Airdate: Jul 10, 2007
Scientist: Michael Hochella
Science Diary: How Toxins Move - Restoration
Restoration work has improved vegetation in areas polluted by mine runoff.
Ambience: river sound
Welcome to Pulse of the Planet's Science Diaries, a glimpse of the world of science from the inside. Today, we join Virginia Tech Geochemist Mike Hochella and colleague Johnnie Moore as they collect water samples from Montana's Clark Fork River. It's been contaminated by years of mining activities upstream.
Johnnie is pointing out plains where heavy metal contamination brought by tailings, a form of mining waste, has settled on the banks of the river. The pollution creates barren areas and it's contrasted by places where restoration efforts have been made.
JM: "This was a place where very early on the State of Montana came in and plowed up the tailings material here and plowed in clean soil and some limestone to try to neutralize all these acids. And the tailings are still there, just kind of down underneath this cleaner soil, but it's definitely kept this runoff during thunderstorms from happening, and the banks are much more stable so not as much contamination is moving into the river in places like this.
MH: I'm on the bank of the river now and I look at the grassy layer on top, the soil is supporting the vegetation.
JM: Yeah, so you can see just right underneath that upper soil layer that's very thin here, this kind of orangish and grayish colored material, and that is the tailings, that's the stuff that they dumped out into the river and it washed downstream, and then it deposited itself out here on the floodplain, it completely covered up everything. So you can see the river's cutting into the bank here, it's exposing those tailings, and that's the main source now of metal contamination in the river. As the river erodes that bank this stuff falls into the river and then gets transported downstream and can have an effect on the fish and biota living in the stream."
You can find out more about Mike Hochella's work on our website, pulseplanet.com. Pulse of the Planet's Science Diaries are made possible by the National Science Foundation.