Measurements of carbonyl compounds around the Arabian Peninsula: overview and model comparison
2020
Abstract. Volatile organic compounds (VOCs) were measured around the Arabian Peninsula using a research vessel during the AQABA campaign (Air Quality and Climate
Change in the Arabian Basin) from June to August 2017. In this study we
examine carbonyl compounds, measured by a proton transfer reaction mass
spectrometer (PTR-ToF-MS), and present both a regional concentration
distribution and a budget assessment for these key atmospheric species.
Among the aliphatic carbonyls, acetone had the highest mixing ratios in most
of the regions traversed, varying from 0.43 ppb over the Arabian Sea to 4.5 ppb over the Arabian Gulf, followed by formaldehyde (measured by a Hantzsch monitor, 0.82 ppb over the Arabian Sea and 3.8 ppb over the Arabian Gulf)
and acetaldehyde (0.13 ppb over the Arabian Sea and 1.7 ppb over the Arabian
Gulf). Unsaturated carbonyls (C 4 –C 9 ) varied from 10 to 700 ppt during the
campaign and followed similar regional mixing ratio dependence to aliphatic carbonyls, which were identified as oxidation products of cycloalkanes over
polluted areas. We compared the measurements of acetaldehyde, acetone, and methyl ethyl ketone to global chemistry-transport model (ECHAM5/MESSy Atmospheric Chemistry – EMAC) results. A
significant discrepancy was found for acetaldehyde, with the model
underestimating the measured acetaldehyde mixing ratio by up to an order of
magnitude. Implementing a photolytically driven marine source of
acetaldehyde significantly improved the agreement between measurements and
model, particularly over the remote regions (e.g. Arabian Sea). However, the
newly introduced acetaldehyde source was still insufficient to describe the
observations over the most polluted regions (Arabian Gulf and Suez), where
model underestimation of primary emissions and biomass burning events are
possible reasons.
Keywords:
- Correction
- Source
- Cite
- Save
- Machine Reading By IdeaReader
78
References
4
Citations
NaN
KQI