News

Guobin Liu’s research team of the Institute of Soil and Water Conservation made progress in the research on the influence of microplastics on soil hydraulic characteristics

Update time:2022-06-20

Recently, the scientific research and innovation team of Liu Guobin Loess Plateau Ecological Restoration of the Institute of Soil and Water Conservation published a research paper entitled “Soil texture is an important factor determining how microplastics affect soil hydraulic characteristics” in Environment International (Double first-class G2 journals of the school, TOP journals of the 1st District of the Chinese Academy of Sciences), a well-known journal in the field of environmental science. Ziqi Guo, a doctoral student at the School of Forestry, Northwest A&F University, is the first author of the paper, Sha Xue, a researcher of the Institute of Soil and Water Conservation, is the corresponding author, and the State Key Laboratory of Soil Erosion and Dryland Agriculture on the Loess Plateau is the first unit. This research work was jointly funded by project such as the National Natural Science Foundation of China (41977076) and Shaanxi Science Fund for Distinguished Young Scholars (2021JC-50).

The accumulation of microplastics have a negtive impact on the soil structure. As a key variable of soil physical properties, soil hydraulic characteristics are strongly affected by soil structure. However, the mechanism of microplastics affecting soil hydraulic characteristics is still unclear. The study focuses on analyzing the effects of microplastics on the hydraulic characteristics of soils with three different textures, and proposed three action mechanisms. The results of the study show that microplastics significantly weakened the water infiltration capacity and water holding capacity of the three soils, which is reflected in a reduction in the saturated water conductivity of loam (7.09%-69.79%), clay (18.72%-77.11%) and sand (50.23%- 95.79%), and increased the slope of the three soil water characteristic curves (Fig. 1). Soil texture is one of the main factors mentioned above, with clay and sand are the most obvious response to microplastic interference. Among them, there are many small particles and high organic matter content in clay. Microplastics can adhere to smaller soil particles, increase the diameter of soil particles, change the soil pore distribution and reduce their water conductivity effect. The pore structure of sand is poor, and microplastics tend to destroy the original pore system by reducing the pore uniformity and reduce its water retention effect (Fig. 2). The concentration and particle size of microplastics are also the main factors leading to the change of soil hydraulic characteristics. The increase of large-particle microplastic concentration and the accumulation of small-particle microplastics in soil pores have led to a sharp reduction in the number of large pores in the soil, resulting in the weakening of soil water conductivity. In addition, the “soil-microplastic mixed particles” formed by microplastics and soil particles increase the soil hydrophobic surface area, causing moisture delays, causing more air replacement water molecules to remain in pore space, and the soil water retention capacity decreases. This study is of great significance to reveal the soil environmental effect of microplastics and its driving mechanism.

Paper link: https://doi.org/10.1016/j.envint.2022.107293