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| Titel |
Temporal variations in the export of REE in boreal catchments of varying character and size |
| VerfasserIn |
S. Köhler, F. Lidman, M. Mörth, L. Björkvald, H. Laudon |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250027767
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| Zusammenfassung |
| Organic matter and iron colloids have a large impact on the mobilisation of trivalent elements
such as aluminium (Al), rare earth elements (REE) and actinides.
Recent results of the relative importance of these colloids are diverging though
(POURRET et al., 2007); STEINMANN and STILLE, 2008) and there is a general lack of
information of the importance of flow pathways and landscape type on the relative
importance of the various colloidal fractions that mobilizes REE from the catchment soils. In
this study we present the data of water chemical analysis of a series of catchments with
varying size and character but all within the boreal zone. Two speciation techniques and two
column separation methods involving ion exchange were used to quantify the causes for
the temporal variation of the dissolved amounts of trivalent ions in these water
courses.
Our study indicates that REE export is controlled mostly by landscape type while changes
in the acid-base character of organic matter are of minor importance. Changes in flow
pathways in a riparian zone in one of the studied areas in a forested site may be used to
decipher the effect of chemical versus physical processes for the mobilisation of REE and
aluminium and open up the possibility for a quantitative modelling of the varying sources of
REE.
Iron and aluminium are mobilized together with organic matter in varying amounts in
different landscape types and this affects the REE export from the various landscape
elements. While the amount of strongly bound aluminium mobilized from the catchments
usually correlate positively with any of the REE this is not the case for strongly bound iron.
Fractionation patterns of REE are discussed and the observed binding of REE to
organic matter was modelled using the speciation program WHAM VI (TIPPING,
1998).
Pourret O., Davranche M., Gruau G., and Dia A. (2007) Organic complexation of rare
earth elements in natural waters: Evaluating model calculations from ultrafiltration data.
Geochimica Et Cosmochimica Acta 71(11), 2718-2735.
Steinmann M. and Stille P. (2008) Controls on transport and fractionation of the rare earth
elements in stream water of a mixed basaltic-granitic catchment basin (Massif Central,
France). Chemical Geology 254(1-2), 1-18.
Tipping E. (1998) Humic Ion-Binding Model VI: An improved Description of the
Intercations of Protons and Metal Ions with Humic Substances. Aquatic Geochemistry 4,
3-48. |
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