Ammonia measurements at Niwot Ridge, Colorado and point arena, California using the tungsten oxide denuder tube technique
✍ Scribed by James M. Roberts; Andrew O. Langford; Paul D. Goldan; Fred C. Fehsenfeld
- Book ID
- 104623131
- Publisher
- Springer Netherlands
- Year
- 1988
- Tongue
- English
- Weight
- 966 KB
- Volume
- 7
- Category
- Article
- ISSN
- 0167-7764
No coin nor oath required. For personal study only.
✦ Synopsis
The applicability of the tungsten oxide denuder tube technique for the measurement of ammonia in the rural troposphere was investigated. The technique is based on selective chemisorption of NHs from a gas stream, thermal desorption, conversion to NO, and analysis by NO-0s chemiluminescence. Nitric acid, which is also collected and desorbed as NO, was distinguished from NHs by differences in desorption temperature. Substituted amines were also collected, but desorbed at a slightly lower temperature than NHs in dry air. At high relative humidities, alkylamines may be hydrolyzed to NHs on the denuder surface and hence detected as NHs . Overheating of the denuder tube during the temperature-programmed desorption was found to cause significant irreversible degradation of system performance.
The technique was used to measure NHs mixing ratios at two rural locations in the United States. At a mountain site in Colorado during the winter of 1984, the average NH3 mixing ratio was 0.20 ppbv (o= 0.08 ppbv). At an isolated coastal site in northern California during the spring of 1985, the average NHs mixing ratio was 0.36 ppbv (o= 0.17 ppbv). Correlations of the latter measurements with wind direction and NOX level suggest that the NH3 mixing ratio in Pacific marine air at 4@ N is ~0.25 ppbv.