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Proceedings Paper

Field measurements of atmospheric methane with a HeNe laser-based real-time instrument
Author(s): J. Barry McManus; Jeff A. Shorter; Paul L. Kebabian; Charles E. Kolb; Byard Mosher; Robert C. Harris; Brian Lamb; Eugene Allwine; Touche Howard
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Paper Abstract

We recently have conducted measurements of distributions and fluxes of methane in several small towns in the U.S. These measurements are made with a real-time methane instrument recently developed at Aerodyne Research. This instrument is based on absorption of infrared light from a Zeeman-broadened HeNe laser operating at 3.39 micrometers . A non-uniform magnetic field applied to the laser plasma results in a nearly flat gain profile, which allows piezoelectric tuning of the laser on and off a methane line. Long path (47 m) absorption occurs in a multipass cell. The instrument has a noise level of 5 ppbv (rms, 1 sec.) and a gas sampling time of 6 sec. The instrument is mounted in a van with a suite of other real-time instruments (CO2 and SF6) which can function while moving at roadway speeds. We map the methane distribution in towns, identify the primary methane sources, and measure fluxes with tracer methods. The simultaneous measurement of CO2 with a commercially available NDIR device is useful in identifying some sources of methane. An SF6 instrument (electron capture) allows precise location and measurement of tracer plumes during flux measurement experiments.

Paper Details

Date Published: 12 February 1993
PDF: 13 pages
Proc. SPIE 1715, Optical Methods in Atmospheric Chemistry, (12 February 1993); doi: 10.1117/12.140179
Show Author Affiliations
J. Barry McManus, Aerodyne Research, Inc. (United States)
Jeff A. Shorter, Aerodyne Research, Inc. (United States)
Paul L. Kebabian, Aerodyne Research, Inc. (United States)
Charles E. Kolb, Aerodyne Research, Inc. (United States)
Byard Mosher, Univ. of New Hampshire (United States)
Robert C. Harris, Univ. of New Hampshire (United States)
Brian Lamb, Washington State Univ. (United States)
Eugene Allwine, Washington State Univ. (United States)
Touche Howard, INDACO Air Quality Services, Inc. (United States)

Published in SPIE Proceedings Vol. 1715:
Optical Methods in Atmospheric Chemistry
Harold I. Schiff; Ulrich Platt, Editor(s)

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