Abstract: The pore structure of reclaimed soil in the bauxite deposit of Guangxi plays a crucial role in soil reclamation quality,but its microstructure characteristics remain unclear. This study aimed to investigate the pore structure features of locally reclaimed soil by examining two reclamation modes:grassland reclamation (RG) and bare land reclamation (RW). X-ray CT scanning technology was employed to scan undisturbed 40 cm soil columns. The ImageJ software and its plugins,in conjunction with the Avizo2020 rendering function,were utilized to obtain parameters that characterize the two-dimensional distribution and three-dimensional characteristics of soil pores. This allowed for the three-dimensional reconstruction,visualization and analysis of soil pore structure. The results indicated a decrease in the quantity of two-dimensional small and medium pores in the soils of the RG treatment model compared to the RW treatment model,while there was a notable increase in the number of large pores in comparison to the RW treatment model. In the 0~20 cm soil layer,the pore surface density of the RG treatment was about 30% lower than that of the RW treatment. In the 20~40 cm soil layer,the pore surface density and pore complexity of the RG treatment surpassed those of the RW treatment. The three-dimensional total pore number was significantly reduced in the RG treatment mode compared to the RW treatment mode. The porosity of the RG treatment (3. 046%) was higher than that of the RW treatment (2. 900%),indicating that the RW treatment resulted in more pores,but not larger ones. The connectivity of the RG treatment (0. 399) exceeded that of the RW treatment (0. 273). However,the tortuosity and specific surface area (1. 329,4. 026 mm-1) were lower in the RG treatment compared to the RW treatment (1. 342,4. 334 mm-1 ). In terms of three-dimensional structure,both treatments had a two-year reclamation time,resulting in a point-like distribution of pore structure and displaying an inclined layered structure. However,compared to the RW treatment,the pores in the RG treatment were mainly distributed in macropores,with clearly visible elongated pores. This suggests that the RG-treated soil is progressing toward a more stable structure. Hence,within the soil reclamation process in Guangxi′s open-pit bauxite mining area,the grassland reclamation model proves more effective in enhancing soil structure and optimizing water and fertilizer transport channels compared to bare land reclamation,ultimately resulting in improved soil quality.

Key words: reclamation mode,pore characteristics,CT scanning,3D reconstruction