EESS talk on "In search for proxies of the past atmospheric oxidants – case of oxygen isotopic composition of sulfate"


Event details

Date 04.10.2022
Hour 12:1513:15
Speaker Dr Sakiko Ishino, Assistant Professor, Institute of Nature and Environmental Technology, Kanazawa University (JP) and visiting professor at EERL, CH
Location Online
Category Conferences - Seminars
Event Language English
Oxidants, such as hydroxyl (OH) radicals and ozone, are major drivers of atmospheric chemistry in Earth’s present atmosphere and affect climate and air quality in a variety of ways. OH radicals can oxidize methane, the second important greenhouse gas, and largely controls its lifetime. Tropospheric ozone itself is an air pollutant as well as the third important greenhouse gas. Therefore, understanding the levels and production/loss processes of oxidants is critical for projecting future climate and air quality. However, the atmospheric oxidant levels in the pre-industrial period remain highly uncertain. Although ice cores from polar regions are often used for reconstructing the past atmospheric composition, most oxidants are highly reactive so they are lost before being preserved in ice. There have been continuous efforts to search for ice core proxies of past oxidant levels. Here I talk about our story of trial and error in utilizing a specific isotope signature, the mass-independent oxygen isotopic composition (Δ17O) of sulfate, to elucidate past oxidant levels. We had found several processes that would complicate extraction of oxidants information from the signature. (i) In the Antarctic atmosphere, Δ17O of sulfate is significantly perturbed by a specific reaction related to snow and surrounding ocean. (ii) Δ17O of sulfate is largely dependent on atmospheric acidity rather than oxidant levels. Exploration of appropriate proxies for past oxidants still continues.

Short biography:
Sakiko Ishino is an assistant professor at Kanazawa University, Japan, and now collaborating with EPFL as a visiting scientist for a research stay at EERL about the climate impact of aerosol particles in polar regions. She obtained her PhD degree in 2019 at the Tokyo Institute of Technology, focusing her thesis on sulfate aerosol formation processes in the Antarctic atmosphere, in which she dived into the mysteries of specific atmospheric chemical processes occurring in the presence of snow and ice by using unique isotope analysis techniques. The series of works made her ponder the impact of those chemical processes on the climate, which led her to collaborate with EERL.

Practical information

  • General public
  • Free
  • This event is internal


  • EESS - IIE


  • Prof. Julia Schmale, EERL


Atmospheric oxidants sulfate aerosols stable isotope analysis ice cores