Spatial Distribution Characteristics And Ecological Risk Assessment Of Heavy Metals In Maozhou River

Heavy metal pollution had a wide range of sources and strong toxicity,so it was paid more and more attention by experts and scholars at domestic and abroad.The river sediments are the main sites of heavy metals in water,and the assessment of heavy metal content and ecological risk can provide a basis for understanding and controlling of water pollution.This paper selected the first river of Shenzhen city-Maozhou river,regarded the upstream,downstream and Shajing tributary as the study area,setted 71 sampling point with the depth of 0-400 cm.These sampling were dried,ground,sieved and digested pretreatment,detected of heavy metal content using ICP-MS to analysis the distribution characteristics,ecological risk assessment and correlation.The conclusions are as follows:(1)The content of heavy metals in the whole basin was Cu>Zn>Cr>Ni>Pb>Cd,and the average content of Cu was as high as 809.17 mg·kg-1,which was about 101 times of the background value of soil environment in Guangdong province.Distribution of heavy metal content in depth mainly concentrated in the range of 0-100 cm,the overall trend for the deeper content is lower.The distribution of heavy metal content in different districts is generally was Shajing tributary>downstream>upstream.(2)The heavy metal pollution in high value areas are mainly concentrated near the intersection.Cr,Ni,Cu,Zn,Pb are distributed in the downstream section,the high value of Cd pollution belt is located in the upper section of intersection.(3)When the depth of estuary reaches 50-100 cm,the change of the content of various metals tends to be stable.There will be no sharp increasing and decreasing,and the nearer to the estuary,the higher the surface sediment content is.Compared the two banks of same section,the content of West Bank was significantly higher than the east bank that described the influence of industrial pollution in Dongguan is higher than Shenzhen.(4)The evaluation results of four different methods show that Cu was the biggest ecological risk,Pb was the last.The ecological risk of Zn was greater than Ni except using the Tomlinson pollution load index method.According to the results of cumulative index method,although the content of heavy metal Cd is less than other heavy metals,the ecological toxicity is large and the lower concentration can cause greater ecological harm.(5)There is a strong correlation between heavy mentals which have the similar pollution sources may due to the artificial sewage or production activities.There are positive correlation between different environmental factors and heavy metals(p<0.01).The correlation between heavy metals and TP is the most significant,explained 13.1% of the variation in the redundancy analysis,followed by organic matter(TC),TN and moisture content.It has the best correlation with heavy metal when the particle size is less than 250 ?m and it is easier to adsorb Cr,Zn,Cd.