JIAO Mingming;ZHUO Yiheng;SUN Zelin;CUI Xingbo;MENG Zhaojun;LIU Manhong;Northeast Forestry University;Heilongjiang Naolihe National Nature Reserve Administration;

Naolihe Nature Reserve;;microplastics;;different types of land use;;abundance;;risk assessment

As an emerging environmental pollutant, microplastics are widely distributed around the world and are greatly concerned by scientists. In order to study the distribution, composition characteristics and ecological risk of microplastics in Naolihe Nature Reserve, we selected four typical land use types: upland field, paddy field, forest and swamp in the reserve, and investigated shape, color, abundance and composition of microplastics by using the improved flotation separation method. We also detected the microplastics in the particle size range of 0.02-5 mm, observed and identified relevent index by stereoscopic microscope and Fourier transform infrared spectrometer(μ-FITR). The ecological risk of microplastics was also evaluated based on risk-index(R) and the pollution load index(PLI). The results showed that:(1) The microplastics shape was fibrous, fragmentary, film-like and granular, of which fibrous and film-like accounted for 31.5% and 37.0%, with a significant difference between upland field and swamp soil(P<0.05). The colors of microplastics included white, black, red, blue, and transparent. There was no significant difference in color components among the four land use types. The microplastics composition included polypropylene(PP), polyethylene glycol terephthalate(PET) and polyethylene(PE), accounting for 54.5%, 27.3% and 18.2%, respectively. There was no significant regression correlation between the compositions.(2) The abundance of microplastics ranged from 3.33 to 30.0 n·kg~(-1), with an average abundance of 14.3 n·kg~(-1), and the average abundance of microplastics in upland field was significantly higher than that in forest and swamp(P<0.05). Spatially, the distribution trend was in the order of upland field(21.1 n·kg~(-1)) > paddy field(12.2 n·kg~(-1)) >swamp(10.7 n·kg~(-1)) > forest(8.89 n·kg~(-1)).(3) Microplastics with a size of less than 1 mm accounted for 87.7%, mainly in the range of0.2 ～ 0.5 mm and 0.5 ～ 1 mm particle size, accounting for 30.1% and 34.2%, respectively.(4) The average risk index of four land use types in the reserve was 3.64, and the overall pollution load index was 2.31×10~(-2). The overall ecological risk level of the reserve was low. These showed that there were different degrees of microplastic pollution in the four land use types in the reserve, with unique occurrence forms and distribution characteristics. The research provides basic support for the pollution prevention and control, migration and transformation of microplastics in the reserve.