| In recent years, the yields of phosphate rock have improved rapidly year by year asthe rapid development of agriculture and the technology. However, this has caused themine environmental problems, especially by the radioactive elements, drawingattention to all countries over the world. This paper aims at studying the natures ofradionuclide content and their mobility in soil, water and stream sediment byinvestigation and laboratory analysis methods in Yangshui area of Kaiyang phosphatemine. Meanwhile, the essay also evaluates the radiation safety level in mining area,discussing the distribution of radioactive nuclides in profile to put forward preventionand protection measures. Mainly have the following achievements and theunderstanding:（1）The environment around the Phosphate deposit is influenced by the radioactivenuclides: The average content of thorium and uranium in soil are11.34μg/g and4.59μg/g respectively, which are higher than that of the world soil（in the world soil,thorium average content:9μg/g and uranium:2μg/g）and that of the crustal abundance（uranium:2.7μg/g, thorium:9.6μg/g） and also richer than other areas in China such asXiangjiang River valley, Tianjin etc. However, the average thorium content in riverwater is very low, only0.0015ng/mL, almost close to0and the concentration of theuranium is higher than thorium, an average concentration of0.89ng/mL, which islower than that of China river （1.66ng/mL）, but higher than the average concentrationof world river（0.309ng/mL）and some rivers of southern China, therefore thedepartments should given special attention to the river water which has influenced byradioactive nuclides, especially the enrichment of uranium in the process of miningphosphate. In the sediment of the river water, average content of thorium is5.43μg/g,lower than the stream sediment elements background value （9.33μg/g）. The averagecontent of uranium4.95μg/g, is higher than China stream sediment background value（2.21μg/g）2.24times, and also higher than other rivers, such as Shi TingJiang, Tuo Jiang,Yangtze river etc. It may come to lead to harmful secondary pollution.（2） Through analyzing the natural radionuclide content and ratio in the sameenvironment system but in different environmental media, the paper indicates thaturanium distributes broadly in rock, soil and stream sediment at relatively degree, butlower in water. Thorium enrichment in soil highly and stream sediments springs fromthe rock, In the water, thorium content is extremely lower than uranium. All theseresult in separation of uranium and thorium in the supergene environment and thewater become separation interface.（3） The radioactive safety evaluation results show that the average content ofuranium is5.37x10-6, the thorium is10.41x10-6and potassium is2.15%in miningarea, which are2.67times,1.65times and1.8times than the value published byUNSCEA respectively (uranium:2.0x10-6,thorium:6.3x10-6, k:1.2%). The airabsorbed rate is22.93（pGy/s） from the ground1m in mining area, which is in linewith the nation average rate and slightly higher than the background value17.64pGy/sof Guizhou province. Resident average effective dose per year in the mining area was0.43mSv, which is lower than that of the world0.46mSv. So the study area is under thenormal radiation range. The value of Ira:0.11lower than1.0, Ir:0.38lower than1.3,complies with the building material radionuclide limit （GB6566-2001） to A class or Bclass decorate material requirements.（4）The results form radionuclide variation in typical geological profile imply thatthere are a few abnormal points in the study area, only one abnormal point among thethree profile for different lithological characters, and that the thorium and Potassiumhas a good correlation, instead, the thorium and uranium has a poor correlation.In a word, mining has influenced the environment at some extent, especially onwater. So relevant departments should take effective prevention measures to realizecleaner. |
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