Analysis of the atmospheric distribution, sources, and sinks of oxygenated volatile organic chemicals based on measurements over the Pacific during TRACE‐P

Abstract

[1] Airborne measurements of a large number of oxygenated volatile organic chemicals (OVOC) were carried out in the Pacific troposphere (0.1-12 km) in winter/spring of 2001 (24 February to 10 April). Specifically, these measurements included acetone (CH 3 COCH 3 ), methylethyl ketone (CH 3 COC 2 H 5 , MEK), methanol (CH 3 OH), ethanol (C 2 H 5 OH), acetaldehyde (CH 3 CHO), propionaldehyde (C 2 H 5 CHO), peroxyacylnitrates (PANs) (C n H 2n+1 COO 2 NO 2 ), and organic nitrates (C n H 2n+1 ONO 2 ). Complementary measurements of formaldehyde (HCHO), methyl hydroperoxide (CH 3 OOH), and selected tracers were also available. OVOC were abundant in the clean troposphere and were greatly enhanced in the outflow regions from Asia. Background mixing ratios were typically highest in the lower troposphere and declined toward the upper troposphere and the lowermost stratosphere. Their total abundance (SOVOC) was nearly twice that of nonmethane hydrocarbons (SC 2 -C 8 NMHC). Throughout the troposphere, the OH reactivity of OVOC is comparable to that of methane and far exceeds that of NMHC. A comparison of these data with western Pacific observations collected some 7 years earlier (February-March 1994) did not reveal significant differences. Mixing ratios of OVOC were strongly correlated with each other as well as with tracers of fossil and biomass/biofuel combustion. Analysis of the relative enhancement of selected OVOC with respect to CH 3 Cl and CO in 12 plumes originating from fires and sampled in the free troposphere (3-11 km) is used to assess their primary and secondary emissions from biomass combustion. The composition of these plumes also indicates a large shift of reactive nitrogen into the PAN reservoir thereby limiting ozone formation. A three-dimensional global model that uses state of the art chemistry and source information is used to compare measured and simulated mixing ratios of selected OVOC. While there is reasonable agreement in many cases, measured aldehyde concentrations are significantly larger than predicted. At their observed levels, acetaldehyde mixing ratios are shown to be an important source of HCHO (and HO x ) and PAN in the troposphere. On the basis of presently known chemistry, measured mixing ratios of aldehydes and PANs are mutually incompatible. We provide rough estimates of the global sources of several OVOC and conclude that collectively these are extremely large (150-500 Tg C yr À1 ) but remain poorly quantified.

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

“…The fraction of acetaldehyde gross production attributed to photochemical production ranges between 16% and 68% for the coastal upwelling and NAG locations, closest to the Cape Verde (Table S2). Our results also demonstrate the significance of surface ocean microbes in reducing and controlling oceanic acetaldehyde concentrations and could account for a lower global oceanic source of 17 Tg y À1 based on in situ seawater concentrations [Beale et al, 2013], compared to estimates of 57-175 Tg y À1 based largely on modeled air data [Millet et al, 2010;Singh et al, 2004].…”

Seasonal, diurnal and nocturnal variations of carbonyl compounds in the semi-urban environment of Orléans, France

“…To evaluate their influence on human health as well as atmospheric chemistry, field measurements of atmospheric carbonyls have been carried out in different areas, including urban (Cheng et al 2014;Lü et al 2010;Weng et al 2009;Pang and Mu 2006;Pang and Lee 2010;Xu et al 2010;Zhang et al 2012;Feng et al 2005;Ho et al 2002;Nguyen et al 2001;Possanzini et al 2002), rural (Xie et al 2008;Villanueva-Fierro et al, 2004;Wiedinmyer et al 2001;Solberg et al 2001;Shepson et al 1991;Cheng et al 2014) and remote areas (Singh et al 2004;Zhou and Mopper 1993;Wagner et al 2001;De Serves 1994). In comparison with urban areas, however, investigations on atmospheric carbonyls in rural or semi-urban areas are still sparse.…”

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

“…The global atmospheric acetaldehyde budget has been reported by Singh et al [2004], but the uncertainties of the estimates are large. Biomass burning directly emits acetaldehyde [Holzinger et al, 1999] and precursors of acetaldehyde as a secondary product of oxidation.…”

“…It is the predominant OVOC in the middle to upper troposphere [Singh et al, 2001[Singh et al, , 2004. It can serve as an abundant source of HO X , particularly in the free and upper troposphere [Tie et al, 2003].…”

“…[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.…”