宝鸡地区典型农田土壤中微塑料赋存特征及其环境效应研究

Occurrence characteristics and environmental effects of microplastics in typical farmland soils in Baoji area

地膜覆盖被普遍应用于农业生产中,形成大量的微塑料,对农田土壤环境产生重要的影响。本文通过野外调查取样与室内实验分析相结合的方法,研究了宝鸡地区辣椒地、玉米地和猕猴桃地三种典型农田土壤中微塑料赋存特征及其对土壤环境的影响。研究结果显示:不同农田土壤中微塑料41%~48%为<1mm粒径,其次为1-2mm和2-5mm粒径。其丰度范围为1974~3656个/kg,丰度值随着土层深度的加深而减小;农田土壤中赋存形态各异的微塑料,如薄膜碎片状、粒状、丝状和孔隙状,其中以薄膜碎片占到70.6%~85.7%,微塑料类型78%为黑色,其次21%为白色,1%为蓝色;微塑料丰度与农田土壤饱和导水率(Ks)之间呈负相关关系;经X射线光电子能谱分析(XPS),发现微塑料表面吸附了土壤中常见Si、Al、Mg、O等元素之外,还聚集了肥料中的主要成分N、C的氧化物和一些重金属元素Cd、Fe。由此可见,微塑料的赋存不仅降低了土壤水分的入渗能力,而且导致了土壤肥料和重金属物质的局部富集,影响了土壤溶质迁移过程,加剧了土壤污染。研究结果将在揭示微塑料对区域农田土壤面源污染及农田环境治理具有一定的指导意义。

Plastic mulch is widely used in agricultural production,which is forming a large number of microplastics and has an important impact on farmland soil environment.In this paper,the microplastics occurrence characteristics and its environmental effects were studied by means of field investigation sampling and laboratory experiment analysis in typical farmland soil,such as,chilies,corn and kiwifruit land.The numbers of particle size of<1mm was 41%to 48%of total microplastic,which was more than the particle size of 1-2mm and 2-5mm.The average numbers of microplastic were from 1974 to 3656 pieces·kg-1,and it decreased with the increase of soil depth.The major categories of microplastics were fragments,grains,filamentous,and porosity in different farmland.The proportions of fragments accounted for 70.6%~85.7%of total microplastic.The color of microplastics included black,white and blue,with the proportions of 78%,21%,and 1%,respectively.There was a negative correlation between the abundance of microplastics and the saturated water conductivity of farmland soil.By X-ray Photoelectron Spectroscopy analysis,it was found that the microplastics not only adsorbed Si,Al,Mg,O and other elements that commonly form the soil,but also gathered the oxides of N and C of fertilizer,and some heavy metal elements,such as Cd and Fe.Therefore,it can be seen that the presence of microplastics not only reduces the infiltration capacity of soil water,but also leads to the local enrichment of soil fertilizer and heavy metals,affecting the migration process of soil solute and aggravating soil pollution.The results of this study will be helpful to reveal the effect of micro plastics on regional farmland soil non-point source pollution and farmland environment control.