Origin of Iron Isotope Signatures in Boreal Estuaries

The geochemistry of iron (Fe) during freshwater transport and estuarine mixing has been investigated. Espescially the changes in the Fe-isotope signature have been studied. The fate of Fe-isotopes during estuarine mixing has been poorly studied. Sampling was performed in Kalix River, Kalix and Råne estuary, and in the open Bothnian Bay, Northern Baltic Sea. Water samples were filtered with 0.22 μm membrane filters. Both particulate (> 0.22 μm) and colloidal fractions (< 0.22 μm) were analyzed. Iron particles and colloids, with a negative Fe-isotope signature, are formed during spring flood in forested catchments. These Fe complexes are associated with organic carbon (OC), and probably have a mixed oxidation state (Fe(II,III)-OC). Negative colloids are labile and flocculate and/or oxidize during riverine transport. Therefore, no negative colloids are detectable in the estuaries of the open Bothnian Bay. Within the estuaries two types of ˜56Fe signatures were measured: negative particles and positive colloids. The open Bothnian Bay shows a third distinct group of positive particles. This group mirrors the rapid removal of Fe colloids and particles at low salinities. Most of the Fe has been removed from surface water at salinities below 1.0 psu. Data in this study show that the Fe-isotopes can be used to trace the origin and cycling of iron particles and colloids in the boreal landscape.Godkänd; 2014; 20141119 (sarcon); Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Sarah Conrad Ämne: Tillämpad geologi/Applied Geology Uppsats: Origin of Iron Isotope Signatures in Boreal Estuaries Examinator: Professor Johan Ingri, Institutionen förs amhällsbyggnad och naturresurser, Luleå tekniska universitet Diskutant: Professor Magnus Mörth, Institutionen för geologiska vetenskaper, Stockholms Universitet Tid: Onsdag den 17 december 2014 kl 10.00 Plats: F531, Luleå tekniska universite