| With the development of science and technology,the beginning of the last century,the beginning of the 60s,countries around the world competing to develop nuclear power.And with the increase of uranium,uranium mining is further expanded,and a large number of abandoned uranium mines are produced at the same time.It has been paid more and more attention to the decommissioning and disposal of heavy metals and radioactive wastes.Heavy metals are toxic,persistent and non-biodegradable.They may accumulate through food chain in the ecosystem and have a potential effect on organisms.When the radioactive material enters the environment,it will dilute and migrate with the diffusion or flow of the medium,and it can be enriched in the body and thus generated in the human body.Long term exposure to radioactive elements in the natural environment,will affect the health of the human body through inhalation.The study on the ecological risk of heavy metals and the investigation of radioactive sources are of great significance to the development of nuclear safety planning.Firstly,in wet seasons of Spring,2016,surface soils(0-60 m)of an abandoned uranium were collected from ten sites to investigate the risk of heavy metal and radioacitive level in in the areas of former mine stope,former mineral ore stockyard and formal mine road.The three areas mean concentrations(mg/kg)of Pb?Cd?Cu?Zn?As?Hg?Cr?Mn?Ni were 2275.69,6.09,71.51,1230.47,47.87,502.81,46.22,422.39,12.01.They were higher than the soil environmental background values of the study area and the two grade standard of soil environmental quality standard(GB15618-1995).The three areas mean activity concentrations(Bq/kg)of 232Th,238U,226Ra and 40K were 27.28,74.05,911.51,1062.62.They were higher than the soil environmental background values of the study area.Secondly,the single factor index method(SFI),the geo-accumulation index method(Igeo),the Nemero index method(NI),the potential risk assessment(RI),and pollution load evaluation method(PLI)were used to evaluate the risk of heavy metal pollution.The level of radioactive contamination was analyzed by four indexes,such as the radium equivalent activity,air absorbed dose,annual effective dose equivalent,and radiation effect of soil utilization.According to the comprehensive evaluation of the pollution level of heavy metals,the value of pollution is from large to small:Hg,Cd,Pb,Zn and As.The soils in the formal mine stope and formal ore stockyard showed a higher risk of contamination.The size of the four radionuclides is:226Ra>238U>40K>232Th.The radium equivalent activity was higher than the safety value,the air absorbed dose is higher than that of Hunan Province field gamma radiation dose rate,the world average radiation dose rate and China average radiation dose rate,annual effective dose equivalent analysis is higher than that of Hunan province and the national per capita annual effective dose level.The internal and external exposure index exceeds the safety value so that the soil as a building material will be greatly limited.The former mine stope and former mineral ore stockyard is the core area of radioactive pollution.Finally,according to the results of this study,I combined with engineering practice.In the former mine stope and former mineral ore stockyard,the use of heavy metal pollution remediation of the plant repair technology and the disposal of radioactive waste in the medium depth disposal site repair design.Heavy metal pollution can be reduced by adding a passivating agent and planting plants.Radioactive contamination can be reduced by soil cover test.It provides suggestions and references for the decision-making department. |
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