Ammonia Measurements at an Iowa Swine Farm Using Infrared Quantum Cascade Laser Absorption Spectroscopy

A novel instrument using quantum cascade tunable infrared laser differential absorption spectroscopy (QC-TILDAS) has been developed for long term monitoring and source characterization of ammonia and other atmospheric trace gases. The instrument uses a long path length (56m) low volume (0.5 liters) absorption cell which provides high precision (0.2 ppb Hz-1/2), wide dynamic range (0.5 ppb to 5000 ppb) and rapid time response (0.1 s). Quantum cascade lasers operate without cryogenic cooling in the pulsed mode which makes them more robust and convenient for field measurements than conventional lead-salt tunable diode lasers. Absolute ammonia concentrations are obtained without calibration gases by real-time fitting of the measured transmission to spectroscopic line parameters from the HITRAN data base. The instrument has been recently tested at an Iowa swine farm as part of the EPA Environmental Technology Verification (ETV) Program.

⁽¹⁾ shorter@aerodyne.com
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