Uptake Measurements of Acetaldehyde on Solid Ice Surfaces and on Solid/Liquid Supercooled Mixtures Doped with HNO₃ in the Temperature Range 203−253 K

Abstract

Uptake of acetaldehyde on ice surfaces has been investigated over the temperature range 203-253 K using a coated wall flow tube coupled to a mass spectrometric detection. The experiments were conducted on pure ice surfaces and on liquid/solid ice mixture both doped with nitric acid (0.063, 0.63, and 6.3 wt %). Uptake of acetaldehyde on these surfaces was always found to be totally reversible whatever the experimental conditions were. The number of acetaldehyde molecules adsorbed per surface unit was conventionally plotted as a function of acetaldehyde concentration in the gas phase. Although the amounts of acetaldehyde adsorbed on solid ice surfaces (pure and HNO(3)-doped ice) were approximately similar and rather limited, the number of acetaldehyde molecules taken up on the HNO(3)-doped solid ice/liquid mixtures are significantly higher, up to 1 or 2 orders of magnitudes compared to pure ice surfaces. At 213 K for example and for low concentrations of acetaldehyde (<1 x 10(13) molecule cm(-3)), the amount of acetaldehyde molecules taken up on solid/liquid doped surfaces is 3.3 and 8.8 times higher than those measured on pure ice respectively for 0.063 and 0.63 wt % of HNO(3). The huge quantities of acetaldehyde taken up by liquid-/solid-doped mixtures are likely dissolved in the nonhomogeneous liquid part of the surfaces according to the Henry's law equilibrium. As a consequence, up to about 10% of acetaldehyde may be scavenged by supercooled liquid droplets of convective clouds in the upper troposphere.

Organics in environmental ices: sources, chemistry, and impacts

“…Where the necessary data are available (parameterizations for Henry's Law constant, activity coefficient, and solubility in the ice matrix), organic species may be modeled in the same fashion as inorganic species. Related to this discussion are experiments by Petitjean et al (2009), which showed increased, solubility-driven uptake of acetaldehyde in the presence of HNO 3 under conditions where it may form a brine at the ice surface, consistent with observations for ethanol (Kerbrat et al, 2007) and acetone (Journet et al, 2005).…”

“…It was also found to be independent of the state (i.e., liquid versus frozen) of the condensed phase; this was attributed to the presence of the DI. Comparable results have also been obtained with many other oxygenated VOC species, such as acetaldehyde (Petitjean et al, 2009), formic and acetic acids (Jedlovszky et al, 2008;Symington et al, 2010), and alcohols (Kerbrat et al, 2007;Abbatt et al, 2008). A few studies have also shown that the coadsorption of a VOC with another trace gas onto the ice surface can be described well using a competitive Langmuir adsorption model Kerbrat et al, 2010) in the absence of chemically-induced surface changes (McNeill et al, 2006).…”

Acetaldehyde in the Alaskan subarctic snowpack

“…2). At 243 K, a value of 3.8 pptw is found, because Petitjean et al (2009) observed of a very weak temperature dependence of acetaldehyde adsorption on ice around 240 K. Even with the approximations made on P CH3CHO , on temperature and on other variables, there is no reasonable scenario that can make the laboratory data of Petitjean et al (2009) agree with our field measurements, confirming that adsorption onto ice surfaces can only explain a negligible fraction of the acetaldehyde concentrations that we measured.…”

“…Despite the lack of data on P CH3CHO , we can nevertheless seek a confirmation of this conclusion from recent laboratory measurements of acetaldehyde adsorption on ice, at temperatures up to 253 K (Petitjean et al, 2009). We nevertheless need an estimation of P CH3CHO , which can be obtained from acetaldehyde measurements at Arctic locations.…”

“…This is thought to be the case for formaldehyde (Burkhart et al, 2002;Perrier et al, 2002). They can also adsorb onto snow crystal surfaces, therefore remaining available for reactions with atmospheric species, and this is thought to apply to acetaldehyde and heavier aldehydes (Petitjean et al, 2009;Sokolov and Abbatt, 2002). Houdier et al (2002) suggested that acetaldehyde might also be incorporated into organic aerosols that can be scavenged by snow crystals during their growth or fall, or dry-deposited to the snow surface after precipitation.…”