The ubiquity of tiny particles of minerals--mineral
nanoparticles--in oceans and rivers, atmosphere and soils, and in
living cells are providing scientists with new ways of understanding
Earth's workings. Our planet's physical, chemical, and biological
processes are influenced or driven by the properties of these minerals.
 | | Earth image by NASA |
So states a team of researchers from seven universities in a
paper published in this week's issue of the journal Science:
"Nanominerals, Mineral Nanoparticles, and Earth Systems."
The way in which these infinitesimally small minerals
influence Earth's systems is more complex than previously thought, the
scientists say. Their work is funded by the National
Science Foundation (NSF).
"This is an excellent summary of the relevance of natural
nanoparticles in the Earth system," said Enriqueta Barrera, program
director in NSF's Division of Earth Sciences. "It shows that there is
much to be learned about the role of nanominerals, and points to the
need for future research."
Minerals have an enormous range of physical and chemical
properties due to a wide range of composition and structure, including
particle size. Each mineral has a set of specific physical and chemical
properties. Nanominerals, however, have one critical difference: a
range of physical and chemical properties, depending on their size and
shape.
"This difference changes our view of the diversity and
complexity of minerals, and how they influence Earth systems," said
Michael Hochella of the Virginia Polytechnic Institute and State
University in Blacksburg, Va.
The role of nanominerals is far-reaching, said Hochella.
Nanominerals are widely distributed throughout the atmosphere, oceans,
surface and underground waters, and soils, and in most living
organisms, even within proteins.
Nanoparticles play an important role in the lives of
ocean-dwelling phytoplankton, for example, which remove carbon dioxide
from the atmosphere. Phytoplankton growth is limited by iron
availability. Iron in the ocean is composed of nanocolloids,
nanominerals, and mineral nanoparticles, supplied by rivers, glaciers
and deposition from the atmosphere. Nanoscale reactions resulting in
the formation of phytoplankton biominerals, such as calcium carbonate,
are important influences on oceanic and global carbon cycling.
On land, nanometer-scale hematite catalyzes the oxidation of
manganese, resulting in the rapid formation of minerals that absorb
heavy metals in water and soils. The rate of oxidation is increased
when nanoparticles are present.
Conversely, harmful heavy metals may disperse widely, courtesy
of nanominerals. In research at the Clark Fork River Superfund Complex
in Montana, Hochella discovered a nanomineral involved in the movement
of lead, arsenic, copper, and zinc through hundred of miles of Clark
River drainage basin.
Nanominerals can also move radioactive substances. Research at
one of the most contaminated nuclear sites in the world, a nuclear
waste reprocessing plant in Mayak, Russian, has shown that plutonium
travels in local groundwater, carried by mineral nanoparticles.
In the atmosphere, mineral nanoparticles impact heating and
cooling. Such particles act as water droplet growth centers, which lead
to cloud formation. The size and density of droplets influences solar
radiation and cloud longevity, which in turn influence average global
temperatures.
"The biogeochemical and ecological impact of natural and
synthetic nanomaterials is one of the fastest growing areas of
research, with not only vital scientific, but also large environmental,
economic, and political consequences," the authors conclude.
Posted 25th March 2008
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