Variability of Dissolved Trace Elements in Rivers and Streams: Seasonal Redox Effects

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9508199 Shiller Recent laboratory work has shown that there is a seasonal variation in the concentrations of dissolved trace elements in the Mississippi River, and limited evidence that other river systems undergo similar seasonal variations. This variation can best be explained by seasonal changes reducing inputs to the river system. The goals of this research are to 1) better understand the origin of the seasonal dissolved trace element variability in the Mississippi River system, 2) look for similar variability in other smaller river and stream systems, 3) lay the groundwork for future trace element work which will focus on the effects of erosional regime, rock composition, and solution chemistry on dissolved trace elements in streams, and 4) verify filtration methods. Seasonal samples of the Mississippi River and its tributaries, as well as other rivers in Mississippi and California, will be collected to better define the seasonal effect and determine how widespread the phenomena is. Also, experiments will be performed to detect temperature-dependent oxidation of manganese oxides -- a process which may play a role in the seasonal cycle. Researchers will also verify filtration methods and develop an easier syringe filtration method which could be used by other workers collecting samples for the research. River samples will be analyzed by atomic absorption, flow injection, and ICP-MS. Characterizing the nature of seasonal variability is a vital component of understanding the concentrations of dissolved trace elements in rivers. The results of this research will be important for understanding some of the controls on fluvial dissolved trace elements, designing and interpreting other basic research aimed at understanding fluvial dissolved trace element geochemistry, designing water quality programs, and interpreting water quality data. ***