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| Titel |
Design and Field Testing of a Fiber Laser Based Formaldehyde Laser-Induced Fluorescence Instrument During BEARPEX 2009 |
| VerfasserIn |
Joshua DiGangi, Joshua Paul, Samuel Henry, Aster Kammrath, Frank Keutsch |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250038175
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| Zusammenfassung |
| The oxidation of volatile organic compounds (VOCs) is central to the production of
tropospheric ozone and the formation of secondary organic aerosol (SOA). Formaldehyde
(HCHO) is one of the most ubiquitous VOC oxidation products and thus an important tracer
of VOC oxidation. We have developed a laser-induced fluorescence (LIF) instrument
for fast, high-sensitivity measurements of HCHO based on a novel UV fiber laser
that is < 1 ft3 and requires < 100 W power. The new fiber laser LIF instrument
is ideal for field instrumentation as it achieves high sensitivity and selectivity in
a small and very robust package and is capable of fast sampling (up to 10 Hz).
In addition to an overview of the instrument design, we will present field measurements of
formaldehyde concentrations and gradients taken during the first deployment of the Madison
FIber Laser-Induced Fluorescence (FILIF) Instrument during the Biosphere Effects on
AeRosols and Photochemistry EXperiment (BEARPEX) 2009 at a rural forest in the Sierra
Nevada mountains. Large nighttime gradients through the canopy were observed with larger
HCHO concentrations above the canopy, whereas smaller reverse gradients were observed
during the day. These results will be discussed in the context of rapid, in-canopy BVOC
oxidation and the uncertainties in the HOx budget inside forest canopies. The detection limit
(3Ï) during BEARPEX 2009 was 1.5 ppbv/s and we will present modifications that will
improve the detection limit to < 40 pptv/s, or < 6 pptv/min. We will also discuss
work toward constructing a spatially optimized version of the instrument, as well as
an evaluation of the ability of the instrument to measure HCHO fluxes via eddy
correlation. |
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