In the Lab
- By Jeff Wilson
- Sep 01, 2001
Nature's Own Detoxins
Economically and ecologically destructive, the kochia weed is not a likely candidate for environmental cleanup. Like other noxious weeds, the kochia can create severe problems for farmers, land managers and homeowners. But scientists at Argonne National Laboratory (ANL) have found that this weed and other toxin-removing plants may be the latest in environmental cleanup.
Argonne-West's Nuclear Technology Division is planning to use kochia weeds to clean a half-acre field of cesium-137 contamination. Kochia plants were chosen to clean up the cesium for a number of reasons. The plants usually require a large amount of potassium. Since potassium and cesium are in the same column on the periodic table, they behave chemically in similar ways. As a result, the kochia takes cesium out of the soil. The kochia also has no known natural predators. Animals do not like the plants, so the contaminants will not be scattered.
In addition to the kochia, the site is using willow trees to remove inorganic contaminants from the soil through their roots. Willows are used because the target chemicals tend to concentrate in the plants' roots, preventing animals from eating them. The willows are located inside the Argonne-West fenced area in surface runoff ditches and separated from the wildlife. However, the effectiveness of the willow trees to absorb soil contaminants has not yet been determined. They are on a two-year growth cycle to allow their roots to spread and absorb as many toxins as possible. This fall, the trees will be unearthed, chipped and sent off for incineration.
Phytoremediation, which uses plants to extract contaminants from the soil along with water and nutrients, is popular for its low maintenance and cost and visual appeal. Argonne-East is using about 770 hybrid poplars and willows in a 10-acre area to remove toxins from the soil. Argonne's Environmental Safety and Health Division and phytoremediation experts in the Energy Systems Division are managing the cleanup endeavor.
Due to hot, dry weather, Argonne-West's kochia plants are doing well in their second year. In the fall, they will get a dose of herbicide before harvesting. "The herbicide stresses the plants, and they respond by extracting everything they can out of the soil in an effort to survive," said Scott Lee, environmental engineer of Argonne-West's Nuclear Technology Division.
But the laboratory is not taking chances with the contaminant-absorbing weeds. The kochia plants will be exhumed using a modified potato harvester, compacted into small cubes using a modified baler and sent off for incineration. The ash will be solidified into concrete and taken to a hazardous waste landfill.
"The ashes will weigh approximately one percent of what the soil would have weighed, if we would have had to dispose of the soil. The large volume reduction conserves landfill space," Lee said.
The process of removing contaminants through plants has so far been successful for light contamination sites in terms of money saved and efficient removal. "We don't think we'll have any damage assessments when this is all over," Lee said, "which could cost millions of dollars in penalties."
For more information, visit Argonne National Laboratory at www.anl.gov or for phytoremediation information, www.mobot.org/jwcross/phytoremediation.
New Field of Oil Technology
Because of a recently developed process, the methods used to produce petroleum could change for the cleaner. The new technique uses biomass, biological material, to produce hydrocarbon mixtures similar to crude petroleum. Obtaining petroleum through the use of the new process could minimize the effects on the environment from mining and the use of fossil petroleum reserves.
Dr. James Catallo, environmental chemist and associate professor of environmental toxicology at Louisiana State University School of Veterinary Medicine, developed the patented procedure, which involves treating biomass in hot water under pressure to generate complex hydrocarbon mixtures. The method uses biological material farmed or acquired from food and agricultural wastes, thus reducing the need for oil exploration and production.
"The approach documented in this patent builds a concept of renewable petroleum sources that have a reduced environmental impact," Catallo said.
The conventional processes of exploring, drilling for and transporting crude oil continue to impact the environment by disturbing the land at drilling sites and through accidents, such as oil leaks and spills. Besides further endangering high conservation value areas across the world, fossil fuel exploration and mining are not sustainable. Some experts predict that petroleum deposits will run out in 100 years at the current rate of use.
"It frequently is hard to specify how new knowledge will be used and how initial plans, when modified over years or decades, will turn out," Catallo said. "But this work has documented an exciting area of organic chemistry that has a wide range of basic and applied implications for environmental scientists, paleobiologists and chemists alike."
Petroleum is crucial to the manufacturing of a wide range of products. In addition to use as a fuel, petroleum is used in the generation of electricity; in materials such as plastic and asphalt; and in products such as fertilizer and pesticides, detergents, photographic film, paints and artificial fibers.
The next step for developers of the new production process is the construction of a pilot operation, with help from investors and external sources. This could be accomplished using the current infrastructure at local refineries and petrochemical plants, according to Dr. Thomas Klei, associate dean of research and advanced studies at LSU School of Veterinary Medicine.
One consequence of current petroleum exploration and production is the release of oily mud during drilling. The release has been greatly reduced through improved technology but still remains a concern. Noise pollution from seismic surveying to map the geologic structure in sea areas can disturb large fish and sea mammals. Large-scale mines today also contribute to surface and groundwater contamination of toxins, such as cyanide and arsenic.
"My approach is an environmentally friendly alternative to petroleum production," Catallow said. "No toxic chemicals are used in the process, no ecosystems are compromised by exploration and drilling activities, and no net increase of atmospheric greenhouse gases is involved in the process."
The current methods of petroleum production will likely continue to be widely used. But the use of biomass to produce petroleum could have a more immediate effect by limiting the need for petroleum exploration and by helping to start a trend toward alternate means of producing hydrocarbons.
For more information about energy sources and production, visit www.energy.gov/sources.
An Ion for an Ion
Edwards Air Force Base is testing ion exchange resin technology at North Base to clean up ammonium perchlorate groundwater contamination. Using a dual-function resin, the process could have Air Forcewide or even nationwide implications, according to James Specht, project manager.
"The base will serve as a proving ground for a cutting-edge perchlorate treatment technique that uses ion exchange resins to selectively remove perchlorate and a chemical regeneration process that may significantly reduce the cost of disposing of perchlorate waste," said Specht.
Edwards plans to refine and demonstrate the technology after testing, by cleaning up perchlorate-contaminated sites across the United States. A test demonstration at Site 285 in June tested the potential of resin and regeneration technologies. The location's groundwater had been earlier contaminated by perchlorate, as a result of solid-fuel rocket testing.
Nearly every state in the nation faces some perchlorate contamination, due to the varied industrial uses of the chemical. Perchlorate is found in solid-rocket propellant and is used in the manufacture of common items such as fertilizer and explosives like fireworks and those found in automotive air bags.
A lab test, developed by Oak Ridge National Laboratory (ORNL), used groundwater from Edwards and compared results using ORNL's bifunctional resin and two monofunctional resins. Results of the test under simulated field conditions found that ORNL technology removed perchlorate at nearly five times that of conventional methods.
ORNL's new resin selectively attracts perchlorate. Through selective ion exchange, perchlorate can be removed at concentrations below four parts per billion (ppb). Ion exchange resin technology involves chemical separation in which an ion of the contaminant is replaced by similarly charged ions on insoluble substances (the resin). The resin acts like a magnet that attracts the contaminant. Tetrachloroferrate displacement for regeneration of the resin cleans the resins for reuse.
"Regeneration of resin in a cost-effective manner is the real challenge for this technology," said Specht. "Bifunctional ion exchange resins may or may not pan out economically. However, its overall promise suggests there would be a definite advantage to moving the technology along to greater maturity, and the Air Force is committed to pushing the envelope."
According to Specht, advantages to selectivity for perchlorate include increased efficiency, because greater selectivity means that ion exchange can occur more rapidly. Also, more water can be treated before the bifunctional resin beds are saturated and need regeneration. "Significant changes in groundwater chemistry and high system operating costs may occur due to rapid resin saturation with other ions," he said. "If competitive ions are present, efficiency is reduced. And a change in groundwater chemistry may require remineralization."
Regulators will review the ion exchange treatability study work plan this year. Treatment system startup and testing will begin in 2002.
For more information, visit the Edwards Air Force Base environmental management site at www.edwards.af.mil/penvmng/index.html.
This article originally appeared in the September 2001 issue of Environmental Protection, Vol. 12, No. 9, p. 8.
This article originally appeared in the 09/01/2001 issue of Environmental Protection.
Jeff Wilson is managing editor of Environmental Protection.