracy to determine the water content of peat soil.