深层地下水稀土元素无机形态及其对稀土特征的影响——以皖北任楼矿煤系含水层为例

Inorganic speciation of deep groundwater and its effect on the characteristics of rare earth elements:with aquifers in coal bearing masures in Renlou coal mine in the north of Anhui Province as example

在对皖北任楼矿煤系含水层地下水常规离子和稀土元素组成分析的基础上,运用Visual Minteq软件对溶解态稀土的无机形态进行了模拟。结果表明:煤系含水层地下水分为富SO24-和富HCO-3(或富CO32-)两类,二者pH值大致以8.20/8.36为界。富SO24-水具有相对富HCO-3水偏低的稀土总量,但二者在PAAS(后太古代平均页岩)标准化图解上均表现为轻稀土亏损的型式。富SO24-水中稀土无机形态包括Ln3+、LnCO3+、LnSO4+、Ln(CO3)2-和Ln(SO4)2-(Ln代表稀土元素),但富HCO-3水中以Ln(CO3)2-和LnCO3+为主,且各形态的相对含量与pH值和元素类型(如轻、重稀土)关系密切。HCO3-含量与地下水∑REE和NdSN/YbSN存在明显的相关性,表明不同含量的稀土元素无机形态(尤其是Ln(CO3)2-)对地下水中稀土元素总量和轻重稀土分异程度存在影响。

Based on analysis of major ions and rare earth element（REEs） concentrations of groundwater in an aq-uifer of coal bearing measures in Renlou coal mine in the north of Anhui Province,the inorganic speciation of dis-solved REEs have been modeled by using the program-Visual Minteq.The results show that the groundwater can be subdivided into SO42– enriched and alkaline（CO32–or HCO–3） enriched water with pH values lower and higher than 8.20/8.36 respectively.The SO24– enriched water has relative lower total REE concentration than HCO–3 enriched water,although they all show light REEs depletion after PAAS（Post Archean Average Shale） normalization.The inorganic species of SO42– enriched waters include Ln3＋,LnCO3＋,LnSO4＋,Ln（CO3）–2 and Ln（SO4）2 –（Ln-REE）,whereas Ln（CO3）2– and LnCO3＋ are predominant in HCO3– enriched water,and the relative proportions of species are closely related to pH values and element types（e.g.LREEs and HREEs）.The concentration of HCO–3 is well corre-lated with ∑REE and NdSN/YbSN ratio,indicating that the total concentration and fractionation of REEs of groundwater probably has been affected by different proportions of different species（especially Ln（CO3） 2–）.