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Photophoretic spectroscopy in atmospheric chemistry - high sensitivity measurements of light absorption by a single particle

Applicant Bluvshtein Nir
Number 190477
Funding scheme Spark
Research institution Institut für Atmosphäre und Klima ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Climatology. Atmospherical Chemistry, Aeronomy
Start/End 01.03.2020 - 31.10.2021
Approved amount 100'000.00
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Keywords (6)

atmospheric chemistry; light absorption; photophoretic spectroscopy; electrodynamic balance; optical properties; aerosols

Lay Summary (German)

Lead
Feste und flüssige Partikel in der Atmosphäre (Aerosole) absorbieren und streuen das einfallende Sonnenlicht. Sie spielen eine wichtige Rolle für das Klima, da sie die Strahlungsbilanz des Planeten beeinflussen. Heutige Klimamodelle behandeln die Strahlungswechselwirkung mit den Aerosolen nur in einer stark vereinfachten Form, weshalb der Einfluss der Aerosole auf das zurückliegende aber auch das zukünftige Klima immer noch sehr unsicher ist. Einer der Gründe dafür ist das fehlende Detailverständnis von organischen Aerosolen, die absorbierenden Moleküle enthalten. Während der Verweildauer dieser organischen Aerosole in der Atmosphäre, die von Tagen zu einigen Wochen reichen kann, unterliegen diese Teilchen physikalischen und chemischen Alterungsprozessen, welche ihre Zusammensetzung und auch die optischen Eigenschaften verändern. Diese Alterung beeinflusst so auch die transmittierte Strahlung.
Lay summary

Das Hauptziel dieses Projektes ist es eine neue, sehr empfindliche Methode zur Messung der Veränderung der Lichtabsorption einzelner Aerosolpartikel während dieser Alterungsprozesse zu entwickeln, um so die bestehenden Unsicherheiten im Verständnis der Prozesse zu verringern-

Ausserdem soll in diesem Projekt die Grundlage für eine neue Methodologie gelegt werden, in der gleichzeitig die sich verändernden Absorptionseigenschaften mit der jeweiligen chemischen Zusammensetzung gemessen werden. Dies könnte ein Meilenstein in unserem Bemühen sein, die Alterung dieser Partikel in der Atmosphäre zu verstehen und einen wichtigen Beitrag zum Verständnis des Klimasystems leisten. 

Direct link to Lay Summary Last update: 03.12.2019

Responsible applicant and co-applicants

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Publications

Publication
Photophoretic spectroscopy in atmospheric chemistry – high-sensitivity measurements of light absorption by a single particle
Bluvshtein Nir, Krieger Ulrich K., Peter Thomas (2020), Photophoretic spectroscopy in atmospheric chemistry – high-sensitivity measurements of light absorption by a single particle, in Atmospheric Measurement Techniques, 13(6), 3191-3203.

Datasets

Photophoretic spectroscopy in atmospheric chemistry – high-sensitivity measurements of light absorption by a single particle

Author Bluvshtein, Nir; Krieger, Ulrich; Peter, Thomas
Persistent Identifier (PID) 10.3929/ethz-b-000419840
Repository ETH Zuerich Research Collection
Abstract
Light absorbing organic atmospheric particles, termed brown carbon, undergo chemical and photochemical aging processes during their lifetime in the atmosphere. The role these particles play in the global radiative balance and in the climate system is still uncertain. To better quantify their radiative forcing due to aerosol-radiation interactions, we need to improve process level understanding of aging processes, which lead to either ‘browning’ or ‘bleaching’ of organic aerosols. Currently available laboratory techniques aim to simulate atmospheric aerosol aging and measure the evolving light absorption, but suffer from low sensitivity and precision. This study describes the use of electrodynamic balance photophoretic spectroscopy (EDB-PPS) for high sensitivity and high precision measurements of light absorption by a single particle. We demonstrate the retrieval of time-evolving imaginary part of the refractive index for a single levitated particle in the range of 10-4 to 10-5 with uncertainties of less than 25% and 60%, respectively. The experimental system is housed within an environmental chamber, in which aging processes can be simulated in realistic atmospheric conditions and lifetime of days to weeks. This high level of sensitivity enables future studies to explore the major processes responsible for formation and degradation of brown carbon aerosols.

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
EGU 2020 Talk given at a conference Photophoresis used for measurements of light absorption by a single particle 04.05.2020 Vienna (on-line), Austria Bluvshtein Nir;


Abstract

Solid and liquid particles in the atmosphere (termed aerosols) directly scatter and absorb incoming solar radiation. Because of this, these aerosols play an important role in the climate system by modifying the radiative balance of the planet. Climate models continue to lack an accurate representation of aerosol-radiation interactions and, therefore, the role aerosols have played in modulating past climate, and may play in modulating future climate, remains uncertain. A key reason for the large uncertainty in the radiative forcing of aerosols is that the temporal evolution of light absorbing organic compounds is poorly constrained. Light absorbing organic compounds are abundant in the atmosphere, but concentration and composition exhibit considerable temporal and spatial variability. During their lifetime in the atmosphere that varies from days to weeks, aerosols are subjected to chemical and physical processing (termed aging) which alters their composition and optical properties. This evolution ultimately affects how radiation is transmitted through the atmosphere. To address the uncertainty in the temporal evolution of light absorbing organic compounds, the primary goal of this proposal is to develop an analytical tool, new to the atmospheric chemistry community, for high sensitivity measurements of evolving light absorption by a single particle during chemical and photochemical processes in realistic atmospheric conditions. The specific objectives of the project are to:1.Extend the application of previous single particle photophoretic-spectroscopy techniques for accurate determination of light absorption by organic particles in the UV-vis wavelength range.2.Implement photophoretic-spectroscopy in an environmentally controlled single particle trap that allows for atmospheric aging processes in real-world conditions. The expected outcome of this study is an analytical tool able to retrieve the evolution of the imaginary part of the complex refractive index for light absorbing organic particles with significantly improved sensitivity and uncertainty compared with currently available techniques. Preliminary simulations showed that this outcome is within reach. Moreover, this project would lay critical foundations for the development of a new methodology to simultaneously measure the evolving light absorption properties and the molecular composition of atmospheric aerosols by coupling photophoretic-spectroscopy to an electrodynamic balance - soft ionization mass spectroscopy. This will lead to a step change in our understanding of how these particles evolve and influence the climate system by directly linking optical properties to chemical composition. The potential prospects form this technology demonstrates the far-reaching impact of this project.
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