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," Dr. 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."
Dr.
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 learned
more about chemical sensor technology from Dr. Luther. In addition
to holding teaching programs in the United States,
he 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 is a marine chemist and the Maxwell
P. and Mildred H. Harrington Professor of Marine Studies
at the University of Delaware. Dr.
Nuzzio is president of Analytical Instrument
Systems in Flemington, New Jersey, and an adjunct professor
in the UD College of Marine Studies. They led the chemistry
team on the Extreme 2003 expedition last year.
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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The scientists also are 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."
One
of the team's goals is to successfully deploy a new remote-controlled
electrochemical analyzer that can be left unattended at a
hydrothermal vent. The new analyzer has four separate instrument
packages that feature working electrodes integrated with
temperature and pH sensors, permitting analysis of four separate
locations or depths. 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.
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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. |
"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," Dr. Luther notes.
Previously,
he 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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