Rare earth elements and yttrium (REY) in glacial meltwaters and their potential impact on the REY distribution in Modern and Precambrian seawater
Zusammenfassung der Projektergebnisse
Within the framework of the project, important gaps in the data base on rare earth elements and yttrium (REY) in natural waters could be filled. For the first time, dissolved concentrations and distribution for the full set of REY (except Pm, of course) in glacial meltwaters from the Arctic (Iceland and Greenland) could be determined and in a pioneering study ultrafiltration could be applied to a small sub-set of these samples to separate nanoparticles and colloids (NPCs) from the truly dissolved REY fraction. The results demonstrate that: - by far the largest fraction of the total dissolved REY content of glacial-fed rivers is not truly dissolved, but bound to inorganic NPCs which control the REY concentrations and distribution; - this NPC-control is observed in rivers in southern Iceland, in which the NPC load is dominated by (glassy) volcanic ash, as well as in rivers in Greenland, in which the NPC load is dominated by rockflour, i.e. ultrafine particles from the local Archean basement with or without contributions from atmospheric dust; - NPCs, therefore, are the most important way how particle-reactive HFS elements such as the REY are transported via rivers to the ocean; - due to this transport mechanism, explosive volcanic eruptions can provide nutrients (e.g., iron] to coastal seas not directly affected by volcanic fall-out; - due to the very efficient and effective aggregation and subsequent removal of NPCs in the low-salinity part of arctic estuaries, riverine REY input into arctic open-ocean seawater is limited, as the REY are associated with the aggregating NPCs and are trapped in the estuaries; - if, however, the specific local hydrological situation allows for aggregated NPCs to react with seawater of higher salinity, the REY are remobilized and affect the REY concentrations and the Nd isotope composition of arctic seawater; - considering that the Early Precambrian mafic landmasses were largely free from vegetation, and that due to higher atmospheric pCO2 levels, river waters were more acidic, the dissolved REY flux into the Precambrian ocean was different from the modern one and dominated by REY released from NPCs.
Projektbezogene Publikationen (Auswahl)
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(2013) Siderophore-promoted transfer of rare earth elements and iron from volcanic ash into glacial meltwater, river and ocean water. Earth and Planetary Science Letters 364, 30-36
Bau, M., Tepe, N. and Mohwinkel, D.
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(2014) Importance of nanoparticles and colloids from volcanic ash for riverine transport of trace elements to the ocean: Evidence from glacial-fed rivers after the 2010 eruption of Eyjafjallajokull Volcano, Iceland. Science of the Total Environment 488-489, 243-251
Tepe, N. and Bau, M.
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(2015) Distribution of rare earth elements and other high field strength elements in glacial meltwaters and sediments from the western Greenland Ice Sheet: Evidence for different sources of particles and nanoparticles. Chemical Geology 412, 59-68
Tepe, N. and Bau, M.
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2016. Behavior of rare earth elements and yttrium during simulation of arctic estuarine mixing between glacial-fed river waters and seawater and the impact of inorganic (nano-)particles. Chemical Geology 438, 134-145
Tepe, N. and Bau, M.
