Va. -- Copper mining in Butte and Anaconda, Montana,
starting in 1860's, poisoned the air, the land, and
the water; well over 100 years later, contaminants
are still found as far as 300 miles down the Clark
Fork River, whose headwaters are in that area.
The presence of the contaminants has been known for
many decades. But the interaction of the heavy metals
and other compounds in the soil, streams, and rivers
were unknown until Virginia Tech professor of geosciences
Michael Hochella went all the way to the University
of Munster, Germany as a Fulbright Scholar, then as
a Humboldt Fellow, to use sophisticated equipment
that allowed him to examine lead, arsenic and other
materials at the nanometer level (a nanometer being
about the size of 10 atoms). He will present his findings,
including the discovery of a new mineral, at the 116th
national meeting of the Geological Society of America
in Denver Nov. 7-10.
When the mine was active, ore
smelting on the site poured arsenic and sulfur into
the air. House cats, because they lick their fur trying
to stay clean, died young. People in the area had
very pale skin as a result of arsenic poisoning.
"Waste material from mining
was dumped in piles that now cover hundreds of acres
of land," said Hochella. "This material
has been rained on and snowed on for a hundred years
and run off into the river. The mining pits have now
filled with water, contaminating ground water. If
you go into the stream beds and flood plains and dig
up muck and dirt, just with a garden trowel, and analyze
that dirt, you will find high levels of arsenic, zinc,
lead, and copper. Zinc and copper, not ordinarily
considered contaminants, are in these concentrations.
Nothing grows in these areas."
"So, we knew the metals
are there, but we have not known where they reside
in the streams and soils," said Hochella. "Is
the lead associated with other minerals or with biological
material, or is it in a separate phase? No one knew."
To predict bioavailability
and movement, you need to know what holds the metal,
Hochella used a transmission
electron microscope (TEM) to take a close look. "It
takes months. You have to prepare the samples properly
before you do the microscopy. But then you can magnify
the material by hundreds of thousands of time. With
that magnification, you can find what you are looking
for," Hochella said.
Hochella, Munster professor
Andrew Putnis, and Japanese post-doc Takeshi Kasama
looked at samples and found important minerals three
to 200 nanometers in size. "We found what we
think is a new mineral, a manganese oxide hydrate
that takes up lead, arsenic, copper, and zinc like
a sponge. We hadn't even known it was there."
The researchers also found
another iron oxide mineral that is well known, ferrihydrite,
that had been thought to be the most active phase
for taking up the contaminant metals. " And we
found other minerals that take up these metals. But
the manganese mineral is much more reactive then even
the ferrihydrite," Hochella said.
"We were not necessarily
surprised," he said. "Former PhD student
Erin O'Reilly did related lab experiments that showed
this activity. But now we've found a real case in
The next step is to find out
what the presence of manganese does to the bioavailability
of the toxic minerals, he said. Virginia Tech will
be purchasing a new TEM soon for this and other research
that requires extremely high magnification.
Pyrite, which is plentiful
throughout the mining area, breaks down in weathering
environments – from sulfides to sulfates – then reforms
to sulfides in the stream, taking up heavy metals
as it crystallizes. "These are extremely tiny
crystals, a couple of nanometers, and are very reactive,"
Hochella said. "It allows the metals to be bioavailable,
when it gets on a fish's gills, for instance."
will present the paper, "The importance of nanoparticles
and their unusual properties in sediments and soils
from heavy-metal contaminated sites," at 3:40
p.m. Monday, Nov. 8, in rooms 104/106 of the Colorado
Convention Center. Co-authors are PhD candidate and
NSF Graduate Student Fellow Andrew Madden, and Johnnie
N. Moore. At the time, Moore was a faculty member
in the department of geology at the University of
Montana and had studied the site for about 20 years.
He is now science director of the California Bay-Delta
The research is funded by the
National Science Foundation and the Humboldt Foundation.
Papers have been accepted in Geochicmica et Cosmochimica
and in American Mineralogist.
Contact: Susan Trulove