Journal ArticleDOI
Air pollution measurement by Fourier transform spectroscopy
TLDR
The use of infrared methods in pollution measurement has been hampered by sensitivity limitations and by interferences from water vapor, but Fourier transform spectrometer systems reduce these limitations by their high optical efficiency and their ability to manipulate spectra for removal of interfering bands.Abstract:
The use of infrared methods in pollution measurement has been hampered by sensitivity limitations and by interferences from water vapor. Fourier transform spectrometer systems reduce these limitations by their high optical efficiency and their ability to manipulate spectra for removal of interfering bands. At the Environmental Protection Agency we have sought to further increase the sensitivity of the infrared technique by evolving optimal long path cell designs and sample concentration techniques. Reactive pollutants such as O(3), H(2)O(2), HNO(3), HNO(2), H(2)CO, HCOOH, PAN, HCl, NH(3), NO, and NO(2) are best measured in the open atmosphere. In this case one strives toward large absorption cells with the paths as long as practical. Our largest cell is being used to measure pollutants in the smog at Riverside, California. This cell uses an eight-mirror system for multiple-passing radiation along a 23-m base path, yielding total paths measured in kilometers. Reactive gases at levels of just a few ppb have been measured. For measuring nonreactive pollutants, such as hydrocarbons and halocarbons, maximum detection sensitivity is achieved with small folded-path cells rather than with large cells. In this case a pollutant concentrate is prepared and introduced into a miniaturized multiple-pass cell designed for maximum path-to-volume ratio. Cryogenic trapping to separate the pollutants from the major constituents of the air has yielded concentration factors as high as one million. The smallest multiple-pass cell we have built to date encloses a 115-cm light path within a volume of 3 cm(3). This cell when used with the FTS spectrometer and mercury-cadmium-telluride detector permits the detection of nanogram quantities of pollutant gases. Measurements have been made of trace gases in the air at mixing ratios as low as 2 x 10(-11).read more
Citations
More filters
Journal ArticleDOI
The chemistry of carbonyl compounds in the atmosphere—A review
TL;DR: In this article, the authors make a synthesis of the studies on the carbonyl compounds chemistry in the trophosphere by successively examining: measurement methods in the Trophosphere, sources of primary carbonyls, formation of secondary carbonyll compounds in the atmosphere, reactivity of carbinear compounds in an atmosphere.
Journal ArticleDOI
Ambient air pollutants: collection, chemical characterization and mutagenicity testing.
TL;DR: Recommendations for the use of integrated chemical-analytical and biological screening systems in further studies of toxic air pollutants are proposed.
Journal ArticleDOI
Combination of Sorption Tube Sampling and Thermal Desorption with Hollow Waveguide FT-IR Spectroscopy for Atmospheric Trace Gas Analysis: Determination of Atmospheric Ethene at the Lower ppb Level
Olga A Pogodina,Victor V Pustogov,Fabiano de Melas,Christina Haberhauer-Troyer,Erwin Rosenberg,Hans Puxbaum,Alexandra Inberg,Nathan Croitoru,Boris Mizaikoff +8 more
TL;DR: The determination of organic trace gases in the ambient environment at the lower ppb level is demonstrated based on a novel technique combining sorption tube sampling on Molsieve and Carbosieve S-III, thermal desorption, and detection of the trace analyte by hollow waveguide Fourier transform infrared (HWG-FT-IR) spectroscopy.
Journal ArticleDOI
Characterization of a mid-infrared hollow waveguide gas cell for the analysis of carbon monoxide and nitric oxide.
TL;DR: Hollow waveguides that transmit in the mid-infrared spectral range have higher optical efficiencies compared to long path length cells due to smaller cell volumes and cost savings can be achieved by using FT-IR spectroscopy, especially in combination with a HW gas-sensing module, which is significantly less expensive than a multipass gas cell.
Journal ArticleDOI
Atmospheric radiation: 1975–1983
TL;DR: In this article, the authors present a review of the geophysical landscape for the last quadrennial review of geophysical research, which is the ideal place in which to do so.
References
More filters
Journal ArticleDOI
Long Optical Paths of Large Aperture
TL;DR: In this article, an absorption cell is described, in which the light traverses a small volume a large and arbitrarily variable number of times, and the angular aperture of the mirrors is not occulted either on or off the optical axis, and can be used for observing spectra that are very weak, or that belong to high boiling point compounds or to compounds obtainable only in very low concentrations.
Journal ArticleDOI
Infrared Measurement of Fluorocarbons, Carbon Tetrachloride, Carbonyl Sulfide, And Other Atmospheric Trace Gases
TL;DR: A cryogenic procedure for concentrating trace gases in the atmosphere has been developed and applied to the ambient air at Research Triangle Park, NC, Atlantic Beach, NC and New York City.
Journal ArticleDOI
Detection of Atmospheric Pollutants at Parts-per-Billion Levels by Infrared Spectroscopy
Philip L. Hanst,Allen S. Lefohn +1 more
TL;DR: In this article, the authors used the scanning Michelson interferometer, cooled solid state detectors, the fast minicomputer, and the multiple pass long path cell for infrared detection of air pollutants.
Journal ArticleDOI
Optical systems unravel smog chemistry
TL;DR: The use of tunable uv laser systems to monitor OH radicals by their resonance fluorescence, the use of laser magnetic resonance in kinetic studies of OH, HO/sub 2/ε, and other free radicals was discussed in this article.
Journal ArticleDOI
Long-Path Infrared Spectrocopy for Air Pollution Research
TL;DR: In this article, a long-path absorption cell was developed for the measurement of gaseous contaminants in the atmosphere and for the studies of reactions of contaminants in a laboratory, which is based on the White multiple-reflection system.