| Microplastics（MPs）,a new type of pollutants,were referred to plastic fragments or particles with a size of smaller than 5 mm,and it was ubiquitous in environmental.Meanwhile,due to its potential negative impact on the ecosystem,microplastic pollution had become an urgent global environmental pollution problem.However,the research on microplastic pollution in the terrestrial environment lacked in depth understanding,especially the microplastic pollution in road dust compared to the water environment.Whereas,as an important"sink"of MPs in road dust,there were few studies on sewer sediments.In addition,due to large specific surface area,hydrophobicity,MPs could combine with heavy metals（HMs）and hydrophobic organic pollutants in environmental,causing harm to the ecological environment.Therefore,in this paper,Ma’anshan City road and sewer of Anhui University of technology were taken as the research area,and the samples of road dust and sewer sediments were collected and the MPs were extracted.The abundance,morphology,spatial and temporal distribution of MPs in different environmental media were investigated.Besides,the occurrence characteristics of MPs and HMs in road dust in the same environmental medium were analyzed.The results showed:（1）The types of MPs in urban road dust were Polypropylene（PP,more in autumn and winter,accounting for 61.62%and 63.18%,respectively）,Polyethylene（PE,more in spring and winter,accounting for 32.53%and 22.1%,respectively）,followed by Polyester（PET）,Polystyrene（PS）,Silicon Rubber（SR）.Besides,the proportion of MPs in road dust had obvious seasonal distribution.Among them,PP and PET were mostly in road dust in winter,spring,autumn,and the colors were black and green.In summer,PE（transparent）and PET（green）were dominant.According to the morphology of MPs in the road dust in all seasons,fragment（50.53%）>fiber（28.56%）>film（19.59%）>foam（1.33%）.（2）For the different functional areas,the abundance of MPs in cultural and educational areas,commercial and residential areas was higher,and the abundance of MPs in suburban and industrial areas was lower.Specifically,the highest abundance of MPs in spring cultural and educational areas(2350.41±1140.41items·kg-1),followed by industrial areas,commercial areas,residential areas and suburbs.The order of the abundance of MPs in summer was:cultural and educational area(753.20±68.20 items·kg-1)>commercial(410.57±49.43 items·kg-1)>industrial(285.00±140.76 items·kg-1)>residential(276.98±274.77 items·kg-1)>Suburban(161.82±70.37 items·kg-1).Whereas commercial,residential,cultural and educational,industrial and suburban in autumn and winter.Besides,the content of MPs in commercial was the highest in summer(330.85±61.15 mg·kg-1)and autumn(467.43±298.78 mg·kg-1),and suburban and residential had the highest abundance of MPs in spring and winter.（3）The main types of MPs in sewer sediments were PP,PE,PET,PS,and Polyvinyl chloride（PVC）.Specially,PP in the sediments（spring and summer）account for a large proportion,and the content of PET in autumn and winter was high.MPs in spring and summer were widely distributed in the range of 1000-2000μm and250-500μm,and 500-1000μm in autumn and winter was the largest.Moreover,black MPs accounted for the largest proportion of sewer sediments in spring and summer,and the color of MPs in autumn and winter was mostly green.The MPs in the sediment had different morphology,fragment（53.58%）>fibers（44.17%）>film（1.20%）>foam（1.04%）.Compared with the abundance of MPs in campus road dust,the abundance of MPs in sewer sediments was high,and the color was single,and the proportion of each type in shape was uniform.（4）The evaluation of the pollution status of HMs showed that:The average content of Zn,Cd,Cr and Cu in urban road dust exceeded the soil background value in Anhui Province,which were 3.12,2.80,1.70,1.32 times the background value,and Pb and Ni were lower than the soil background value.The coefficient of variation of Zn（127.70%）and Cd（220.68%）indicated that significantly affected by human activities.The results from correlation analysis and principal component analysis（PCA）showed that:In spring,there was a significant positive correlation between Cu and Zn,Ni and Cr;in summer,there was a very significant positive correlation between Zn and Cu and Cd,and between Ni and Cr.The correlation between Zn and Pb and Cr,and between Pb and Cr（in autumn,p<0.01）were significant.As for the winter,Pb had a positive correlation with Cr（p<0.05）.The sources of HMs in road dust in different seasons:the production of Cr and Ni was related to traffic sources（in spring）,while Cd and Pb were consider to be from man-made sources.In summer,Zn in dust had complex sources,and the main source and traffic were industrial sources.Zn,Pb and Cd might be affected by outdoor traffic and industrial pollution.Meanwhile,Cr,Zn and Pb mainly came from traffic pollution（in autumn and winter）.（5）The sources of MPs and heavy metals in road dust were similar.The MPs in road dust were mainly divided into traffic source,domestic pollution source and industrial source.PP were mostly caused by industrial and traffic pollution.The damage and falling of automobile tires made a great contribution to SR.PE and PS came from domestic and industrial sources,urban building materials,daily plastic products and waste incineration residues respectively.The pollution of PET in dust was closely related to human activities.The main sources of MPs in sewer sediments were plastic bags and boxes,clothing fibers,plastic runways（particles and fibers）,surface runoff and human activities.At the same time,the content of micro plastics was relatively good near dormitories,playgrounds,teaching buildings and canteens with high human activities,large traffic flow and high population density,which indicates that the pollution of MPs in the area was greatly affected by human activities.Meanwhile,in the dormitory,playground,teaching building,canteen and other areas with high human activities,large traffic flow and high population density,the content of MPs was relatively high,and the pollution of it was more serious. |
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