Pore Distribution Characteristics of Layered Soil Profile in Dam Land of Loess Plateau

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    The purpose of this study is to clarify the pore distribution characteristics of layered soil widely existing in nature. The soil profile of typical dam land in the Loess Plateau was taken as the research object, and the three-dimensional structure of topsoil, plow pan and core soil was analyzed by CT scanning technology. The changes of pore parameters of layered soil with soil structure and the pore characteristics of interface layer were discussed. The results showed that: (1) Slender pores ( pore shape coefficient ≤0.2 ) were the main forms of soil pores in each soil layer. The pore parameters of each soil layer were significantly different. The total porosity of the tillage layer was the highest, and the macropores (≥1 mm) were more distributed. The total number of pores in plow pan was the highest, containing more isolated small pores (≥0.1~0.5 mm) and tiny pores (≥0.06~0.1 mm), but the connectivity was the worst. The pore parameters of the core soil layer were mostly between the upper two layers. (2) The layered soil in the dam section had a certain thickness of the interface layer, and each pore parameter had a sudden change point at the interface of the soil layer, with obvious boundary phenomenon. The pore characteristic parameters showed the law of gradual change of transition position and abrupt change of interface position. In the interface layer, the total soil porosity and connectivity of the plow pan decreased by 41.6% and 69.8%, respectively, compared with the tillage layer. The total soil porosity and connectivity of the interface layer in the subsoil layer were significantly increased by 30.4% and 52.3%, respectively, compared with the plow pan. (3) The size of pores was closely related to the pore shape, with large pore morphology mostly slender and micropore shapes being regular. (4) The deeper the soil layer, the stronger the correlation between connectivity and total porosity, total number of pores, pore size distribution and pore shape. The appearance of interface layer changed the soil pore quality of adjacent soil layer. The artificial action changed the soil pore characteristics of the tillage layer and the plow pan, which was mainly manifested in the disturbance of the tillage layer, which made the plow pan passively pressure-bearing, while the soil layer was less disturbed, and the soil as a whole presented a natural state. The results of this study can enrich the understanding of heterogeneous soil structure and provide a scientific basis for understanding the characteristics of layered soil pores and their possible effects on soil water, air and heat transport at the micro level.

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  • Received:March 13,2023
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  • Online: December 27,2023
  • Published: December 28,2023