| Pavement sediment is also an important source of microplastic pollution in rainwater runoff,and it is also rich in nutrients such as DOM,nitrogen and phosphorus,which enter the aquatic system with runoff under the erosion of rainfall,causing complex pollution phenomenon to the water body.However,relevant studies on the pollution characteristics of urban pavement microplastics and the combined pollution characteristics of dissolved organic matter and nutrient salts are still limited.Beijing is the largest city of our country and the political and cultural center of our country.In this paper,the north-south central axis of Beijing,Chang ’an Street and all the ring roads along it are selected as the research area.The sediment samples of the pavement are collected,and the bulk impurities are removed to determine the abundance and characteristics of microplastics,DOM component characteristics,nutrient and other physical and chemical indexes,and the correlation analysis is carried out.Pollution load index(PLI),polymer hazard index(PHI),potential ecological risk assessment(PERI),ground accumulation index(Igeo)and human exposure risk assessment were used to evaluate the ecological risks and human health risks caused by microplastics in pavement sediments in Beijing.The main research results are as follows:(1)The average abundance of microplastics in pavement sediments in Beijing was 960.9 n·kg-1.The main color of microplastics was black,accounting for 22.49 %,and the color microplastics accounted for 50.67%.The main shape of microplastics was fibrous,accounting for 55.29 %.The proportion of microplastics with small and medium size(10-500 um)was the highest(46.95 %),and the average size of microplastics was 1013.2um.The main polymer type of microplastics was PE,accounting for 30.69 %.The abundance of microplastics in the fourth ring road was the highest,and the proportion of colored microplastics in the second ring road was the highest.Compared with different urban functional areas,the commercial area had the highest abundance of microplastics,reaching 1629.7 ±187.60 n·kg-1.The abundance of microplastics in pavement sediments in different functional areas is related to population density and human activities.Green is the main microplastic color in park road and subway platform,black is the main microplastic color in bus station and business district,and transparent is the main microplastic color in residential area.(2)By analyzing the DOM related data of the collected pavement sediment samples,it can be seen that DOC content levels in different loop areas are in the following order: fifth ring road > second Ring Road > fourth Ring Road > third Ring road.The order of DOC content in different functional areas was as follows: park road > subway platform > commercial area > residential area >Bus stop.Pearson correlation analysis showed that the abundance of microplastics was significantly correlated with β:α values in DOM(P < 0.05),the correlation coefficient was 0.391.The significance levels of other indicators were all more than 0.05,indicating that there was no correlation between other indicators and the abundance of microplastics.(3)According to the assessment of pollution load index method,the PLI risk of Chang ’an Avenue and the Third Ring Road was the highest,and the microplastic pollution load index of the commercial district was the highest;According to the polymer hazard risk assessment,most of the microplastics deposited on the pavement in the sampled sites in Beijing are at level III hazard risk.The human exposure risk assessment shows that the human body ingests 29.33 ~ 677.53 ng microplastics per day. |
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