There’s arsenic in the groundwater in Wisconsin’s Outagamie and Winnebago counties.
To hydrogeologists—and for that, matter, the people who live there and drink the water--this is very much yesterday’s news. Extensive research into the aquifers and rock formations in those two northeastern counties has rendered that finding indisputable, so much so that the Wisconsin Department of Natural Resources (DNR) changed requirements for well casings in 2005 to increase public safety.
But while water-quality problems in those particular areas are by now well-documented and addressed, they’re not the only ones in Wisconsin at risk for contaminated groundwater.
“Geology does not stop at political boundaries,” said John Luczaj, a professor of geoscience at the University of Wisconsin-Green Bay.
Supported by funding from the UW Water Resources Institute, Luczaj spent several years studying the Paleozoic sedimentary rocks in less-populated Oconto, Marinette, Shawano, and other northeastern Wisconsin counties. Approaching the issue from the perspective of how the rock chemistry might be influencing the water chemistry he found that the same geologic mechanisms—specifically, the same Mississippi Valley Type (MVT) mineralization--also existed in those areas. Luczaj’s findings appear in a recent edition of the journal Geosciences.
“I knew there was probably more to the story than two counties,” said Luczaj. “The question I wanted to answer was, are we missing anything?”
The answer was a loud and resounding “yes.” Using whole-rock chemical analysis and scanning electron microscopy on 310 samples of dolomite, sandstone and shale, Luczaj’s research group discovered that the rock formations north and to the east of the heavily-studied areas were not just leaching arsenic into the groundwater, but also other concerning minerals, too. “We knew nickel and cobalt were in the wells,” explained Luczaj. “But I had never put a percentage on the number of wells that exceeded limits for both of those minerals.”
Luczaj’s research found that between 2-8 percent of wells in the area studied had exceedances. And while the health impacts aren’t as severe as those conferred by arsenic and strontium, the
Three crystals of cubic bravoite (nickel-cobalt-iron sulfide) from Oconto County,
Wisconsin. The large darker crystals are mineral dolomite. (Photo credit John Luczaj).
subjects of other geologic projects Luczaj has headed, bioaccumulation of cobalt and nickel in humans also causes health problems.
Madeline Gotkowitz, a hydrogeologist with the Wisconsin Geological and Natural History Survey, said that Luczaj’s project is an important example of the Wisconsin Idea in action—the notion that UW research reaches all areas of the state, not just the populous ones.
“What John has managed to accomplish is to get funding to look at the extent of the problem in areas of the state that get far less attention,” she said. “In these rural areas, there is no option for a public water supply. Everyone has a well, which means everyone is at risk.”
Luczaj said his study likely marks the end of new geological research into these particular rock formations, although a graduate student will continue to study arsenic in the region.
“This sets the baseline for what the state of metals concentrations is in these areas and how they’re changing over time,” he said. “This shows that we have this phenomenon occurring across the region. If you’re looking at water quality, you have to be able to predict if it will become worse with population increase and the drawdown of the aquifer.”
Luczaj points to communities in Southeast Outagamie County that haven’t recovered water levels that have been drawn down over the last decade. The deeper an aquifer drawdown goes, the more a community’s arsenic problems—and, depending on the location, nickel and cobalt problems, too--are likely to be exacerbated.
Luczaj suggests the issue could become an important one in ways we may not necessarily expect. For instance, while wells can be cased to minimize risk to drinking water, minerals in concrete aggregate broken up and used to repair roads could easily leach as part of storm runoff, polluting nearby lakes and streams.
“It’s not always what you can see,” he said. “it’s often the fine things that cause problems. People often look at places with large ore depots, but areas that get less attention don’t always have these big deposits. They’re disseminated, but definitely important from a public health perspective.”