High Molybdenum Levels in Wisconsin Water Are From Natural Sources, Not Coal Ash



Molybdenum was first recognized as an official element in the late 1700s and has been used in countless applications over the past 200 years. But however useful it may be in certain industries, it’s not something you want to find in large amounts inside your drinking water. In southeast Wisconsin, water samples recently showed an unusually high level of molybdenum, and no one seemed to know why.

That is, until Clean Wisconsin called in a Duke University-led team to get to the bottom of the issue.

Some people in the area suspected that coal ash deposits from construction sites and landfills might have seeped into the water supply, thus causing the presence of molybdenum. But Professor Avner Vengosh and his graduate students found that this was not likely to be the source of contamination.

Vengosh said in the paper published by Environmental Science and Technology, “If this molybdenum-rich water had come from the leaching of coal ash, it would be relatively young, having been recharged into the region’s groundwater aquifer from coal ash deposits on the surface only 20 or 30 years ago,” he explained. “Instead, our tests show it comes from deep underground and is more than 300 years old.”
In other words, the molybdenum comes from natural sources. This was a bit of a shock to Paul Matthewson, a staff scientist with Clean Wisconsin, the environmental group that helped to pay for the study.

“It was a surprise in that levels this high of molybdenum had always, as far as we could tell from past literature, been associated with [human-caused] contamination,” Matthewson told the Herald Sun.

But even though this molybdenum was naturally occurring, that doesn’t mean it gets the seal of approval. While it may be necessary to cell-based life, higher concentrations can lead to joint pain, tremors, anemia, and weakness. Therefore, it’s still a problem for regional public health, notes Jon Drewson, chief spokesperson for Clean Wisconsin.

“It’s now a matter of taking what we’ve learned and making good decisions to solve the problem confidently going forward,” Drewson said in a statement.

In addition, both Drewson and Vengosh made it clear that these findings don’t indicate that coal ash is completely absent from the water contamination conversation. Many other studies have found links between coal ash — and its pollutants, including arsenic — and groundwater issues.

“Because there’s a lack of causation in this study doesn’t mean that lack of causation applies elsewhere,” Drewson cautioned.

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