(Press-News.org) A team of scientists has, for the first time, completely characterized an important chemical reaction that is critical to the formation of ground-level ozone in urban areas. The team's results indicate that computer models may be underestimating ozone levels in urban areas during episodes of poor air quality (smoggy days) by as much as five to 10 percent.
Ground level ozone poses significant health hazards to people, animals and plants; is the primary ingredient of smog; and gives polluted air its characteristic odor. It is known that even small increases in ozone concentrations can lead to increases in death from respiratory problems. Because of the health hazards caused by ozone exposure, the research team's results may have regulatory implications.
The team's research, which was funded by the National Science Foundation (NSF), NASA and the California Air Resources Board CARB), appears in the October 29 issue of Science.
Big role of one reaction in predicting ozone in smoggy air
The reaction studied by the researchers plays an important role in controlling the efficiency of a sunlight-driven cycle of reactions that continuously generates ozone. In this reaction, a hydroxyl radical (OH) combines with nitrogen dioxide (NO2), which is produced from emissions generated by vehicles, various industrial processes and some biological processes.
When a hydroxyl radical and nitrogen dioxide collide, these molecules may stick together to form a stable byproduct known as nitric acid (HONO2). Because of the stability of nitric acid, its formation locks up hydroxyl radicals and nitrogen dioxide, and thereby prevents these molecules from contributing to ozone formation; this reaction thereby slows the formation of ozone.
Although scientists have long recognized the importance of the formation of nitric acid, they have, until now, been unable to agree on the speed, or "rate," at which hydrogen radicals and nitrogen dioxide combine to form this end product. "This reaction, which slows down ozone production, has been among the greatest sources of uncertainty in predicting ozone levels," said Mitchio Okumura of the California Institute of Technology--a member of the research team. This uncertainty has affected computer models that simulate air pollution chemistry.
An experimental challenge
Why is there so much uncertainty about the speed or rate of formation of nitric acid? In large part, because instead of combining to form a stable form of nitric acid, a hydroxyl radical may combine with nitrogen dioxide to form a less stable form of nitric acid (HOONO)--a snake-like molecule that quickly breaks apart in the atmosphere. This breakdown of the unstable form of nitric acid releases its hydroxyl radical back into the atmosphere where it may once again become available to form ozone; this breakdown therefore speeds the formation of ozone. Nevertheless questions about the existence, amount, speed and formation of the unstable form of nitric acid have, until now, complicated measurements of the speed or rate of the formation of the more stable form of nitric acid.
But through experiments conducted at the Jet Propulsion Laboratory (JPL) and at the California Institute of Technology using state-of-the-art techniques, Okumura and his colleague, Stanley P. Sander at JPL, led a team of researchers that accurately measured: 1) the overall speed at which hydroxyl radicals and nitrogen dioxide combine, or react, in given atmospheric conditions; 2) the ratio of stable nitric acid to unstable nitric acid that is formed under given atmospheric conditions.
In addition, new laser methods enabled researchers to directly detect the presence of the unstable form of nitric acid in microseconds. And with the help of companion calculations performed at Ohio State by Anne McCoy, they could quantify its yield as soon as it was formed.
The research team's experiments show that the stable form of nitric acid forms slower than previously believed. These results indicate that there is more OH available in polluted, ground-level air for the formation of ozone than previously believed, and thus probably more ozone in the atmosphere than previously predicted.
More ozone than previously believed
To demonstrate the significance of the new results, modelers on the research team led by Robert Harley and William Carter fed their newly quantified reaction rates and ratios into computer models to predict levels of ground-level ozone during the summer of 2010 in the Los Angeles Basin. Their results indicate that many current models have been underestimating ground-level ozone levels in the most polluted areas (where nitrogen dioxide is highest) by about 5 to 10 percent. The research team concluded that relatively small changes in the rates and proportions of reactions forming unstable and stable nitric acid could lead to small but significant changes in ground-level ozone levels.
The importance of the study
"The study illustrates the importance of developing new and improved experimental approaches that interrogate atmospheric systems at the molecular level with high accuracy," said Zeev Rosenweig, an NSF program officer. "This is imperative to reducing uncertainties in atmospheric model predictions."
"The determination of a more accurate value of the rate of nitric acid formation from a hydroxyl radical and nitrogen dioxide will be important in future air-quality modeling," said Anne B. McCoy, a member of the research team. "The research was made possible by bringing together several laboratories with different capabilities and expertise, including my lab at Ohio State, and labs at CalTech, JPL and Berkeley."
Regulatory implications
The ozone prediction models incorporated into the research team's study are similar to those used by regulatory agencies, such as the Environmental Protection Agency and the California Air Resources Board. Therefore, the team's results may have implications for future predictions of ground-level ozone used by regulatory agencies in developing air quality management plans.
INFORMATION: END
A recent scientific discovery made by researchers at the Institut de recherches cliniques de Montréal (IRCM) led by Dr. Javier Marcelo Di Noia, Director of the Mechanisms and Genetic Diversity research unit, was published online today by The Journal of Experimental Medicine. The team identified a mechanism regulating activation-induced deaminase (AID), which could be important for the therapy of some types of lymphoma and leukemia.
AID is a B-lymphocyte enzyme that creates deliberate mutations in the DNA encoding antibodies, which helps produce an appropriate immune ...
Because primary lung adenocarcinoma is exceedingly rare in the pediatric population, it is difficult to properly classify certain lung tumors in children and adolescents. While anecdotal reports of pediatric patients with lung cancer lesions exist, little research has been conducted to link the disease in children to similar pulmonary malignancies in adults. Through an assessment of clinical, tissue-based and molecular data for pediatric lung cancer, research published in the November edition of the Journal of Thoracic Oncology determined that pulmonary lesions found in ...
Tracy Collier, an employee at Home Technologies in Newport News, Virginia, was walking her employer's Westie around the Center's manmade lake on Thursday when she saw a large, mysterious blob floating in the water.
Co-worker Charlie Schmuck says "The lake is behind our office. Tracy was walking by the lake, saw the object, and asked everyone else to come out and take a look."
Tracy thought it was "a huge dead snake."
Charlie thought it "looked like some weird underwater fungus, like the ones that explode when you poke them."
Perhaps because it was just a few days ...
The Institute of Medicine (IOM) recently released a study, The Future of Nursing: Leading Change, Advancing Health. The report calls for new and expanded roles for nurses in a redesigned health care system. It recommends improving education for all nurses and allowing nurses to practice to the full extent of their license and ability. It advocates overhauling state scope of practice acts and suggests that advanced practice registered nurses (APRNs) -- certified registered nurse anesthetists, certified nurse-midwives, clinical nurse specialists, and certified nurse practitioners ...
Boston – November 1, 2010 – The Autism Consortium, an innovative Boston area collaboration of researchers, clinicians, funders and families dedicated to catalyzing research and enhancing clinical care for autism spectrum disorders (ASDs), announced that it will begin a new initiative on Translational Medicine and Autism Therapeutics. The new focus was introduced at the Consortium's fifth annual symposium held October 26th, 2010, at Harvard Medical School in Boston.
"As scientists are starting to connect genetics to brain function and behavior, we believe it is time ...
CHAMPAIGN, Ill. — Money may not grow on trees, but energy could grow in grass. Researchers at the University of Illinois have completed the first extensive geographic yield and economic analysis of potential bioenergy grass crops in the Midwestern United States.
Demand for biofuels is increasing as Americans seek to expand renewable energy sources and mitigate the effects of fluctuating energy prices. Corn ethanol is the main biofuel on the market, but demand for ethanol competes with corn's availability as a food, and rising ethanol consumption could lead to higher food ...
BOSTON (3:00 p.m. ET, November 1, 2010) — A class of compounds that interferes with cell signaling pathways may provide a new approach to cancer treatment, according to a study published online this week in the Proceedings of the National Academy of Sciences (PNAS) Early Edition. The compounds, called PITs (non-phosphoinositide PIP3 inhibitors), limited tumor growth in mice by inducing cell death.
"PITs cause cells to self-destruct by interfering with the signaling pathways that regulate cell survival. As compounds that promote cell death, PITs show promise in halting ...
Anger is an interesting emotion for psychologists. On the one hand, it's negative, but then it also has some of the features of positive emotions. For a new study published in Psychological Science, a journal of the Association for Psychological Science, researchers find that associating an object with anger actually makes people want the object—a kind of motivation that's normally associated with positive emotions.
People usually think of anger as a negative emotion. You're not supposed to get angry. But anger also has some positive features. For example, it activates ...
Excess nitrogen from agricultural and urban lands is contaminating groundwater, streams, lakes and estuaries, where it causes harmful algal blooms and contributes to fish kills.
Cost-effective approaches to removing this nitrogen from croplands and urban stormwater runoff before it reaches sensitive water bodies have been elusive.
But simple and inexpensive technologies are on the horizon. A recent scientific workshop on denitrification brought together ecologists, engineers and policy experts to find answers.
Denitrification is a biological process carried out by ...
Researchers at New York University's Courant Institute of Mathematical Sciences have developed a novel algebraic model of DNA "hybridization," a process central to most biotechnology devices that monitor changes in cell's gene expression or characterize a cell's genome. Their work, which is described in the journal Physical Review E, provides an additional tool for understanding how biological systems function and could enhance methods and designs of technologies used in cancer and genetics research.
Biology researchers seek to measure cell activity, but the task is a ...