Distribution Characteristics Of Microplastics In Sewage Discharge Outlets In Tianjin And Their Toxicological Effect On Artemia

In recent years,microplastic pollution has attracted global attention,and it is widely existed in seawater,sediment and organism.Terrestrial input is considered to be one of the main sources of marine microplastics(MPs),while the number of sewage outlets into the sea is large and the types of sewage are diverse,which is an important way for terrestrial input of MPs.The microplastic particles in the environment are small and large in quantity,which are easy to be intake into the body by organisms,and pose toxic effects on them.Therefore,it is of great significance to investigate the distribution of microplastics in the coastal waters and to carry out the study on the toxicology of MPs for the prevention and control of MPs pollution.At present,great progress has been made in the research of MPs at home and abroad,but the research on the distribution characteristics of sewage discharge outlets in Tianjin and toxicology of MPs to marine organisms is still less.In this paper,the samples of MPs were collected from 32 sewage discharge outlets in three areas,Dagang area,Tanggu area and Hangu area.The samples were analyzed and characterized by optical microscope and micro infrared spectrometer,and the distribution characteristics of MPs in Tianjin sewage discharge outlets were studied.Then the toxicological effects of polyethylene(PE)and polystyrene(PS)MPs on Artemia were studied.Our results show that:(1)Shapes of MPs are mainly fibers,fragments and thin films in the sewage discharge outlet of Tianjin.Fiber has the highest abundance with the proportion of 75.6%.39.5% of MPs have the particle size of 1-5mm and 33.0% of MPs have the colour of black.The main components of MPs are polyethylene terephthalate(PET)and polypropylene polyethylene blend(PP-PE),with the proportion of 34.80% and 21.46%,respectively.The main sources may be residential sewage,plastic packaging,clothing and textiles,tourism and fisheries.In addition,MPs could reduce the growth rate of Artemia,and the body length of PE group and PS group decreased by 17.92% and 14.95%,respectively.MPs were mainly distributed in the intestinal tract of Artemia.32 and 11 kind of Phylun were detected in intestinal and fecal samples,respectively.They are mainly for Proteobacteria and Actinobacteria.Intake of MPs increased the proportion of Actinomycetes in intestinal and fecal samples,and the diversity of intestinal microorganisms was also increased.The diversity of microorganisms in fecal samples was lower than that of intestinal samples,Microplastics may have toxicological effects on Artemia.The results of this study provide a preliminary data support for the understanding of the distribution,source,toxicology and risk assessment of the microplastics in Tianjin's sewage discharge outlets,which is conducive to the further treatment of marine garbage and MPs in the Bohai Bay.