Marine Corps Base Quantico --
The murky waters at Abraham’s Creek at Marine Corps Base Quantico
have the potential to provide a solution to the problem of
polychlorinated biphenyls (PCBs) entering the food chain.
The creek is the location of a year-long study conducted by
scientists at University of Maryland Baltimore County and funded by the
Department of Defense’s Environmental Security Technology Certification
Program (ESTCP).
On Tuesday, Sept. 15, the scientists made their fourth visit to
Abraham’s Creek to collect 12-inch core samples of the sediment at the
creek bottom. They also deployed 16 square sheets of polyethylene
plastic throughout the creek to collect PCB particles in order to
measure their prevalence.
PCBs are stabilizing, long-lasting chemicals that were used in many
products prior to being banned in the 1970s, explained Dr. Kevin Sowers,
Professor at UMBC’s Institute of Marine and Environmental Technology
and one of the scientists on the team.
“There are lots of sources of PCBs,” Sowers said. “They were used in
paints, in caulks, in carbonless copy paper, in oil to reduce its
flammability.”
The team identified the Abraham’s Creek site with input from ESTCP.
It’s not clear what caused the levels of PCBs in Abraham’s Creek, but
Sowers theorises that decades-old pesticides are the culprit. PCBs were
also used as extenders in pesticides.
PCBs are primarily exposed to the ecosystem through clams, snails,
and worms that live in muddy sediment, explained Dr. Upal Ghosh,
Professor of Chemical, Biochemical, and Environmental Engineering at
UMBC, another member of the team.
“Fish then eat these small animals. Therefore, human exposure to PCBs is often through fish,” he said.
Ghosh and Sowers said that PCBs are probable carcinogens, because
there is evidence that rats develop cancer when exposed to high levels.
PCBs are also teratogens (agents that disrupt the development of a fetus
in the womb), endocrine disrupters, and neurotoxins. They do not,
however, affect the physical environment.
“If we can block the availability of the PCBs to the food chain,
that’s more relevant than getting the overall levels down,” Sowers said.
The team has discovered a potential way to accomplish this, using a combination of carbon and helpful microorganisms.
“The PCBs absorb to the carbon, kind of like what a Brita filter does when it filters water,” Ghosh explained.
Anaerobic microorganisms, which do not require oxygen for breathing or growth, are then introduced.
“PCBs are made up of chlorine attached to two rings of benzene,”
Sowers explained. “The anaerobes use the chlorine in the PCBs to
respirate. Once they’ve clipped the chlorine from the benzene rings,
aerobes — organisms that require oxygen — can then degrade the
chlorine.”
These methods worked in the lab, and the team hopes they will work in the real world as well.
Earlier this year, the team set up four plots in Abraham’s Creek — a
control area and three test plots. They treated one of the test plots
with activated carbon and one with carbon and microorganisms. At their
visit last week, they pulled core samples from the different plots and
distributed polyethylene sheets to absorb the PCBs and measure their
levels. They will return in October or early November to collect the
sheets. After that, it will take about 30 days to process the data.
Pending the results, the goal is to write a peer-reviewed paper for submission to an environmental journal.
— Writer: auphausconner@quanticosentryonline.com
]]>