United States
Environmental Protection
Agency
Research and
Development
(RD-672)
EPA/600/N-92/007
April 1992
v>EPA Science Notes
No. 1
Possible CFC
Substitutes,
Disposal Studied
ByORD
Potential CFC-114
Alternative
North Slope Study
As the December 31,1995, deadline approaches for phasing out U.S.
production of certain chemicals linked with stratospheric ozone
depletion, scientists with ORD's Air and Energy Engineering Research
Laboratory are helping to find ways to replace and dispose of these
compounds.
Using a state-of-the-art refrigeration test unit, the scientists are
evaluating potential substitutes for chlorofluorocarbons (CFCs). In
addition, they are conducting studies to evaluate whether incineration
is an efficient process for disposing of CFCs.
"We've been doing CFC research for five or six years now, which is
a fairly long track record for this relatively new line of study," said
Frank T. Princiotta, Director of the Laboratory, located in Research
Triangle Park, NC.
The ORD researchers have identified 11 chemicals that appear from
preliminary research to be good alternatives to CFCs. One of the
compounds is HFC-236ea, a hydrofluorocarbon that may be a potential
substitute for a CFC used mainly by the U.S. Navy.
Computer analysis show that the physical properties of HFC-236ea
are almost identical to those of CFC-114, used as a refrigerant in the
Navy's shipboard air conditioning systems. However, HFC-236ea does
not contain chlorine or bromine—the CFC components linked with
ozone depletion.
The ORD scientists are evaluating HFC-236ea to determine if it will
refrigerate as well as CFC-114, and if it poses any risks to human health
or the environment. Studies so far indicate that the hydrofluorocarbon
is nonflammable, and that it is unlikely to contribute to air pollution
that may lead to global warming.
The Laboratory has conducted some limited tests to assess the
toxicity of the compound, but more are needed before a definitive
evaluation can be made, according to N. Dean Smith, the project officer
for the study.
The Laboratory also is working with several petroleum companies
and the U.S. Coast Guard to find alternative chemicals to replace Halon
1301, a critical safety material at oil and gas production facilities on the
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northern coast, or North Slopes, of Alaska. Halons also have been
linked with stratospheric ozone depletion.
Chemically inert, Halon 1301 is released to stabilize the atmosphere
inside the North Slope buildings, thereby reducing the risk of a fire or
an explosion, whenever sensors detect any buildup of gas from any
leaks in pipelines or process equipment.
In looking at potential replacements, the ORD scientists initially
identified 32 perfluorocarbons, hydrofluorocarbons and
hydrochlorofluorocarbons with boiling points similar to that of
halon—an important consideration for determining whether the
potential substitutes would be compatible with the fire prevention
system used in the North Slopes buildings.
Some 20 of the compounds subsequently have been examined in
laboratory-scale tests for their ability to extinguish flames and prevent
explosions. More studies are planned to further assess their physical
properties, toxicity, compatibility with equipment used at the North
Slopes facilities, commercial availability, and environmental
characteristics.
Incineration Studies As CFCs and halons are phased out, users may look to incineration
as a way of disposing of remaining supplies. Some studies have shown
that other compounds—called products of incomplete combustion, or
PICs—can be generated by thermochemical reactions in the
combustion process.
ORD scientists are conducting research to better determine what
these materials are, why they form, and what quantities are produced.
In a small-scale study, the scientists recently incinerated two widely
used types of CFC refrigerants (CFC-11 and CFC-12), and analyzed
PIC emissions.
The study found a wide variety of PICs, an indication that complex
reactions occur during CFC incineration. Among these compounds
were dioxins and furans. The scientists theorized that trace amounts of
copper in the incinerator's flue duct, interacting with CFC combustion
products at the particular range of temperatures in the duct, may have
been partially responsible for these emissions.
Further tests are needed to determine how the creation of dioxins
and furans can be avoided, according to Robert E. Hall, one of the
project officers for the study. Hall theorized that modifications in
incinerator operating conditions can be made to prevent these
emissions in full-scale processes. For example, burning CFCs at
significantly higher temperatures than were used in small-scale
incinerator and injecting steam into the incinerator might eliminate
dioxin and furan and/or enhance destruction.
[Contact Rhoda Ritzenberg, Office of the Senior Official for Research
and Development, Research Triangle Park, NC 27711. Telephone (919)
541-2615.]
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Significant
Clean Up With
Fungus Seen In
Study
A field study by scientists at ORD's Risk Reduction Engineering
Laboratory provides new evidence that a common wood-degrading
fungus may be an effective means for cleaning up toxic waste.
The scientists applied white rot fungus to soil samples
contaminated with pentachlorophenol and other toxic compounds.
Through a series of biochemical reactions, the fungus transformed
significant amounts of the contaminants into safer materials.
ORD conducted the study at a Brookhaven, MS, site where a
company used PCP and creosote to treat telephone poles from 1946-
1986. The researchers laid out 11 plots of soil from a waste sludge pile,
sampled the plots to determine what contaminants were present at
what levels, and then applied white rot fungus using techniques
developed jointly by the Risk Reduction Engineering Laboratory and
the U.S. Department of Agriculture's Forest Service.
Spores from three species of white rot fungus were added to
specified plots in a statistically based experimental design. Wood chips
also were added as a food source for the fungi, which subsist on
cellulose in wood. Control plots were included as part of the study. The
experiment compared results from plots treated with different
combinations of the fungal species, at different concentrations.
Preliminary data show that PCP levels deceased to some extent in
the control plots. This was a result of naturally occurring biochemical
interactions between the contaminants and soil organics. However, the
treated plots showed significant further reductions as well. PCP
concentrations of up to 1,000 parts per million were reduced by 85 to
90 percent.
The study represents the first phase of a technology demonstration
under ORD's Superfund Innovative Technology Evaluation (SITE)
program, which fosters the development and commercialization of
new technologies for less costly, more efficient clean-up of hazardous
waste.
The ORD researchers are still analyzing the data including time-
series data that will provide snapshots of reduction levels all through
the course of the two-month study. A large-scale demonstration study
will be conducted later this year.
[Contact John Glaser, Manager, Soil Remediation Program, ORD Risk
Reduction Engineering Laboratory. Telephone: (513) 569-7568.]
New Risk
Assessment Policy
Set By EPA
Science Panel
An EPA science panel has established a significant new policy for
the agency on assessing human health risks from environmental
exposure to chemicals. Generally, risk assessments assume that any
chemical which causes tumors in test animals also may cause cancer in
humans. However, based on an extensive scientific review, a new
report by the EPA Risk Assessment Forum recommends for the first
time that agency risk assessors not use animal data under specific
conditions for trying to predict whether certain chemicals may pose a
cancer hazard for humans.
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The report pertains to studies that have found chemically induced
kidney tumors in male rats. Certain of these tumors apparently
resulted from a series of physiological processes that initially involved
an excessive accumulation in the kidney of alphas-globulin, a protein,
following exposure to high doses of chemicals such as 1,4-
dichlorobenzene, isophorone, d-limonene, and 2,2,4-trimethyl-pentane.
The same processes are not known to occur in the female rat or in
any other animal species. Consequently, these findings probably are
not relevant for trying to determine whether such compounds pose a
human cancer risk, according to the report.
The Risk Assessment Forum is composed of experts from
throughout EPA who develop scientific analyses, guidelines, and
methodology for the agency. The panel's reports are extensively peer-
reviewed by scientists from other agencies, academia scientific
organizations, and private industry .
Copies of the report, "Alpha2u-globulin: Association with
Chemically Induced Renal Toxicity and Neoplasia in the Male Rate"
(EPA/625/3-91 /019F) are available from the ORD Publication Office,
CERI-FLN, U.S. Environmental Protection Agency, 26 West Martin
Luther King Dr, Cincinnati, OH 45268; telephone (513) 569-7562. Also
available is a companion document, "The Report of the EPA Peer
Review Workshop on Alpha2u-globulin: Association with Renal
Toxicity and Neoplasia in the Male Rat" (EPA/625/3- 91/021).
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United States
Environmental Protection
Agency
Research and
Development
(RD-672)
EPA/600/N-92/010
July 1992
&EPA Science Notes
No. 2
Oysters: Pollution
Markers On The
Half-Shell
Scientists at EPA's Office of Research and Development (ORD)
laboratory in Gulf Breeze, FL, are evaluating the potential of oysters as
early-warning indicators of environmental problems in coastal waters.
The research is based on the fact that oysters, in the routine course
of feeding, will ingest and accumulate pollutants from the water
around them By examining these contaminants and determine if the
substances pose any risk to local ecosystem.
As a first step in their research, the scientists are trying to decide
which physiological tests would best indicate adverse effects. In a
preliminary study the researchers conducted 22 assays on 82 oysters
from six sites in Tampa Bay, FL, to assess (1) the specimens' physical
and metabolic conditions, (2) the presence of parasites and microbes in
their systems, (3) genetic abnormalities in their cells, and (4) the status
of their immune systems.
Some of the tests found physiological differences among oysters
collected at different sites in the bay (such as differing parasite levels
and variations in the condition of the digestive glands). This was
important for judging the general precision of the tests, even though
the preliminary analysis did not attempt to determine whether the
differences were due to contaminants at any of the sites, the scientists
noted.
Two factors made it difficult to assess some of the results clearly, the
study found. The researchers said these factors should be considered in
any future studies:
• Salinity: The salinity of the water differed at the various sites. Water's
salt content may affect some metabolic functions in oysters that
influence physiological and immunological responses. Therefore,
studies should look at oysters from both polluted and unpolluted
sites having the same salinity.
• Reproductive cycles: Some differences between oysters may be due to
the fact that the oysters are at different stages of the reproductive
cycle. Researchers should collect oysters at different times of the year
so that different reproductive stages are represented.
[Contact Raymond G. Wilhour, Acting Director, ORD Environmental
Research Laboratory, Gulf Breeze, FL 32561; (904) 934-9213.]
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Minimizing
Waste:
Case Studies
ORD has published a collection of case studies from four programs
that help companies and federal agencies find ways to prevent
pollution by minimizing hazardous waste from manufacturing
processes and other operations.
The programs are funded by ORD's Risk Reduction Engineering
Laboratory and provide technical assistance, demonstration projects,
and technology transfer through universities, state and local
governments, and federal scientists. They are:
• The Waste Reduction Innovative Technology Evaluation Program,
conducted with the states of California, Connecticut, Illinois,
Minnesota, New Jersey, and Washington, and Erie County, NY.
• The Waste Minimization Assessments Program, conducted under a
cooperative agreement with the New Jersey Department of
Environmental Protection and the New Jersey Institute of
Technology.
• The University-Based Assessments Program for small businesses,
conducted with the University City Science Center, Philadelphia,
PA.
• The Waste Reduction Evaluations at Federal Sites Program, a
cooperative pro- gram involving EPA, the Department of Defense,
the Department of Energy, and other federal agencies.
Projects discussed in the case studies include these:
• A small chemical manufacturer was looking for ways to reduce
chemical wastes from the production of acrylic emulsions and other
specialty mixtures. Researchers suggested that the company
upgrade some of the sensing and control devices on its reactor lines,
and install a gas-fired dry-off oven to reduce the volume of sludge
hauled off-site.
• A manufacturer of aluminum parts sought advice on reducing
toluene wastes from a solvent-based painting process. Researchers
suggested that the company convert to an electrostatic-powder
painting system.
• Researchers assisting an ice-machine manufacturer found that the
company discharged 5 million gallons of waste water per year from
rinsing steel sheets. Researchers recommended that the company
recycle the rinse water instead of discharging it. In each instance,
long-term savings would offset a one-time investment cost for
taking the suggested action, the case studies indicate. For example,
switching to an electrostatic painting process would cost the
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EPA Outlines
Framework For
Ecological Risk
Assessment
aluminum company $147,580, but the change would net $1 million
in annual savings from elimination of solvent wastes and the lower
cost of powder coatings.
[For further information on the programs, contact Harry Freeman, Risk
Reduction Engineering Laboratory, (513) 569-7529. "Pollution
Prevention Case Studies Compendium" (EPA/600/R-92/046) is
available from the EPA Center for Environmental Research
Information, Cincinnati, OH 45268; (513) 569-7562]
EPA has taken a first step in a long-term effort to develop agency-
wide risk assessment guidelines for ecological effects.
The agency recently issued "Framework for Ecological Risk
Assessment" (EPA/600/R-92/001), a new report that outlines a simple,
flexible approach for conducting and assessing ecological risk
assessments. The non-mandatory document is intended to foster
consistent approaches to ecological risk assessments, identify key
issues, and provide a foundation for development of future guide-
lines.
The report recommends a three-phase approach:
• Problem Formulation: A planning process to establish the goals,
breadth, and focus of the risk assessment.
• Analysis: Using scientific information to develop profiles of
environmental exposures and adverse ecological effects.
• Risk Characterization: Integrating exposure and effects data to
describe the expected risk.
The recommendations, which were developed by EPA's Risk
Assessment Forum, reflect input from numerous ecologists and
ecotoxicologists from EPA, other Federal and state agencies, academia,
and industry, including scientists who met in two peer review
workshops.
Copies of the document are available from the EPA Center for
Environmental Research Information, telephone (513) 569-7562. Also
available are two related documents, "Peer Review Workshop on a
Framework for Ecological Risk Assessment" (EPA/625/3-91/022) and
"Report on the Ecological Risk Assessment Guidelines Strategic
Planning Workshop" (EPA/630/R-92/002).
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United States
Environmental Protection
Agency
Research and
Development
(RD-672)
EPA/600/N-92/014
August 1992
&EPA Science Notes
No. 3
ORD Studies
New Way To
Deliver Cleanup
Agents
Mobile homes for contaminant-fighting bacteria? That could be one
way of describing a new process being studied by EPA's Office of
Research and Development (ORD) for storing and releasing
microorganisms to clean up hazardous waste and prevent pollution.
The technique is encapsulation, and scientists in ORD's Gulf Breeze,
FL, Environmental Research Laboratory think it has potential for
enhancing the ability of certain types of bacteria, fungi, and other
minute life forms to convert toxic organic compounds into simpler,
non-hazardous materials through biochemical reactions.
Encapsulation involves surrounding a microorganism with an
environmentally safe polymer material, and then dehydrating it. The
resulting product "looks like crumbly powder, in odd shapes and
sizes," according to Hap Pritchard, chief of Gulf Breeze's Microbial
Ecology and Biotechnology Branch.
Already used in agriculture for controlled release of pesticides,
encapsulation could offer several valuable features for bioremediation
and pollution prevention:
• Pollution-fighting microorganisms could be conveniently
transported and stored. Preliminary studies show that cells
encapsulated in a polyvinyl alcohol material have a shelf life of
about two months.
• Release of the microorganisms could be controlled for maximum
effectiveness. For example, the cells could be applied to pesticide-
treated fields, and would remain inactive while the pesticides
functioned to protect crops. However, if heavy rains came, creating
the potential for the pesticides to leach into soil and groundwater,
the shell material would dissolve, freeing the microorganisms to
block contamination.
• The microorganisms could be co-encapsulated with nutrients that
would enhance their activity. Thus, these additives could be
specially used for the added microorganisms, out of the reach of
indigenous, competitive organisms.
Preliminary small-scale tests at Gulf Breeze have shown promising
results for degradation of toxic 2,4-D. Further laboratory studies
simulating field conditions are planned.
[Hap Pritchard, Microbial Ecology and Biotechnology Branch, Gulf
Breeze ERL, (904) 934-9260.]
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ORD, DOE
Collaborate On
Portable Toxics
Monitor
EPA's Office of Research and Development (ORD) and the
Department of Energy's Oak Ridge National Laboratory in TN have
collaborated to develop a portable analytical device to speed cleanups
at hazardous waste sites and leaking underground storage tank sites.
One way of using the device, called a synchronous luminescence
(SL) monitor, is to attach a fiber-optic probe for on-site analysis of
organic contaminants. The monitor, which is battery-powered and
about the size of a small suitcase, can be carried to the field and can
provide on-site readings of fluorescent toxic or hazardous organic
compounds, such as polyaromatic hydrocarbons (PAHs) or
polychlorinated biphenyls (PCBs) even at levels as low as parts per
billion.
Cleanup of a waste site begins with the process of analyzing
samples from the site to identify the "hot spots" where the most
hazardous wastes occur in the largest amounts, allowing those parts of
the site to be cleaned up first. Under conventional methods, soil and
water samples are taken from the site and analyzed at a laboratory to
provide that information.
The SL monitor makes that activity faster and simpler because:
• The monitor, a field screening instrument, can immediately analyze
water samples on-site, reducing the number of samples that need to
be sent to a laboratory for analysis. A quick micro-extraction step
also readies soil samples for on-site analysis.
• Under conventional methods, samples are sent to the laboratory,
but the analytical information may not be available for several
weeks. As a field screening instrument, the SL monitor provides
immediate analysis that helps to identify the location of the
hazardous waste "hot spots," so that cleanup can begin at once.
After the cleanup operation, samples may be taken for more
accurate laboratory analysis to confirm the effectiveness of the
hazardous waste removal.
The SL monitor was developed by Tuan Vo-Dinh, group leader of
the Advanced Monitoring Development Group, Health and Safety
Research Division, Oak Ridge National Laboratory, with major funding
by ORD. The product will be manufactured and commercialized by
Environmental Systems Corp., Knoxville, TN.
[Contact William H. Engelmann (702) 798-2664 or Charlita G. Rosal
(702) 798-2179, Advanced Monitoring Systems Division,
Environmental Monitoring Systems Laboratory.]
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United States Research and EPA/600/N-93/004
Environmental Protection Development February 1993
Agency (RD-672)
vvEPA Science Notes
No. 4
Studying Climate Scientists in EPA's Office of Research and Development (ORD) are
/~>i . T-1 i preparing to recreate the evergreen tree stands of the U.S. Pacific
° * Northwest in high-tech miniature.
High-Tech Their purpose: to better predict the possible effects of climate
change on North American plant life.
Twelve terracosms, or miniature stands of Douglas fir in specially
controlled test chambers, are being constructed at ORD's
Environmental Research Laboratory in Corvallis, OR, under the TERA
(Terrestrial Ecophysiological Research Area) research project. The trees
will be planted this spring — 20 per chamber — and scientists expect
to begin collecting data this summer. The study is expected to take
three or four years.
The trees in each terracosm will be exposed to different elevated
temperatures and different elevated levels of carbon dioxide to
simulate potential future conditions associated with global warming.
Using state-of-the-art monitoring equipment, the scientists then will
measure the trees' growth, rates of photosynthesis, and other
biological processes to identify changes that may be associated with
those environmental variations.
The conditions in the chambers will simulate potential climate
changes that could result from increases of carbon dioxide and other
"greenhouse gases" in the environment, based on computer models.
Although some researchers outside EPA are studying the individual
effects of temperature or carbon dioxide change on trees, TERA will be
unique in addressing the joint effects of these factors, said David T.
Tingey, the project officer for the study.
If global warming occurs, "both the temperature and CO2 levels
should change," Tingey said. "So it's important to see how the plant
responds to that joint change."
The Douglas fir was chosen for the study because of its ecological
importance in the Pacific Northwest (it is the first species of tree to
return to a site that has been cleared) and its economic importance (it is
the major species commercially harvested and replanted in the region).
[For further information, contact David T. Tingey, Program Leader,
Global Processes and Effects, Corvallis Environmental Research
Laboratory, tel: (503) 754-4621.]
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United States
Environmental Protection
Agency
Research and
Development
(RD-672)
EPA/600/N-93/018
October 1993
v>EPA Science Notes
No. 5
Research To Aim
DNA Process At
IDing Parasite
Police laboratories use an advanced DNA technique called polymerase
chain reaction (PCR) to help catch criminals. Under a new cooperative
research and development agreements (CRADA), the Environmental
Protection Agency's Office of Research and Development (ORD) will
conduct a collaborative study with Roche Molecular Systems, Inc., to
determine if the same process can be used to make a positive ID on a
microscopic, disease-causing parasite.
ORD's Environmental Monitoring Systems Laboratory-Cincinnati
(Ohio) will work with the company a subsidiary of Hoffmann-La
Roche, Inc., to develop and evaluate the use of PCR for identifying the
infectious form of the Giardia parasite from water through analysis of
DNA material in laboratory samples. Giardia, which is carried in the
feces of infected humans and animals, causes gastrointestinal disorders
in humans.
Compared with current methods, PCR offers potentially a faster
and more precise tool for detecting and identifying Giardia parasites
infectious to humans, according to Mark Rodgers, a molecular
biologist with the ORD laboratory who will serve as the EPA principal
investigator under the agreement.
Among its many current applications outside the area of
environmental research, PCR is used by police laboratories in
analyzing hair, blood, or other evidence found at crime scenes and
matching a specimen with an individual through comparison of DNA.
In the PCR process, scientists use biochemical reactions at the
molecular level to make multiple copies of a given DNA segment or
sequence that serves as a unique "marker" for a particular organism.
The purpose is to produce enough copies so that this particular
sequence stands out from millions of other genes in a laboratory
sample, making it easily identifiable using a gene probe.
The PCR process requires these components: a specific double-
stranded DNA sequence as a template or model for the formation of
copies; two primers, or single strands of synthetic DNA that
biochemically complement the strands of the template; DNA
polymerase, an enzyme that initiates the synthesis of DNA chains; and
oligonucleotides, the building blocks for producing DNA.
Researchers apply heat and reagents to separate the double strands
of the template, then lower the temperature to bind each strand to its
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complementary primer. The polymerase acts as a catalyst to begin the
replication, in each of the newly paired set of strands, of the sequence
of genetic material unique to the template. Each time the cycle is
repeated, additional copies of the segment are made.
Under the CRADA, EPA and Roche will develop and validate
methods for recovering Giardia genetic material from water samples,
compare different PCR systems for creating copies of DNA sequences
unique to the parasite, and select and test the system that appears to be
the most effective for identifying this parasite.
One major aim of the cooperative study will be to find methods for
separating Giardia DNA material in water samples from substances
that chemically inhibit the action of DNA polymerase, Rodgers said.
These "inhibitors" include substances such as humic acid (formed by
the organic breakdown of leaves) that are commonly found in organic
debris in water, the EPA scientist noted. EPA and Roche will both
provide research personnel and expertise. Additionally, EPA will
provide analytical samples, and the company will provide
instrumentation and special reagents for the tests. The research is
starting this month.
The Federal Technology Transfer Act authorizes EPA laboratories to
enter into CRADAs with private industry and academic institutions to
more effectively develop and commercialize innovative, cost-effective
environmental technologies.
[For additional information, contact Larry Fradkin, EPA Federal
Technology Transfer Act coordinator, telephone (513) 569-7960.]
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United States
Environmental Protection
Agency
Research and
Development
(RD-672)
EPA/600/N-94/008
July 1994
vxEPA Science Notes
No. 6
'Netting' New
Data On
Ultraviolet
Exposure
The sun also rises...and when it rises, it bathes the earth in ultraviolet (UV)
rays. Increasingly, scientists are examining the environmental effects of this
everyday solar activity. But they lack definitive data to answer many of the
questions their studies raise.
For example, how do UV levels change over time, and what causes those
changes? How do actual ground-level exposures compare with
measurements taken above the atmosphere by satellites? What exposures are
associated with specific adverse effects in humans, animals, and ecosystems?
To further scientists' ability to answer such questions, the U.S.
Environmental Protection Agency's (EPA) Office of Research and
Development (ORD) is establishing a network of sites using high-tech
instrumentation to measure ground-level UV exposures. The fourth and
latest station in the network begins operation this month in the Washington,
DC, area.
At each site, a sophisticated device called a spectrophotometer switches
on automatically at sunrise. Through the day, in recurring cycles, it measures
UV intensity as well as atmospheric levels of ozone, sulfur dioxide, and
nitrogen dioxide, which affect the amount of UV that reaches the earth's
surface. The data are stored in nearby computers.
The network will measure intensities across the UV spectrum. Once they
have a long-term record of these detailed data, ORD scientists anticipate that
researchers will be able to say whether, and why, fluctuations in ground-level
UV are occurring. The data also will help scientists study the effects of UV
exposure by better defining the portions of the UV spectrum at which effects
are seen.
The first site in the network began operation more than a year ago in
Research Triangle Park, NC. Other sites followed in June 1994 in Boston and
the Atlanta area. In all, 15 stations were planned.
The data from the network also will enhance the mathematical models
used by the National Weather Service to predict UV exposures under an
experimental index announced June 28. The data will help "ground-truth"
the index; that is, it will reduce the amount of extrapolation that scientists
currently must use to account for cloud-cover and other conditions when
they calculate ground-level exposures from measurements taken above the
atmosphere by satellites.
[For further information, contact Larry T. Cupitt, Director, Methods Research
and Development Division, Atmospheric Research and Exposure
Assessment Laboratory, ORD, (919) 541-2454.]
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United States
Environmental Protection
Agency
Research and
Development
(RD-672)
EPA/600/N-94/012
September 1994
&EPA Science Notes
No. 7
Water Weeds:
Experimental
Cleanup Tool
How to get rid of soil contamination from trinitrotoluene (TNT) wastes
at old munitions sites? Weed it out. That's the promising technique
being tested by the U.S. Environmental Protection Agency's (EPA)
Office of Research and Development (ORD).
The experimental process developed by scientists from ORD's
Athens (Ga.) Environmental Research Laboratory uses common pond
weeds to transform TNT in contaminated soil into non-hazardous
materials through enzyme reactions.
With support from the interagency Strategic Environmental
Research and Development Program (whose participants include the
Departments of Defense and Energy and EPA), ORD has moved the
process on a fast track from bench study to pilot-scale field research.
The plants, which include stonewort, hornwort, and parrot feather,
contain enzymes called nitro-reductase that react with the nitro group
on the TNT molecule. After these enzymes break the compound down
into triaminotoluene, another enzyme called laccase oxidizes the
triaminotoluene rapidly into biodegradable materials.
In a scaled-up pilot study researchers created an artificial pond
containing contaminated soil, and added parrot feather to the water.
In-situ remediation at a hazardous waste site would involve the same
process on a larger scale. In the pilot, the treatment successfully
reduced saturated TNT levels in the water from 128 parts per million
(the water solubility of TNT under the conditions of the test) to below
the limit at which the compound is detectable (10 parts per billion) in
about three days.
To identify the right plants for the job, the researchers used a simple
test called an immuno-specific assay. They mashed different types of
common aquatic plants, extracted liquid from each sample, and added
the individual extracts to a clear solution containing an antibody that
reacts chemically with nitro-reductase. The researchers were able to
determine which extracts contained the enzyme by seeing which ones
turned the solution blue.
An EPA patent is pending on the cleanup process, and other
scientists are pursuing further research to apply the technique to
treatment of chlorinated solvents and other organic pollutants.
[For further information, contact Lee Wolfe, Research Chemist, Athens
Environmental Research Laboratory, ORD, (706) 546-3429.]
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Energy-tfficiency In Europe, some refrigerator manufacturers have begun to use
Seen in Possible hydrocarbon mixtures as coolants to replace chlorofluorocarbons,
which have been linked with stratospheric ozone depletion. In the U.S.,
Alternatives interest is growing but manufacturers and consumers have questions:
Do these mixtures perform well? Do they pose concerns about
flammability?
As part of its ongoing research on potential CFC alternatives (EPA
Science Notes, April 1992), ORD's Air and Energy Engineering Research
Laboratory is addressing these questions. In recent tests, scientists
found that two mixtures of isobutane and propane in refrigerators
cooled just as well as the widely used chlorofluorocarbon CFC-12, and
consumed 3 percent less energy. The mixtures contained, respectively,
60 percent isobutane and 40 percent propane, and 70 percent isobutane
and 30 percent propane.
The laboratory also is assessing whether, with the addition of
flame-suppressing fluoroiodocarbons, the mixtures become less
flammable with no reduction in performance. This research is
continuing.
[For further information, contact Evelyn Baskin, Air and Energy
Engineering Research Laboratory, ORD, (919) 541-2429.]
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