July 22, 2004
BOULDER—A group of chemists from the National Center for Atmospheric Research (NCAR) is joining U.S. and European colleagues for a massive experiment to gauge air quality on both sides of the North Atlantic. One part of the project--the $9 million New England Air Quality Study (NEAQS), unfolding this July and August--will serve as the springboard for air-quality forecasts that could someday become a fixture of U.S. life.
Organized by NOAA, NASA, and the University of New Hampshire, NEAQS will call on an unprecedented array of instruments to assess pollution and air quality. The project involves NOAA's Ronald H. Brown research vessel, 12 research aircraft, and more than 50 ground stations. NEAQS is one component of a larger pollution study called the International Consortium for Atmospheric Research on Transport and Transformation (ICARTT), which involves U.S., British, French, and German scientists.
Below are the teams from NCAR's Atmospheric Chemistry Division planning to deploy equipment on aircraft based at Pease International Airport in Portsmouth, New Hampshire, during NEAQS.
The search for PAN
Aboard the NOAA P-3 aircraft, NCAR's Frank Flocke and Aaron Swanson are using a new instrument that can measure small amounts of PAN, or peroxyacetyl nitrate--a key agent in low-level ozone--in two seconds or less. The previous method, which used gas chromatography, took about two minutes. The new technique's speed makes it ideal for detecting PAN on fast-moving research aircraft.
PAN is a naturally occurring but uncommon chemical in the atmosphere. With no known direct sources, it forms from reactions that involve hydrocarbons and nitrogen oxides, the ingredients of ground-level ozone. If transported to high altitudes, PAN can travel for thousands of miles before descending, breaking apart, and releasing nitrogen oxide. As a result, it can contribute to elevated levels of ground-level ozone in otherwise pristine regions.
A team led by NCAR's Alan Fried will gather other clues to ozone formation by sampling formaldehyde from NASA's DC-8 aircraft. Formaldehyde levels help scientists to infer how quickly ozone and atmospheric radicals (highly reactive molecules) are being produced and how hydrocarbons are reacting with oxygen and sunlight. The NCAR group will be measuring formaldehyde levels as often as once every second.
As part of an ICARTT component called the Intercontinental Chemical Transport Experiment - North America (INTEX-NA), Fried's group is accompanying the DC-8 on a multiweek journey eastward. The group began by measuring the arrival of pollution from Asia into the western United States in early July. They then moved to the Midwest and South, analyzing the pollution generated over these regions. In New Hampshire, they'll help document the fate of these pollutants as they exit North America and sweep toward Europe.
Sunlight and its impact on air chemistry
Also on the cross-country journey aboard NASA's DC-8, Richard Shetter and colleagues will be measuring actinic flux and other aspects of photochemically important molecules, such as ozone and nitrogen dioxide. Actinic flux--the amount of light reaching molecules from all directions--serves as a useful marker for photochemical (solar-driven) processes, which are the driving force for much of the chemistry in the atmosphere. Measuring the pace of these processes is an important step in understanding how quickly ozone and hydrogen radicals are being generated and destroyed.The data collected by Shetter's team will be used in creating computer models of air parcels being tracked by INTEX scientists as they flow eastward across the United States and into the Atlantic. The group will also be flight-testing a new instrument that analyzes actinic flux in a new, faster way with CCDs (charge-coupled devices), the ultra-sensitive silicon-based chips used in many of today's digital cameras.
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