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| Titel |
Diode laser based photoacoustic instrument for ammonia concentration and flux monitoring |
| VerfasserIn |
A. Pogany, A. Mohacsi, Z. Bozóki, T. Weidinger, L. Horvath, G. Szabó |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250022546
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| Zusammenfassung |
| A diode laser based near infrared (1532 nm) photoacoustic ammonia monitoring instrument
was combined with a preconcentration unit in order to reach sub-ppb detection limit with a
compact, automatic measuring instrument. The system has no measurable cross-sensitivity to
common atmospheric gases, most importantly to water vapor and carbon dioxide. The
minimum detectable amount of ammonia is 2.9 ng, which means a minimum detectable
concentration of 0.5 ppb with a 30-minute measurement time. The instrument was calibrated
with the widely accepted, wet-chemical AMANDA instrument, and was tested
in several inter-comparison campaigns with various instruments. Results of the
inter-comparison campaigns show that the instrument is highly reliable even under harsh
field conditions and accurate enough for environmental ammonia concentration
monitoring.
The instrument can be operated with three sampling inlets and thus can be used for
ammonia flux measurements with the gradient method. The instrument was successfully
tested in a flux measurement campaign on an agricultural field near a cattle farm, the
purpose of which was to quantify ammonia load to the field originating from the
cattle farm, taking advantage of the wide dynamic range of the instrument. In a
second campaign, long term flux measurements were carried out for several months
above semi-natural grassland, where the stability of the instrument was tested. In
this campaign, ammonia emission was observed during the day (with a typical
maximum of about 220 μgN/m2⋅h) and deposition during the night (-10 μgN/m2⋅h on
average), and the measured flux values were within the theoretically estimated range. |
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