Journal
ATMOSPHERIC MEASUREMENT TECHNIQUES
Volume 9, Issue 8, Pages 3851-3861Publisher
COPERNICUS GESELLSCHAFT MBH
DOI: 10.5194/amt-9-3851-2016
Keywords
-
Categories
Funding
- National Science Foundation [1455588]
- NSF Major Research Instrumentation (MRI) grant [1428738]
- NASA Earth and Space Science Fellowship (NESSF)
- Alfred P. Sloan Minority Ph.D. (MPHD) Scholarship
- NSF [1262033]
- Directorate For Geosciences
- Div Atmospheric & Geospace Sciences [1262033] Funding Source: National Science Foundation
- Div Atmospheric & Geospace Sciences
- Directorate For Geosciences [1455588, 1428738] Funding Source: National Science Foundation
Ask authors/readers for more resources
Hydroperoxy radicals (HO2) play an important part in tropospheric photochemistry, yet photochemical models do not capture ambient HO2 mixing ratios consistently. This is likely due to a combination of uncharacterized chemical pathways and measurement limitations. The indirect nature of current HO2 measurements introduces challenges in accurately measuring HO2; therefore a direct technique would help constrain HOx chemistry in the atmosphere. In this work we evaluate the feasibility of using chemical ionization mass spectrometry (CIMS) and propose a direct HO2 detection scheme using bromide as a reagent ion. Ambient observations were made with a high-resolution time-of-flight chemical ionization mass spectrometer (HR-ToF-CIMS) in Atlanta over the month of June 2015 to demonstrate the capability of this direct measurement technique. Observations displayed expected diurnal profiles, reaching daytime median values of similar to 5 ppt between 2 and 3 p.m. local time. The HO2 diurnal profile was found to be influenced by morning-time vehicular NOx emissions and shows a slow decrease into the evening, likely from non-photolytic production, among other factors. Measurement sensitivities of approximately 5.1 +/- 1.0 cps ppt(-1) for a bromide ion (Br-79(-)) count rate of 10(6) cps were observed. The relatively low instrument background allowed for a 3 sigma lower detection limit of 0.7 ppt for a 1 min integration time. Mass spectra of ambient measurements showed the (BrHO2-)-Br-79 peak was the major component of the signal at nominal mass-to-charge 112, suggesting high selectivity for HO2 at this mass-to-charge. More importantly, this demonstrates that these measurements can be achieved using instruments with only unit mass resolution capability.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available