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Exploring
the World
with New Technology
The
electrochemical analyzer developed by University of Delaware
researchers George
Luther and Don
Nuzzio has been used to explore a wide variety of habitats,
from Delaware's
Inland Bays, where it helped detect the source of recent
fish kills, to the Black Sea, the world's largest body of water
containing poisonous hydrogen sulfide.
The
Black Sea occupies an area larger than California. Nearly 90%
of the over 700-mile-long, mile-deep system is a zero-oxygen "dead
zone" that supports only a few bacteria. This oxygen-less
zone is the result of natural and human factors. Due to the
Black Sea's nearly landlocked status, little mixing occurs
between the surface waters, which receive major freshwater
inputs from rivers, and the denser, saltier bottom waters that
enter the system from the Mediterranean Sea through the Bosporus.
This
natural state is compounded by serious pollution problems generated
by the over 160 million people who live in the 16 countries in
the Black Sea's watershed. While only six nations border the
Black Sea, half of continental Europe drains into it through
the Danube and other major rivers.
"Besides
having a substantial zone where no oxygen exists and high levels
of sulfides occur, the Black Sea has an unusual region known
as the 'suboxic zone' that lies between its oxygen-rich suface
waters and its oxygen-starved depths," Luther says.
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The
scientists visited the Great Bazaar in Istanbul, Turkey,
before heading out on the Black Sea expedition. The
540-year-old covered shopping mall contains 64 streets,
4,000 shops, and 25,000 workers!
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"This
zone is of particular interest to us because it has both minimal
oxygen and minimal sulfide concentrations. Typically, when the
oxygen level increases in an aquatic system, the sulfide level
decreases, and vice versa, but that's not what happens here.
And it's a remarkably stable area, extending over a depth ranging
from 20 to 50 meters."
Luther
and his team used their chemical sensor to verify the suboxic
zone. The device was mounted in a pressure housing and deployed
at various depths in the Black Sea's water column. The data they
collected will be used to predict and understand changes in the
Black Sea system.
Scientists
from around the world have visited Dr. Luther's lab or have invited
Dr. Luther to their labs to learn more about chemical sensor
technology. In addition to holding teaching programs in the United
States, Dr. Luther has instructed colleagues from Argentina,
Canada, France, Germany, The Netherlands, New Zealand, Sweden,
and the United Kingdom
To
learn more about Dr. Luther's Black Sea expedition, check out
this Web site: http://www.ocean.udel.edu/blacksea.
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A "Magic
Wand" for Detecting
Vent Chemistry
The
state-of-the-art analyzer that scientists George Luther and Don Nuzzio
have developed looks like a wand and works like magic in revealing
the chemical recipe of the hot, toxic stew flowing out of hydrothermal
vents deep in the ocean.
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The
submersible Alvin holds the "magic wand" (the
electrochemical analyzer) over a vent site to capture real-time
water chemistry readings.
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Dr.
Luther, a Maxwell P. and Mildred H. Harrington Professor of
Marine Studies at the University of Delaware, is leading the chemistry
component of the Extreme 2003 expedition. Dr.
Nuzzio is president of Analytical Instrument Systems in Flemington,
New Jersey, and an adjunct professor in UD's College of Marine
Studies.
Housed
within the foot-long wand are several probe-like, gold-tipped electrodes,
which are coated in super-tough plastic to protect them from heat.
Once the wand is attached to one of the submersible Alvin's highly
maneuverable arms and placed near a hydrothermal vent, it can instantaneously
reveal the chemical compounds erupting from the Earth's crust. Previously,
scientists had to collect vent water samples using the sub and then
analyze them hours later aboard ship after chemical changes may have
occurred.
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The
analyzer contains electrode sensors like these. For work in
the water column, the gold wire in the electrode is soldered
to a conductor wire and then placed in a durable plastic called
PEEK (shown at top) and sealed with a non-conductive epoxy.
The tips are carefully polished and then electrochemically
plated with mercury for measurement of the target chemicals.
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During
the Extreme 2003 expedition, the scientists will be using the analyzer
to help track down ancient life forms at the vents.
"If
our sensors measure the simultaneous presence of hydrogen sulfide
and iron monosulfide, that indicates that pyrite, or "fool's
gold," and hydrogen gas are being formed," Dr. Luther notes. "Hydrogen
gas is a chemical that Archaea — descendants of ancient life
forms — can use for growth. So we can use this information
to prospect for life forms that live off that chemical reaction."
The
chemistry team's second major goal is to successfully deploy a new
remote-controlled electrochemical analyzer, which can be left unattended
at a hydrothermal vent. Luther and his colleagues recently received
more than $2 million in research grants from the National Science
Foundation to develop and test the system.
The
new chemical analyzer has four separate instrument packages that
feature working electrodes integrated with temperature and pH sensors,
permitting analysis of four separate locations or depths.
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With
a handshake for good luck, Dr. George Luther (right) and Dr.
Don Nuzzio prepare to deploy their electrode analyzer in a
research expedition in the Chesapeake Bay in July 2003.
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"To
our knowledge," Luther says, "no other sensor system has
this broad capability for chemical analysis."
Left
at a vent site, the sensors will be able to collect data continuously
and document any short-term changes up to about a week.
"These
results will indicate how the chemistry of a site varies with time
and should give us insight into how organisms respond to such chemical
changes," he notes.
Previously,
Luther and his colleagues used the analyzer to document how the chemistry
at a particular vent site dictates what organisms can live there.
The tall, plumed tubeworm (Riftia pachyptila) lives where
hydrogen sulfide exists, but it can not survive where iron monosulfide
exists. Alternatively, the fleecy Pompeii worm (Alvinella pompejana) can
exist where iron monosulfide is found because the iron detoxifies
the hydrogen sulfide, which otherwise would be lethal to the worm.
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