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(Last updated 3/24/06)

[Editor's note: Images of sediment particles (before and after ultrasonic vibration) are available from Pam Frost Gorder.] Larger format here.

Previous stories pertaining to Professor Weavers' research:

"Ultrasound Cleans Ceramic Filters: Could Aid Water Treatment," (4/10/02).

"Six Ohio State Researchers Win CAREER Award From NSF," (5/27/01).

Previous stories pertaining to Professor Sayre's research:

Researchers Get To The Root Of Cassava's Cyanide-Producing Abilities (5/12/03).

Research Team Receives $7.5 Million To Study Cassava (6/28/05).

[Embargoed for release until 5:00 p.m. on Monday, March 27, 2006, to coincide with presentation at the American Chemical Society national meeting in Atlanta.]

ULTRASOUND AND ALGAE TEAM UP TO CLEAN MERCURY FROM SEDIMENTS

ATLANTA - Ultrasound and algae can be used together as tools to clean mercury from contaminated sediment, according to an Ohio State University study.

Linda Weavers
Richard Sayre

This research could one day lead to a ship-borne device that cleans toxic metals from waterways without harming fish or other wildlife, said Linda K. Weavers, the John C. Geupel Chair in Civil Engineering at Ohio State.

Doctoral student Ziqi He described the group's latest results in a poster session March 27 at the American Chemical Society meeting in Atlanta.

Weavers' research group previously determined that ultrasonic vibrations can shake mercury loose from sediment.

"We found ultrasound to be very effective at getting mercury out of sediment and into water," He explained. "But then we needed a third party to get the mercury out of the water. That's how we got the idea to add a biological element to the treatment."

Weavers and He joined with Richard Sayre, professor of plant, cellular and molecular biology at Ohio State, and Surasak Siripornadulsil, a former graduate student in the university's biophysics program. Sayre's team has genetically modified a species of algae to boost its natural ability to absorb heavy metals.

In laboratory tests, student He vibrated an ultrasonic probe inside beakers containing water, sediment, and algae. The vibrations freed mercury from the sediment, and within seconds, the algae adsorbed up to 60 percent of the mercury from the water. The combined system of ultrasound and algae removed 30 percent of the mercury from sediment within the first few minutes.


In laboratory tests, they vibrated an ultrasonic probe inside beakers containing water, sediment, and algae. The vibrations freed mercury from the sediment, and within seconds, the algae adsorbed up to 60 percent of the mercury from the water.


There are alternative cleanup methods that also absorb a high percentage of metals, Sayre admitted, but they are less selective -- they absorb all metals. His modified algae species absorbs five times the normal amount of a select group of toxic metals, including mercury, cadmium, copper, and zinc.

"Say you were trying to clean water that contained effluent with a lot of calcium or iron in it -- or seawater, which contains sodium," Sayre said. "If your algae aren't selective, they'll absorb those other metals and you'll recover less mercury. So the advantage of these modified algae is that other metals don't interfere with the cleanup."

Weavers envisions that boats could dredge sediments from contaminated waterways and clean them on board using ultrasonic equipment and algae-based filters. Then the clean sediment could be returned to its original location. Or, the equipment could be placed directly on sediment to treat it in place. Either procedure would leave wildlife unharmed, she said.

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Contact: Linda K. Weavers, (614) 292-4061; Weavers.1@osu.edu [Weavers is currently on sabbatical at the University of Minnesota ; she can be reached by phone at (612) 625-2397 or through her Ohio State email address.]

Ziqi He, (614) 688-9230; He.74@osu.edu

[During the American Chemical Society meeting, contact Pam Frost Gorder to reach He directly.]

Richard Sayre, 614-292 2587; Sayre.2@osu.edu

Written by Pam Frost Gorder, (614) 292-9475; Gorder.1@osu.edu