Could a Toxic Lake Yield Life-Saving Microbes?
By Mark Matthews
One fall night a few years ago, more than 200 snow geese landed on the water inside the Berkeley Pit, an abandoned copper mine on the edge of this hillside town. The next morning all the birds were dead, floating feet up on the lake's blue surface.
Researchers once thought all living things that landed in the pit surely died, but they've had some surprises lately. Some single-celled life forms, unseen by the human eye, that blow into the pit or drift in with surface water are surviving. Some have even evolved to the point where they can't exist outside the toxic stew. Scientists have identified some of these life forms, but others remain a mystery.
The 1.5-mile-wide, 1,800-foot-deep pit, part of the nation's largest Superfund site, has been filling for the last 17 years with a poisonous broth laced with heavy metals and arsenic--a legacy of Butte's copper mining days. When mining officials abandoned the pit about 17 years ago and stopped the pumps that kept it dry, they opened the spigots to about 3 million gallons of water per day. Today, the lake is about 850 feet deep and contains more than 3 billion cubic feet of water. It is supplied by an aquifer that contains approximately 57 billion gallons of metal-laden water.
The contamination in the Berkeley Pit is typical of many existing and former hard rock mining sites where exposed sulfide minerals have reacted with water and air to produce highly acidic waters, said Mary Ann Harrington-Baker of MSE Technology Applications Inc., which co-administers the Mine Waste Technology Program with the University of Montana College of Technology.
For years, engineers who have monitored the pit assumed the water, which is about 10,000 times more acidic than normal--like battery acid--could not support life. Then a few years ago, a curious analytic chemist, William Chatham, noticed a small vegetative clump floating on the water's surface. It turned out to be made up of "protists," one-celled microorganisms. Since then, biologists and natural products chemists have isolated 42 different kinds of organisms living in the acid solution, including algae, bacteria, protozoans and fungi.
"There's every organism you could imagine," said Grant Mitman, a Montana Tech biologist who has identified many of the creatures.
The survivor microbes are far from prolific, but can be found at various depths. And their numbers sometimes fluctuate with the seasons. Scientists are studying the microbes and their biological products to see if they can't be used in some way, perhaps even to clean up the pit itself.
"We're looking at the bright side of the Berkeley Pit," said Andrea Stierle, a natural products research scientist who, with her husband Don, is looking for novel sources of anticancer, antifungal and antibacterial agents.
A few years ago, the Stierles isolated a fungus from the bark of the yew tree that produces taxol, an important new anticancer drug. They think some pit microbes might also produce compounds with drug potential. Many drugs, like penicillin, are produced by fungi or bacteria. Scientists often don't understand how the organisms use these natural products in their own life cycles--to attract mates? to kill off competitors?--but the compounds often can be put to work for human benefit. The Stierles have already put some of the pit-organism compounds through a widely recognized initial anticancer biological test.
"We have come up with a few compounds that have shown this activity," Andrea Stierle said. The researchers have sent some of the compounds off to cancer research labs.
Some pit organisms develop after spores blow into the water. While these seem to barely survive in the extreme environment, others thrive. "There is a percentage of the organisms that luxuriate in pit broth," Andrea Stierle said. Some organisms may even have evolved in the pit since the waters began accumulating. "Fourteen years equals thousands of generations for these organisms," Stierle said. "We may be seeing the results of natural selection."
Other researchers hope that some of the organisms, especially algae, will eventually help clean up the toxic stew. In about 22 years, engineers predict the water level will rise high enough to overflow into the groundwater and begin migrating down the Clark Fork River drainage. It could contaminate water all along its course to the Pacific Ocean, via the Columbia River.
"We could drink the [Berkeley Pit] water tomorrow if [society] wanted to pay for it," said Karl Burgher of Montana Tech. "There are a number of technologies that have proved feasible, but there are issues with each, like process byproducts and the costs associated with remediation. It would be very expensive, and there would be lots of sludge we'd have to get rid of."
Mitman's goal is to let the organisms take care of cleansing the water. "Organisms grow exponentially," he said. "If we're able to figure out a way to make the pit come alive, we may be able to remediate the metals naturally. What we want are big algae blooms. Just the opposite of what you want on natural lakes. The algae will use carbon dioxide from the air to produce oxygen and sugar. The sugar will feed other organisms. The key is to get the algae growing."
The microorganisms in the surface water may already be transforming iron into small particles, which appear orange, said Jim Jonas of Montana Tech.
"As the surface water temperature increases, the biological activity also increases. On a summer morning, the water is blue. But in the afternoon, you can see orange plumes across the pit. It could mean that the higher temperature creates a favorable environment for the iron particulates to form, which then drop to the bottom. And getting rid of the iron also cuts down on the arsenic."
In 1982, when the lake began forming, almost all the iron in the water was in a soluble state, Jonas said. Today, the upper 25 feet of the lake is highly oxidized and the amount of iron has decreased in that strata. Researchers are looking for a way to constantly keep a clean layer of water on top of the lake.
"By stratifying the lake, the surface water would be significantly less harmful to migratory birds that may use it as a layover during migration," Jonas said.
Although companies could eventually reclaim the copper, zinc and other valuable metals from the water using various technologies, Burgher thinks clean water would be the most valuable resource that could be extracted from the pit.
"It could be used for instream flows, for municipality and industrial use, power generation, fisheries, recreation and agriculture," he said. "The amount of water flowing into the pit is worth about $250,000 a year."
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