Distribution Characteristics Of Microplastics And Attached Microorganisms In Water And Sediments Of The Yellow River In Shanxi Province

Due to its large specific surface area,strong ability to absorb pollutants,and small volume characteristics,microplastics(MPs)can migrate to a wider range in the environment along with wind and water transport,causing greater and more lasting harm to the environment and the food chain of the ecosystem.MPs were first discovered in the ocean.When researchers tracked the source of MPs in the ocean,they found that most MPs came from inland surface water.Inland MPs first entered surface water,then,along with surface water,entered inland rivers and eventually merged into the ocean.In addition,MPs,as a typical biological habitat with unnatural media,have attracted more and more researchers’ attention to its attached microbial community in recent years.In this study,MPs in water bodies and sediment in the Yellow River Basin in Shanxi Province were studied.The surface morphology of MPs and its attached biofilm were observed.The distribution characteristics of MPs in abundance,shape,color and particle size were statistically analyzed.The three-dimensional structure of MPs surface biofilm was observed.The α diversity of MPs attached microbial community,the taxonomic composition of bacterial community,and potential pathogenic bacteria were analyzed by 16 S RNA sequencing technology.The main findings are as follows:(1)The abundance of microplastics in the water and sediments of the Yellow River Basin in Shanxi was 160-275 n/L and 287-480 n/kg,respectively.The overall trend was that the abundance of MPs in sediments was higher than in water,and the abundance of MPs in the lower reaches was higher than that in the upper reaches.(2)Scratches,gully,grooves and other weathering marks were observed on the MPs’ surface by SEM.The shape,particle size gradient and color distribution of the MPs in the sample were analyzed by metallographic microscope.MPs particles were divided into four categories: fragmentation,membrane,fibrous and spheroid.Fragmentation accounted for the largest proportion of MPs(up to 50%),followed by fibre(30%-40%).MPs were divided into four groups according to particle size gradient: >0.1 mm,0.1～0.5 mm,0.5～1 mm,1～5 mm,particle size;>1 mm microplastics accounted for up to 70%;MPs in the samples were divided into four categories according to color: blue,black,red and white.The proportion of white microplastics was as high as 60%,followed by red and black.The sum of the two accounted for 20%-30%,and the proportion of blue was only about 10%.(3)The main components of MPs polymer in water and sediment of Shanxi Yellow River Basin are polypropylene,polypropylene and polystyrene,corresponding to the shape.The main components of fragmented MPs are polypropylene.The main component of fibrous MPs is polyethylene,and the main component of thin film and small ball MPs is polystyrene.(4)SEM indicates that there is obviously microbial attachment and growth on the surface of MPs,and microorganisms are concentrated in grooves and gullies;By observing the stereoscopic structure of MPs by CLSM,we conclude that the stereoscopic structure of MPS is as follows: dead cells,living cells/extracellular polymers from the inside out.(5)16s RNA gene sequencing technology was used to analyze the bacterial community structure on MPs surface in the water and sediment of the Yellow River in Shanxi Province.The dominant bacterial species on MPs surface of horizontal water were as follows:Flavobacterium,Limnohabitans,Burkholderiaceae,Pseudomonas,Rhodoferax,Flectobacillus,Methylotenera,Pseudarcicella,Acinetobacter,Polaromonas,etc.Dominant bacteria at genus level in the MPs surface bacterial community in sediments are:Pseudomonas,unclassified Micrococcaceae,Exiguobacterium,Psychrobacter,Arthrobacter,Massilia,Allorhizoium-Neorhizobium-Pararhizobium-Rhizobium,Pantoea,Flavobacterium, Paracoccus,etc.Common dominant bacteria in water and sediment were Flavobacterium,Pseudomonas,etc.(6)Potential pathogenic bacteria on the surface of MPs in the water bodies and sediments of the Yellow River in Shanxi Province: Acinetobacter,Flavobacterium,Bacillus,Clostridium,Pseudomonas,Bacillus,Rhodococcus.