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Using Photothermal Interferometry to Improve our Understanding of Carbonaceous Aerosol Impacts

English title Using Photothermal Interferometry to Improve our Understanding of Carbonaceous Aerosol Impacts
Applicant Weingartner Ernest
Number 172649
Funding scheme Project funding
Research institution Institut für Aerosol- und Sensortechnik Hochschule für Technik Fachhochschule Nordwestschweiz
Institution of higher education University of Applied Sciences and Arts Northwestern Switzerland (without UTE) - FHNW
Main discipline Climatology. Atmospherical Chemistry, Aeronomy
Start/End 01.07.2017 - 31.12.2020
Approved amount 375'404.00
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All Disciplines (2)

Climatology. Atmospherical Chemistry, Aeronomy
Other disciplines of Physics

Keywords (10)

health effects; source apportionment; diesel particulate matter; soot particle; climate change; wood combustion; aerosol particles; air polution; black carbon; light absorption

Lay Summary (German)

Untersuchung von Verbrennungspartikeln mittels photothermischer InterferometrieUsing Photothermal Interferometry to Improve our Understanding of Carbonaceous Aerosol ImpactsInvestigation des particules de combustion en utilisant l'interférométrie photothermiqueKleine Schwebepartikel in unserer Luft - auch Aerosolpartikel genannt - sind von grosser Bedeutung, da sie einerseits klimaaktiv sind und andererseits unsere Gesundheit negativ beeinflussen können. Eine besondere Rolle fällt dabei den Russpartikeln zu, da sie vorwiegend anthropogenen Ursprungs sind.Zentrale Fragen, die es hierbei zu beantworten gilt: •Wie wirken diese Partikel auf unser Klima und Gesundheit?•Welche Quellen sind zu welchem Anteil an den Russpartikel-Konzentrationen in unserer Aussenluft verantwortlich?
Lay summary
Inhalt und Ziel des Forschungsprojekts

Unser neuer Ansatz, der Antworten zu diesen Fragen liefern soll besteht darin, die physikalischen Eigenschaften der Russpartikel mittels so genannter photothermischer Interferometrie (PTI) zu erfassen. In einem ersten Schritt wird dieses Messprinzip, das die ausgeprägt starke Lichtabsorption der Russpartikel nützt, weiterentwickelt. Der wesentliche Unterschied zu den heutigen Standard-Messmethoden liegt darin, dass die PTI-Methode sehr empfindlich ist und kaum durch Messartefakte belastet wird, da die Messung in-situ erfolgt. Das heisst, die Partikel werden in ihrem luftgetragenen Zustand untersucht.

Nach Abschluss der PTI-Entwicklungsphase werden Labor- und Feldexperimente durchgeführt um besser zu verstehen, wie sich die Eigenschaften und Wirkungen der Russpartikel aufgrund von Alterungsprozessen in unserer Atmosphäre ändern. Des Weiteren erhoffen wir uns, dass die neue Methode auf einfache Art Information über die Herkunft der Russpartikel (z.B. Holzverbrennung / Verkehrsruss) liefert.

Wissenschaftlicher und gesellschaftlicher Kontext des Forschungsprojekts

Unsere Arbeit wird einen wichtigen Betrag leisten, die gegenwärtigen Unsicherheiten in der Klimawirkung von Aerosolen (insb. Russ) zu reduzieren. Die neue Messmethode kann auch dazu eingesetzt werden, um die verschiedenen Quellen von Russ (wie z.B. Fahrzeuge, Holz-Heizungen, Kohlekraftwerke) zu ermitteln. Dies ermöglicht, wirksamere technologische und politische Massnahmen einzuleiten, die eine Verbesserung unserer Luftqualität zur Folge haben.


Direct link to Lay Summary Last update: 19.06.2017

Responsible applicant and co-applicants


Project partner


A single-beam photothermal interferometer for in situ measurements of aerosol light absorption
VisserBradley, Röhrbein Jannis, SteigmeierPeter, DrinovecLuka, MočnikGriša, WeingartnerErnest (2020), A single-beam photothermal interferometer for in situ measurements of aerosol light absorption, in Atmospheric Measurement Techniques, 13(12), 7097-7111.


Group / person Country
Types of collaboration
Felix Betschon, Vario Optics AG Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Industry/business/other use-inspired collaboration
William Whelan, Centre for Advanced Photonics & Process Analysis, Cork Institute of Technology Ireland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Industry/business/other use-inspired collaboration
Griša Mocnik, Center for Atmospheric Research, University of Nova Gorica Slovenia (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure

Communication with the public

Communication Title Media Place Year
Media relations: print media, online media MIT LASER SPURENSTOFFE IM WASSER ENTDECKEN Digital Bytes International German-speaking Switzerland 2020


Title Year
Unsere Absolventin Frau Manuela Wipf wurde für Ihre Bachelor-Arbeit im Kontext des Projektes mit dem Förderpreis 2020 von ausgezeichnet. 2020

Associated projects

Number Title Start Funding scheme
135356 Interaction of Aerosols with Clouds and Radiation 01.12.2011 Project funding
100280 The effects of organic compounds on the hygroscopic properties of inorganic aerosols 01.07.2003 Project funding


Atmospheric aerosols are fine particles suspended in the air. These small particles have a big impact on our health, and on our climate. They are climate active due to their interaction with solar radiation, thus changing the Earth’s radiation balance. Aerosols can have a cooling or a warming effect depending on the balance of light scattering to light absorbing components. Of particular relevance are soot or black carbon (BC) particles, which are highly efficient light absorbers that are emitted by combustion processes. Nowadays, these BC particles are predominately human-made, and this brings them into the focus of anthropogenic climate debates: Estimates show that BC is the second strongest man-made contributor (after CO2) to global warming. In addition, small BC particles pose a significant threat to public health. They contain many toxic substances and can enter deeply into our lungs and bloodstream. The World Health Organization has classified diesel exhaust as carcinogenic to humans. Due to these serious climate and health effects, BC emission reductions came into political focus. Successful BC mitigation strategies will result in immediate and multiple benefits for human well-being.The commonly used method for quantifying BC mass loadings is based on measuring light absorption of deposited particles in fibrous filters. With this proposal, we want to employ a new aerosol absorption measurement technique using photothermal interferometry (PTI). This promising in-situ technique has the potential to deliver more precise and accurate data with a fairly robust and simple tool. PTI is expected to be very sensitive, almost free of artefacts, and is traceable as it can be calibrated against gases with known absorption. Besides the precise measurement of the BC concentration, PTI will also allow the determination of specific properties of light absorbing particles, such as their effective size and the absorption Angström exponent. These additional parameters are useful to apportion emissions to BC emitting sources (i.e. diesel engines vs. wood burning appliances). This is e.g. of importance since legislation enforces the reduction of traffic emissions, while on the other hand wood stoves enjoy great popularity as a CO2 neutral energy source. Consequently, the contribution of atmospheric BC from wood stoves is expected to increase. PTI, as an improved practical technique, could therefore be employed in monitoring networks, and PTI will contribute to better evaluating the success of BC mitigation strategies.The implementation phase of PTI will be conducted in close collaboration with our colleagues at PSI and EMPA. Extensive laboratory experiments will provide a better understanding of how atmospheric aging processes change the optical properties of BC particles. The newly developed PTI will then be employed together with state-of-the-art instruments at the PSI smog chamber to investigate how the mass absorption coefficient (MAC) of the BC aerosols depends on the coating thickness, core size, relative humidity, and light wavelength. In these aging experiments, we will elucidate how transparent hydrated organic coatings enhance the ability of BC to absorb visible radiation. These insights will help to better parameterize the aging processes in climate and air quality models. We also plan to operate the new PTI instrument at air quality monitoring stations, at which aerosol light absorption and BC mass loadings are measured on a routine basis. Intercomparison measurements at several sites, influenced by various types of BC aerosols, are foreseen during different seasons. This will be the final evaluation of whether the PTI instrument can be used for the envisaged source apportionment of BC. These intercomparison campaigns, with the benefits provided by PTI (traceability and in-situ measurements), will also help to improve the correction algorithms used for traditional filter-based instruments.