Study On The Radionuclide Uranium Contents Of Rice In Xiangshan Uranium Mine Area

As the largest volcanic-type uranium mine of China,Xiangshan uranium mine has a mining history of more than 50 years.There are nearly 100 thousand people living in the mining area,with the exception of a small number of uranium production workers,mainly for farmers,and the main crops in the mining area is rice,with the annual of double-cropping system.During the mining process,large quantities of tailings and ore-containing wastewater have been produced and caused serious radioactive pollution to mining environment due to ineffective disposal.While,investigations mainly focus on the geological mineralization for years,a very small amount of special investigations to the radioactive environmental.Few studies about the content of radionuclides in rice of Xiangshan uranium mine have been reported.This dissertation focuses on investigation about the radionuclide uranium contents in rice,analysises radionuclide uranium contents and distribution characteristics of rice in Xiangshan uranium mine area,discusses reasons for characteristics of rice uranium contents in sub-regions,and uranium contents relationship between paddy soil and rice,than carries out pollution assessment and health risk assessment of rice,which are of great significance to strengthen food safety and protect citizens' health of study area,but also provide reference data for management work of whole mining environment.Main results are as follows:(1)The average uranium contents(1.39 ng·g-1)of 129 rice samples is 1.19 times of average uranium contents in unexploited mine area,with 51.16 % of exceeded samples.And those samples have resulted in a threat to food security in whole mining area.The average uranium contents of exploiting mine area(1.69 ng·g-1)and hydrometallurgy plant area(1.39ng·g-1)are 1.44 and 1.19 times of average uranium contents in unexploited mine area,with68.89 % and 50 % of exceeded samples respectively.It shows that exceeded samples are mainly located in the two sub-regions.The order of average value of uranium contents in sub-regions can be described as: exploiting mine area(1.69 ng·g-1)>hydrometallurgy plantarea(1.39 ng·g-1)>unexploited mine area(1.17 ng·g-1)>abandoned mine area(0.96 ng·g-1).(2)Uranium contents in paddy soil is mainly concentrated in the surface layer,little related to uranium contents in underlying bedrock.The confirming migration path of uranium is as follows: first,in uranium tailings;then,the surface water;third,in paddy soil;at last,in rice,and resulting in characteristics of uranium contents in rice.Meanwhile,as the whole mine area,uranium contents in paddy soil have always had a complicated relationship with uranium contents in rice,under effects of complex factors,such as ore-transportation conditions,open-air tailings,drainage pipeline etc.For exploiting mine area,uranium concentrations of rice increases with uranium concentrations of paddy soil,and a exponential function regression equation with high fitting degree can be structured.(3)The average value of Single Factor Index(2.31)for whole mine area reaches moderate pollution level.And rice samples with unpolluted,mild pollution,moderate pollution and severe pollution account for 14.73 %,35.66 %,27.90 %,21.71 % of total samples respectively.The order of average value of Single Factor Index for rice in sub-regions and contrast area can be described as: exploiting mine area>hydrometallurgy plant area>unexploited mine area>abandoned mine area>contrast area.The average value of Single Factor Index for rice in exploiting mine area and hydrometallurgy plant area both are moderate pollution,while unexploited mine area and abandoned mine area both are mild pollution and contrast area unpolluted.(4)The slope factor(SF)of carcinogenic risk of rice for adults and children in Jiangxi Province are referred to as 1.04×103,3.98×102(d·kg)·mg-1 respectively.The order of CR among adults and children in sub-regions both are exploiting mine area>hydrometallurgy plant area>unexploited mine area>abandoned mine area>contrast area.Adults and children are exposed to a certain risk of cancer by consuming rice from exploiting mine area and hydrometallurgy plant area,while with no risk of cancer by consuming rice from unexploited mine area,abandoned mine area and contrast area.