Abstract
A new inlet and instrument have been developed for the rapid measurement of gas phase nitric acid (HNO3) from an airborne platform. The inlet was kept near ambient temperatures with a very short sampling time (100 ms) to minimize desorption of particle nitrates. In addition, inlet surface adsorption problems were minimized by the use of extruded perfluoroalkoxy as a sampling material. Nitric acid was detected by selected ion chemical ionization mass spectrometry using deprontonated methanesulfonic acid as a reagent ion. Laboratory tests showed no interferences from NO, NO2, NO3, and N2O5 under wet (relative humidity (RH) = 100%) or dry (RH = 0%) conditions at levels exceeding those found in the troposphere. The inlet and instrument were flown on the NASA P-3B aircraft as part of the NASA Transport and Chemical Evolution over the Pacific (TRACE-P) field campaign off the coast of Asia during February-April 2001. Nitric acid was measured every 5 s for a 3 s integration period with a limit of detection of ∼ 10 parts per trillion by volume (pptv). The instrument was calibrated by the addition of isotopically labeled H15 NO3 near the front of the ion source on a continual basis. Absolute uncertainties including systematic errors are the limit of detection (10 pptv) plus ±20% for HNO3 > 200 pptv, ±25% for HNO3 100-200 pptv, and ±30% for HNO3 < 100 pptv (±2 σ). Rapid changes in ambient HNO3 were resolved, suggesting minimal influences from instrument surfaces. Finally, the measurements compared favorably with the University of New Hampshire's mist chamber/ion chromatography instrument flown on board the NASA DC-8 aircraft during two intercomparison flights. The in-flight performance of the instrument is demonstrated under the wide range of conditions observed in TRACE-P.
Original language | English (US) |
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Pages (from-to) | GTE 14-1 - 14-18 |
Journal | Journal of Geophysical Research: Atmospheres |
Volume | 108 |
Issue number | 20 |
DOIs | |
State | Published - Oct 27 2003 |
All Science Journal Classification (ASJC) codes
- Geophysics
- Oceanography
- Forestry
- Aquatic Science
- Ecology
- Water Science and Technology
- Soil Science
- Geochemistry and Petrology
- Earth-Surface Processes
- Atmospheric Science
- Space and Planetary Science
- Earth and Planetary Sciences (miscellaneous)
- Palaeontology
Keywords
- CIMS TRACE-P inlet instrument