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Topic Name: Brookhaven National Laboratory Scientists developed Atmospheric Measuring Device for Understanding Smog Formation

Category: Chemical

Research persons: Stephen Springston, Judy Lloyd

Location: Brookhaven National Laboratory, DOE, United States

Details

Scientists at the U.S. Department of Energy's Brookhaven National Laboratory have developed a new tool for quantitatively measuring elusive atmospheric chemicals that play a key role in the formation of photochemical smog. Better measurements will improve scientists' understanding of the mechanisms of smog formation and their ability to select and predict the effectiveness of various mitigation strategies. The Brookhaven scientists have been issued a U.S. patent for their apparatus, which is available for licensing.

The device measures atmospheric hydroperoxyl radicals - short-lived, highly reactive intermediates involved in the formation of ozone, a component of photochemical smog - in the lowest layer of Earth's atmosphere. The levels of these radicals can indicate which of a variety of chemical pathways is predominant in converting basic starting ingredients - hydrocarbons, nitrogen oxides, and water vapor - into smog in the presence of sunlight.

"Understanding the relative importance of the various pathways can help you tailor your mitigation strategies," said Brookhaven atmospheric chemist Stephen Springston, one of the inventors. "For example, are you better off spending your money reducing hydrocarbon emissions or nitrogen oxide emissions?"

"Our measurements will help predict which strategy would be most successful for a particular set of atmospheric conditions - and make modifications to the strategy as those conditions change," said co-inventor Judy Lloyd of the State University of New York at Old Westbury, who holds a guest appointment at Brookhaven Lab.

Because hydroperoxyl radicals are so reactive, getting accurate measurements is not easy. "These chemicals are so fragile you cannot take a bottle home with you," Springston said. "You have to measure them where they form, in the atmosphere, before they react and disappear."

Various groups have developed detectors for hydroperoxyl radicals, but these have been cumbersome and costly. The new device is comparatively small, lightweight, and inexpensive, has low power requirements, and gives a sensitive, fast response. It works by detecting a "glowing" signal from a chemiluminescent compound - similar to the compound that makes fireflies glow - when it reacts with the hydroperoxyl radicals in atmospheric samples fed into the device during flight.

"The chemiluminescence produced in solution creates a strong and readily detectable signal without the need for complex amplification procedures," said Lloyd.

The device has been tested in a mountaintop setting, but has not yet been deployed on an aircraft for a sampling mission. It is designed to be flown on atmospheric sampling aircraft, such as the Department of Energy's Gulfstream 1, which has been used by Brookhaven and other national laboratory scientists for a variety of atmospheric studies.

This work was funded by the Office of Biological and Environmental Research within the U.S. Department of Energy's Office of Science and by the National Science Foundation.
In figure 1, Victorian London was notorious for its thick smogs, or "pea-soupers", a fact that is often recreated to add an air of mystery to a period costume drama.
In figure 2, Judy Lloyd (left) and Stephen Springston
In figure 3, Smog in New York City as viewed from the World Trade Center in 1988.

Note for Smog

Smog is a kind of air pollution; the word "smog" is a portmanteau of smoke and fog. Classic smog results from large amounts of coal burning in an area and is caused by a mixture of smoke and sulphur dioxide.

Smog is a problem in a number of cities and continues to harm human health. Ground-level ozone, Sulfur dioxide, Nitrogen dioxide Carbon monoxide are especially harmful for senior citizens, children, and people with heart and lung conditions such as emphysema, bronchitis, and asthma. It can inflame breathing passages, decreasing the lungs' working capacity, and causing shortness of breath, pain when inhaling deeply, wheezing, and coughing. It can cause eye and nose irritation and it dries out the protective membranes of the nose and throat and interferes with the body's ability to fight infection, increasing susceptibility to illness. Hospital admissions and respiratory deaths often increase during periods when ozone levels are high.

Note for Earth's atmosphere

Earth's atmosphere is a layer of gases surrounding the planet Earth and retained by the Earth's gravity. It contains roughly (by molar content/volume) 78% nitrogen, 20.95% oxygen, 0.93% argon, 0.038% carbon dioxide, trace amounts of other gases, and a variable amount (average around 1%) of water vapor. This mixture of gases is commonly known as air. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation and reducing temperature extremes between day and night.

There is no definite boundary between the atmosphere and outer space. It slowly becomes thinner and fades into space. Three quarters of the atmosphere's mass is within 11 km of the planetary surface. In the United States, people who travel above an altitude of 80.5 km (50 statute miles) are designated astronauts. An altitude of 120 km (~75 miles or 400,000 ft) marks the boundary where atmospheric effects become noticeable during re-entry. The Kármán line, at 100 km (62 miles or 328,000 ft), is also frequently regarded as the boundary between atmosphere and outer space.

Note for Hydroperoxyl radical

HO2*, usually termed either hydroperoxyl radical or perhydroxyl radical, is the protonated form of superoxide; the protonation/deprotonation equilibrium exhibits a pK(a) of around 4.8. Consequently, about 0.3% of any superoxide present in the cytosol of a typical cell is in the protonated form. This ratio is rather accurately reflected by the published literature on the two species, as identified by a PubMed search; at the time of writing only 28 articles mention "HO2," "hydroperoxyl" or "perhydroxyl" in their titles, as against 9228 mentioning superoxide. Here it is argued that this correlation is not justifiable: that HO2*'s biological and biomedical importance far exceeds the attention it has received. Several key observations of recent years are reviewed that can be explained much more economically when the participation of HO2* is postulated. It is suggested that a more widespread appreciation of the possible role of HO2* in biological systems would be of considerable benefit to biomedical research.