Professor in Citizen Science and Director of SEI York, University of York

Air quality citizen science: the benefits and challenges

I will talk about about using a citizen science approach to explore air quality, describing the benefits for researchers and participants, along with some of the challenges relating to recruitment and engagement, hidden costs and pitfalls.

Professor of Atmospheric Science

Why are aerosol effects on climate so uncertain, and what are we doing about it?

Anthropogenic aerosols cool the planet and have offset a substantial fraction of greenhouse gas warming for substantial periods of the last century. Although global aerosol cooling is slowly diminishing, accurate quantification of the effect is vital for understanding the pathway to the 1.5 or 2.0 degree Paris targets. In this presentation I will discuss why aerosol effects on global climate are so hard to quantify and how we might achieve the “maximum feasible reduction” in uncertainty. The first task is to properly compute the uncertainty and diagnose the causes, rather than relying on small sets of simulations that prevent statistical analysis.

Full Professor, Physical Chemistry, Department of Chemistry and Applied Biosciences, ETH Zurich, Switzerland

Accelerated in-particle photochemistry and accelerated vapor nucleation

Ruth Signorell

Department of Chemistry and Applied Biosciences, ETH Zurich, CH-8093 Zurich, Switzerland

rsignorell@ethz.ch

Photochemical processes have been identified as the main cause of the degradation and oxidation of matter in atmospheric aerosol particles. When light interacts with an aerosol particle, the light intensity inside the particle can be significantly increased as the latter acts as a light-amplifying cavity. These optical confinement effects lead to an acceleration of photochemical reactions in aerosol particles compared to reactions in extended condensed matter. We studied and quantified the acceleration of in-particle photochemistry using photoacoustic spectroscopy [1] and X-ray spectroscopic imaging of single aerosol particles [2].

The formation of new particles through condensation from the gas phase is an important source of aerosols. Volatile vapor components can accelerate the nucleation of other, less volatile vapor components by orders of magnitude. To investigate the molecular mechanism behind accelerated vapor nucleation, we developed a new nucleation tool based on Laval expansions combined with soft cluster ionization [1]. We find that a catalytic cycle involving transient heteromolecular clusters is the origin of this acceleration phenomenon.

1. J.W. Cremer, K.M. Thaler, C. Haisch, R. Signorell, „Photoacoustics of single laser-trapped nanodroplets for the direct observation of nanofocusing in aerosol photokinectics”, Nat. Commun., 7, 10941 (2016)

2. P.C. Arroyo, G. David, P.A. Alpert, E.A. Parmentier, M. Ammann and R. Signorell, „Amplification of light within aerosol particles accelerates in-particle photochemistry”, Science, 376, 293-296 (2022).

3. C. Li, J. Krohn, M. Lippe and R. Signorell, Sci. Adv., 7, eabd9954 (2021).