Category Archives: 科研进展

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:

https://www.sciencedirect.com/science/article/pii/S1352231018307374

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).

ES&T:室内光催化涂料可能产生/释放大量二次挥发性有机污染物(VOCs)

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.

ES&T视角: 中国应加强室内空气(光)化学与健康研究

Sasho 研究员

Sasho Gligorovski, a research professor in Guangzhou Institute of Geochemistry of CAS,  suggests that advancing the scientific knowledge on indoor (photo)chemistry and resulting health effects in the coming years in China, requires stronger interactions between atmospheric chemists/physicists, and scientists from the fields of toxicology, epidemiology, and medicine.

In this viewpoint, the latest exciting findings on the HONO formation processes and OH radical production through photolysis of HONO have been reviewed and commented. For a long time, the contribution of HONO photolysis to indoor OH radicals has been overlooked and, the indoor levels of OH radicals and the resulting health impact are very likely underestimated, especially within a short time-frame or a small confined space. In China, the concentrations of indoor pollutants are 100 to 1000 times higher than that inside European and US homes, not to mention 3.1 million deaths in rural China caused by indoor air pollution every year. However, our knowledge on the processes related to OH radical formation in the indoor environments of Chines dwellings is very limited, which makes it becomes an urgent need to take actions from now on. The authors believe that, by taking full consideration of real-life indoor scenarios in China (e.g., coal burning for heating in the North China, cooking) and with the assistance of advanced experimental and analytical techniques lately emerged, comprehensive understanding on the indoor photochemistry and resulting health impact in China indoor environments is attainable in the near future.

Just as the outdoor atmospheric chemistry community has focused in recent years on developing an understanding of specific topics, such as haze and PM2.5, it is just now starting to address the photochemistry in the environment in which we live 90% of our time.

In this manner this viewpoint informs the readers of research questions of direct relevance to their lives. It also points out that this complex chemistry will become even more important as we live more and more of our lives indoors, i.e. increased indoor exposure will arise as Chinese society rapidly industrialize.

Fo r more informtaion, please see:  S. Gligorovski, X. Li, H. Herrmann, Indoor (Photo)chemistry in China and Resulting Health Effects, Environ. Sci. Technol., 2018, 52, 10909–10910.