Nathalie Tepe

• Rivers are the major source of many trace elements, such as rare earth elements (REE; or REY if yttrium is included) to the oceans. While many studies focus on the REY behavior and distribution in natural terrestrial waters, little is known about the impact of glacial meltwaters on the seawater distribution of particle-reactive elements, such as REY, due to (i) a practically non-existing data base with regard to REY distribution in glacial meltwaters and (ii) a lack of knowledge about the behavior of those REY that are truly dissolved and those that are bound to inorganic (nano-) particles during estuarine mixing of polar rivers with seawater. This thesis is structured as a compilation of seven independently published and submitted manuscripts and manuscripts in preparation, covering the topics of REY behavior and distribution in arctic rivers from southern Iceland and western Greenland, and the arctic estuarine mixing between glacial-fed river waters and seawater. Furthermore, the interplay between surface-scavenging and solution-complexation of REY in presence of the siderophore Desferrioxamine B (DFOB) is studied in two different incubation experiments. The first incubation experiments were performed to investigate the impact of DFOB on the mobilization of REE from volcanic ash particles into river water from Iceland and the second incubation experiments studied the competitive complexing behavior of surface-complexation of REY onto manganese (hydr-)oxides and of solution-complexation of DFOB-REY complexes. Additionally, a study comparing natural and anthropogenically influenced aquatic systems is included and is focusing on the strong increase of anthropogenic gadolinium levels in tap water of Berlin, Germany, from 2009 to 2012.