Occurrence Characteristics Of Marine Debris And Microplastics In Sediments Of Liaodong Bay Estuary

Marine litter is defined as "persistent,man-made or processed solid waste in marine and coastal environments" according to the UNEP(United Nations Environment Programme)definition.The problem of marine litter has become a global pollution problem,and marine microplastics are an important part of marine litter.As a new type of pollutant,microplastics(particle size less than 5 mm)have many characteristics,such as large quantity,small particle size,wide distribution range and low degradation.It is highly susceptible to being ingested by organisms in the marine environment and can be enriched through the food chain,posing a threat to the marine ecosystem and human health.Therefore,how to separate microplastics from environmental media and the environmental risks caused by marine debris and micro-plastics have become the hot issue in academic research and have received extensive attention.In order to provide basic data support for China’s control of marine debris and marine microplastics,this study designed a separation flotation device to establish a method for separating microplastics in sediments.Taking the rivers into the sea and the offshore waters in Liaodong Bay as an example,the microplastic occurrence characteristics of marine debris and sediments in the estuary of Liaodong Bay were preliminarily analyzed.The main findings are as follows:Six survey sections with a length of 5-10 km were laid in the coastal waters of Liaodong Bay,and sea drift garbage and seabed garbage were collected simultaneously by trawling.The survey found that the main components of marine debris in the coastal waters of Liaodong Bay are plastics,polystyrene foams,fabrics(cloths),glass,wood products,rubbers,and other man-made items.Among them,the amount of plastic waste is the largest,accounting for about 50.9%.What’s more,the proportion of plastic waste on the seabed(62.1%±26.7%)is significantly higher than the proportion of floating plastic waste on the sea(37.5%±45.8%).The average density of floating garbage is 67 items/km2,the average mass density is 741g/km2,the average density of underground marine waste is 19 items/km2,and the average mass density is 2544g/km2.About 84.9%of marine debris come from human land activities,and 14.1%come from human maritime activities.Based on the theory of density flotation,the experimental steps of sample pretreatment,agitation,ultrasonication,flotation overflow,digestion and suction filtration were determined by independent design of the separation flotation device.Trichloromethane,sodium chloride,zinc chloride with acid addition and zinc chloride without acid added as flotation liquid,test their effects on the properties of microplastics,practical application effects and microplastics recycling effect.It was determined that the zinc chloride solution with acid addition was the best flotation liquid.The average recoveries of PP,PC,CA,and PET were 100±0%,100 ±0%,77.78 ± 6.85%,and 98.89 ± 1.57%respectively with this flotation solution and the reliability of the experimental method was demonstrated.29 sampling points were arranged in the offshore waters of Liaodong Bay and two rivers into the sea(Shuangtaizi River and Daliao River).Through the analysis and identification of the samples,it was found that microplastics were common in the Liaodong Bay channel and offshore sediments.Among them,the microplastics abundance of sediments in the Shuangtaizi River,Daliaohe River and Liaodong Bay is 392.59±84.07/kg,407.41±180.11/kg and 189.09±51.85/kg,respectively.The abundance of the microplastics in the Shuangtaizi and Daliaohe rivers is greater than that in the offshore waters of the Liaodong Bay.In the sediments of the Liaodong Bay,the fiber-shaped microplastics are the most,and the particle-shaped microplastics are the least.The average particle size of the microplastics was 872.6±676.7 μm,and there are 87.06%microplastics with a particle size of less than 1500μm.There are up to 30 kinds of microplastics materials,mostly in Rayon,PE,PP and PET.This study reveals the pollution level and source of microplastics in marine debris and sediments in the region by preliminary investigation of the occurrence characteristics of microplastics in marine debris and sediments in the Liaodong Bay.Providing the scientific methods and data support for the realization of plastic waste source management and scientific assessment of ecological risks from marine debris and microplastics.