Transport Mechanisms of Microfibers and Their Effects on Soil-Plant Systems

Microplastics (MPs) have emerged as a global environmental concern due to the uncertainties surrounding their occurrence, fate, and potential implications for environmental and human health. While research on the impact of MPs on aquatic systems is expanding, studies investigating their influence on terrestrial systems are limited. Agricultural soil acts as a dominant reservoir for MPs, with microfibers being a predominant form due to the application of organic amendments. Despite their ubiquity, the transport mechanisms of these particles and their effects on soil-plant systems remain largely unknown. This study addresses critical knowledge gaps by conducting a series of soil incubation experiments aimed at exploring the effects of polyester (PES) microfibers on soil quality and the growth of three common crops: lettuce, Chinese cabbage, and radish. Plants were cultivated in glass jars containing 100mg/kg fluorescent microfibers thoroughly mixed with the soil. Microfiber distribution was visualized using EVOS Auto FL 2. Soil endpoints revealed that the presence of microfibers induced significant alterations in soil bulk density, with minimal impact on soil carbon and nitrogen content across all plant treatments. Additionally, microfibers exerted a significant decrease in soil pH in lettuce-growing soil, while exhibiting a marginal pH increase in cabbage-growing and radish-growing soils. Microfibers were also found to diminish the formation of water-stable aggregates, particularly in the cabbage-growing soil. In terms of plant endpoints, the study observed accelerated germination of lettuce in the presence of microfibers, while the root length of radish was substantially affected. Microfibers led to a reduction in chlorophyll content in lettuce and cabbage leaves, whereas radish leaves exhibited an increase when exposed to microfibers. Microfibers were detected in both lettuce and radish roots and stems, and weak fluorescence was detected in lettuce leaves. Notably, the impact of microfibers varied among plant species, emphasizing the necessity for species-specific considerations. Furthermore, this study highlights the negative, positive, and neutral effects of microfibers on soil properties and plant performance and proves the potential uptake of microfibers by certain edible plants. The observed outcomes are attributed to the distinctive characteristics of fibers, including their unique shape, surface area, and flexibility, which may interact with soil particles and crops. Given the widespread distribution and accumulation of microfibers in agricultural soil, this study provides crucial insights for ecotoxicological assessments related to soil and terrestrial higher plants. It also holds implications for stakeholders in environmental pollution, food safety, and human health.