Atmospheric and surface chemistry

AAS project 4032

Principal Investigator: Robyn Schofield

Onboard: Ruhi Humphries and Caitlin Gionfriddo

Every year in the polar spring large quantities of highly reactive bromine radicals are released into the atmosphere from sea-salt that has accumulated on the sea-ice over the polar winter. This happens predominantly over the young – 1 year old – sea-ice and is known as “Bromine explosion events” or “Mercury deposition events”.

Bromine radicals completely change the chemistry of the atmosphere from OH (which is considered the vacuum cleaner of the troposphere) to BrO. Bromine radicals are more effective oxidizing agents than OH and they remove all of the surface ozone and oxidize mercury – meaning mercury is converted into a form that readily deposits.

Human activities have doubled the amount of atmospheric mercury found in the atmosphere. By combining atmospheric bromine, ozone and mercury and the biological response to mercury from microbes within the sea-ice with modeling we aim to quantify the toxic mercury flux into the biosphere due to perturbed boundary layer chemistry in the Antarctic polar spring during SIPEX II.

To measure the atmosphere we have 5 measurement suites on the ship:

  • A remotely sensing Multiple Axis Differential Optical Absorption Spectrometer (MAX-DOAS) will spectrally measure profiles of BrO in the boundary layer. This instrument is provided through collaboration with NIWA at Lauder, in particular Karin Kreher and Paul Johnston.
  • Ozone in near surface air will measure ambient ozone monitor using ultra violet absorption of ozone. This instrument is from CSIRO in Aspendale through collaboration with Ian Galbally.
  • Mercury air samples will be measured using a Tekran Cold Vapor Atomic Fluorescence Spectrometer (CVAFS). This instrument is from the U.S. Geological Survey through collaboration with David Krabbenhoft and Mike Tate.
  • “New particle formation” will be measured using two particle counters. These instruments are supplied from CSIRO in collaboration with Melita Keywood.
  • The methyl halides will be measured using a “Dirac” GC-ECD. This instrument is provided in collaboration with Alan Thomas at NIWA and Andrew Robinson and Neil Harris.

The modeling effort will be lead by this project’s PI Robyn Schofield at the University of Melbourne and Andrew Klekociuk and Simon Alexander at AAD.

We have two expeditioners ‘going south’ – Ruhi Humphries an atmospheric chemistry PhD candidate from the University of Wollongong and Caitlin Gionfriddo a biogeochemist research assistant from the University of Melbourne.

At the ice stations Caitlin and Ruhi will be taking sea-ice and ocean samples to look for microbial responses telling us how much of the deposited mercury is being returned to the atmosphere and mercury levels in the sea-ice and the ocean. This work is in collaboration with Klaus Meiners and the trace-metal team of Delphine Lannuzel and Andy Bowie. Post-campaign analyses will be performed at the University of Melbourne and the USGS with John Moreau and colleagues.

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