Lecomte K L, Sarmiento A M, Borrego J, Nieto J M
CICTERRA CONICET-Universidad Nacional de Córdoba, Argentina.
Dpto. Ciencias de la Tierra, Universidad de Huelva, 21071 Huelva, Spain; Research Center of Natural Resources, Health and the Environment, University of Huelva, 21071 Huelva, Spain.
Mar Pollut Bull. 2017 Aug 15;121(1-2):282-291. doi: 10.1016/j.marpolbul.2017.06.030. Epub 2017 Jun 16.
Huelva Estuary is a transition zone where REE-rich acidic waters interact with saline-alkaline seawater. This mixing process influences the geochemical and mineralogical characteristics of particulate and dissolved fractions. The Tinto River has >11,000μgL dissolved REE (pH=1.66), whereas seawater only reaches 8.75·10μgL dissolved REE (pH=7.87). REE-normalized patterns in "pH<6 solutions" are parallel and show similarities, diminishing their concentration as pH increases. Sequential extraction performed on the generated precipitates of mixed solutions indicates that most REE are associated to the residual phase. In a second order, REE are associated with soluble salts at pH3 and 3.5 whereas in sediments generated at pH4 and 5, they are distributed in salts (1° extraction), poorly crystallized Fe-bearing minerals (schwertmannite, 3° extraction) and well crystallized Fe-bearing minerals (goethite - hematite, 4° extraction). Finally, precipitated REE are highest at pH6 newly formed minerals with a release to solution in higher pH.
韦尔瓦河口是一个过渡区域，富含稀土元素的酸性水与盐碱海水在此相互作用。这种混合过程影响着颗粒态和溶解态组分的地球化学和矿物学特征。廷托河溶解态稀土元素含量大于11000μg/L（pH = 1.66），而海水溶解态稀土元素含量仅为8.75×10μg/L（pH = 7.87）。“pH < 6溶液”中的稀土元素标准化模式呈平行状且具有相似性，随着pH值升高其浓度降低。对混合溶液生成的沉淀物进行连续萃取表明，大多数稀土元素与残留相相关。其次，在pH为3和3.5时稀土元素与可溶性盐相关，而在pH为4和5时生成的沉积物中，它们分布在盐类（一级萃取）、结晶程度差的含铁矿物（施韦特曼石，三级萃取）和结晶良好的含铁矿物（针铁矿 - 赤铁矿，四级萃取）中。最后，在pH为6时沉淀的稀土元素最多，新形成的矿物在更高pH值时会向溶液中释放稀土元素。
