Sources and sinks of acetone in the troposphere: Behavior of reactive hydrocarbons and a stable product

Abstract

Acetone, a relatively unreactive carbonyl compound in the atmosphere, has been detected in concentrations of ≃500 parts per trillion in surface air over the central Atlantic and several hundred ppt (volume) near the tropopause. This represents a substantially higher mixing ratio than anticipated from previous descriptions of its sources which are primarily much more reactive hydrocarbon emissions and skinks. We assimilate new information about the tropospheric sources and sinks of this substance into a numerical model of its chemistry, cloud transport, and removal. Simulations relevant to the tropical and the mid‐latitude atmosphere are presented. Photolysis provides a rather slow sink, giving a first‐order decay time scale of 40 days (near the surface) to 10 days (at 200 mbar). Attack by HO radicals is of comparable importance, with a time scale of about 20 days (near the surface) to a hundred days (at 200 mbar). A significant amount of carbon, approximately 70 Tg (C) yr−1, appears to be cycled as acetone. Many of the sources of acetone involve the oxidation of higher molecular weight hydrocarbons, but the relative contribution of primary, nonanthropogenic, sources, e.g., biogenic and oceanic, may be significant. Acetone, like CO, is a useful tracer recording previous photochemical activity in an air parcel, a tracer that might be used to describe the photochemical production of compounds like ozone. The mid‐latitude simulations required some adaptation of the Chatfield (1982) transport model. The activity of vertical transport was constrained to reproduce available 222Rn data. Simulations of these data suggest that mid‐latitude vertical transport is less active than tropical, but rather more active than Kz parameterizations suggest.

Atmospheric concentrations and temporal variations of C1C3 carbonyl compounds at two rural sites in central Ontario

“…For acetone this observation can be reconciled taking into account the relatively slow rates for its formation and removal processes. As discussed by Chatfield et al (1987). OH reaction with propane can account for perhaps halfof the acetone production in the troposphere.…”

North American acetone sources determined from tall tower measurements and inverse modeling

“…Globally, the oceans appear to be both a gross source and a gross sink for atmospheric acetone (Fischer et al, 2012); however, the magnitude and variability of the corresponding net flux is quite uncertain (de Reus et al, 2003;Williams et al, 2004;Lewis et al, 2005;Marandino et al, 2005;Sinha et al, 2007;Taddei et al, 2009;Fischer et al, 2012;Read et al, 2012;Sjostedt et al, 2012). Along with gross oceanic uptake, sinks of atmospheric acetone include photochemical oxidation by OH, photolysis, and deposition to land (Chatfield et al, 1987;McKeen et al, 1997;Gierczak et al, 1998;Blitz et al, 2004;Karl et al, 2010). The mean tropospheric lifetime of acetone is estimated to be between 14 and 35 days (Jacob et al, 2002;Arnold et al, 2005;Fischer et al, 2012).…”

“…Acetone (CH 3 C(O)CH 3 ) is the simplest ketone and one of the most abundant volatile organic compounds (VOCs) in the atmosphere, with typical mixing ratios ranging from a few hundred parts per trillion (pptv) to several parts per billion (ppbv) or more (Chatfield et al, 1987;Singh et al, 1995;Arnold et al, 1997;Riemer et al, 1998;Goldstein and Schade, 2000;Karl et al, 2003;Lewis et al, 2005;Aiello and McLaren, 2009;Gao et al, 2013). It affects atmospheric chemistry as an important source of hydrogen oxide radicals (HO x = OH + HO 2 ) in the upper troposphere (Jaeglé et al, 1997(Jaeglé et al, , 2001McKeen et al, 1997;Wennberg et al, 1998;Folkins and Chatfield, 2000;Arnold et al, 2005), and as a precursor of peroxyacetyl nitrate (PAN, CH 3 C(O)OONO 2 ), which is a key reservoir for nitrogen oxides (NO x = NO Acetone is emitted by terrestrial vegetation as a by-product of plant metabolic processes, such as cyanogenesis and acetoacetate decarboxylation Jardine et al, 2010), and during plant decay (de Gouw et al, 1999;Warneke et al, 1999).…”

Acetone variability in the upper troposphere: analysis of CARIBIC observations and LMDz-INCA chemistry-climate model simulations

“…The significance of acetone was later confirmed using Chemistry-Climate Models: for example Folberth et al (2006) showed using the LMDz-INCA model, that acetone and methanol play a significant role in the upper troposphere/lower stratosphere budget of peroxy radicals, with an increase in OH and HO x concentrations of 10 to 15 % being attributed to acetone. Chatfield et al (1987) noted that acetone can be considered an indicator of properly modelled atmospheric chemistry in the UT, for instance as a tracer of previous photochemical activity in an air parcel.…”