基于油提取的土壤与沉积物中微塑料的分离方法

微塑料作为一种全球性新兴污染物受到学界与社会的广泛关注.由于土壤和沉积物中的微塑料难以分离提取，目前关于微塑料的研究主要集中于水体中，而关于土壤与沉积物中微塑料的丰度、分布与环境行为尚不清楚，迫切需要一种经济、快速、可靠的前处理手段将微塑料从土壤或沉积物中分离出来进而开展检测与监测工作.油提取法不同于传统密度浮选法，其利用塑料的亲油性，使用植物油代替密度液分离土壤与沉积物中的微塑料.通过油提取法在砂土（二长花岗岩风化层残坡积物）、壤土（菜地黄棕壤）、黏土（稻田水稻土）、泥质湖泊沉积物中获得的总加标回收率分别为88.3%±6.29%、88.3%±3.82%、90.0%±2.50%、90.8%±1.44%.其中，对于密度浮选法较难提取的聚氯乙烯（PVC）、聚对苯二甲酸乙二醇酯（PET），其回收率分别为93.3%±11.6%（壤土）、96.7%±5.77%（壤土）.植物油的加入会对后续微塑料的光谱表征识别产生影响，但可通过无水乙醇冲洗去除，与拉曼光谱仍具有良好的兼容性.利用该方法开展的实地研究获得黄冈市残坡积物（砂土）、武汉市菜地（壤土）、武汉市水稻田（黏土）、武汉市东湖泥质湖泊沉积物中的微塑料丰度分别为1 679、1 612、1 766、7 629个/kg.研究显示，油提取是当下密度浮选技术的可替代方案. 

Separation of Microplastics in Soils and Sediments with Oil Extraction Protocol

Microplastics have received extensive attention as an emerging global pollutant in recent years. However, few studies have focused on the abundance, spatial distribution and environmental behavior of microplastics in soils and sediments because it is hard to separate and extract them from soils and sediments matrix. It is imperative to develop an economical, fast, and reliable pretreatment method to isolate microplastics from soils or sediments for detection and monitoring. Oil extraction protocol uses the plant oil to extract microplastics from soils and sediments. It differs from traditional density flotation techniques in that it uses the lipophilic properties of plastics rather than the density differences between plastics and solution for flotation. The total spike recovery of oil extraction in sandy soil (talus material of monzonitic granite), loam (yellow-brown soil of vegetable field), clay (paddy soil) and lake muddy sediments were 88.30%±6.29%, 88.30%±3.82%, 90.00%±2.50% and 90.80%±1.44%, respectively. For PVC and PET which were difficult to extract by density separation methods, the recovery rates of oil extraction protocol were 93.9%±11.6% and 96.7%±5.77% (loam), respectively. The addition of oil interfered with the spectral analysis of the microplastics, but it could be removed by washing with absolute ethanol, and the samples could be analyzed by Raman spectroscopy. Our analysis determined that the microplastics abundances of the talus material (sandy soil) in Huanggang City, vegetable field (loam) in Wuhan City, paddy field (clay) in Wuhan City and lake sediments in Dong Lake of Wuhan City were 1679, 1612, 1766 and 7629 items/kg, respectively. This studies shows that the oil extraction method is an alternative to the current density flotation technology.