Evaluation Of Microplastic Pollution And Ecological Risk Studies At The Hu-men Entrance Of Pearl River

Microplastics have received a great deal of attention as an emerging pollutant widely distributed in the environment.Microplastics generally have particle size less than 5 mm,large specific surface area and strong adsorption capacity,and adsorb many heavy metals（copper,cadmium,etc.）and persistent organic pollutants（PCBs,PAHs and organic pesticides,etc.）in the environment.They interact with each other and their toxicity increases leading to more serious environmental hazards.The ocean,as the largest sink on earth,accumulates a large amount of microplastics,but its distribution in the environmental media involved in the transport pathway to the sea still needs further study.With the rapid economic development,the Pearl River Delta has created the largest urban agglomeration of Guangdong,Hong Kong and Macao in China,which also brings increasingly serious environmental pollution problems.The rapid development of agriculture and industry and the explosive population growth have led to the Pearl River estuary receiving various pollutants from surface runoff and direct coastal discharges,and it is an important storage site for microplastics.Compared with other ecosystems,the Pearl River estuary is under greater pressure of environmental pollution.Therefore,in this study,microplastic pollution characteristics in sediment,surface water and marine organisms of Hu-men beach were systematically analyzed by taking Hu-men inlet watershed of Pearl River as the research object,and the ecological risk evaluation of microplastics in Hu-men was carried out by using pollution load index method and potential ecological risk index method.The samples were separated and extracted by continuous flow separation flotation device,5 mm aperture screen,3:1 mixture of 65%HNO3 and 30%H₂O₂by volume as abatement solution,and the composition,particle size distribution,color,type and abundance of microplastics were counted with the help of Raman spectroscopy,microinfrared spectroscopy,body microscopy and biological microscopy.The results showed that the types of microplastics detected in the beach sediments of Hu-men inlet of Pearl River were mainly fiber type,and the microplastic polymer type accounted for the largest proportion of polypropylene（33%）,which was widely sourced,mainly from textile production debris and waste gas electronic parts,followed by foaming microplastics polystyrene（PS）accounting for 27%,debris type,film type microplastics polyethylene（PE）accounting for 23%,and other components microplastics Relatively small share of other components of microplastics.The microplastic particle size was 17.8μm-5.21 mm,with the most microplastics in the<1 mm range,accounting for 61%,followed by 1-3 mm（31%）and 3-5 mm（8%）.12samples had an abundance of 163-583 microplastics/kg.The most abundant type of microplastics in the surface water was also fiber type,which was consistent with the sediment.The most abundant polymer type was polypropylene（34%）,followed by polyethylene terephthalate（26%）.Microplastic particle size was most detected in the<0.5 mm range（66%）,followed by microplastics in the 0.5-3 mm range（22%）and least in the 3-5 mm range（12%）.microplastic abundance in the eight water samples ranged from 88/m³-207/m³,with an average abundance of 143/m³.influenced by human activities and the location of sampling sites（tourist spots,estuaries）,the abundance varied greatly.Fibrous species still accounted for the largest proportion of the organisms,57%.Small spherical microplastics were found in the organisms and accounted for 23%,and no microplastics of this type were found in the sediment and surface water.Microplastic colors were mainly blue（37%）,transparent（22%）,red（18%）,black（14%）,yellow（6%）and green（3%）.Fibrous and small spherical microplastics were also predominantly blue in color.The abundance of biomass microplastics ranged from 0.8/g to 2.4/g.The microplastic pollution and indices were calculated by the pollution load index method at the entrance of Hu,and the PLI value of 1.19 at the coastal station（T9）of sediment was the highest among all sampling sites.The total pollution load index（PLIzone）of the three environments were 0.98,0.99 and 0.97 close to 1,which were at the threshold of light and moderate pollution.The environmental pollution by polymer types was assessed by the calculation of the potential risk ecological index method.The results showed that the ecological risk index（E_rⁱ）of PS,PP,PE,PA and PET were small and had less impact on the environment of Hu-men,all of them were lightly polluted.the ecological risk index（E_rⁱ）of PVC and ABS were higher,among which ABS produced heavy pollution to organisms,PVC was heavily polluted in beaches and organisms,and the surface water table was seriously polluted.In summary,this thesis characterized microplastic pollution in different media（sediment,surface water and organisms）in the Hu-men Inlet of the Pearl River and proved that microplastics were widely present in the Hu-men Inlet.The pollution characteristics of microplastics in different media differed.Microplastics not only harm the marine environment through themselves,but also act as carriers for other pollutants（heavy metals,persistent organic pollutants）to compound the pollution of the environment,which should be studied more comprehensively in the future for their toxic hazards to the ocean.In addition,this study also evaluated the ecological risk of microplastics in Hu-men,and found that polyvinyl chloride（PVC）has the highest potential risk index,which is more harmful to the environment and affects human health.This thesis provides data support for the study of microplastics in the Pearl River,and also makes up for the key data of microplastics in Hu-men.