Study On Microplastics And Heavy Metals In Main Rivers Of Zhejiang Province

Microplastics are plastic pellets with a particle size of less than 5 mm.Relevant studies have shown serious microplastic contamination in China’s offshore ecosystem.Therefore,studying the occurrence and distribution characteristics of microplastics in the estuary area and near-shore sea area is of great significance for understanding the status of microplastic pollution in China’s coastal areas.Moreover,China’s current survey of microplastics is still in its infancy,and there are few survey data on microplastics in rivers mainly involved in the East China Sea.Therefore,seven rivers that mainly flow into the East China Sea were selected in Zhejiang Province,the microplastic abundance,size,color,shape and other characteristics were investigated.The results of microplastic distribution characteristics show that the detection rate of microplastics in 27 stations is 100%.The microplastics of all stations range from 1000-13100 n/m~3,and the average density is 2977.8±2248.1 n/m~3.The size distribution of microplastics ranges from 16.9-3931.8μm,and there is a rule of 0-0.5mm>0.5-1.0 mm>1.0-2.5 mm>2.5-5.0 mm in the percentage composition;The color composition of microplastics shows that green accounted for 30.1%,black accounted for 20.2%,and other colors accounted for similar proportion.The percentage of microplastic shape is relatively uniform,with fiber(40.6%)>chip(39.3%)>film(13.6%)>spherical(4.2%)>wafer(2.4%).Microplastics can adsorb heavy metals and release heavy metals into the environment.Therefore,the ecological risk of heavy metals in the study area was assessed by the method of HPI and SSD at 27 stations where micro-plastic water samples were collected for concentration determination.The results showed that the concentrations of Cu、Pb、Zn、Cd、Cr and As were 7.14-1787.19μg/L and0.50-372.79μg/L,2.60-508.54μg/L,0.03-0.80μg/L,3.76-2063.48μg/L and0.21-68.41μg/L,respectively;The Heavy Metal Pollution Index Method(HPI)shows that there are 7 stations with high pollution level of heavy metals,one station with moderate pollution level,the remaining 19 stations are low pollution level.The heavy metals causing high pollution in water are Cr and Pb;The ecological risk ranking of six heavy metals is as follows:Cu>As>Zn>Cr>Pb>Cd.The two evaluation methods are complementary to each other.It is suggested that in practical application,the stations with high pollution degree of heavy metals in water should be determined by HPI evaluation method,and then the heavy metals with high harmfulness to aquatic organisms should be determined by SSD evaluation method,and the key prevention and control measures should be carried out.The correlation analysis was used to explore the relationship between the abundance of microplastics and the concentration of heavy metals in the study area.Generally speaking,the correlation between microplastics and heavy metals in the study area is very low.Except Jiaxing and Hangzhou are relatively high,there is no correlation in other areas(Shaoxing and Ningbo,Taizhou,Wenzhou).It is concluded that microplastics have no obvious effect on the concentration of heavy metals in water,and will not increase the ecological risk of heavy metals.