Leçon inaugurale Prof. Athanasios Nenes

Abstract
Human activities profoundly alter the composition of the atmosphere, leading to a cascade of effects on climate, ecosystems and human health. Atmospheric particulate matter, or aerosols, play a central role in all these changes; they affect climate by modulating the Earth’s energy balance, clouds and precipitation; they contain toxic compounds which upon inhalation cause millions of premature deaths every year. The same particles also contain substances that act as nutrients when deposited in ecosystems, which in turn can affect primary productivity. Much of the predictive uncertainty surrounding human impacts on the Earth System are related to poorly understood processes involving the emission, transformation and related impacts of atmospheric aerosol. This talk will present key aspects of aerosol-related research carried out at the Laboratory of Atmospheric Processes and their Impacts at EPFL, emphasizing findings, directions and future outlook.
We will first present research related to the climate effects of aerosol. We will show how improvements in the representation of droplet and ice formation in climate models, instrument development efforts and related field observations have transformed our ability to understand the most uncertain aspect of anthropogenic change: aerosol-cloud-climate interactions. Afterwards, we will focus on research focused on aerosol composition – specifically on aerosol acidity (pH). Despite its importance as a driver of aerosol concentration, chemistry, toxicity and nutrient bioavailability, aerosol pH remains poorly constrained because its direct measurement is currently not possible. We present recent advances in constraining in-situ particle pH from the thermodynamic analysis of aerosol and gas-phase composition, and show that strong acidity (pH of 0 to 3) is ubiquitous in global aerosol. We then continue on showing how this renewed understanding of aerosol pH can help unravel the observed trends in aerosol toxicity and bioavailability of nutrients contained within them.

Short Bio
Athanasios Nenes is a Professor and head of LAPI at IEE/ENAC/EPFL. He is affiliated with the Institute of Chemical Engineering Science (Patras, Greece) and the National Observatory of Athens (Athens, Greece). He authored 270 manuscripts, developed the ISORROPIA aerosol model, and instrumentation to measure aerosol properties and Cloud Condensation Nuclei. He serves as President of Atmospheric Sciences of the European Geophysical Union, and member of the UN Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection (WG38: Atmospheric input of chemicals to the ocean), the Committee on Nucleation and Atmospheric Aerosols, Editor in Atmospheric Chemistry and Physics and served on the US National Academies Committee on the Future of Atmospheric Chemistry Research (2014-2016), Secretary of Atmospheric Sciences of the American Geophysical Union (2012-2016), and Board of Directors of the American Association for Aerosol Research (2014-2017). His distinctions include an ERC Consolidator Grant (2016); Vaughan Lectureship, California Institute of Technology (2014); Ascent Award, American Geophysical Union (2012); Whitby Award, American Association for Aerosol Research (2011); Houghton Award, American Meteorological Society (2009); Sigma Xi Young Faculty Award (2007); Friedlander Award, American Association for Aerosol Research (2005); NASA New Investigator Award (2004) and a National Science Foundation CAREER Award (2004).