The Migration Behavior And Distribution Of Radioactive Contamination Of Decommissioned Uranium Mine In Northern Guangdong Province

The population has soared with the development of modern society in recent years,and human beings’demand of nuclear energy has also expanded.Meanwhile,uranium as the main raw substance of nuclear fuel,it has relative long half-life and ability of combination with heavy metals.And uranium mines show a long-term negative impact for the ecology,quality of environment and health of residents.Then this negative effect has been recognized as a serious problem in the whole world.The work about the retired uranium mines in China has been started for several years,but Chinese know little about the safety and stability of the decommissioned uranium mine about some specific geological,climatic and hydrological conditions.After activities of final management and disposal,some uranium mines still have various problems that cannot be ignored with unconscious action.These problems reflect in variety environmental aspects（soil and water）.The main objective of this work has been to study comprehensively the relevant behaviors of three retired uranium mining areas of No.745 China National Nuclear Corporation in the northern region of Guangdong province.Two sampling events have been conducted:November 2016（dry period）and May 2017（flood season）.Through the process of samples’collection,the global positioning system（GPS）tool was used to systematically locate the sampling points.Some figures and related information of in-situ water recorded as well.After did pre-treated works and collected some basic features,the soil samples measured for radioactive metals(²³⁸U,²³⁵U,²²⁶Ra,²³²Th and ⁴⁰K)by the high purify germanium gamma spectrometer.Besides,the inductively coupled plasma mass spectrometry（ICP-MS）was used for detecting the sorts and quantities of heavy metals.In addition,the soil samples which contain obvious high concentration of radioactive elements were detected the appearance and ingredient by SEM and XRD analysis respectively.On the other hand,the heavy metals of aquatic environment also tested by ICP-MS.Finally,the research gets the correlation the heavy metals,radioactive substances and anions of water,mobilize mechanism and the characters of space and time in this region.This study showed meaningful results as following:Firstly,a number of soil samples of this retired region show pH<7,and this phenomena is helpful to radioactive and heavy elements’transportation and diffusion.The main radioactive metals in soils of this area are ²³⁸Uand ²²⁶Ra,and the peak of it shows in sampling depth 20-22 cm.At same time,the heavy metal of soil mainly shows in manganese（Mn）,and it associates the certain concentrations of arsenic（As）,lead（Pb）,cadmium（Cd）.Additionally,the soil samples from various mining regions contain quartz（SiO₂）,different type uranium compounds and secondary minerals（Kaolinite and Cronstedtite）.Secondly,the quantities of pollutants of dry season were less than flood season.The maximum concentration of uranium can be seen that achieves 1.12 mg/L,and its average figure achieves 0.184 mg/L;the maximum concentration of thorium is 0.296 mg/L,and the average figure of it achieves 0.052 mg/L.The metalloid mainly lists arsenic（0.0002-0.012mg/L）,and it shows a positive relationship with the quantities of uranium.Considerably,the radioactive substances and metalloids of mining carven and the downstream water（W10）of Jiaoping region show the highest values in this work.Overall,target radioactive materials and associated heavy metals can be detected out from the soil and water samples.The concentrations are significantly higher than those of un-mining area and other reference values of Beijiang River.And the situation shows large scale harmful impact after the elements mobilized through natural rainfall and rivers’flow.Furthermore,the results highlight the potential risk for people directly contact mining water and irrigate agricultural plants.