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Investigating Acidic Waters in the Inland Northwest, South America and Beyond
Oct. 22, 2008
Photos are available at www.today.uidaho.edu/PhotoList.aspx
Written by Ken Kingery
MOSCOW, Idaho – One of the biggest environmental concerns in northern Idaho and western Montana is acidic water systems caused by decades of mining operations. However, researchers at the University of Idaho are working hard to better understand these dangerous water systems in hopes of finding ways to fix the problems.
Acidic waters not only are impossible for most forms of life to live in, they also lead to high levels of toxic heavy metals such as lead. The natural processes controlling the levels of metals in acidic water are not well understood. However, recent studies – including one from a similar system in Argentina – may help understand processes that affect the levels of toxins in northern Idaho waters and even may shed light on the water systems of ancient Mars.
“The goal of this line of research is to learn more about how acidic water and natural minerals interact and to understand processes that allow toxic metals to flow into the environment,” said Scott Wood, dean of the College of Science at the University of Idaho. “We also may be able to learn how the acid could be naturally neutralized.”
With colleague Chris Gammons from Montana Tech, Wood recently studied the variations in the concentrations of rare earth elements in Montana's Fisher Creek Mine drainage system and in the Rio Agrio, a naturally acidic river in Argentina. Though not especially dangerous themselves, rare earth elements have been used for a long time to understand the behavior of more dangerous materials, including toxic heavy metals and radioactive elements.
The recent report published in the Journal of Volcanology and Geothermal Research shows, among other things, that the levels of rare earth elements rise and fall throughout the day. However, depending on the river’s acidity, the levels of metals behave differently.
In acidic waters, the levels of some toxic heavy metals and iron are much higher at night – as much as nine times higher than during the day. The variation is related to photochemical processes due to intense sunlight during the day. The rare earth elements do not show this 24-hour cycling in acidic waters.
But when the waters become neutralized, sunlight no longer plays a direct role, and rare earth element levels fluctuate throughout the day, along with iron and toxic heavy metals.
The differences will help scientists discover what processes drive the changing levels of various metals in these acidic systems. The findings have implications in future studies as well as testing to meet Environmental Protection Agency standards.
“One time of day, the levels might be below the limit, but above it at another time,” said Wood. “If you’re doing studies comparing different areas of the river, you have to be mindful of the time of day the tests were done to take this variation into account.”
Many similarities were found between the Rio Agrio system and the Fisher Creek system, even though one is formed naturally in Argentina and the other artificially from mining operations in southern Montana.
The Rio Agrio’s acidity is caused nautrally by gases emitted from a volcano. Acidic waters throughout the Inland Northwest, though created artificially when exposed minerals such as fool’s gold interact with water and oxygen, can be equally harsh. The pH levels in both Argentina and Montana can be as low as 1.5, roughly the same as battery acid.
The two systems revealed common traits that point toward common interactions between rocks and contaminated water, affecting the levels of rare earth elements dissolved within.
“Any study of rare earth elements has many potential applications, including understanding what might happen in an environment where nuclear waste interacts with the natural water system,” said Wood.
Additionally, the studies give clues as to how the acids in the water become neutralized, causing the rare earth elements to be pulled out of solution and absorbed by iron oxides and minerals like jarosite.
Jarosite is a mineral commonly found in acid water systems. Because it absorbs elements out of the streams, it can be used as a sort of time capsule to infer what the water carried in years past.
The research may have future applications on another river system that is much older, and much further away than Argentina.
An interesting fact about jarosite is that it has been found in abundance on the surface of Mars. This, and the fact that all acidic water systems seem to behave in similar ways, could help scientists determine what water systems were like on ancient Mars.
“We can’t take samples of water from the surface of Mars, obviously, because it doesn’t exist now,” said Wood. “But some day we might be able to analyze the minerals in the jarosite on the surface and infer back to what might have been there in the ancient past.”
For other University of Idaho scientific discoveries that have impact on the state, the region and the world, visit www.sci.uidaho.edu.
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About the University of Idaho
Founded in 1889, the University of Idaho is the state’s flagship higher-education institution and its principal graduate education and research university, bringing insight and innovation to the state, the nation and the world. University researchers attract nearly $100 million in research grants and contracts each year; the University of Idaho is the only institution in the state to earn the prestigious Carnegie Foundation ranking for high research activity. The university’s student population includes first-generation college students and ethnically diverse scholars. Offering more than 150 degree options in 10 colleges, the university combines the strengths of a large university with the intimacy of small learning communities. For information, visit www.uidaho.edu.
Media Contact: Ken Kingery, University Communications, (208) 885-9156, kkingery@uidaho.edu
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