Microplastic Pollution In Different Waters From Yangtze River Delta,China

Under the effects of the environment,bulk plastic can become numerous even smaller plastic pieces,and those with the diameter less than 5mm are defined as microplastics.Relevant researches showed that microplastics have already been widely detected in the marine environment,and the microplastic pollution in the estuary region is especially serious.This indicates that the input from the urban rivers is one of the most important sources of microplastics in the offshore waters.Compared with marine environment,inland fresh water environment is more closely related to human activities,but we still have little knowledge when it comes to how the microplastics migrate from fresh water into marine environment.Researchers have revealed that the level of microplastic pollution and the density of population are positively correlated,and it is inextricably linked to the industry structure in the city.However,the analysis into the land based source of microplastics is still at its initial stage,and there is still a lack of investigation with regards to whether the difference in the economic industry has any effect on the microplastic pollution.Therefore,in the present thesis,we conducted the research for the above mentioned questions:(1)study microplastic pollution starting from the land based source input of textile industry;(2)analyze the physical and chemical characteristics,influencing factors of the microplastics in different function areas which were categorized by the main functions of the study area;(3)with reference to the stream order concept,study the spatial distribution of the microplastics in the water systems of different orders,and discuss the similarities and differences,as well as the transmitting mechanism of the microplastics' spatial distribution from both the local and holistic perspectives.Firstly,the study carried out the research into the distribution of the microplastics in the waters and sediments at 29 sites in the typical textile industry zone(in Shaoxing and Yuyao),and found that the microplastic abundances of the water samples from the river courses range from 2.1-71.0 items/L,and the microplastic abundances of the sediments range from 16.7-1323.3 items/kg.The distributions of the sizes of the microplastics from the waters and the sediments vary significantly(p?0.01),and the small size microplastics in the water samples are more concentrated,which proves that microplastics are more likely to break in water environment.The microplastics from the water samples and sediments are mainly polyesters mostly in the form of fiber,which account for more than 79%,while the pellets only exist in the water samples.Moreover,there is a higher correlation between the microplastic pollution in the water sample and the density of the textile factories,but the correlation between the microplastic pollution in the sediments and the density of the textile trading companies is even higher.It can be concluded from this that the production and trading activities of textiles are one of the main sources of microplastic pollution.Secondly,in order to further probe into the pollution characteristics of the microplastics from different function areas,this paper selected and analyzed the water samples from the river courses in Chongming farmland area and scenic area.The results indicate that there is a relatively big difference in the microplastic pollution of the water samples from different function areas.Among them,the average abundance of the microplastics in the farmland area is 8.11 items/L,and the average abundance of the microplastics in the scenic area is 5.17 items/L.It can be seen from this that the microplastic pollution of the water sample from the farmland area is more serious;and the physical and chemical characteristics of the microplastics of the water samples from different function areas are similar,all of them mainly in the form of fiber and in the sizes of 0.1-1.0 mm.Combined with the microplastic pollution data of the soil in the farmland area,it is found that there is a significant difference in the size distribution of the microplastics in the water sample and the soil sample,and that the microplastics in the water sample have more shapes and colors.The main content of the microplastics in the water sample is polyester,and that of the microplastics in the soil sample is mainly polypropylene and polyethylene.It can be concluded from this that the physical and chemical characteristics of the microplastics are not related to the category of the function area,but rather highly related to the object of study(carrying object).Finally,in order to probe into the microplastic pollution characteristics of the study object(water)in the water basins of different orders,this paper conducted classified research into the Yangtze River Delta.Different water systems(Shanghai creeksSuzhou River-Huangpu River-Yangtze River Estuary-offshore area of East China Sea)were chosen to analyze the spatial distribution characteristics of microplastics,and it was found that in the water systems of different orders,there was a significant difference in the abundance of the microplastics.The abundance of microplastics in the fresh water area(1.8-2.4 items/L)is higher than that in the estuary and offshore water area(0.9 items/L);the microplastic abundance in the river courses(Suzhou River and Huangpu River)gradually increases from upstream to downstream;the abundance of microplastics and the distance to the urban center and Yangtze River estuary are in negative correlation.It can be seen that the microplastics may keep accumulating from the network of urban rivers to the ocean.The most commonly seen shape of microplastics in the water systems of different orders is fiber,but the percentage varies a lot and the main type is polyester.It is thus clear that the microplastic pollution in the fresh water is more serious,and that the spatial distribution characteristics of the microplastics in the water systems of different levels vary.In conclusion,the typical textile industry contributes more to the microplastic pollution in the rivers;the correlation varies in the microplastic pollution of the production factories,trading companies and the water sample from the river course,and the sediment;there is an obvious correlation between the microplastic pollution in the inland rivers and its surrounding economic industries.In addition,there is a significant difference in the effects of different function areas(farmland area and scenic area)on the same object of study(water sample).Exploring the spatial distribution characteristics and transmitting features of the microplastics from the perspective of stream order can better clear up the source-accumulation relation.Meanwhile,there are specific rules in the microplastic pollution of different water systems from urban river courses to oceans,and this can reflect the correlation between the microplastic pollution and the hydrological movement of the river,and the density of population to a certain extent.