We propose a study of dissolved and colloidal trace elements in the Yukon River system and the relationship of DOC concentration and character to the trace elements. Dissolved and colloidal trace elements will be determined in a variety of mainly small catchments within the basin, representing major landscapes/environments (e.g., glacial systems, permafrost-dominated systems, etc.) as well as geological variability. Dissolved organic carbon (DOC) will be analyzed and characterized through a collaboration with G. Aiken (USGS). Experiments will be performed to examine the behavior of trace elements and DOC during mixing of tributaries having different particle and DOC character. The partitioning of dissolved trace elements between labile and organic-complexed fractions will be examined. The electrophoretic mobility of colloidal particles will be examined to better ascertain the interaction of organic matter with inorganic colloids.
Intellectual Merit: Basic information on the fluvial fluxes of dissolved and colloidal trace elements and the processes controlling those fluxes is generally lacking, especially in relatively pristine systems and in high latitude systems such as the Yukon River Basin. Studies that combine trace element work with DOC characterization are even less common, despite the importance of DOC in controlling the dissolved and colloidal concentrations of many trace elements as well as the importance of elements such as Fe in affecting organic matter. The Yukon system is particularly interesting for a number of other reasons including the presence of extensive wetlands, glaciers, and permafrost within the basin; its extreme temperature ranges; and the seasonal ice cover of the rivers-all of which can be factors in trace element mobilization and transport. Insight into the effect of landscape on trace element mobilization could be gained by comparing sub-systems within the Yukon Basin differing in glaciation, permafrost, wetlands and other physiographic factors. Comparison of the trace element geochemistry of the Yukon with that of temperate and tropical systems will indicate whether/why trace element fluxes from high latitude systems differ from low latitude systems and may provide a useful analogy between typical glacial and interglacial systems. Within the Yukon Basin, comparison of similar glaciated and unglaciated subsystems could also provide a useful glacial/interglacial analogy and allow us to examine the relative trace element chemical weathering yield of glaciated systems. Especially important is that the Yukon Basin is particularly sensitive to climate warming which can be expected to thaw permafrost, shrink wetlands, dry soils, and lengthen the growing season-factors which, again, can affect trace element mobilization. If we can associate certain chemical concentrations, ratios, or variabilities with specific types of landscapes (e.g., glacial versus permafrost-dominated basins) then we will have a tool for integrated monitoring of landscape changes in arctic watersheds such as might occur with climate change. We present preliminary data supporting this concept but also indicate why further data are required. The Yukon River basin is well suited to serve as a model system since we can isolate both glacial and permafrost related influences and obtain samples at a frequency required to define controls on the system.
Broader Impacts: Results of this work will be applicable in three areas of general benefit to society. First, by understanding the nature and causes of natural temporal variability in water quality, monitoring programs can better design their sampling strategies. Second, if our river chemistry comparisons provide a frame of reference for understanding what should be the "natural" concentrations in human-disturbed systems, then this will be pertinent to those workers trying to establish fluvial pollution limits. Finally, our work should allow an understanding of how changes in watersheds (including climate change) can affect stream chemistry and thus serve as a basis for using stream chemistry to monitor the state of a watershed. Additional impacts include the PI's integration of research and teaching; his history of involvement of undergrads in research; the education/training of two graduate students; a collaborative sampling effort with a local school; an enhanced collaboration with a USGS researcher; and the broad dissemination of information through the PI's web site as well as informal public dissemination of information in native villages within the Yukon River Basin.
