内蒙白云鄂博稀土矿土壤-植物稀土元素及重金属分布特征

Distribution Characteristics of Rare Earth Elements and Heavy Metals in a Soil-Plant System at Bayan Obo Rare Earth Mine,Inner Mongolia

白云鄂博是世界最大的稀土矿山,研究白云鄂博矿区土壤及植物等环境介质中的稀土元素和重金属元素的分布特征,可以为调查矿区环境现状提供基础数据,同时为矿山环境修复提供参考依据。本文采集了白云鄂博稀土矿区的土壤、植物,以及背景区本巴台地区的岩石、土壤、牛粪五类样品,采用电感耦合等离子体质谱法(ICP-MS)测定了样品中15种稀土元素(La、Ce、Pr、Nd、Sm、Eu、Gd、Tb、Dy、Ho、Er、Tm、Yb、Lu、Y)及8种重金属元素(Cr、Mn、Ni、Cu、Zn、Cd、Pb、As)的含量,研究这些元素地球化学行为及其在空间上的变化规律。结果表明:①矿区土壤和植物样品均显示出明显的轻稀土富集、重稀土亏损的特征。土壤和植物中含量最高的稀土元素均为Ce,分别达到49.95%及48.55%,与白云鄂博稀土矿富Ce的特征高度一致。②铁花植物的稀土元素总量在空间上呈现出主矿>东矿>东介勒格勒矿段的趋势,与三处矿体本身含矿性变化一致,说明该种植物稀土含量基本受矿体含矿性控制,对生长环境中稀土富集程度指示较准确。③矿区土壤中存在一定程度的Zn(465~778mg/kg)、Cd(1.35~2.23mg/kg)、Pb(181~431mg/kg)累积,其中部分点位Cd、Pb存在超出风险管制值的现象。综上,白云鄂博的矿石、土壤、植物样品均表现出富Ce的特征,且植物稀土含量与其所生长处的矿体含矿性强弱高度相关,三者之间稀土含量特征表现出明显继承性。此外,矿区局部点位土壤存在的Zn、Cd、Pb累积需要引起适当关注。

BACKGROUND:Rare earth resources are essential for a wide range of advanced technologies,which have received considerable attention in the world.Bayan Obo is the largest rare earth mine in the world.The study on the distribution characteristics of rare earth elements(REEs)and heavy metal elements in the environmental media such as soil and plants in the Bayan Obo mining area can provide basic data for the investigation of the environmental status of the mining area and provide reference for its environmental restoration.OBJECTIVES:To investigate the distribution characteristics of REEs and heavy metal elements in various environmental media at different areas in the Bayan Obo mine.METHODS:Nine plant samples,six soil samples,one rock sample and one cow manure sample were collected from the Bayan Obo rare earth mine and surrounding areas.The contents of 15 rare earth elements and 8 heavy metal elements of these samples were determined by ICP-MS,which were used to study the behavior of elements and the variation rules in space.RESULTS:The results showed that the distribution patterns of REEs in rocks,soil,plants,and cow manure samples were similar:obvious enrichment of light-REEs and depletion of high-REEs.The richest rare earth element in soil and plant was Ce,reaching 49.95%and 48.55%,respectively.The spatial variation law of the total content of rare earth element in Limonium bicolor(Bag.)Kuntze was consistent with the mineralization change of the three ore bodies:the main ore>the east ore>Dongjielegele ore.This indicated that the rare earth content of this plant was basically controlled by the minerality of the ore body,and it was more accurate to indicate the enrichment degree of rare earth in the growth environment.In addition,there was accumulation of Zn(465-778mg/kg),Cd(1.35-2.23mg/kg),Pb(181-431mg/kg)in the soil of the mining area.Some points of Cd and Pb were beyond the risk control value.CONCLUSIONS:The ore,soil,and plant samples in Bayan Obo all show the characteristics of Ce enrichment.Moreover,the rare earth content of plants is highly correlated with the ore body where it grows.The REE content characteristics among the three media show obvious inheritance and consistency.Special attention should be paid to the mining and agricultural activities in the main mining area in Bayan Obo because of the accumulation of Zn,Cd,and Pb in these mining areas.