Talk title: Solute Exclusion during River Ice Formation
Talk authors: Michael D. DeGrandpre, Ella L. DeGrandpre, Benjamin P. Colman, and H. Maurice Valett, University of Montana, Missoula, Montana, 59812, USA
Abstract: Natural waters in cold climates can experience episodic ice formation. When ice forms, solutes are excluded from the ice, potentially increasing solute concentrations in the water. Solute ice exclusion, also known as ice rejection, could be important in rivers and streams where ice can be a significant fraction of the total discharge. Solute concentrations, including those of potentially toxic chemicals, could significantly increase during ice formation events. Short-term variability of river solutes is not well characterized during ice formation, however. To investigate this process, a variety of solutes were measured during three ice formation events in the mine-waste-polluted Clark Fork River. A laboratory study was also conducted to determine how different metal cations partition when ice forms. It was found that solute (e.g. potassium) concentrations increase by as much as 25% during the early stages of ice formation. Correlations with both ionic size and changes in temperature support that ice exclusion played a significant role in solute variability during these periods. The size dependence of solute ice exclusion was confirmed by the laboratory study. These observations could have important implications for predicting the environmental impacts of toxic solutes in rivers and streams subject to seasonal ice formation.
Bio: Mike DeGrandpre obtained his Ph.D. in Analytical Chemistry from the University of Washington in 1990. He carried out postdoctoral research at Woods Hole Oceanographic Institution in Massachusetts from 1990 to 1993 and held a research associate position there from 1993 through 1995. He joined the chemistry faculty at UM in January of 1996. Mike is an analytical/environmental chemist specializing in developing and using autonomous sensors to study aquatic biogeochemistry, the ocean carbon cycle, and ocean acidification. Learn more here.
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