EESS talk on "The chemical composition of the interface of (some) atmospheric particles: A molecular view"

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Event details

Date 07.12.2021 12:1513:15  
Speaker Dr Michel Rossi, Emeritus Senior Scientist, Group Ludwig, EPFL
Location Online
Category Conferences - Seminars
Event Language English
Abstract:
A flowing gas experiment is used to “interrogate” the gas-solid interface of specific atmospheric particles using reactive probe gases that interact to various extents with surface functional groups making up the interface.
For instance, a basic probe gas such as trimethylamine may interact with surface acidic functional groups such as carboxylic acids or acidic OH groups in a neutralization reaction. We will first explain the advantages and disadvantages of the used method based on molecular beam sampling mass spectrometry and subsequently present three examples that describe applications of the method to atmospheric chemistry: (a) the interface of amorphous carbon generated from incomplete combustion/oxidation processes or biomass burning has a wealth of surface functional groups revealing both its provenance as well as past atmospheric processing. More often than not the interface has both acidic and basic as well as oxidizing and reducing properties side-by-side;
(b) The atmospheric fate of semivolatile organic compounds that are partially oxidized is subject to the presence of secondary organic aerosols and atmospheric mineral dust particles. We will undertake a brief tour of the heterogeneous interaction of three partially oxidized semivolatile compounds with two proxies of mineral dust particles (Kaolinite, Arizona Test Dust) in terms of adsorption and desorption kinetics. We will highlight the relationship between organic structure and abundance of surface functional groups of the mineral dust proxy; (c) the interfacial composition of an atmospheric particle greatly controls the role it plays in oxidative stress on living organisms in terms of supporting Reactive Oxygen Species (ROS) through interfacial reactions in the presence of atmospheric oxygen. Laboratory experiments using antioxidants in solution correlate with the abundance of redox-cycling surface functional groups. It turns out that the interface acts as a redox catalyst in order to accelerate surface oxidation in the presence of excess atmospheric oxygen.

Short biography:
PhD in physical chemistry (University of Basel, 1975). postdoctoral fellow at Stanford Research Institute (SRI International, 1976-78); Swiss National Science Foundation fellowship (1979); rose through the ranks of Stanford Research Institute to end up as program manager/senior scientist in the Chemical Kinetics Department/Physical Sciences Division (1991); adjoint scientifique and chargé de cours at EPFL/DGR, Laboratoire de Pollution Atmosphérique et Sol (LPAS), in charge of the heterogeneous atmospheric chemistry program (1991-2008); senior scientist at PSI in the Laboratory of Atmospheric Chemistry (LAC/ENE) (2009- 2019); guest scientist at EPFL since 2017 maintaining a level of scientific activity in the GR-Lud/IIE Department to date.

Practical information

  • General public
  • Free
  • This event is internal

Organizer

  • EESS - IIE

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Tags

Chemical kinetics heterogeneous (interfacial) processes atmospheric particles and aerosols free radicals in combustion and atmospheric oxidation free radical thermochemistry

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