Pollution Characteristics Of Microplastics In Dongshan Bay And Its Ecological Risk Assessment

Microplastics usually refer to plastic particles with particle size less than 5 mm.Because of its direct and potential threat to the ecological environment and human health,microplastics pollution has been listed as a new global problem and challenge by the United Nations.Taking Dongshan Bay as the research area,the characteristics of microplastic pollution in surface water,coastal and submarine sediments,shellfish and fish organisms in Dongshan Bay were studied,and the characteristics of abundance,polymer type,particle size,shape and color were analyzed.The pollution level of microplastics in Dongshan Bay was preliminarily revealed,and the ecological risk assessment of microplastics pollution in Dongshan Bay was carried out by using different methods.The main results are as follows:(1)The average abundance of microplastics in surface water of Dongshan Bay in summer(1.66 ±1.41 items m-3)was higher than the average abundance in winter(1.31±0.58 items m-3),Zhangjiang and foam floating row are the main sources of microplastic in Dongshan Bay surface water.A total of 8 polymers were identified,the main types are PE,PP,PS;the main shape is foam,fragments,the main color is white,and the particle size is mainly 1.0-2.5 mm and 2.5-5.0 mm.(2)A total of 23 sampling stations were set up along and in the Dongshan Bay.The abundance of microplastics in the sediments ranged from 31.09-971.12 items kg-1 d.w..The average abundance of microplastics in the sediments along the coast of Dongshan Bay was 153.45±214.23 items kg-1 d.w.,the average abundance of microplastics in seabed sediments in Dongshan Bay is 62.39±34.43 items kg-1 d.w..A total of 8 polymers were identified,the main types are PP,PES,PET;the main shape is fiber,the main colors are white and black,and the particle size is mainly<0.5 mm and 0.5-1.0 mm.(3)To conduct microplastic research and microplastic inspection on 8 typical economic organisms such as Ruditapes philippinarum、Perna viridis、Azumapecten farreri、Crassostrea gigas、Johnius belengerii、Sebastiscus marmoratus、Osteomugil cunnesius、Konosirus punctatus.The yield rate is above 80%,the abundance is between 0.15±0.12-1.15±0.99 items g-1 w.w,and the abundance of fish microplastics is higher than that of shellfish;A total of 8 polymers were detected,the main types are PES,PS,PET;the main shape is fiber,the main color is white,and the particle size is less than 1000 μm.(4)The pollution load index(PLI),potential ecological risk index(RI),and microplastic polymer risk index(H)are used to evaluate the ecological risk of Dongshan Bay’s surface water,sediment,and biological microplastic pollution.The pollution level of microplastics in the surface water of Dongshan Bay is level Ⅱ;the pollution level of microplastics in sediments varies greatly between regions.The western coastal area has the highest risk level and the seabed sediments in the bay have the lowest pollution level;organisms are more severely polluted by microplastics.The risk level of Azumapecten farreri、Crassostrea gigas and Osteomugil cunnesius is level Ⅴ,and the risk level of the other 5 organisms is level Ⅳ.