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SUMMARY:EESS talk on "In search for proxies of the past atmospheric oxidan
 ts – case of oxygen isotopic composition of sulfate"
DTSTART:20221004T121500
DTEND:20221004T131500
DTSTAMP:20260916T012408Z
UID:57732c91037786b0030021a50a94ff06e6ce4fbf526fd0a402544c99
CATEGORIES:Conferences - Seminars
DESCRIPTION:Dr Sakiko Ishino\, Assistant Professor\, Institute of Nature 
 and Environmental Technology\, Kanazawa University (JP) and visiting profe
 ssor at EERL\, CH\nAbstract:\nOxidants\, such as hydroxyl (OH) radicals an
 d ozone\, are major drivers of atmospheric chemistry in Earth’s present 
 atmosphere and affect climate and air quality in a variety of ways. OH rad
 icals can oxidize methane\, the second important greenhouse gas\, and larg
 ely controls its lifetime. Tropospheric ozone itself is an air pollutant a
 s well as the third important greenhouse gas. Therefore\, understanding th
 e levels and production/loss processes of oxidants is critical for project
 ing future climate and air quality. However\, the atmospheric oxidant leve
 ls in the pre-industrial period remain highly uncertain. Although ice core
 s from polar regions are often used for reconstructing the past atmospheri
 c composition\, most oxidants are highly reactive so they are lost before 
 being preserved in ice. There have been continuous efforts to search for i
 ce core proxies of past oxidant levels. Here I talk about our story of tri
 al and error in utilizing a specific isotope signature\, the mass-independ
 ent oxygen isotopic composition (Δ17O) of sulfate\, to elucidate past oxi
 dant levels. We had found several processes that would complicate extracti
 on of oxidants information from the signature. (i) In the Antarctic atmosp
 here\, Δ17O of sulfate is significantly perturbed by a specific reaction 
 related to snow and surrounding ocean. (ii) Δ17O of sulfate is largely de
 pendent on atmospheric acidity rather than oxidant levels. Exploration of 
 appropriate proxies for past oxidants still continues.\n\nShort biography:
 \nSakiko Ishino is an assistant professor at Kanazawa University\, Japan\,
  and now collaborating with EPFL as a visiting scientist for a research st
 ay 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 Antarc
 tic atmosphere\, in which she dived into the mysteries of specific atmosph
 eric chemical processes occurring in the presence of snow and ice by using
  unique isotope analysis techniques. The series of works made her ponder t
 he impact of those chemical processes on the climate\, which led her to co
 llaborate with EERL.
LOCATION:GC B1 10 https://plan.epfl.ch/?room==GC%20B1%2010 https://epfl.zo
 om.us/j/63802032408
STATUS:CONFIRMED
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