Abstract. The Arctic is a climatically sensitive region that has experienced warming at almost 3 times the global average rate in recent decades, leading to an increase in Arctic greenness and a greater abundance of plants that emit biogenic volatile organic compounds (BVOCs). These changes in atmospheric emissions are expected to significantly modify the overall oxidative chemistry of the region and lead to changes in VOC composition and abundance, with implications for atmospheric processes. Nonetheless, observations needed to constrain our current understanding of these issues in this critical environment are sparse. This work presents novel atmospheric in situ proton-transfer-reaction time-of-flight mass spectrometry (PTR-ToF-MS) measurements of VOCs at Toolik Field Station (TFS; 68∘38′ N, 149∘36' W), in the Alaskan Arctictundra during May–June 2019. We employ a custom nested grid version of theGEOS-Chem chemical transport model (CTM), driven with MEGANv2.1 (Model ofEmissions of Gases and Aerosols from Nature version 2.1) biogenic emissionsfor Alaska at 0.25∘ × 0.3125∘ resolution, to interpret the observations in terms of their constraints onBVOC emissions, total reactive organic carbon (ROC) composition, andcalculated OH reactivity (OHr) in this environment. We find total ambientmole fraction of 78 identified VOCs to be 6.3 ± 0.4 ppbv (10.8 ± 0.5 ppbC), with overwhelming (> 80 %) contributions are from short-chain oxygenated VOCs (OVOCs) including methanol, acetone and formaldehyde. Isoprene was the most abundant terpene identified. GEOS-Chem captures the observed isoprene (and its oxidation products), acetone and acetaldehyde abundances within the combined model and observation uncertainties (±25 %), but underestimates other OVOCs including methanol, formaldehyde, formic acid and acetic acid by a factor of 3 to 12. The negative model bias for methanol is attributed to underestimated biogenic methanol emissions for the Alaskan tundra in MEGANv2.1. Observed formaldehyde mole fractions increase exponentially with air temperature, likely reflecting its biogenic precursors and pointing to a systematic model underprediction of its secondary production. The median campaign-calculated OHr from VOCs measured at TFS was 0.7 s−1, roughly 5 % of the values typically reported in lower-latitude forested ecosystems. Ten species account for over 80 % of the calculated VOC OHr, with formaldehyde, isoprene and acetaldehyde together accounting for nearly half of the total. Simulated OHr based on median-modeled VOCs included in GEOS-Chem averages 0.5 s−1 and is dominated by isoprene (30 %) and monoterpenes (17 %). The data presented here serve as a critical evaluation of our knowledge of BVOCs and ROC budgets in high-latitude environments and represent a foundation for investigating and interpreting future warming-driven changes in VOC emissions in the Alaskan Arctic tundra.
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Space‐Based Constraints on Terrestrial Glyoxal Production
Glyoxal is a volatile organic compound (VOC) in the atmosphere that is a precursor to ozone and secondary organic aerosol, can be a measure of photochemical activity, and is one of a small number of VOCs observable from space. However, the global budget of glyoxal is not well understood, and there has been limited exploration of whether current chemical transport models reproduce satellite observations of this VOC. In this work we take advantage of recent advances in the retrieval of glyoxal from the Ozone Monitoring Instrument along with retrieved formaldehyde and the GEOS‐Chem model to constrain global glyoxal sources. Model glyoxal is produced by direct emissions from fires (6.5 Tg/year) and secondary chemical production (32.9 Tg/year) from biogenic and anthropogenic precursors. The model reproduces the annual average terrestrial spatial variability in formaldehyde and glyoxal reasonably well, with an
- NSF-PAR ID:
- 10459941
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Atmospheres
- Volume:
- 123
- Issue:
- 23
- ISSN:
- 2169-897X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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