Research On The Status Of Microplastic Pollution In Surface Sediments Collected From Typical Intertidal Zones And Bay In China

Microplastics are generally defined as plastic particles that are smaller than 5 mm in size.As a new emergence pollutant,microplastic has aroused wide concern from both scholars and the public in recent years.Because of their stable chemical properties,microplastics can exist in the marine environment for hundreds of years,with lasting impact on the environment.Microplastics not only cause physical damage to marine organisms via ingestion,but also seriously threaten the safety of marine life and marine ecology due to the inherent and extern toxic substances carried by microplastics.The intertidal zone and the nearshore bay areas are close to the human settlements,which are the sinks of various pollutants.In this study,we investigated the surface sediments collected from the typical intertidal zone and bay of China to reveal the microplastic pollution level through quantification the abundance of microplastics,analysis the characteristics of the size,shape and chemical composition of the microplastics and combined sediment particle size and organic matter to analyze the potential sources of microplastics.Our results provide basic data for ecological risk assessment of microplastics in marine environment of China.(1)Microplastic pollution in surface sediments of typical intertidal zone in ChinaSurface sediments from 13 typical intertidal zones of China were collected to study the distribution and characteristic of microplastics.The results showed that microplastics were widely distributed in intertidal zone of China,the average abundance of microplastics was347.18 ± 88.45/kg of dry weight sediment(i.e.,dw),ranging from 255.56-555.56/kg(dw).The ZJ site(Pearl River estuary)had the highest microplastics abundance,followed by the JLJ site(Chiu-lung River estuary)and the BDH site(Beidaihe).The main shapes of microplastics were fiber and fragment,accounting for 71.54% and 21.61%,respectively.Fiber was the most dominant component at all stations except the JLJ site.The average size of microplastics was 1117.49 ± 1022.32?m and the majority of the microplastics(35.01%)comprised particles with a diameter of <500? ?m.Microplastic particles were analyzed by?-FT-IR,and rayon,Polypropylene(PP),Polyethylene terephthalate(PET)and polyethylene(PE)were detected at all sites,accounting for 41.16%?23.31%?18.49% and 10.13%,respectively.The shape and composition distribution of microplastics in different regions were affected by economic structure and maritime activities.Compared with other studies,the microplastic pollution of surface sediments in the intertidal zone of China was moderate.(2)Microplastic pollution in surface sediments collected from Sishili Bay,North Yellow SeaSurface sediment samples were collected from 28 stations in Sishili Bay,the results showed that microplastics were widely distributed in the surface sediments collected fromSishili Bay,and the average abundance of microplastics was 499.76±370.07 items/kg(d.w.).Fiber was the majority shape of microplastics in sediments,accounting for 86.37%,followed by film and fragment,and pellet was only detected in several stations.The abundance of microplastics showed a decreasing trend with the increase of particle size,and microplastics that less than 500?m in size accounted for more than half of the total microplastics.According to the infrared spectral analysis,the total of 8 polymer types of microplastics were identified,including rayon,polyethylene(PE),polypropylene(PP),polyamide(PA),polyethylene terephthalate(PET),polystyrene(PS),poly(methyl methacrylate)(PMMA),polyurethane(PU).The main component was rayon,with a proportion of 58.41%,followed by PP and PET.The microplastic pollution in surface sediments of Sishili Bay was moderate compared with other studies.The similar spatial distribution patterns of OM and microplastic indicated that they probably derived from the same source.Microplastic pollution level in port,sewage outfall,estuary and aquaculture area of Sishili Bay was relatively high,which indicated that microplastic pollution was mainly sourced from river and sewage discharge and maritime activities.(3)The ecological risk of microplastic pollution in typical intertidal sediments in China was discussed preliminarily.Polymers with high damage scores such as polyacrylonitrile and polyvinyl chloride are important sources of microplastic ecological risk.Due to the different distribution and characteristics of microplastics in various regions,the risk indexes are quite different.The potential risk level of the Yangtze River Estuary,Dongzhai Port,Minjiang Estuary and Yellow River Estuary is the highest.