Sources and sinks of acetone, methanol, and acetaldehyde in North Atlantic marine air

Abstract

Abstract. Measurements of acetone, methanol, acetaldehyde and a range of non-methane hydrocarbons have been made in North Atlantic marine air at the Mace Head observatory. Under maritime conditions the combination of OVOCs (acetone, methanol and acetaldehyde) contributed up to 85% of the total mass of measured non methane organics in air and up to 80% of the OH radical organic sink, when compared with the sum of all other organic compounds including non-methane hydrocarbons, DMS and OH-reactive halocarbons (trichloromethane and tetrachloroethylene). The observations showed anomalies in the variance and abundance of acetaldehyde and acetone over that expected for species with a remote terrestrial emission source and OH controlled chemical lifetime. A detailed model incorporating an explicit chemical degradation mechanism indicated in situ formation during air mass transport was on timescales longer than the atmospheric lifetime of precursor hydrocarbons or primary emission. The period over which this process was significant was similar to that of airmass motion on intercontinental scales, and formation via this route may reproduce that of a widespread diffuse source. The model indicates that continued short chain OVOC formation occurs many days from the point of emission, via longer lived intermediates of oxidation such as organic peroxides and long chain alcohols.

First space-borne measurements of methanol inside aged southern tropical to mid-latitude biomass burning plumes using the ACE-FTS instrument

“…Typical background concentrations are 400-1000 pptv in clean air in the boundary layer (Lewis et al, 2005) or in the free troposphere (Singh et al, 1995). The atmospheric lifetime is about 16 days in the free troposphere (Singh et al, 1995) due primarily to OH oxidation to produce formaldehyde.…”

“…Methanol is involved in HO x chemistry because the reaction with OH forms the CH 3 O and H 2 COH radicals, which rapidly react with O 2 to give HO 2 and H 2 CO. Formaldehyde chemistry produces additional HO 2 radicals and CO so methanol is a significant source of both H 2 CO and CO (Palmer et al, 2003). The majority of measurements of atmospheric methanol concentrations are performed in surface air (Heikes et al, 2002;Lewis et al, 2005). Recent aircraft campaigns have allowed the measurement of a few methanol profiles in the free troposphere up to 12 km (e.g., Singh et al, 2001Singh et al, , 2004.…”

Production of methanol, acetaldehyde, and acetone in the Atlantic Ocean

“…In remote marine air, oceanic sources and sinks of OVOCs are assumed to be significant in controlling air concentrations [Read et al, 2012], although the magnitude and direction of the OVOC air-sea fluxes are a matter of debate [Beale et al, 2013;Carpenter et al, 2004;Heikes et al, 2002;Marandino et al, 2005;Taddei et al, 2009;Williams et al, 2004] largely as a consequence of extremely limited OVOC measurements in oceanic surface waters. Knowledge of OVOC production and loss rates, and an appreciation of the mechanisms involved in our oceans are also lacking.…”

“…[2] Oxygenated volatile organic compounds (OVOCs) including methanol, acetaldehyde, and acetone are ubiquitous in the atmosphere [e.g., Lewis et al, 2005;Singh et al, 1995Singh et al, , 2003 where they affect the tropospheric ozone budget, are precursors to peroxy acetyl nitrate and, in the remote marine environment, represent a significant sink of the hydroxyl radical and thus the oxidizing capacity of the lower atmosphere [Folkins and Chatfield, 2000;Lewis et al, 2005]. In remote marine air, oceanic sources and sinks of OVOCs are assumed to be significant in controlling air concentrations [Read et al, 2012], although the magnitude and direction of the OVOC air-sea fluxes are a matter of debate [Beale et al, 2013;Carpenter et al, 2004;Heikes et al, 2002;Marandino et al, 2005;Taddei et al, 2009;Williams et al, 2004] largely as a consequence of extremely limited OVOC measurements in oceanic surface waters.…”

Carbon isotopic signatures of methanol and acetaldehyde emitted from biomass burning source

“…[2] The global troposphere contains considerable amounts of oxygenated volatile organic compounds (OVOCs) [e.g., Lewis et al, 2005;Singh et al, 1995Singh et al, , 2001Singh et al, , 2004. Their occurrence influences oxidant distributions in the atmosphere and the atmospheric chemistry of important trace gases and particles.…”