Research

Heterogeneous Reactive Nitrogen Chemistry

Anonymous — Sat, 26 Jan 2019 07:00:00 +0000

Heterogeneous Reactive Nitrogen Chemistry Anonymous (not verified) Sat, 01/26/2019 - 00:00

Gas-particle reactions of reactive nitrogen represent an important but variable atmospheric chemical cycle. For example, uptake of N₂O₅to aerosol regulates the lifetime of NO_x(=NO+NO₂) and oxidant burdens in the troposphere. Uptake of N₂O₅to chloride-containing aerosol to produce ClNO₂is an efficient halogen activation mechanism that may represent a substantial fraction of tropospheric halogen budgets. Our group has developed instrumentation and led major ground, ship and aircraft based field intensives in New England, Texas and the Gulf Coast, New York City, California, Colorado and Hong Kong. The recent WINTER field campaign on the NSF C-130 aircraft on the U.S. East Coast, collaborative with the Thornton Group at the University of Washington, specifically targeted heterogeneous nitrogen chemistry.

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Nocturnal Biogenic Oxidation

Anonymous — Fri, 25 Jan 2019 07:00:00 +0000

Nocturnal Biogenic Oxidation Anonymous (not verified) Fri, 01/25/2019 - 00:00

Biogenic VOC from terrestrial vegetation (e.g., isoprene, monoterpenes) and biogenic marine sulfur compounds (e.g., dimethyl sulfide, DMS) undergo rapid nocturnal degradation in the presence of the nitrate radical, NO₃. Since NO₃ is derived from NO_x, an anthropogenic pollutant, these oxidative processes represent an anthropogenic perturbation of a biogenic atmospheric input. These perturbations can have important consequences, such as the formation of organic and sulfate aerosol that affect Earth's climate. These processes have been studied through field studies from ships (New England), aircraft (New England, Texas, the Southeast), ground sites (Colorado,Alabama) and in large environmental chambers.

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Winter Air Quality

Anonymous — Thu, 24 Jan 2019 07:00:00 +0000

Winter Air Quality Anonymous (not verified) Thu, 01/24/2019 - 00:00

Several regions of the United States, particularly in the west, experience poor air quality during winter meteorological conditions that confine local emissions in shallow layers near the surface. However, different regions have widely different responses to local emissions in the winter. Sparsely populated oil and gas producing regions are subject to ozone pollution, while urban regions experience very low ozone but high levels of particulate matter comprised primarily of ammonium nitrate. These disparate issues are related both chemically and meteorologically. Recent field studies investigating processes relevant to winter air quality include WINTER, the Uintah Basin Winter Ozone Studies, and the Utah Winter Fine Particulate Study.

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Atmospheric Chemistry of Wildfires

Anonymous — Wed, 23 Jan 2019 07:00:00 +0000

Atmospheric Chemistry of Wildfires Anonymous (not verified) Wed, 01/23/2019 - 00:00

Wildfire frequency and intensity is increasing in western North America, with impacts on regional air quality and climate. The FIREX-AQ initiative is a set of laboratory and field studies designed to provide detailed understanding of the complex emissions and subsequent chemical transformations that define these impacts. Recent measurements at the Missoula Fire Sciences Laboratory using the Airborne Cavity Enhanced Spectrometer have provided emission factors for glyoxal (CHOCHO), nitrous acid (HONO) and nitrogen dioxide (NO₂), species that define photochemical impacts of fire emissions. Deployment of the NOAA Twin Otter to the western U.S. in 2019 will provide near field emissions profiles and an investigation of fire plume photochemistry and nighttime chemistry to determine ozone and secondary organic aerosol formation in fire plumes.

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Broadband Aerosol Extinction

Anonymous — Tue, 22 Jan 2019 07:00:00 +0000

Broadband Aerosol Extinction Anonymous (not verified) Tue, 01/22/2019 - 00:00

Aerosols both scatter and absorb incoming solar radiation, influencing Earth's climate. Recent developments of visible cavity ring-down and photoacoustic instruments have enabled new and detailed understanding of ambient aerosol optical properties. We have undertaken the development of broadband aerosol extinction (= absorption + scattering) at short wavelengths using cavity enhanced spectrometers with LED and other light sources. This instrument concept provides spectrally resolved measurements over a wavelength range where some aerosol species, such as "brown carbon", may have wavelength dependent absorption. The instrument has recently participated in measurements at the U.S. Forest Service Fire Lab (FLAME IV), at the SOAS campaign in the southeast U.S., and through a collaborative project with Dr. Yinon Rudich at the Weizmann Institute of Science.

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High Sensitivity Optical Instruments

Anonymous — Mon, 21 Jan 2019 07:00:00 +0000

High Sensitivity Optical Instruments Anonymous (not verified) Mon, 01/21/2019 - 00:00

Direct absorption spectroscopy is an absolute technique for measurement of atmospheric trace gases and aerosol extinction that has been traditionally limited in atmospheric science applications because of its low sensitivity. Optical cavities (e.g., two mirrors aligned such that light makes multiple reflections between them) greatly enhance the sensitivity and utility of direct absorption methods. Multiple field and laboratory instruments based on cavity ring-down and cavity enhanced absorption spectroscopies are currently in use and / or under development.

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