Heavy metal concentrations and environmental quality in three Wisconsin lakes

The environmental history of lake ecosystems in the United States is broadly defined by a slow increase in contamination triggered by the Industrial Revolution and urbanization beginning around 1850, a sharper increase around 1950, and a general decrease following environmental legislation in the 1970s. This study examined sediment cores taken from three Wisconsin lakes spanning a range of human influence: Sparkling Lake (relatively pristine), Shadow Lake (remediated), and Lake Monona (impacted). Sediment cores were analyzed for heavy metal concentrations using X-ray Fluorescence (XRF) as well as for correlations with organic and calcareous content using loss on ignition (LOI). Sparkling Lake experienced the least amount of change in metal concentrations above background levels, while Shadow Lake and Lake Monona showed greater increases in concentrations toward the top of their cores as the result of higher human impacts in their watersheds. Additionally, Lake Monona displayed spikes in copper and arsenic concentrations resulting from a weed removal program by the Madison Public Health Department as well as increases in lead concentrations caused by cars and industry. These concentrations and relative trends are generally supported by previous, similar studies. The heavy metal concentrations of the cores reaffirm the impact humans have on lake ecosystems and help to construct a more complete picture of the lakes’ health.