Markus Ammann

📢 We are excited to announce Prof. Dr. Martijn Schaap, principal scientist at TNO and Extraordinary Professor at the Free University of Berlin, as our next speaker for the #ReCLEAN Seminar Series.

📅 Tuesday, April 15, at 1 pm via Zoom: epfl.zoom.us/j/6460420839...

💡 More info: reclean.epfl.ch

Iodine Activation from Iodate Reduction in Aqueous Films via Photocatalyzed and Dark Reactions Iodine in the atmosphere destroys ozone and can nucleate particles by formation of iodic acid, HIO3. Recent field observations suggest iodate recycles from particles sustaining significant gas-phase IO radical concentrations (0.06 pptv) in aged stratospheric air, and in elevated dust plumes. However, laboratory evidence for iodine activation from aerosols is currently missing. Here, a series of coated-wall flow tube (CWFT) experiments test for iodine release from thin aqueous films containing iodate. Photocatalyzed reactions were studied using iron(III) citrate (Fe–Cit), Arizona Test Dust (ATD), and Fe2O3, along with the dark reaction of iodate with H2O2 at 90% RH and 293 K. Fresh films were separately irradiated with visible and UV-A light, and the efficient release of molecular iodine, I2, was observed from all irradiated films containing photocatalysts. For films with Fe–Cit, visible light reduced larger amounts of iodate than UV-A light, activating ∼40% of iodate as I2. The formation of oxygenated volatile organic compounds (OVOC) and iodinated OVOC was also observed. Dark exposure of films to H2O2 led to I2 release in smaller amounts than suggested by Bray–Liebhafsky kinetics, consistent with H2O2 salting-out in the films, or possibly other reasons. Photochemical activation is enhanced by dust proxies in the film, and by aging the film with H2O2 in the dark prior to irradiation. These findings help explain recent field observations of elevated IO radical concentrations in lofted dust layers, and warrant the inclusion of photocatalyzed iodate reduction in atmospheric models.

New publication out: doi.org/10.1021/acse.... Iodate Recycling. Great job, Mago and Lucia! Great collaboration with UC Boulder (Rainer Volkamer 's group)

The U.S. Is Building an Early Warning System to Detect Geoengineering Balloon launches from around the world are part of a new kind of global alarm system: One that can detect if another country tries to dim the sun.

Very interesting article from the NYTimes about scientists on the front lines of monitoring the stratosphere to detect if someone starts geoengineering.

gift link: www.nytimes.com/2024...

Scientists as political advocates Science, both teaching and doing, is under attack. The recent US presidential election of a person and platform with anti-science bias exemplifies this. The study of climate processes and patterns and...

"Being purely reactive to political attacks (only playing defense) or assuming an artificial air of neutrality and seeking to 'stay on the sidelines' are both ethically problematic and practically detrimental."
www.science.org/doi/10.1126/...

Metals from spacecraft reentry in stratospheric aerosol particles | PNAS Large increases in the number of low earth orbit satellites are projected in the coming decades [L. Schulz, K.-H. Glassmeier, Adv. Space Res. 67, 1...

Aerosols in the stratosphere—which partially control the ozone layer—are being significantly impacted by ablation of satellites reentering the atmosphere. This effect will only increase as we put more and more stuff in low earth orbit.

I am still recruiting a PhD student! Impact of transition metals on formation and aging of SOA. Chamber experiments, EESI-MS, STXM, multilayer modelling. PhD enrolment at ETH Zürich. Last week for application at www.psi.ch/en/hr/job-op.... #psi, #aerosol, #atmoschem