Distribution Characteristics Of Microplastics In Different Media In Mariculture Areas And Mangroves In Hainan Province

Microplastics（MPs）are plastics that smaller than 5 mm in diameter and are resistant to degradation and widely distributed.The distribution and migration characteristics of microplastics in different environmental media and the impact of microplastics on organisms have become a global concern.At present,there are few reports on the distribution characteristics of microplastics in different media in Mariculture areas and mangroves in Hainan.Through on-site sampling,density flotation,dissection and Raman spectrum identification,this study aims to preliminarily study the distribution characteristics of microplastics in different media of Mariculture areas and mangroves in Hainan,and reveal the pollution characteristics and main sources of microplastics in the eastern breeding areas and mangroves in Hainan.The results enrich the basic data of microplastics distribution in mariculture areas and mangroves in Hainan,provide theoretical basis for the ecological risk assessment of MPs in mariculture areas and mangrove wetlands in Hainan,and provide important data support and application basis for MPs monitoring,prevention and control,management and control,and coastal zone protection.The specific research results are as follows:（1）The abundance range of microplastics in seawater in the eastern mariculture area of Hainan（Wan Ning）was 1150～9650 n·m^-3,and the average abundance was 5272.73n·m^-3.The main types of microplastics were fiber types（91.30%）.The color type of microplastics is mainly brown（46.64%）.The abundance range of microplastics in the sediments was 8～370 n·kg^-1,and the average abundance was 98.36n·kg^-1.Fiber microplastics accounted for the majority（96.86%）.The color type of microplastics is mainly white（48.06%）.In the two media,the particle size types of microplastics are mainly smaller than 1mm.The components of microplastics are mainly polyamide（commonly known as nylon）,followed by polyethylene.Due to the same pollution sources,the size,shape and composition of microplastics in sediments and seawater are similar.（2）The abundance of microplastics in the sediments of Hainan Mangrove was20～66n·kg^-1,and the average abundance was 36.80 n·kg^-1.The composition type of microplastics was mainly fiber type（76.09%）,followed by film type（11.96%）,with great differences among stations.The color types of microplastics are abundant,and brown occupies a large proportion（28.62%）,with great difference among different stations.The main particle size types of microplastics in mangrove sediments were smaller than 2mm（86.18%）.The composition type of microplastics is mainly polypropylene（56.25%）.（3）The organisms of 22 species have been collected in Hainan Mangrove forest,which can be divided into three categories:crabs,bivalves and snails.Microplastics are found in benthic organisms and the abundance level is very different.The plastic abundance in benthic organisms ranged from 0.83 to 12.00 n·item^-1,and the average abundance was 3.90 n·item^-1.The mean abundance relationship between species was as follows:crab(1.11n·item^-1)>bivalve(0.88n·item^-1)>mollusks(0.22n·item^-1)showed significant difference in the abundance of microplastics in benthos,and the microplastics composition type was mainly fiber（80.13%）.The main color type is brown（37.18%）.The grain size distribution of microplastics in benthic organisms has the same rule as that of sediments,mainly with the microplastics less than 2 mm（80.77%）,and the proportion decreases gradually with the increase of grain size.Microplastics are mainly composed of polypropylene（94.44%）.The abundance of microplastics in mangrove sediments in Hainan is similar to that of benthic organisms.（4）The hainan mangrove benthic sediments and micro plastic pollution level of risk inⅠ,Ⅱlevel respectively,need to consider and explore the micro plastic control management.