USING TRACE METAL ANALYSIS TO DETERMINE POLLUTION SOURCES IMPACTING LAKE ALTOONA, WEST-CENTRAL WISCONSIN

Large algal blooms are typically the result of high inputs of nitrate and phosphate into lake waters. In natural lake systems, low levels of available nitrate and phosphate limit algal growth, while in lakes with high nutrient input (eutrophic lakes), no such limitation on growth occurs. The large algal blooms result in reduced clarity and low oxygen content due to oxygen uptake during the decomposition of algae. These factors contribute to conditions in lakes such that only a few species of fish and types of vegetation can survive.

The primary cause of the eutrophication of Lake Altoona located east of Eau Claire, WI, has been assumed to be agricultural input of nitrate and sediment entering the lake from the Eau Claire River. However, high bacterial counts indicate that wastewater may be reaching the lake from residential septic systems near the lake. If this is true, then domestic wastewater may be a significant source of nutrient input into the lake. In addition, other components that can be found in domestic wastewater, such as trace metals and endocrine disrupting compounds, may be present in the water and sediment of Lake Altoona. This is a matter of some concern as various trace metals, when present in significant concentrations, have been linked to adverse human and environmental health effects due to bioaccumulation and biomagnification.

The focus of this study is to determine if concentrations of trace metals can be used to estimate the relative inputs of nutrients from agricultural and domestic sources. Minor concentrations of many trace metals are prevalent in waters from both domestic and agricultural sources. Trace metal concentration analyses is being performed using HR-ICPMS for copper, zinc, lead, and cadmium. Preliminary results indicate that water flowing out of Lake Altoona contains 28%, 31%, and 56% more copper, zinc, and lead, respectively, than water sampled at the inflow of the lake. This difference may be the result of domestic input into the lake. Additional sampling and data analyses, which includes several other trace metals, is currently underway to test this hypothesis. It is the aim of this study to combine the trace metal data with a basic water balance budget to evaluate the proportional input of relevant chemicals into the lake from agricultural and domestic sources.