大沽河流域地下水中稀土元素的地球化学特征

近岸地下水排泄是近海稀土元素的重要来源，目前对地下水中稀土元素的地球化学行为的认识还十分有限。本文通过现场调查和模拟计算对山东大沽河流域地下水中溶解态稀土元素的分布、影响因素及络合形态进行了研究。结果表明：稀土元素在地下水中的分布具有较大的空间差异，pH和铁锰氧化物/氢氧化物的还原性溶解是影响稀土元素含量的重要因素。稀土元素的络合形态以LnCO+3和Ln(CO3)-2为主，但是在硫酸根含量较高的情况下，轻稀土较中稀土和重稀土更易于形成LnSO+4。大沽河流域地下水表现为重稀土富集，含水层中负电荷颗粒物对LnCO+3的优先吸附可能是富集的原因。受周边炼油厂影响，所有样品中的La均表现为正异常，人为源La在地下淡水和再循环海水中所占比例分别为34%~75%和42%~57%。

Geochemistry of rare earth elements in the groundwater of Dagu River Basin

Submarine groundwater discharge is a significant source of the rare earth elements (REEs) in the coastal waters, studies on the geochemistry of REEs in the groundwater are very limited. In this study, the distribution, influencing factors and complex speciation of dissolved REEs in the groundwater of Dagu River Basin in Shandong Province were examined by field investigation and simulation. The conclusions have been obtained as follows: the distribution of REEs in groundwater has a great spatial variation, pH and the reductive dissolution of Fe, Mn oxides/hydroxides may be the important factors affecting the concentration of rare earth elements. The REEs speciation mainly exists as LnCO+3 and Ln(CO3)-2. However light rare earth elements are more likely to form LnSO+4 than middle rare earth elements and heavy rare earth elements in the case of high sulfate. And the patterns of the REEs generally show heavy rare earth elements enrichment in groundwater, the preferential adsorption of LnCO+3 by electronegative particles in the aquifer may be the reason for heavy rare earth elements enrichment. Affected by surrounding refineries, all samples have positive lanthanum anomalies. The proportion of anthropogenic lanthanum in fresh groundwater and recirculated seawater are 34%-75% and 42%-57%, respectively.