Dissolved and Colloidal Trace Elements in Glacial Watersheds of the Yukon River Basin
Abstract
Dissolved and colloidal trace elements were determined in rivers and streams within the Yukon River Basin in Alaska and Canada. Glacially-affected catchments tend to have low dissolved organic matter (DOC) and high suspended loads (SPM). Thus, for elements where a balance between complexation and adsorption/solubility determines the dissolved/particulate partitioning (e.g., Fe, Cu, light rare earths), dissolved (< 0.02 μm) concentrations tend to be much lower in glacial catchments than in other stream basins. We also observe that the percentage of these and other elements found in the colloidal suspended phase (0.02 - 0.45 μm) is higher in glacial systems than in non-glacial systems. Additionally, the glacial colloidal suspended phase frequently has significant Si and Al, suggesting that some of colloidal metals may be associated with fine alumino-silicates rather than iron oxides. Seasonally in the early spring, some glacial catchments look more like non-glacial systems due to a snowmelt-driven soil-flush input of DOC and low SPM. For the longer term, to examine possible changes resulting from climate change induced glacial retreat, we collected samples from extra-glacial streams in the immediate foreland of the Gulkana Glacier. These streams had similar compositional trends as the sub-glacial streams. This suggests that from a stream chemistry standpoint, conversion of a glacial basin to non-glacial requires further landscape changes such as the development of stabilizing vegetation and generation of DOC. Finally, we conducted an experiment in which enriched 57Fe was added to samples from glacial and non-glacial streams. In the glacial streams, the 57Fe spike partitioned immediately to the particulate phase whereas in non-glacial systems most of the spike remained in the colloidal phase with measurable amounts also in the dissolved phase. This again emphasizes that the high SPM of glacial streams plays an important role in the partitioning of their trace element loads.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFM.C11A0481S
- Keywords:
-
- 1065 Major and trace element geochemistry;
- 1615 Biogeochemical cycles;
- processes;
- and modeling (0412;
- 0414;
- 0793;
- 4805;
- 4912);
- 1806 Chemistry of fresh water;
- 1823 Frozen ground;
- 1871 Surface water quality