First-time direct proof of chemical reactions in particulates

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Paul Scherrer Institute

André Prévôt (right) und Urs Baltensperger at the newly developed device that analyses molecules in particulate matter. Credit: Paul Scherrer Institute/Mahir Dzambegovic

André Prévôt (proper) und Urs Baltensperger on the newly developed gadget that analyses molecules in particulate matter. Credit score: Paul Scherrer Institute/Mahir Dzambegovic

Researchers on the Paul Scherrer Institute PSI have developed a brand new methodology to analyse particulate matter extra exactly than ever earlier than. With its assist, they disproved a longtime doctrine: that molecules in aerosols endure no additional chemical transformations as a result of they’re enclosed in different suspended particulate matter. Within the smog chamber at PSI, they analysed chemical compounds immediately in aerosols and noticed how molecules dissociated and thus launched, for instance, gaseous formic acid into the ambiance. These findings will assist to enhance the understanding of worldwide processes concerned in cloud formation and air air pollution and to refine the corresponding fashions. The outcomes of this investigation are revealed in the present day within the journal Science Advances.

Anybody who takes a stroll by means of a coniferous forest and enjoys the tangy, refreshing air is inhaling α-pinene. This is without doubt one of the risky natural compounds within the oils of conifer bushes, and it additionally happens in eucalyptus and rosemary. The odor triggers nice emotions in most individuals. Much less nice is that the compound modifications within the ambiance, below the affect of radicals, into different compounds, so-called extremely oxidised natural molecules. A few of these are reactive, to some extent dangerous substances. They’ve solely lately come below scrutiny by atmospheric researchers, and their position, for instance in cloud formation, is just not but understood.

These extremely oxidized natural molecules are much less risky than the beginning substance α-pinene and due to this fact condense simply. Along with mud particles and different stable and liquid substances within the air, they kind what we name particulate matter or aerosols.

“Thus far it was thought that such molecules are shielded from additional transformations as soon as they’ve landed in particulate matter,” says Andre Prévôt of the Laboratory of Atmospheric Chemistry at PSI. “It was believed that they then wouldn’t change any extra, however would merely unfold out over the ambiance and ultimately rain down.”

This widespread opinion doesn’t correspond to actuality, nonetheless, as Prévôt and his fellow researchers at PSI confirmed: “The reactions proceed, even within the particulate matter.” The molecules stay reactive and both react with one another to kind bigger particles or disassociate, thereby releasing for instance formic acid. This widespread compound is discovered not solely in ants and stinging nettles, but in addition within the ambiance, the place it is a crucial indicator of air air pollution.

The PSI researchers’ observations ought to assist to enhance simulation fashions, akin to these for cloud formation and air air pollution. The fashions simulate what occurs within the ambiance to foretell, for instance, how a discount in sure emissions will have an effect on air high quality.

From the aerosol into the measuring gadget

For the primary time, PSI researchers analysed chemical compounds immediately in particulate matter below atmospheric circumstances. For this they used the PSI smog chamber, by which processes within the ambiance might be simulated. The researchers injected a droplet of α-pinene into the chamber and precipitated the compound to react with ozone. Over a interval of 15 hours, they noticed which chemical compounds fashioned from α-pinene and which disappeared once more afterwards.

This was made doable by a brand new analytic gadget for atmospheric measurements that the researchers developed in cooperation with the corporate Tofwerk in Thun, Switzerland: a so-called EESI-TOF (extractive electrospray ionisation time-of-flight mass spectrometer). “It additionally detects bigger molecules immediately within the aerosol,” explains atmospheric chemist Urs Baltensperger. “Earlier measurement strategies, however, chop up the molecules into smaller fragments at excessive temperatures.” The brand new gadget ionises with out fragmentation. “We are able to file every molecule individually.”

Tofwerk has now introduced the gadget to market with the assistance of PSI, in order that different atmospheric researchers can even profit from the brand new methodology.

Measurements in Zurich

The brand new analytic methodology can be utilized not solely within the laboratory, but in addition immediately on web site.

In the course of the winter of 2018/19 and the summer season of 2019, PSI researchers used it to analyze aerosols within the air in Zurich.

Because it turned out, a very good third of Zurich’s particulate matter in summer season consists solely of response merchandise of α-pinene and related molecules. In winter, nonetheless, emissions from wood-burning techniques and their response merchandise come to the fore.

The researchers have deliberate additional measurement campaigns in China and India. There they need to analyse which molecules kind within the air of a metropolis with greater than 1,000,000 inhabitants.


The analysis outcomes are being revealed on 13 March 2020 within the journal Science Advances.

Textual content: Paul Scherrer Institute / Brigitte Osterath

About PSI

The Paul Scherrer Institute PSI develops, builds and operates massive, advanced analysis amenities and makes them accessible to the nationwide and worldwide analysis group. The institute’s personal key analysis priorities are within the fields of matter and supplies, power and atmosphere and human well being. PSI is dedicated to the coaching of future generations. Due to this fact about one quarter of our workers are post-docs, post-graduates or apprentices. Altogether PSI employs 2100 individuals, thus being the most important analysis institute in Switzerland. The annual finances quantities to roughly CHF 407 million. PSI is a part of the ETH Area, with the opposite members being the 2 Swiss Federal Institutes of Know-how, ETH Zurich and EPFL Lausanne, in addition to Eawag (Swiss Federal Institute of Aquatic Science and Know-how), Empa (Swiss Federal Laboratories for Supplies Science and Know-how) and WSL (Swiss Federal Institute for Forest, Snow and Panorama Analysis).

Unique publication

On the destiny of oxygenated natural molecules in atmospheric aerosol particles
V. Pospisilova, F. D. Lopez-Hilfiker, D. M. Bell, I. El Haddad, C. Mohr, W. Huang, L. Heikkinen,
M. Xiao, J. Dommen, A. S. H. Prévôt, U. Baltensperger, J. G. Slowik
Science Advances, 13 March 2020 (on-line)
DOI: 10.1126/sciadv.aax8922

Additional info

An extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF) for on-line measurement of atmospheric aerosol particles
F. D. Lopez-Hilfiker, V. Pospisilova, W. Huang, M. Kalberer, C. Mohr, G. Stefenelli, J. A. Thornton, U. Baltensperger, A. S. H. Prévôt, J. G. Slowik
Atmospheric Measurement Methods, 11 September 2019 (on-line)
DOI: 10.5194/amt-12-4867-2019

Natural aerosol supply apportionment in Zurich utilizing an extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF-MS) – Half 1: Biogenic influences and day-night chemistry in summer season
G. Stefenelli, V. Pospisilova, F. D. Lopez-Hilfiker, Okay. R. Daellenbach, C. Hüglin, Y. Tong, U. Baltensperger, A. S. H. Prévôt, J. G. Slowik
Atmospheric Chemistry and Physics, 10 December 2019 (on-line)
DOI: 10.5194/acp-19-14825-2019

Natural aerosol supply apportionment in Zurich utilizing an extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF-MS) – Half 2: Biomass burning influences in winter
L. Qi, M. Chen, G. Stefenelli, V. Pospisilova, Y. Tong, A. Bertrand, C. Hueglin, X. Ge, U. Baltensperger, A. S. H. Prévôt, J. G. Slowik
Atmospheric Chemistry and Physics, 20 June 2019 (on-line)
DOI: 10.5194/acp-19-8037-2019

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