Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Aquatic Plant Sequesters Toxins, Removes Contaminants from Wetlands

25.08.2004


Researchers have found that a common aquatic plant removes many persistent organic compounds that are discharged into natural waters and engineered wetlands.

Environmental engineers at the Georgia Institute of Technology have found that various chlorinated, fluorinated and mixed chloro-fluoro compounds are taken up and sequestered in the plant tissue of their model plant species – duckweed (Lemna minor), a floating aquatic plant. These organic compounds are representative of the pool of persistent compounds discharged into the nation’s waters. Sources include agro-chemicals, such as pesticides, and pharmaceutical residuals, such as those from anti-depressants, which are excreted in human waste.

Though the compounds are sequestered in the plant, there is concern about their ultimate fate in the ecosystem as the plants are eaten by animals, or die and decay in wetland sediments, researchers noted.



“The compound goes into the plant, and the plant has no choice about the uptake. Whether the compound is water-loving or water-hating does not appear to be a major factor,” explained Professor Michael Saunders of the School of Civil and Environmental Engineering. “… And our plants take up this large class of compounds quickly, at rates faster than bacteria would degrade the contaminants.”

These findings have implications for both water monitoring regulations and wastewater treatment practices.

Saunders’ Ph.D. student Dawn Reinhold will present their research on Aug. 23 at the 228th national meeting of the American Chemical Society in Philadelphia. Reinhold conducted the research, in part, with former Ph.D. student Jacqueline Tront, who graduated in May 2004, and Angela Wrona, also a recent graduate. This study built upon previous research in Saunders’ lab funded by the U.S. Department of Energy.

The research has focused on halogenated phenolic molecules as indicators of chlorinated, fluorinated and mixed chloro-fluoro compounds in natural waters and engineered wetlands. Previously, researchers found that various chlorinated phenols were sequestered in duckweed cell tissue. The current study shows that mono, di and tri fluoro-phenols and mixed chloro-fluoro phenols are also taken up and sequestered at varying rates.

These compounds can be toxic to duckweed, so the plant has evolved a defense mechanism to deal with the threat, Reinhold explains. Duckweed does not degrade the compound, so the plant fixes it inside cell walls and tissue, eliminating the compounds’ toxic effect on the plant. She compared this process to human excretion of toxic products. “Plants don’t always have the option of excretion, so they package it away into their cell tissue,” she explained.

This research has led Saunders and his students to believe duckweed and probably other aquatic plants are acting as “sinks” for persistent organic compounds. Saunders noted that regulators monitoring contaminants in the water may be missing something by not considering the plant uptake of these compounds – a process that is affecting the overall removal time of the contaminants from the water.

“These types of compounds we have studied are emerging in the regulatory sector as the ones we need to know more about,” Saunders says. “They may soon meet with more regulatory control. They are not well regulated now.”

Of some concern is the movement of these contaminants up the food chain by ducks that feed on duckweed. Researchers are also interested in what happens to these contaminants when the plants die and decay in wetland sediments. They are likely being degraded by microbes in the sediments, Saunders said. Both processes may be areas of future research for Saunders and his students.

The researchers’ current findings may also have an impact on water treatment and reclamation practices. “Are we taking advantage of duckweed’s ability to remove contaminants from the water?” Saunders asked. “The answer is ‘yes, but indirectly.’ Constructed wetlands are used in some places as a means of removing nitrogen and phosphorus from treated wastewater. These wetlands are not designed for duckweed and other plants to remove organic contaminants, but it’s happening even though it’s not generally recognized or included with the design concept…. So here’s another tool in the toolbox for getting additional removal of contaminants.”

In the next phase of this research, Saunders’ research team will investigate whether duckweed sequesters additional compounds – those in the tri-fluoro methyl group. These compounds are found in medications such as Prozac and in pesticides.

Reinhold will also culture undifferentiated plant cells – similar to stem cells in humans – to determine how quickly duckweed processes and metabolizes the studied compounds. Researchers want to understand this activity because it may be an indicator of metabolic inhibition by the contaminants. Plants may take up a small amount of the contaminant and then stop, Reinhold said. “It looks like the overall uptake rate is highly dependent on plant metabolic rates based on the Ph.D. work of my colleague Jackie Tront,” she added.

The researchers’ overall goal is to create a modeling tool that measures the plant’s rate of oxygen production -- an indicator of the organism’s health -- in response to its uptake of various contaminants at various rates.

“We know that if oxygen activity is shut down with contaminant uptake, this process is having an impact on the environment,” Saunders said. “This shows the contaminant is having an impact at a lower concentration than if you are just monitoring how many plants die (such as is the case with a current EPA suite of ecotoxicology testing in waterways). Then we can go back to the regulators and give them some insight into how these trace levels of persistent organic compounds are affecting the ecological balance out there.”
“…. We may find that nature is taking care of this problem for us,” he added. “The question is whether we can put these compounds into a wetland system and put them back into the global carbon cycle and call it sustainable. The answer is that maybe we can, but we don’t know for sure yet.”

| newswise
Further information:
http://www.gatech.edu
http://www.gtresearchnews.gatech.edu

More articles from Ecology, The Environment and Conservation:

nachricht Upcycling of PET Bottles: New Ideas for Resource Cycles in Germany
25.06.2018 | Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF

nachricht Dry landscapes can increase disease transmission
20.06.2018 | Forschungsverbund Berlin e.V.

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Future electronic components to be printed like newspapers

A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.

The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

A smart safe rechargeable zinc ion battery based on sol-gel transition electrolytes

20.07.2018 | Power and Electrical Engineering

Reversing cause and effect is no trouble for quantum computers

20.07.2018 | Information Technology

Princeton-UPenn research team finds physics treasure hidden in a wallpaper pattern

20.07.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>