In the Lab
Study: Worldwide CFC Ban Slowing Destruction of Ozone Layer
Thanks to a worldwide reduction in chlorofluorocarbon (CFC) pollution, the rate at which ozone is being destroyed in the upper stratosphere is slowing, according to a new study.
"This is the beginning of a recovery of the ozone layer," said Professor Michael Newchurch of the University of Alabama in Huntsville (UAH), the scientist who led the ozone trend-analysis research team. "We had a monumental problem of global scale that we have started to solve."
Using data from three NASA satellites and three international ground stations, the team found that ozone depletion in the upper stratosphere has slowed since 1997. The results of this work have been accepted for publication in the American Geophysical Union's Journal of Geophysical Research -- Atmospheres.
Ozone is a damaging pollutant in the lower atmosphere near the ground, but in the stratosphere, it shields the Earth from harmful ultraviolet solar radiation. Almost 30 years ago, scientists Mario Molina, F. Sherwood Rowland and Paul Crutzen showed that chlorine released into the stratosphere from CFCs, chemicals used as refrigerants and aerosol propellants, was destroying the protective ozone layer. This discovery led to an international ban on CFC-based products and to the 1995 Nobel Prize in Chemistry for the three scientists.
"There have been several amendments to that ban, each of which tightened restrictions on CFCs and other halogenated hydrocarbons," said Newchurch, an associate professor of atmospheric science at UAH. "We are now at the point where restrictions are tight enough to result in measured turnaround of CFC amounts at the surface. Now, we can say that what we're doing is working, and we should continue the ban."
New Catalyst May Reduce Cause of Acid Rain, Smog
With the help of a $200,000 grant from the U.S. Department of Energy, over the next three years researchers at Hampton University will design and test a tin oxide-based catalyst designed to remove large amounts of nitrogen oxide from power plant gases.
Hampton chemical engineering professors Jale and Ates Akyurtlu will study how to turn nitrogen oxide into two harmless gases: nitrogen and oxygen.
"The main goal of the research is to design a catalyst which will eliminate nitrogen oxide from power plant stacks," said Jale Akyurtlu.
Nearly 30 million tons of nitrogen oxide, a known cause of acid rain and urban smog, is released into the earth's atmosphere each year and is largely responsible for serious respiratory problems. The United States, with numerous power plants and motor vehicles, is accountable for nearly two-thirds of the emissions.
Hampton University professors, along with their students, will determine whether a tin oxide-based catalyst could be the solution for eliminating nitric oxide, a harmful side product of combustion in power plants, like carbon monoxide and sulfur dioxide.
The emphasis of the study will be on the catalysts' ability to resist poisoning, which can reduce the life of the catalyst and the effect of temperature on catalyst performance.
"We will look at the composition of the catalyst, the pre-treatment and preparation as well as the cost effectiveness and its long-term performance," said Jale Akyurtlu. "We want to know how it will perform for nitrogen oxide removal in the presence of various stack gas components; also, overtime, whether it will survive under realistic power plant conditions."
The researchers will use simulated smokestack gases and various versions of catalysts to test the effectiveness of the design and the atmospheric output.
"We hope that the findings from this study will result in a feasible industrial process for the abatement of nitrogen oxides from stationary sources," said Jale Akyurtlu.
Catalysts usually work at high temperatures, but the tin-based catalyst is expected to work at lower temperatures, and is also being studied by NASA for use in catalytic converters, which turn car exhaust into harmless gas. The idea to use the tin-based catalyst originally came from NASA and has been used to regenerate carbon dioxide for a space laser to study winds in the atmosphere.
"This is a great evolution and good interaction for both science and technology to go forward," said Jale Akyurtlu about working with the NASA idea.
The researchers are excited about the potential findings and how it will impact the future, but acknowledge that this is an early step in the research.
"There are many factors that need to be investigated to see what the best conditions are to prepare and use the catalyst," said Ates Akyurtlu. "There are many tests that need to be conducted before we can see this become a commercial product."
For more information, visit www.hamptonu.edu.
Pathogen Genome Sequence Helps Protect Food Supply
U.S. Department of Agriculture (USDA) officials have announced the release of the 10X draft genome sequence of Fusarium graminearum, the microorganism that causes head blight (scab) in both wheat and barley.
Researchers at the Whitehead Institute at the Massachusetts Institute of Technology (MIT), Center for Genome Research, in partnership with the International Gibberella zeae Genomics Consortium, released the initial draft of the genome sequence of this fungal plant pathogen. A roadmap for scientists to better understand a microorganism, the availability of the sequence will greatly increase the odds that control measures can be developed, preventing the large-scale losses that have been caused by this pathogen in the past.
Wheat scab epidemics in the 1990s resulted in more than $3 billion in losses to U.S. farmers, devastating farm communities in the upper Midwest and elsewhere. Now, the disease is also threatening the world's food supply due to recent outbreaks of head blight in Asia, Europe, Canada and South America.
"This research, funded by USDA's Cooperative State Research, Education and Extension Service's (CSREES) National Research Initiative (NRI) is critical to controlling and eliminating a grain production problem as well as ultimately a food safety concern," said Colien Hefferan, CSREES administrator. "This microorganism and its impact on U.S. and world agriculture, as well as animal and human health, must be mapped for better understanding and control."
As a food safety issue, vomitoxins produced by the fungus pose a serious hazard to human and animal health by inhibiting cellular protein production. Vomitoxin causes weight loss and feeding refusal in non-ruminant livestock. Human ingestion of grain contaminated with F. graminearum has been associated with illness characterized by nausea, vomiting, anorexia and convulsions with possible long-term effects on resistance to infectious disease by altering immune response.
"CSREES's NRI is proud to support basic research projects, such as the sequencing of the F. graminearum genome, which are the basis for improved control of pathogens that threaten agricultural security and plant productivity, as well as animal and human health," said Hefferan.
For information about Fusarium graminearum and this project, go to www.genome.wi.mit.edu/annotation/fungi/fusarium/index.html.
Study: City Air Pollution Tougher on Country Trees
Trees planted downwind of city pollution grow only half as well as identical trees planted within the city -- a finding that ecologists in a Cornell University-based study, reported in the July 10, 2003, issue of Nature, attribute to an atmospheric-chemistry "footprint" that favors city trees.
"I know this sounds counterintuitive, but it's true. City-grown pollution -- and ozone in particular -- is tougher on country trees," said Jillian Gregg, lead author of the Nature article.
As a graduate student pursuing a PhD in ecology, Gregg started planting identical clones of cottonwood trees at sites in and around New York City, including the New York Botanical Garden and the Hunts Point water works in the Bronx, a Consolidated Edison fuel depot in Astoria, Queens, as well as Long Island's Brookhaven National Laboratory in Upton, Eisenhower Park in Hempstead, and the Cornell Horticultural Research Laboratory in Riverhead. She also planted cottonwood clones at the Millbrook Institute about 50 miles north of Manhattan.
With a goal to show the impact of city life on plants, the fast-growing cottonwoods were to serve as a kind of "phytometer" to gauge the net effect of urban and industrial pollutants on urban and rural ecosystems.
For three consecutive growing seasons, Gregg returned to the sites to plant cottonwoods, harvesting them to weight their biomass and to perform other analyses. She controlled for differences in light, precipitation, season length and soil factors, making air quality the primary factor of concern.
The city trees thrived, with an urban biomass that was sometimes "double that of rural sites," as reported in Nature.
While Gregg knew that some fallout from pollutants and warmer microclimates in "heat islands" could actually enhance plant growth, nutrient budgets, chamber experiments and regression analyses showed that these factors could not account for the increased urban tree growth.
The difference is ozone, according to the researchers. While desirable in the upper atmosphere, excess ozone at ground level can interfere with plants' metabolism, with severe exposures resulting in necrosis. But, in some areas of New York City, Gregg and her colleagues have found "footprints" of lower-than-expected ozone exposures. "Ozone is what we call a secondary pollutant. So while the primary precursors for ozone are emitted in the city, they must act in the presence of sunlight, over time, before ozone is formed. By then, the air mass has moved to rural environments," she said.
New York City is in fact downwind from New Jersey, another densely populated and industrialized region. However, Gregg said the reactions of ozone formation are cyclical, with the presence of one of the primary precursors, nitric oxide -- which occurs in high concentrations in the urban atmosphere -- destroying ozone once it has formed. As new nitric oxide compounds develop, three-atom oxygen is reduced to the more benign, two-atom kind.
Nitric oxide concentrations are low in most rural areas, so ozone remains in the atmosphere there and plants' exposure period to the harmful gas is extended, according to researchers.
Other authors of the Nature report and study participants include Clive Jones, an ecologist at the Institute of Ecosystem in Millbrook, and Todd Dawson, professor of integrative biology at the University of California, Berkeley, and a professor at Cornell when the study began.
This news item originally appeared in the October 2003 issue of Environmental Protection, Vol. 14, No. 8.
This article originally appeared in the 10/01/2003 issue of Environmental Protection.