Partitioning of REE between solution and particulate matter in natural waters: a filtration study

摘要

Rare earth element (REE) concentrations were determined in filtered and unfiltered fractions of one stream water and five shallow ground waters from springs and wells from the Palouse region of Idaho/Washington to characterize the contribution of suspended, colloidal, and solution fractions to the REE contents of each water sample. Similar characteristics were observed in the shallow ground waters as reported in the literature for rivers. In almost all cases the LREE were depleted substantially in filtered fractions relative to the unfiltered fractions, indicating substantial partitioning of LREE onto particulate matter. In some, but not all samples, the HREE were far less depleted, indicating greater mobility of the REE as dissolved species or small colloidal particles. Increased solubility of HREE relative to LREE in these neutral to slightly alkaline waters may be due to preferential complexation of the HREE with ligands such as carbonate, hydroxide, fluoride or organic anions. In one water studied, filtration through a finer pore-size filter resulted in markedly more pronounced Cc anomalies. Cerium anomalies are likely controlled by preferential sorption of Ce4+ onto Fe-Mn particle coatings. (C) 2002 Elsevier Science (USA). All rights reserved. [References: 22]