Author Archives: sklog2017



Sasho: Ionic strength effects on the absorption properties of acetosyringone, a typical lignin derived compound

Sasho 研究员

Secondary organic aerosols (SOA) can be formed through aqueous-phase reactions in aerosol deliquescent particles, clouds and fogs, which has been widely observed in both ambient studies and lab simulations. However, the aqueous-phase formation of SOA and its impacts on oxidation degree are far from being clearly understood, particularly in heavily polluted atmospheres. For example, in conditions of severe Beijing Haze with PM2.5 levels higher than 300 μg m-3 the ionic strength in the wet particles varies between 13 and 43 M. This high ionic strength can affect the kinetics and products distribution within the aerosol deliquescent particles and, thus, it can affect aerosol composition and optical properties. However, the ionic strength effects on aqueous phase reactions of atmospheric relevance have been barely studied in the past.

In this work, Gligorovski and his-coworkers advanced the knowledge on ionic strength effects on the absorption properties of acetosyringone (AcS), a typical lignin derived compound and on the photoinduced degradation of AcS itself.

Surprisingly, it can be observed a bathochromic (red) shift of the n→π* absorption band of AcS, from λmax = 297 nm in the dilute aqueous phase to λmax = 355 nm at in the presence of 6 mol L-1 NaClO4. Also the π → π* band underwent a red shift, from λmax = 214 nm to λmax = 247 nm. They are also showing that the photodegradation of AcS is six times faster in the presence of elevated ionic strengths, demonstrating that photochemical processes in aerosol deliquescent particles may result in different kinetics than in the analogous diluted aqueous-phase chemistry, with the potential to significantly affect aerosol composition and optical properties.

Finally, the light-induced transformation of AcS leads to a pH decrease, which in the atmosphere would translate into a light-induced acidification of the aerosol particles due to liberation of protons.

For more information, see the paper recently published in Atmospheric Environment at:

Figure: The absorption spectra of AcS (1´10-4 mol L-1 concentration) at zero ionic strength (black line), and in the presence of different concentrations of NaClO4: 0.5 M (red line), 1 M (blue line), 2 M (green line), 5 M (cyan line) and 6 M (yellow line).


Photocatalytic paints based on titanium dioxide (TiO2) nanoparticles represent a promising treatment technology for cleaning the air at our dwellings. A few studies have shown that instead of elimination of harmful indoor air pollutants the production of carbonyl compounds occurs from the photocatalytic paints.

Gligorovski (a corresponding author of the contribution) and his coworkers published an article in Environmental Science & Technology focused on photocatalytic paints based on titanium dioxide (TiO2) which represent a promising remediation technology for cleaning the air at our homes. The photocatalytic paints are typically used to eliminate the gas-phase pollutants, like nitrogen oxides (NOx) and volatile organic compounds (VOCs) in particular the harmful aldehydes, formaldehyde and acetaldehyde. However, few studies have shown that instead of elimination of these harmful pollutants the emission of carbonyl compounds occurs during the irradiation of the photocatalytic paints. The main source of such carbonyls was assumed to be the photoinduced decomposition of paint binders, without performing further investigations.

The authors report unexpectedly high levels of volatile organic compounds (VOCs) released by photocatalytic paints. The concentrations of the VOCs were measured continuously and on-line with the state of the art PTR-ToF-MS (Proton Transfer Reaction-Time of Flight-Mass Spectrometry) coupled to a flow tube photoreactor. The authors describe a detailed reaction mechanism responsible for the production of harmful indoor air pollutants. The produced hydroxyl radicals (OH) upon activation of TiO2, react with the organic constituents of the paint leading to generation of formaldehyde and acetaldehyde, among the others. It is demonstrated that the quantity of TiO2 embedded in the paint and the constituent of the binder are of paramount importance with respect to the formation of these harmful indoor air pollutants.

Finally, the obtained laboratory results are rescaled to real-life scenario to determine the implications induced by these paints to indoor air quality.

The photocatalytic paints represent an important source of formaldehyde, acetaldehyde and other carbonyls. In addition to these harmful carbonyl compounds an important number of saturated and unsaturated carboxylic acids (C2, C3, C4 and C5), alkenes (C3, C4, C5 and C6) and saturated and unsaturated cyclic compounds, were observed suggesting that this remediation technology must be well optimized prior to be launched on the market and used in our dwellings.

Sasho 研究员

Paper info: A. Gandolfo, S. Marque, B. Temime-Roussel, R. Gemayel, H. Wortham, D. Truffier-Boutry, V. Bartolomei, S. Gligorovski, Unexpectedly high levels of organic compounds released by indoor photocatalytic paints, Environ. Sci. Technol., 2018, 52, 11328-11337.