Copper Binding Depending on Source and Chemical Quality of DOM in the Colorado Front Range (2008)

Undergraduates: Caitlin Cox, Diane Mcknight, Matthew Miller

Faculty Advisor: Greg Gangi
Department: Environmental Science

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In alpine and sub-alpine lakes and the Colorado Front Range, the source, concentration and quality of the dissolved organic material (DOM) changes during the spring snowmelt and summer period because of decreasing rates of mountain run-off and increasing algal growth in the lakes. We examined seasonal changes in copper binding properties of DOM in an alpine lake (Green Lake 4) and a subalpine lake (Lake Albion) in Green Lakes Valley by conducting potentiometric titrations of lake water using a cupric ion selective electrode. Depending on the copper-binding characteristics of the DOM, the concentration of bioavailable cupric ion (Cu2+) and other metal ions may be below the toxicity threshold for aquatic biota. The seasonal DOC trend showed the expected decrease throughout the summer months because of the decrease in streamflow and decreasing source of terrestrial DOM. Lake Albion had a greater DOC concentration because of the more extensive surrounding vegetation at the lower elevation. DOM from Green Lake 4 was found to have more Cu binding capacity than DOM from Lake Albion, due to the different quality of DOM. The lesser copper- binding capacity in the summer in both lakes was associated with the decrease in DOC and relative stable level of fulvic acid percentage. The changes in metal binding capacity may also be related to changes in source of DOM and UV induced photodegradation. These data indicate that the seasonal DOM source changes may influence metal binding