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| Titel |
Characterization of the formaldehyde-H2O system using combined spectroscopic and mass spectrometry approaches |
| VerfasserIn |
A. Oancea, B. Hanoune, S. Facq, C. Focsa, B. Chazallon |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250029074
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| Zusammenfassung |
| The atmosphere is a multiphase reactor in which physical exchange processes,
heterogeneous reactions and photochemical reactions take place. The oxygenated
organics (formaldehyde, ethanol, acetone etc.) present at trace concentrations into the
atmosphere are known to play an important role in atmospheric chemistry due for
example to their contribution in the production of HOx radicals, which largely
determine the lifetime of pollutants [1]. Further, it has been shown that the interaction of
oxygenated organics with ice particles in the atmosphere has the potential to promote
heterogeneous chemistry [2]. In the polar lower troposphere, formaldehyde (H2CO) was
measured in concentrations that are much higher that those predicted by chemistry
models [3]. The mechanism at the origin of the formaldehyde production remains
however controversial as the incorporation / partitioning of H2CO in ice crystal
has to be determined first. Incorporation of formaldehyde into ice can take place
according to several different physical mechanisms like co-condensation, riming,
adsorption/desorption. The partitioning of formaldehyde between the gas phase, the liquid
and the solid phases is an important parameter that leads to a better understanding of the
incorporation mechanisms. In our work, different experimental approaches are used to
characterize the partitioning between the different phases in which the H2O-H2CO system
exists.
Recently, we investigated by mass spectrometry and infrared diode laser spectroscopy the
vapor liquid equilibrium (VLE) of formaldehyde aqueous solutions of different
concentrations at room temperature. From the data collected on the vapor pressures at
atmospherically relevant formaldehyde concentrations, we derived the Henry’s coefficients at
295 K [4].
In this study we present first results on the solubility of formaldehyde in ice. This allows a
better characterization of the partitioning of formaldehyde vapors above supercooled
droplets and/or ice at low temperatures (233-283K) and low dissolved fraction of
formaldehyde. Also presented is the thermal evolution of thin structured films of
condensed H2CO/H2O or H2CO/acid-doped (HNO3)-ice layers. This is examined using
temperature programmed desorption (TPD) experiments and Raman spectroscopy. The
results are compared with those obtained on co-condensed H2CO/H2O mixtures
[5].
[1] Atkinson R., Atmospheric Environment, 2000, 34: 2063
[2] Abbatt J.P.D., Chem.Rev. 2003, 103: 4783
[3] Dominé F., Shepson P.B., Science, 2002, 297: 1506
[4] Oancea A. et al. Environ. Sci. Technol. in press
[5] Chazallon B. et al. , Phys.Chem.Chem.Phys., 2008, 10: 702 |
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