塑料及其制品被广泛应用于生产生活，但大部分塑料制品最终会废弃于自然环境，并在光照、风化等影响的作用下被降解破碎，造成微塑料污染。微塑料是指粒径或某一维度小于5 mm的塑料微粒，目前微塑料的分布已呈现全球化趋势，然而目前利用有效手段对农田土壤中微塑料的赋存及降解现状的研究较少。本研究以微塑料在环境中的污染现状与环境效应为研究背景，参考了环境微塑料的分离与分析方法，对微塑料在环境中的降解及重金属复合污染的吸附性能及生态影响进行研究。通过建立一种高效提取土壤微塑料的方法，本研究对不同类型的土壤样品中的微塑料进行了分离纯化、种类鉴定、表面形态及能谱分析，发现不同类型土壤环境中提取的微塑料普遍具有明显缝隙和破碎结构，在自然环境下的老化降解可能是由表及里、层层剥落并破碎的过程。通过紫外辐照模拟微塑料在土壤环境中的光氧化降解过程，发现微塑料在光氧化降解过程中都有不同程度的黄化、卷曲、破裂现象的发生，表面聚合物的力学性能发生变化。微观上微塑料在降解过程中表面均明显产生了裂缝，同时伴随表层剥落及微纳米级次生微塑料的产生迹象。从化学结构上，微塑料降解过程中的整体趋势为C-H键在断裂后形成了C=O与C-O键，氧化程度升高，微塑料表面极性基团增加，结晶度增高，导致微塑料的脆性增加、变得翘曲、表面粗糙程度加深，更容易产生次生微塑料，其中PP与PE具有较大次生微塑料产生潜力。微塑料的表面粗糙程度、单位质量面积、结晶度、官能团和极性等理化性质，均会影响其对重金属的吸附容量，微塑料的比表面积越大、聚合物链间距离越大、极性越强，微塑料对重金属的吸附容量越大。在一定范围内，微塑料对重金属的吸附能力随着pH、温度和降解时长的增加而增加。微塑料及其复合污染的植物生长实验表明，微塑料及其复合污染在土壤环境中的存在对小麦种子的发芽率无明显影响，但是可能会降低其发芽指数，延缓种子的发芽出苗时间，对其后续的生长发育造成不利影响。同时土壤环境中存在的微塑料及其复合污染可能会对土壤微生物产生一定的趋避倾向，以自身为载体形成与所在环境不同的由微生物组成的微生态圈。

Plastic and its products are widely used in production and life, but most of the plastic products will eventually be abandoned in the natural environment, and will be degraded and broken under the influence of light and weathering, resulting in microplastic pollution. Microplastics refer to plastic particles of size or a certain dimension less than 5 mm. The distribution of microplastics has shown a global trend, but there are few studies on the occurrence and degradation of microplastics in farmland soil by effective methods. This research studied the pollution status and environmental effect of microplastics in the environment, referring to the separation and analysis methods of environmental microplastics, the degradation of microplastics in the environment and the adsorption performance and ecological impact of heavy metal composite pollution in the environment. By establishing an efficient extraction of soil microplastics method, the separation and purification of microplastics from different types of soil samples, species identification, morphology and surface spectrum analysis were studied. It is found that microplastics extracted from different types of soil environment generally had obvious cracks and broken structure, which may mean there could be peeling and crushing process of microplastics aging in the natural environment. Through UV irradiation simulation of the photooxidation degradation process of microplastics in soil environment was carried out. It is found that the phenomenon of yellowing, curling and rupture occurred in different degrees in the process of microplastics, which could be the result of the change of mechanical properties of the polymer in the degradation process. In the process of degradation, cracks were obviously produced on the surface, accompanied by surface peeling and the production of micro and nano scale secondary microplastics. From the chemical structure, the overall trend of the process of microplastics degradation could be formation of C=O and C-O bond after break of C-H bond. With the increase of oxidation degree, surface the amount of polarity group on the surface of microplastic could increases, so as crystallinity, which may increase the brittleness of microplastics, make it easily warped, have more rough surface, and also are more likely to produce secondary microplastics, PP and PE in particularly. The factors that affect the adsorption capacity of microplastics on heavy metals may mainly include the specific surface area of microplastics, the interchain distance of polymer and the polarity of microplastics, which are the physical and chemical properties such as surface roughness degree, area per unit mass, crystallinity, functional group and polarity. Within a range, the capacity of microplastics to absorb heavy metals increased with pH, temperature and degradation duration. The plant growth experiment of microplastics and its compound pollution showed that the existence of microplastics and its compound pollution in the soil environment had no obvious effect on the germination rate of wheat seeds, but may reduce their germination index, delay the germination time of seeds, and have adverse effects on their subsequent growth and development. At the same time, the microplastics and their composite pollution existing in the soil environment may have a certain tendency to avoid the soil microorganisms, and form a microecosphere composed of microorganisms different from the local environment.