Soil Gannan REE Distribution Characteristics Of Rare Earth Mine

Rare earth elements have significant "hormesis effect"on biology.It means that rare earth hasstimulative effect at low concentration and suppressive effect at high concentration. And theyshow that bio-concentration,elective absorption and accumulation of animal’s organ,etc.Therefore there is environmental risk.With the influence of development activities of rare earthresources,a mount of rare earth enters into the mining area’s soil system through all kinds ofways. Due to the soil adsorption, rare earth is massively accumulated and threaten the security ofthe soil eco-environment.Taking the ion-type rare earth mining areas in southern of China asresearching object, the combinative method of adopting sampling and simulative experiment inthe Lab,this project has been studied the cumulative distribution and influencing factors of therare earth elements in the farmland soil environment under the influence of developmentactivities of rare earth resources.The results are described as follows:(1) With the influence of development activities of rare earth resources,rare earth hassignificant migrative and cumulative effect in the soil of mining areas.The index ofgeo-accumulation about available state of rare earth is2.79.The concentration of available formof rare earth elements(336.06mg/kg) is higher in the soil of mining areas than in the soil ofcontrol areas which is48.74mg/kg.It is obvious that light rare earth has been accumulated whenheavy rare earth has been run off.Besides,the rare earth form has been distributed again.As timepassed, rare earth elements has been combined again.LREE/HREE has been from3.51to2.48.Rare earth has weak migrational ability in the soil environment and the concentration of rareearth is much higher in surface soil than in deep soil.(2) Rare earth can make soil acidification, the concentration of available phosphorusdecreased,and that the organic matter has significant "hormesis effect" on biology insoil.Meanwhile,there are different effects to available nitrogen when rare earth is in differenttypes of soil.(3) The adsorption capacity is stronger in farmland soil than in dryland soil.In the two typesof soils within30days,it is up to2.26mg/kg of difference about the adsorption capacityofavailable state. Along with the concentration of the external rare earth increased,the concentrationof exchangeable form firstly increases and then decrease.At the same time,the concentration ofFe-Mn oxide form and compact organic form increases constantly.Soil absorbs most La、Ce、Y,more Pr、Nd、Sm、Gd than the other rare earth elements.(4) With the pH of soil increased,a single rare earth form has the same regular curve as itselements.On the one hand,available form of rare earth elements has been cumulated largely in acid soil.On the other hand,it has been changed in alkaline soil.It has changed up to89.80mg/kg.The concentration of water soluble form is only cumulated largely in a very sour or veryalkaline condition.For example,its total amount is up to30.11mg/kg when pH of soil is3. Withthe pH of soil increased,the concentration of exchangeable form is increased constantly.Theconcentration of Fe-Mn oxide form and compact organic form has maximum at pH7nearly.And ithas a positive correlation with pH when pH is lower than7.On the contrary, it has a negativecorrelation with pH.