微塑料-重金属污染对植物-丛枝菌根真菌共生体系的生态毒性效应研究进展

Research Progress on Toxicological Effects of Microplastics-Heavy Metal Pollution on Plant-Arbuscular Mycorrhizal Fungi Symbiosis System

近年来,土壤微塑料(microplastics,MPs)备受关注,土壤中不仅存在微塑料,还有重金属等污染物,微塑料与重金属的共存直接影响到土壤中植物的生长和植物-真菌共生体系。研究表明,植物-丛枝菌根真菌(arbuscular mycorrhizal fungi,AMF)共生体系可以提高植物对土壤重金属的耐受能力,但微塑料的存在会影响AMF对植物的定殖以及AMF对重金属的过滤螯合作用,进而影响植物体对重金属的累积。微塑料降解过程中会释放增塑剂、稳定剂和阻燃剂等有害物质,亚微米和纳米级的塑料颗粒还会直接进入植物体,而且微塑料还会粘附在植物种子和根系上影响植物的发芽和幼苗生长,进而改变AMF对植物根系的定殖。此外,由于微塑料具有比表面积大、疏水性强和难降解等特性,可以吸附重金属离子,但这种吸附会受到微塑料和重金属本身以及外界环境的影响。对于土壤环境而言,微塑料会改变土壤pH、有机碳、阳离子交换量等,同时微塑料与土壤颗粒产生竞争吸附会改变重金属的生物有效性,进而影响到植物对重金属的累积。尽管目前已开展大量对微塑料和重金属复合污染的研究,但是,对于微塑料和重金属复合污染对植物-AMF共生体系的研究尚不充分。因此,本文根据现有的研究综述了土壤微塑料与重金属复合污染对植物和AMF的影响,为进一步开展对土壤微塑料和重金属复合污染的研究做出一些思考与建议。

In recent years,more and more attention has been paid towards the microplastics(MPs)in soil.H owever,not only microplastics but also heavy metals are present in the soil.The coexistence of microplastics and heavy metals in soil will affect plants growth and plant-fungi symbiotic system.Some studies have shown that the tolerance of plants to heavy metals is enhanced by plants-arbuscular mycorrhizal fungi(AMF)symbiotic system.However,the colonization of AMF in plant roots and the abilities of AMF to filter and chelate heavy metals would be affected by microplastics,thus affecting the accumulation of heavy metals in plants.The plasticizers,stabilizers,flame retardants,and other harmful substances,which can be toxic to plants and AMF,will be released along with the microplastics as they degrade.Furthermore,the sub-micron plastics and nano-plastics directly entered plant root,stem,leaf and fruit.Microplastics adhered to plant seeds and roots to affect plant germination and seedling growth,consequently altering the colonization of AMF on plant roots.Additionally,heavy metals are adsorbed by microplastics due to their characteristics of large surface area,strong hydrophobicity,and slow degradation.However,the influence factors of adsorption included the type of microplastics,heavy metals and environmental conditions.M icroplastics will affect the soil physical and chemical properties,such as the soil pH,organic carbon,cation e xchange capacity.Moreover,competitive adsorption of microplastics and soil particles for heavy metal ions will change the bioavailability of heavy metals and affect heavy metal accumulation in plants.Although numerous s tudies have been conducted on the co-contamination of microplastics and heavy metals,there is insufficient information regarding the impacts of co-contamination of microplastics and heavy metal on the plant-AMF symbiotic system.Therefore,this article provides a summary and some suggestions about effects of co-contamination of microplastics and heavy metals on plants and AMF for further studies.