| The ion adsorbed rare earth ore(weathered crust drenching type rare earth ore)is an important environment for the enrichment of rare earth elements,which is new in type,large in reserves,wide in distribution and high in heavy rare-earth content.In recent years,due to the excessive exploitation of human or the use of improper means to develop mining areas,the ecological environment around the mining area,especially its soil environment,has a certain negative impact.Soil environmental problems caused by rare-earth elements have become an inevitable problem and attracted more and more international scholars’ attention.Therefore,this paper selects the Zhu Xi watershed in the granite red soil erosion watershed of Changting County of Fujian Province as the study area,taking the surface soil and rice plant of the Zhu Xi watershed as the research object,and studies the spatial distribution of the soil rare earth elements through the land statistical analysis method.On this basis,the total amount of rare-earth elements in paddy soil and the content of each form are measured.Through the migration coefficient,the migration law of the rare earth elements from the soil to the various organs of the rice plants is revealed,and the internal stability model is used to explore the internal stability control of the various organs of rice plants to the rare earth elements,in order to evaluate the potential health risks.The main research results are as follows:(1)In this study,the bulk density of the surface soil in Zhu Xi watershed is 0.93g/cm～1.55g/cm and the moisture content is 8.35%～36.7%.The soil pH is between 3.74～5.80,the average value of organic matter is 22.18g/kg,the average value of total nitrogen is 0.42g/kg;the average value of total phosphorus is 0.25g/kg;the average value of total potassium is 9.56g/kg;the average value of available nitrogen is 79.42g/kg;the average value of available phosphorus is 14.32g/kg;the average value of available potassium is 41.08mg/kg.The total amount of REE is negatively correlated with the content of clay(P<0.01),and the content of rare earth elements is significantly correlated with the content of potassium(P<0.05).(2)The average value of REE in the surface soil of Zhu Xi watershed is 251.34rmg/kg.The average contents of all rare earth elements ranged from high to low in order of Ce>La>Nd>Pr>Sm>Eu>Gd>Tb>Dy>Ho>Er>Tm>Yb>Lu follow the Oddo Huggins rule.The spatial distribution of rare-earth elements in the West showed a low trend in the eastern part of the west,with a zonal distribution as a whole,decreasing from the northeast to the southwest in the northeast to the southwest.The lowest rare-earth edement is in the eastern part of the Zhu Xi Watershed,with a value of 120mg/kg-180mg/kg;the highest area is in the southwest of the Zhu Xi Watershed,with a value of 600mg/kg-660mg/kg,(3)The average value of exchangeable state of soil rare earth elements in this study is 17.36mg/kg;the average value of the carbonate bound state is 4.34mg/kg;the average value of the bound state of iron and manganese oxide is 15.31mg/kg;the average value of the organic binding state is 26.79mg/kg;the mean value of the residue state is 262.67mg/kg.The forms of REE in soil are:residue state>organic combination>exchangeable>iron manganese oxide bound>carbonate bound state.The relationship between the exchangeable state and the total amount shows an exponential fiunction,and the relationship between the carbonate bound state,the binding state of iron and manganese oxide,the organic bound state and the total amount is two times linear,and the residue state and the total amount are linear and linear.(4)The average values of rare-earth elements in rice roots,leaves and rice were 152.63mg/kg,5.03mg/kg and 0.64mg/kg in this study,which showed the rule of root>leaf>rice.The transfer coefficients of soil rare earth elements to rice roots,leaves and rice were 0.27～0.68,7.24×10-3-2.36×10-2 and9.09×10-4-1.13×10-2,respectively,showing the rule of root>leaf>rice.(5)The internal stability index of rice roots,leaves and rice was 1.68,0.44 and-1.31 respectively,showing the law of root>leaf>rice.The daily intake of rare earth elements in the lower reaches of the Zhu Xi Watershed is 5.33μg/kg,which does not exceed the safe dose of the daily average daily intake of rare earth elements(70μg/kg),and does not exceed the critical value of the human subclinical damage dose(6.0mg/kg-6.7mg/kg).But because the internal stability of the rare-earth elements is very poor,it is susceptible to the influence of the surrounding environment.There are also some potential health risks for long-term consumption of local residents. |
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