Surface-atmosphere exchange of ammonia over a corn field: eddy covariance flux measurements using QC-TILDAS
Abstract
Atmospheric ammonia (NH3) is an important precursor of fine particulate matter in the atmosphere, adversely affecting air quality, climate and biodiversity. Agricultural activities are the predominant source of NH3, including the volatilization of N fertilizers, most commonly urea. Therefore, it is important to quantify the variability of ammonia exchange between crops and the atmosphere to better understand the source contribution of N fertilizers applied. The study presents direct eddy covariance (EC) NH3 flux measurements from a urea treated corn field in Ottawa, Canada, over two growing seasons in the years of 2017 and 2018. A flux tower was equipped with a 3-D sonic anemometer (CSAT3; Campbell Scientific, UT), and a fast time-response Quantum Cascade Tunable Infrared Differential Absorption Spectrometer (QC-TILDAS; Aerodyne Research, MA) for NH3 measurements at 10 Hz. During the 2017 season, NH3 emissions reached up to 500 ng m-2 s-1 within one week after fertilizer application, as the urea hydrolysis occurred quickly due to significant rain within this period. As the canopy started growing, the NH3 emissions decreased and at the end of the growing season deposition of ammonia dominated. This highlights the importance of performing flux measurements across the growing season to understand the bi-directional exchange of ammonia and its contribution to the nitrogen budget. In 2018, there was little evidence of NH3 emission immediately following fertilizer application, but sustained emissions occurred following a rainfall event two weeks later. Differences between the two growing season might be linked to variability of meteorological parameters, which will be presented.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.B14A..03S
- Keywords:
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- 3322 Land/atmosphere interactions;
- ATMOSPHERIC PROCESSESDE: 0469 Nitrogen cycling;
- BIOGEOSCIENCESDE: 0478 Pollution: urban;
- regional and global;
- BIOGEOSCIENCESDE: 1615 Biogeochemical cycles;
- processes;
- and modeling;
- GLOBAL CHANGE