Study On Microplastics Pollution In Different Water Environment And Case Analysis Of Its Ecological Effect

Microplastics,commonly defined as plastic particles less than 5 mm,are widely present in various environmental compartments.Microplastics bear the features such as small size,adsorption affinity to heavy metals and organic pollutants.They may be ingested by marine biota,and then enter into human body through food web,thereby causing threats to human health.In this paper,different water environment systems such as surface water in the Northwestern Pacific,the Western Pacific and Zhangjiang River Estuary in Fujian are studied,then the microplastics were separated and extracted.The abundance,color,shape,particle size,chemical composition and surface morphology of microplastics were determined.The basic information and latest pollution levels of microplastics in the Western Pacific and Zhangjiang River Estuary were explored.The seasonal variation characteristics of microplastics in the Northwest Pacific were revealed.At the same time,the response of Prorocentrum donghaiense to different exposure condition of polystyrene microplastics was studied through laboratory culture experiments,and the ecological effect of microplastics pollution was preliminarily explored.The results show that:?1?The average microplastic abundance in the surface waters of the Northwestern Pacific in spring(7.4×10⁴ items·km^-2)is higher than that in summer(1.9×10⁴ items·km^-2),which may be caused by the Kuroshio current.Southeast Asia region may be the main source of microplastics.In spring and summer,the main types of microplastic polymers are both polypropylene and polyethylene,the shape is dominated by debris and the proportion of foam is the minimum,the particle size is dominated by 0.5?1 mm and 1?2.5 mm.The results of the characteristic investigation verify that the microplastics in the study area in spring and summer may all come from Southeast Asia.?2?The abundance of microplastics in the surface waters of the Western Pacific ranged from 1.6×10⁴ to 1.1×10⁵ items·km^-2,with an average of 5.0×10⁴ items·km^-2.The main types of microplastic polymers are polyethylene and polypropylene,accounting for 50%and 36%,respectively.The shape of microplastics in this region is mainly composed of film,accounting for 41%,followed by fiber and line,accounting for 35%and 15%,respectively.The main colors of microplastics in this region are white and transparent,accounting for 43%and 41%,respectively.Microplastics with particle sizes of 0.5?1 mm and 1?2.5 mm account for 59%and 24%,respectively.The possible migration direction of microplastics is station D1?D4?D2?D3.?3?The abundance of microplastics in the surface waters of Zhangjiang River Estuary ranged from 50 to 725 items·m^-3,with the highest microplastics abundance of725 items·m^-3 at station Z1?117°20'33"E,23°57'06"N?and the lowest of 50 items·m^-3at station Z2?117°21'27"E,23°57'04"?.The main types of microplastic polymers are polypropylene and polyethylene,accounting for 52%and 23%,respectively.The shape of microplastics in this region is mainly composed of fragments,accounting for43%,followed by film and pellets,both accounting for 18%.The main colors of microplastics in this region are white,black and yellow,accounting for 56%,14%and14%,respectively.Microplastics with particle sizes of 0.5?1 mm and 1?2.5 mm account for 33%and 31%,respectively.Sewage discharge,land runoff and aquaculture near Zhangjiang River may be the main factors leading to the high microplastic abundance in Zhangjiang River Estuary.?4?The results of exposure experiment showed that:high concentration of DOM(5 mg·L^-1)can promote the growth of Prorocentrum donghaiense.Polystyrene microplastics?0.1?m and 10 ppm?can affect the growth of Prorocentrum donghaiense in the early stage,which is inhibited first and then promoted.Polystyrene microplastics can inhibit the growth of Prorocentrum donghaiense in the stable period and decline period,the inhibition of microplastics increases with the decrease of particle size and the increase of concentration,the inhibition effect of the concentration is stronger than that of the particle size.Our research will improve the understanding of ecological effect of miroplastic pollution on the Prorocentrum donghaiense and will provide a new scientific basis for the marine ecosystem protection.