Changes in the thermal conductivity of soil with different salts

Purpose Soil thermal conductivity (λ) is an important physical parameter in agricultural, meteorological, and geophysical processes. Few datasets are available for investigating the response of the λ in soils containing different salts. In this study, we compared the effects of different salt types and contents on the λ of quartz sand and determined the changes in λ of various salt-affected soils before and after salt leaching. Materials and methods Quartz sand and different types of salt with different contents were mixed, and various salt-affected soils were collected. The λ of different samples with a series of known water contents was determined by using a portable thermal property tester. Results and discussion The salts did not influence the λ of the sand in the dry state or at relatively high moisture contents. At intermediate moisture contents, the λ was lower by 0.11 W m −1 K −1 , 0.07 W m −1 K −1 , and 0.05 W m −1 K −1 for the sand with chloride, sulfate, and bicarbonate, respectively, than that of soil without the salts. The salinity insignificantly influenced the λ of the sand with 3–9 g kg −1 salts when the salt content in the sand was greater than 3 g kg −1 for most salt types. The effects of salt type on the decrease in λ followed the order of chloride > sulfate > bicarbonate. The λ of quartz sand with added CaCl 2 and KCl decreased the greatest, followed by soil with NaCl and MgCl 2 . After washing away salts, λ increased significantly by 13.1% and by 15.1% for the saline soil with a large amount of sodium chloride and for the soils characterized by strong chloride-sulfate with a medium moisture content, respectively. A slight difference in the λ was observed for sodic soil with a relatively high bicarbonate content. Conclusions The effects of salts in soil on λ were different with different water contents. At intermediate water content, the λ decreased to various degrees in various saline soils. The λ decreased significantly for the soil with chloride salts. This study aimed to support the qualification of the thermal regime and the modeling of coupled heat and water transfer in salinized soil.