A Duke University earth-science lab that’s shaken up the debate in North Carolina about coal-ash disposal and groundwater pollution is now doing likewise in Wisconsin, thanks to a new study an environmental group there asked the lab to do.
The group, Clean Wisconsin, asked professor Avner Vengosh and his graduate students to figure out why an element called molybdenum was unusually noticeable in water samples gathered in a region of southeast Wisconsin near Milwaukee. It suspected that coal ash deposits in landfills and construction sites might be responsible.
But the professor and his team found that the ash deposits are “an unlikely cause” of the specific type of contamination because it shows up mostly in water that’s taken a long time to get to the surface.
“The results were pretty clear,” Vengosh said, summarizing the findings of a paper published in the journal Environmental Science & Technology. “The water being affected by molybdenum is very old, over 300 years. If this was something that had happened in the last 20 or 25 years, there would have been different chemicals and different isotopes.”
The environmental group helped pay for the study, and its staff scientist, Paul Mathewson, received a co-author’s credit on the paper. It acknowledges the results were not what it expected.
“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,” Mathewson said.
And regardless of how the element got into the water, “it’s important not to lose sight of the fact there’s still a problem” for public health in the region, said Jon Drewson, Clean Wisconsin’s chief spokesman. “It’s now a matter of taking what we’ve learned and making good decisions to solve the problem confidently going forward.”
Molybdenum is, in small amounts, a necessary contributor to cell-based life but in high enough concentrations can trigger health issues like anemia, joint pain, tremors and weakness, Vengosh’s team said in its report. It shares a column on the periodic table with metals like chromium and tungsten.
Both Drewson and Vengosh cautioned the finding doesn’t mean that coal-ash is clear of suspicion when it comes to water pollution. Ash is laced with pollutants, sometimes including arsenic, and other studies have found links between ash and specific groundwater problems.
“Because there’s a lack of causation in this study doesn’t mean that lack of causation applies elsewhere,” Drewson said.
But what the controversies over the disposal of coal ash and the use of hydraulic fracturing – fracking – in gas drilling have done is focus more attention on groundwater pollution and its causes, Vengosh said.
Attention translates into funding, and the studies the funding pays for illuminate problems both suspected and unexpected.
“It’s just that sometimes things lead to another,” said Vengosh, an earth-science specialist who trained in Australia and Israel. “Sometimes new contaminants can lead to better research and better understanding of water quality.”
In that way, the Wisconsin study resembled one on coal-ash here in North Carolina that another Vengosh-led team published about a year ago. It found that a known carcinogen called hexavalent chromium that some people think is linked to leaking coal-ash ponds is actually somewhat common in North Carolina groundwater and likely naturally occurring because of the state’s geology.
The Wisconsin study came about because both state regulators and Clean Wisconsin knew molybdenum was showing up in groundwater. Why was less clear, coal ash being a suspect because it’d gone into some landfills in the area and into construction fill “under roads, buildings, parks and schools,” according to the team’s report.
Clean Wisconsin elected to call in the private-university Duke team because it’s become “the recognized expert” in tracing groundwater pollutants via their isotopic signatures, Mathewson said.
Wisconsin’s Department of Natural Resources had done some preliminary sampling in the area that pointed toward geological sources, the Vengosh team’s paper said.
But Clean Wisconsin saw those results as “inconclusive,” and “wanted to dig deeper into it,” Mathewson said, adding that a follow-up from regulators wasn’t immediately forthcoming.
The state department had gone through a round of science-staff cuts at the behest of Wisconsin’s governor, Scott Walker, and had water-contamination problems to look at elsewhere.
And aside from its expertise, the Duke team’s involvement also got around the issue that a lot of professors in Wisconsin are trying to keep their heads down and avoid “doing anything that would get them seen as having an agenda,” he said, alluding to the fights between Walker’s administration and the University of Wisconsin system.