Occurrence Differences and Sources of Microplastics in Surface Sediments and Farmland Soil in Yangzong Lake

YUAN Zhiwei; LI Ju; CHEN Dan; WANG Rui; DENG Chunnuan

doi:10.19672/j.cnki.1003-6504.1661.23.338

Abstract：To understand the occurrence differences and main sources of microplastics in surface sediments in Yangzong Lake and surrounding farmland soil,samples were collected at 24 surface sediments sampling points and 11 farmland soil sampling sites in June 2022.Density flotation was used to separate microplastics in the samples,and microscopic examination and compositional identification of microplastics were carried out using stereoscopic microscope and Raman spectrometer,respectively.As shown by the results,the abundance of microplastics in the surface sediments and farmland soil was(323.7±115.6)items/kg and(93.0±50.1)items/kg,respectively,and microplastics were spatially distributed mainly in the northern and central regions.Fibers was the common shape of microplastics,accounting for 76.28%and 69.79%of the total number of microplastics in surface sediments and farmland soil,respectively.The amount of fragments in farmland soil was 11.73%higher than that of surface sediments,and the amount of granular in farmland soil was 5.57%lower than that of surface sediments.Blue and transparent were common colors of microplastics,and both account for 92.36%and 86.41%of the combined amount in surface sediments and farmland soil,respectively.Small particle size(<1 mm)microplastics dominate,and the amount of small particle size microplastics in surface sediments was 14.21%higher than farmland soil.As revealed by Raman spectroscopy results,the proportion of microplastics composed of polyethylene terephthalate and polyester in surface sediments was 11.84%and 7.84%higher than that of farmland soil.The amount of polypropylene microplastics was 16.57%lower than that of farmland soil.Combined with the human activities in the surrounding area,it was inferred that microplastics in the surface sediments might mainly come from fishing gear and textiles,and microplastics in farmland soil might mainly come from mulching,pesticide bags and plastic bottles.