Work

In situ soil moisture and thermal properties estimated using a dual-probe heat-pulse

Year: 2024

Type: article

Abstract: In situ monitoring of the temporal and spatial distribution of soil moisture and thermal properties are important for studying the water and energy transport in the vadose zone. The single-probe heat-pulse method based on fiber Bragg grating technology (SPHP-FBG) has become a research focus in field monitoring because of its capability to realize quasi-distributed and real-time monitoring. However, the SPHP-FBG method can only obtain thermal conductivity. This study developed a dual-probe heat-pulse method based on FBG (DPHP-FBG). The DPHP-FBG method can measure thermal conductivity ( λ ), volumetric heat capacity ( C v ), and thermal diffusivity ( k ). Consequently, volumetric soil water content ( θ ) can be estimated from its linear relationship with C v . The accuracy of the DPHP-FBG method in the estimation of C v , λ , and θ was tested under different heating duration and various soil moisture conditions. In addition, Monte Carlo simulation was performed to investigate the impact of FBG measurement errors on accuracy. Finally, a field test was conducted to verify the effectiveness of the developed DPHP-FBG system. The results show that the DPHP-FBG method allows accurate soil moisture and thermal properties estimation without soil-specific calibration. The mean errors of the C v and θ decrease with the extended heating duration. When the heating lasts 20 s, the measured C v and θ have mean errors of 0.02 MJ m −3 K −1 and 0.01 m 3 /m 3 , respectively, for various moisture conditions. In the field test, the spatio-temporal distribution of soil moisture and thermal properties can be obtained in real time. Thereby, the proposed DPHP-FBG monitoring system is potential to conduct in situ coupled heat and soil moisture measurements at a large scale.

Source: Geoderma

DOI: 10.1016/j.geoderma.2024.117064

Authors: Jie Liu, Bin Shi, Meng-Ya Sun, Jun-Cheng Yao, Ke Fang

Institutions: Nanjing University, Hohai University, City University of Hong Kong

Language: English

Topic: Soil and Unsaturated Flow

Subfield: Civil and Structural Engineering

Field: Engineering

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $2,990

Funders: National Natural Science Foundation of China, Shanxi Provincial Key Research and Development Project, Key Research and Development Projects of Shaanxi Province