Effects of microplastics on the pore structure and connectivity with different soil textures: Based on CT scanning

Abstract

Soils contaminated with microplastics have disorganized pore structure, which reduces soil fertility. However, few studies have focused on morphological characteristics and connectivity of soil pores under microplastic enrichment. This study evaluates how different concentrations of polyvinyl chloride microplastics (0 %, 2 %, and 4 %) affect the pore structure characteristics (pore distribution and porosity, pore characterization parameters, and pore connectivity) of soils with different textures (sandy, sandy loam, and loamy). Computed tomography were used to reassemble images of soil micropores following microplastics enrichment. The pore network model, Euler characteristics number, and tortuosity were used to characterize the complexity of connected pores. The results revealed that the effects of microplastics on pore structure varied substantially depending on soil texture, with sandy and sandy loam soils rapidly reducing or eliminating connected pores after introducing microplastics. However, loamy soils could still maintain a certain degree of pore connectivity. Adding microplastics reduced the porosity of all three soils, with sandy soil showing the most significant drop (89.51 %) at 4 % microplastics concentration dramatically. The overall impact of microplastics on the pores of loam soil is minimal. As the microplastics abundance increased, the pore network model of loam-connected pores became simpler. Under a 4 % microplastics enrichment, the loam soil’s Euler characteristic number of connected pores grew by 91.17 % In summary, even though the overall structure of the pores of soils of different textures differed due to microplastics addition, microplastics deposition would still severely disrupt the connectivity of soil pores and reduce soil infiltration capacity regardless of soil texture.