土壤中微塑料对陆生植物的毒性及其降解机制研究进展

微塑料(MPs)作为一种新型环境污染物，自2004年被英国科学家提出以来受到广泛关注.土壤作为微塑料的重要聚集地，随农田灌水和翻耕等农业操作的进行，微塑料污染范围和积累量不断扩大并对陆生植物产生多种毒性，且由于其粒径小、难降解和吸附能力强的特点给土壤微塑料污染治理带来了较大挑战.从微塑料的直接和间接毒性及其与其他污染物结合时产生的联合毒性这3个方面综述了微塑料对陆生植物的毒性，主要表现为微塑料存在对植物造成机械损伤、诱导植物产生氧化应激、细胞毒性和基因毒性，导致植物生长和植物组织代谢受阻等一系列问题.进一步，基于当前研究阐述了微塑料的物理、化学和微生物降解机制：微塑料的物理和化学降解主要通过改变微塑料的粒径大小和表面性质并产生中间产物；而更小粒径微塑料及其中间产物可以在物理、化学和微生物这3种因素同步影响下最终转化为水和二氧化碳，但该过程极其复杂和缓慢.最后，对微塑料的进一步研究方向进行展望，可为未来微塑料的陆地生态系统领域研究重点和污染控制提供资料借鉴.

Research Progress on Toxicity of Microplastics in Soil to Terrestrial Plants and Their Degradation Mechanism

Microplastics(MPs), as a new type of environmental pollutants, have gradually attracted widespread attention since they were introduced by British scientists in 2004. Soil is an important accumulation site for microplastics, which can expand the scope of contamination and accumulate with agricultural practices such as irrigation and tillage. Microplastics in soil cause a variety of toxicities to terrestrial plants. The small particle size, difficult degradation, and strong adsorption capacity bring a challenge to the microplastic pollution treatment of soil. In this study, the toxicity of microplastics to terrestrial plants was reviewed in terms of their direct or indirect toxicity and combined effects with other pollutants, mainly in terms of mechanical injury, induction of oxidative stress, and cytotoxicity and genotoxicity to plants, resulting in plant growth and plant tissue metabolism obstruction. In general, the toxicity of microplastics depended on the polymer type, size, and dose; plant tolerance; and exposure conditions. In addition, the production of secondary microplastics and endogenous contaminants during their degradation in soil enhanced the biotoxicity of microplastics. Further, the physical, chemical, and microbial degradation mechanisms of microplastics were introduced in this study based on the current research. At first, the physical and chemical degradation of microplastics mainly occurred by changing the particle size and surface properties of microplastics and producing intermediates. Then, smaller-sized microplastics and their intermediates could eventually be converted to water and carbon dioxide through physical, chemical, and biological functions. Finally, further prospects regarding soil microplastics were introduced, and we provided information for future improvement and pollution control of microplastics.