Researchers Test Sediment-Scrubbing Technology In Cocheco River
By Beth Potier, Media Relations
June 25, 2008
UNH research assistant professor Jeffrey Melton (l) and associate professor Kevin Gardner, both of the Contaminated Sediments Center, are testing a new treatment for contaminated sediment at the edge of the Cocheco River in Dover, N.H. Photos: Lisa Nugent, UNH Photo Services.
In a mud flat at the edge of the Cocheco River, just outside downtown Dover,
scientists from UNH’s Contaminated Sediments Center are testing an innovative
way to treat polluted sediment in coastal waterways.
Rather than dredging up the problem, or burying it under several feet of sand,
they’ve created a patch — black geotextile mats designed to cap
and stabilize pollution in place. During the next two years, associate professor
Kevin Gardner, research assistant professor Jeffrey Melton, and a team of UNH
students will monitor these mats to evaluate the effectiveness of this new
“We need to know how these mats behave when they’re buried under
mud for a few years, compared to how they performed in the lab,” says
Melton. “What will happen to them in this intertidal zone with boats,
waves, birds, and weather? How will they impact bugs and other aquatic life
in the sediment?”
The mats are six feet square and one inch thick. They consist of a mixture
of reactive materials sandwiched between two layers of geotextile fabric, creating
a sort of quilt that traps pollutants but allows water to flow through. The
reactive “filling” of this quilt contains three different substances
that bind and stabilize different pollutants. One such substance — a
UNH-patented technology based on a natural form of phosphorus — treats
toxic heavy metals associated with industrial pollution such as lead, copper,
zinc and cadmium.
A close-up of the inside of the mats, where reactive substances are distributed through a lofty fiber, where they trap and treat pollutants in the contaminated sediment.
“But you don’t just find one pollutant at a site,” says
Melton. “Everything is all mixed up in the sediment.” So he and
his colleagues added organoclay and activated charcoal (“like in your
Brita filter,” he says), which adhere to and treat toxic chemicals such
as polychlorinated biphenyls (PCBs), polyaromatic hydrocarbons, (PAHs), and
petroleum products that routinely enter waterways through stormwater runoff.
The project is funded by the Cooperative Institute for Coastal and Estuarine
Environmental Technology (CICEET), a partnership of UNH and the National Oceanic
and Atmospheric Administration, and NH Sea Grant.
“Polluted sediment is a nationwide problem,” says Richard Langan,
CICEET’s UNH co-director. “We need better tools to identify and
treat areas where this pollution has the potential to threaten human and ecosystem
health. Technology demonstrations like these, that take advantage of cutting-edge
science, are key to making that happen.”
The mats present an alternative approach to remediating contaminated sediment;
more common responses include dredging or capping sediment beneath several
feet of sand. But dredging is expensive, disrupts habitats and poses the problem
of how to move — and where to put — all that toxic sediment. Sand
caps have questionable long-term effectiveness and can hinder boat traffic
and impact aquatic life. “There’s no silver bullet. What we are
exploring is potentially a great tool to add to the tool box,” says Melton.
Melton admits that even as Americans grow increasingly aware of environmental
woes, sediment pollution does not score high on the “green glamour” scale.
Yet, he points out, everyone is already feeling its impact through regular
advisories that close shellfish beds or warn of eating fish contaminated by
heavy metals and persistent organic pollutants like PCBs or PAHs.
“You can enjoy a great day of fishing, but if you can’t eat the
catch, there’s a problem,” says Melton. It’s estimated that
20 percent of the top six inches of all sediment in U.S. rivers, lakes, streams
and estuaries is contaminated. In 2004, the U.S. Environmental Protection Agency
reported there were 3,221 fish consumption advisories in state waters.
Melton and Gardner chose the Cocheco not because its sediment is especially
polluted, but rather because its characteristics as a well-used tidal river
and its proximity to UNH make it an ideal laboratory. They plan to compare
the performance of the mats in the Cocheco to those they’ve laid in Cottonwood
Bay in Grand Prairie, Texas, adjacent to the Dallas National Air Station, in
a demonstration funded by the Department of Defense’s Strategic Environmental
Research and Development Program (SERDP).
Moving forward, researchers from the Contaminated Sediments Center, part of
UNH’s Environmental Research Group, plan to test new sampling technologies
that measure the scope and potential threat of contamination in sediment. In
addition, they’re always on the lookout for new test sites.
To learn more about UNH’s Contaminated Sediments Center, go to http://www.unh.edu/erg/ccsr/index.html.