Photocatalytic chlorine atom production on mineral dust–sea spray aerosols over the North Atlantic

Atmospheric methane Cape verde Mineral dust Sea spray Sink (geography) Atmospheric chemistry
DOI: 10.1073/pnas.2303974120 Publication Date: 2023-07-24T19:08:10Z
ABSTRACT
Active chlorine in the atmosphere is poorly constrained and so its role oxidation of potent greenhouse gas methane, causing uncertainty global methane budgets. We propose a photocatalytic mechanism for atom production that occurs when Sahara dust mixes with sea spray aerosol. The validated by implementation atmospheric model thereby explaining episodic, seasonal, location-dependent 13C depletion CO air samples from Barbados [J.E. Mak, G. Kra, T. Sandomenico, P. Bergamaschi, J. Geophys. Res. Atmos.108 (2003)], which remained unexplained decades. Cl can also explain anomaly CO:ethane ratio found at Cape Verde [K. A. Read et al., Atmos.114 (2009)], addition to observation elevated HOCl [M. Lawler Atmos. Chem. Phys.11, 7617-7628 (2011)]. Our finds 3.8 Tg(Cl) y-1 produced over North Atlantic, making it dominant source region; globally, increases 41%. shift sink budget due increased means isotope-constrained top-down models fail allocate 12 Tg (2% total emissions) 13C-depleted biological sources such as agriculture wetlands. Since 2014, an increase African emissions has isotope CH4, partially masking much greater decline this isotope, implications interpretation drivers behind recent atmosphere.
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