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Brett Walker (REU from UCSC) on the R/V Tioga cruising up the Hudson River to take water samples for Re and Mo analyses. (BPE)
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Dr. Petra with the dipper, sampling a stream in the Catskill Mountains on a soggy day in October 2004. Filtered water samples from Hudson River tributaries will be analyzed by isotope dilution ICPMS for rhenium and molybdenum concentrations. (BPE)
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Christan Miller (left) and Cpt. John Lipscomb (right) on the RIVERKEEPER patrol boat on the Hudson River (June 2006). (BPE06)
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The aquatic behavior of rhenium and molybdenum
Collaborators:
Brett Walker (UCSC)
Christian Miller (MIT/WHOI JP student)
Prof. Franco Marcantonio (Tulane Univ.)
Prof. Pete Raymond (Yale University)
Max Holmes (Woods Hole Research Center)
Schlumberger's SEED Program
Rhenium is considered a conservative element in seawater (~40 pM) and
freshwater (~2 pM) with a long marine residence time (~750,000 years).
The first systematic investigation of the geochemical cycle of rhenium
was carried out in the early 1990s by Debra Colodner and coworkers at
MIT (EPSL 117, 205-221, 1993; EPSL 131, 1-15, 1995). Debbie Colodner's
data for the Amazon estuary hint at a more complex, non-conservative,
geochemistry with a potential source of dissolved Re in the
low-salinity zone of the esturary.
Intrigued by this feature, Summer Student Fellow Brett Walker (UCSC)
and I decided to take a fresh look at the behavior of Re (and Mo) in
estuaries. In July 2004, we joined a group of physical oceanographers
(Jim Lerczak and Rocky Geyer) on a cruise with R/V TIOGA, the newest
addition to the WHOI fleet, to the Hudson River. His research was
sponsored by the WHOI Summer Student Felloship Program and support by
Pancha and Karl Peterson. Brett presented data indicating
non-conservative behavior in the low-salinity mixing zone of the Hudson
River at the 2004 Fall AGU meeting in San Francisco and at the 2005
ASLO Conference in Salt Lake City. With NSF-EAR funding (grant
EAR-0519387) Christian Miller and I been back to the Hudson on the
RIVERKEEPER patrol boat with Cptn. John Lipscomb of the Riverkeepter
Org. (see photo) to track down the source of the dissolved Re to the
Hudson. In collaboration with Franco Marcantonio (TAMU), we have
started to investigate Re and Mo concentrations in the Mississippi
River and its major tributaries.
In collaboration with Pete Raymond and Max Holmes (WHRC - PARTNERS
Project) we have also started investigating the flux of Re and Mo from
major rivers draining into the Arctic Ocean
Commercial use of Re for metallurgical purposes (~75%) and petroleum
refining (~20%, production of high-octane fuel) consumes about 20,000
kg Re per year in the U.S. alone. How much Re (and Mo) is released into
the environment by industrial processes, including mining and coal
burning, is currently not known. Debbie Colodner et al. (1995), based
on data from rivers draining into the Black Sea, speculated that such
contamination (here from coal burning) may be pervasive in
industrialized regions. Our group is currently investigating other
potential (anthropogenic) sources of Re and Mo in rivers that
contribute to the natural background flux.
River Sampling:
We have developed a simple syringe-filtration method for sampling small
(125 ml) volumes of river water. The method involves sampling rivers
with the help of a 12-feet plastic dipper (see photo 2). Water is then
sucked into a plastic syringe and pressed through a 0.22 or 0.45
micrometer cartridge filter into precleaned plastic bottles. The cost
of sampling is less then $10 per sample and can be done by untrained
helpers. We are currently testing this method.
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