Study On Distribution Characteristics And Sedimentation Rate Of Heavy Metals In Sediments Of Hanyuan Section Of Dadu River

The rapid development of economic globalization,the improvement of human liv ing standards and the endless demand,man-made activities such as industry and minin g have led to the deposition of various types of heavy metals into water bodies in diffe rent forms,and finally enriched in the human body through the food chain.There are many large-scale lead-zinc mines in Hanyuan,and the environmental problems caused by mineral development are also serious.Therefore,based on the study of the heavy metal characteristics of the sediments in the Hanyuan section of the Dadu River and th e ²¹⁰Pb side years,it can provide a scientific basis for pollution prevention and control.The quality of the local environment is important.In this paper,by collecting 11 surface sediments and 2 columnar sediments（28）,combined with the methods and principles of environmental geochemistry and trace el ement geochemistry,the heavy metals in the study area are determined for sediment c ontent,occurrence morphology and grain size characteristics.The pollution was evalu ated,and the deposition rate of sediments was calculated based on the 210Pb side year s.Combined with the above studies,the following conclusions were drawn:（1）Through the study on the grain size characteristics of the sediments in the Ha nyuan section of the Dadu River,the surface sediments and columnar sediments are d ominated by silt（3.9⁶3μm）,clay（<3.9μm）and sand（63μm）.Relatively few,the surf ace sediment mainly accounts for 79%of silt,the content of clay and sand is 10.25%,10.75%,and the average particle size is 29.20μm.The sorting is better;The sediments of 1-1 and 1-2 were mainly silt,accounting for 75.6%and 81.94%,and the clay conte nt was only 1.52%and 5.16%.The average particle size was 41.20 and 31.34μm,resp ectively.it is good.（2）The average content of heavy metals in the sediments of the Hanyuan section of the Dadu River is Mn>Zn>Pb>Cr>Cu>As>Cr,among which the heavy metals of Z n,Pb and Cd are highly polluted,and the average content of heavy metals in Cd is hig h.It is 16.3 times the local background value,and several of the points have reached d ozens of times.The spatial distributions of As,Cu,Pb,Zn and Cd are similar.The hea vy metal content at the point where there is no obvious pollution source is small,and t he heavy metal content increases significantly in the middle reaches and downstream of the pollution source.The HYC7,HYC10 and HYC11 points are particularly seriou s.Combined with four pollution assessment methods,the surface sediments of the Ha nyuan section of the Dadu River were evaluated for pollution.According to the ecolo gical hazard risk,it can be concluded that only one point of HYC9 is a medium ecolog ical hazard,and the other points are in a strong-very strong ecological hazard.It comp rehensively reflects the serious pollution of the Hanyuan section of the Dadu River.（3）The sediment samples are mainly in the residual state,and the extractable stat e of weak acid which is harmful to the environment is relatively small,among which Cr element is the most stable;while the Cd element is mainly weak acid dissolved stat e,and deposition by RSP method.The pollution occurrence evaluation of the object o ccurrence pattern,the main Cd in the study area is seriously polluted,and Pb is second,which needs us to pay enough attention.（4）By measuring 210Pb in sediment,the specific activity interval of column 1-1is 26¹18Bq/kg,and the specific activity interval of column 1-2 is 26⁷9 Bq/kg,colu mn 1-The sediments of 1 are in the range of 1917-2017,the average sedimentary dep osition rate is 0.632g/cm2·a-1,the sediment age of column 1-2 is 1961-2015,and the average sedimentary deposition rate is 0.737 g/cm2·a.-1Through the above methods to investigate the heavy metal pollution of sediments,we can learn more about the local heavy metal pollution level,the environment and p otential threats to local residents,and take corresponding measures to control.