Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Light-absorbing aldol condensation products in acidic aerosols: Spectra, kinetics, and contribution to the absorption index
AbstractThe radiative properties of aerosols that are transparent to light in the near-UV and visible, such as sulfate aerosols, can be dramatically modified when mixed with absorbing material such as soot. In a previous work we had shown that the aldol condensation of carbonyl compounds produces light-absorbing compounds in sulfuric acid solutions. In this work we report the spectroscopic and kinetic parameters necessary to estimate the effects of these reactions on the absorption index of sulfuric acid aerosols in the atmosphere. The absorption spectra obtained from the reactions of six different carbonyl compounds (acetaldehyde, acetone, propanal, butanal, 2-butanone, and trifluoroacetone) and their mixtures were compared over 190–1100nm. The results indicated that most carbonyl compounds should be able to undergo aldol condensation. The products are oligomers absorbing light in the 300–500nm region where few other compounds absorb, making them important for the radiative properties of aerosols. Kinetic experiments in 96–75wt% H2SO4 solutions and between 273 and 314K gave an activation energy for the rate constant of formation of the aldol products of acetaldehyde of −(70±15)kJmol−1 in 96wt% solution and showed that the effect of acid concentration was exponential. A complete expression for this rate constant is proposed where the absolute value in 96wt% H2SO4 and at 298K is scaled to the Henry's law coefficient for acetaldehyde and the absorption cross-section for the aldol products assumed in this work. The absorption index of stratospheric sulfuric acid aerosols after a 2-year residence time was estimated to 2×10−4, optically equivalent to a content of 0.5% of soot and potentially significant for the radiative forcing of these aerosols and for satellite observations in channels where the aldol products absorb.
Light-absorbing aldol condensation products in acidic aerosols: Spectra, kinetics, and contribution to the absorption index
AbstractThe radiative properties of aerosols that are transparent to light in the near-UV and visible, such as sulfate aerosols, can be dramatically modified when mixed with absorbing material such as soot. In a previous work we had shown that the aldol condensation of carbonyl compounds produces light-absorbing compounds in sulfuric acid solutions. In this work we report the spectroscopic and kinetic parameters necessary to estimate the effects of these reactions on the absorption index of sulfuric acid aerosols in the atmosphere. The absorption spectra obtained from the reactions of six different carbonyl compounds (acetaldehyde, acetone, propanal, butanal, 2-butanone, and trifluoroacetone) and their mixtures were compared over 190–1100nm. The results indicated that most carbonyl compounds should be able to undergo aldol condensation. The products are oligomers absorbing light in the 300–500nm region where few other compounds absorb, making them important for the radiative properties of aerosols. Kinetic experiments in 96–75wt% H2SO4 solutions and between 273 and 314K gave an activation energy for the rate constant of formation of the aldol products of acetaldehyde of −(70±15)kJmol−1 in 96wt% solution and showed that the effect of acid concentration was exponential. A complete expression for this rate constant is proposed where the absolute value in 96wt% H2SO4 and at 298K is scaled to the Henry's law coefficient for acetaldehyde and the absorption cross-section for the aldol products assumed in this work. The absorption index of stratospheric sulfuric acid aerosols after a 2-year residence time was estimated to 2×10−4, optically equivalent to a content of 0.5% of soot and potentially significant for the radiative forcing of these aerosols and for satellite observations in channels where the aldol products absorb.
Light-absorbing aldol condensation products in acidic aerosols: Spectra, kinetics, and contribution to the absorption index
Nozière, Barbara (Autor:in) / Esteve, William (Autor:in)
Atmospheric Environment ; 41 ; 1150-1163
02.10.2006
14 pages
Aufsatz (Zeitschrift)
Elektronische Ressource
Englisch
Visibility in absorbing aerosols
| Elsevier | 1982
New Directions: Light absorbing aerosols and their atmospheric impacts
| Elsevier | 2013
Regioselective aldol condensation of pyrrolobenzoxazinetriones with cycloalkanones
| British Library Online Contents | 2014