Study On The Distribution And Aging Characteristics Of Microplastics In Real Environment

The problem of environmental microplastics pollution is becoming increasingly serious,and biodegradable microplastics have attracted more attention.Under the action of environmental stress,plastic polymers are easily broken to produce micro-nano plastics with smaller particle size and larger specific surface area.Micro-nano plastics are more likely to be ingested by organisms for transmission in the food chain,and are more likely to migrate in various environmental media.After weathering,the surface morphology,hydrophobicity,mechanical strength and other physical and chemical properties of microplastics will change and affect the interaction with pollutants,posing a potential threat to the ecological environment.Therefore,in this paper,the time and space distribution characteristics and aging characteristics of microplastics in the actual environment are deeply studied by sampling and separating the actual environmental samples,as well as the process of simulating the release and aging of microplastics from biodegradable plastics and the potential environmental impact in the laboratory.The main research conclusions of this paper are as follows:1.Occurrence and aging characteristics of microplastics in surface water,sediments and crabs of artificial breeding pondsA set of microplastics separation device was built in the laboratory,and the distribution characteristics and microplastics characteristics of a freshwater aquaculture base in the Yangtze River Delta region of China were studied.The research in this chapter shows that the abundance of microplastics in surface water is 4.4～10.8 items/L,the abundance in sediment is 28.6～54.3 items/100g dry weight sediment.In the surface water sample,fibers are the main microplastic shape,accounting for 66.77%of the overall shape.In the sediment sample,fibers account for 54.84%of all microplastic shapes.Polyethylene（PE,45.71%）and polyester（PET,45.72%）are the main components of microplastics in the surface water sample,while polyethylene（43.55%）is the main component in the sediment sample,followed by polyester（PET,38.71%）,The microplastics in surface water and sediment exhibit strong similarity in microplastic characteristics.The abundance of microplastics in adult crabs is 23.9 items per individual.The total number of microplastics particles detected in the intestine accounts for 51.88%of the total,followed by 35.56%in the gills and 12.55%in the liver and pancreas tissues.No microplastics particles were detected in the two muscles.Polyethylene（PE）is the main microplastics in crab bodies,accounting for 44.76%,while the rest are polyethylene terephthalate（PET,39.75%）,polypropylene（PP,11.72%）,and polystyrene（PS,3.34%）.Fiber is the main shape of microplastics in crab bodies,accounting for 62.8%,followed by fragments accounting for 13.4%,and blue is the main color accounting for 51.5%.The detected MPs particles all exhibit a certain degree of weathering with MPs being the most severely weathered in sediment environments.The complexity of the aquaculture process and human activities may be attributed to the presence of microplastics in the ecosystem caused by aquaculture ponds.In addition,the migration mode of microplastics in artificial culture ponds tends to be diversified compared with that in the field culture mode due to more complex human factors.At the same time,the artificial ponds have been proved to have certain self-purification capacity.2.Weathering and degradation of polylactic acid mask in simulated environmentThis part simulates the degradation and release of microplastics of the new polylactic acid mask in weakly alkaline water,aquaculture water,marine and strong oxidants,and discusses the impact of polylactic acid microplastics degraded in different environments on plant growth through the ryegrass soil culture experiment.The study found that weathering will lead to cheese like and ditch like erosion on the surface of the fiber fabric layer.The outer,middle and inner layers of the mask tend to be hydrophilic,with lower mechanical strength,which will eventually lead to fiber fracture and the release of microplastics.The average number of microplastics released continuously within four weeks is 149.5 items/piece,the weakly alkaline group（124±2.4 items/pie）released the least amount of MPs,followed by the sea group（146±4.1 items/pie）,the pond group（148±2.9 items/pie）,and the Fenton group（180±0.8 items/pie）,and the particle size is20～500μm（44%）,63.57%is transparent fiber.The germination rate of ryegrass seeds significantly decreased(R_Alk=60%,R_Sea=79%,R_Pond=82%,R_Fenton=53%)in the planting soil treated with fibrous MP under different conditions,indicating that the treated polylactic acid fibers all inhibited the growth of winter ryegrass..3.Evaluation and calculation of plastic load in water bodyThis part calculates and simulates the plastic load in a wide range of water bodies and assesses the potential microplastic load through field measurements.The research method involves disassembling complex plastic agricultural tools and measuring individual plastic products in four different water environments to calculate the plastic load per unit area,in order to infer the overall plastic load.The calculation results show that the plastic load in various typical water bodies in China is serious,and the amount of plastic garbage on land around the water body is huge.The plastic load in the landscape aquaculture area was 3.670 g/m²,in private ponds 1.558 g/m²,in recreational fishing grounds 12.904 g/m²,in artificial ponds 4.089 g/m².Most of the land plastic waste and the waste exposed to the water environment are in the state of severe weathering,which needs to be paid enough attention.The research results in this chapter provide a method to evaluate the practice and operability of plastic loading in large water bodies,and to assess the potential risk of microplastic pollution.