Evaluation of thermal properties of soils amended with microplastics, vermicompost and zeolite using experimental and modeling data

Abstract

The thermal properties of soils can be influenced by additives of different origins (non-organic, organic and mineral) and roles in soil quality. This study aims to evaluate the effects of microplastics, vermicompost, and zeolite on the thermal properties of two soil types using a combination of experimental data and modeling approaches. Laboratory experiments were conducted using surface layer samples of a clay soil (Vertic Phaeozem) and a loam soil (Haplic Cambisol). Each additive was applied at a mass ratio of 10% to the soil samples. The thermal conductivity (λ), thermal diffusivity (D) and volumetric heat capacity (Cv) were measured with the SH1 sensor of a KD2Pro device during the drainage process of the soil samples at different matric potentials. The relationships between λ, Cv, D, gravimetric water content, and matric suction (h) were analyzed using linear and polynomial regression models (for Cv and D) and a closed-form equation (for λ). The fitted models exhibited small errors, such as a root mean square error (RMSE) of 0.03-0.06 W m-1 K-1, and high coefficient of determination R2>0.9. The effects of the different additives on water retention, λ, Cv and D were found to be specific to each soil type and depended on the properties of both the soil and the additives. These findings highlight the significance of additives in modifying soil thermal properties and emphasize the importance of considering the interactions between soil characteristics and additive properties. The combination of experimental data and modeling approaches provides valuable insights into understanding the complex dynamics of soil thermal properties and the potential impacts of additives on soil functionality and quality.

Keywords

• microplastics
• thermal conductivity
• thermal diffusivity
• vermicompost
• volumetric heat capacity
• zeolite