Identification of Naturally Occurring Fluoride and Selected Metals in Northwestern Wisconsin Groundwater

According to Wisconsin Department of Natural Resources (WDNR) well construction reports (http://prodoasext.dnr.wi.gov/inter1/watr$.startup, accessed 23 October 2017), residents within eleven northwestern Wisconsin counties obtain their drinking water from over 56,000 wells, including more than 48,000 private wells. Although groundwater in northwestern Wisconsin aquifers may not be as impacted by anthropogenic contaminants as groundwater in other areas of the state, baseline data regarding naturally-occurring inorganic contaminants and metals is severely lacking. Within the past ten years, commercial interests in the region have led to actual and proposed large-scale land use changes that have the potential to impact groundwater quality. A comprehensive set of baseline data are needed in order to measure these impacts long term.

Fluoride and the metals aluminum, arsenic, iron, lead, and manganese are groundwater contaminants that may impact public health, and for which little is known regarding baseline concentrations present in northwestern Wisconsin aquifers. Fluoride is a naturally-occurring inorganic ion, which has a narrow range of therapeutic concentrations. Aluminum, arsenic, iron, and manganese are naturally-occurring metals that could be present in groundwater depending upon the underlying geology and water quality of the aquifer. Lead is introduced to drinking water most commonly by corrosion of plumbing materials which contain lead. Corrosive groundwater can dissolve lead and other metals from these plumbing materials and contaminate drinking water. It is also possible that corrosive groundwater may cause lead-containing minerals in aquifers to leach lead.

The objectives of this research were to:
1. Identify naturally-occurring fluoride and selected metals in groundwater within northwestern Wisconsin.
2. Increase the groundwater quality data available to residents of northwestern Wisconsin.

Data to support these objectives were obtained through private drinking water samples collected by volunteers who were supplied with drinking water sample kits, and were instructed on how to collect well water samples. All samples were analyzed for fluoride, and a randomly-selected subset of private drinking water samples were analyzed for aluminum, arsenic, iron, manganese, and lead. At the end of the project, the findings from this study were presented at several regional venues from which volunteers were recruited.