Project

4032

Chief Investigator

SCHOFIELD, Dr Robyn - University of Melbourne

Title

Bromine control of the mercury flux into the biosphere of the Southern Ocean and Antarctic regions

Project aims

In the polar spring large quantities of highly reactive bromine radicals are released into the atmosphere, over the young - 1 year old - sea-ice. These bromine radicals destroy ozone and oxidize elemental mercury. Human activities have approximately doubled the amount of atmospheric mercury. By measuring atmospheric bromine, ozone and mercury (elemental, reactive) and the biological response in the sea-ice, this project aims for the first time to quantify the toxic mercury flux into the biosphere due to perturbed boundary layer chemistry in the Antarctic polar spring during SIPEX II.

Project gallery


Project Summary of the Season 2012/13

The most comprehensive atmospheric and hydrospheric observations to date to understand springtime mercury depletion events in the Antarctic were made during the Sea Ice Physics and Ecosystems eXperiment of 2012. A suite of five atmospheric monitoring instruments measuring reactive bromine radicals, ozone, mercury, biogenic bromine and aerosols made almost continuous measurements over the 60 day voyage. Multiple mercury depletion and re-emission events were observed. Snow, sea-ice and ocean measurements of total- and methyl-mercury samples made at the 8 ice stations indicate an important role of microbial processing within the sea-ice. This unique and comprehensive dataset promises to be invaluable for modelling efforts to understand the global biogeochemical cycle of mercury as a global pollutant.

Project Summary of the Season 2013/14

All datasets are archived in the AAD data centre, the first project of the 2013/2014 to reach this milestone. In all 9 datasets: 6 observational and 3 modelling products are available with digital object identifiers allocated that will be made public as soon as the planned publications are through the peer-review process. The scientific interpretation of the data is well underway, with the biogeochemical modelling showing some unexpected results challenging our understanding of the interaction between bromine, ozone and mercury in the atmosphere. Microbial community genetic sequencing of the snow and ice samples is commencing, with new collaborations with interests in iron and antibacterial functionality, to complement the mercury methylation gene expression information.

Final Summary of Project Achievements

The most comprehensive atmospheric chemistry observations to date to understand springtime mercury depletion events in the Antarctic were made during the Sea Ice Physics and Ecosystems eXperiment of 2012. A suite of five atmospheric monitoring instruments measuring reactive bromine radicals, ozone, mercury, biogenic bromine and aerosols made almost continuous measurements over the 60 day voyage. Multiple mercury depletion and re-emission events were observed. Snow, sea-ice and ocean measurements of total- and methyl-mercury samples made at the 8 ice stations indicate an important role of microbial processing within the sea-ice. This unique and comprehensive dataset aided in efforts to understand the global biogeochemical cycle of mercury as a global pollutant. Scientific advances in our understanding of mercury in aerosol nucleation and the role of sea-ice in mercury methylation have been made. Also gas precursors from the sea-ice region were found to be crucial in determining the background aerosol concentrations over the southern ocean generally.

Category 1: Peer-reviewed literature

Humphries R.S., Schofield R., Keywood M.D., Ward J., Pierce J.R., Gionfriddo C.M., Tate M.T., Krabbenhoft D.P., Galbally I.E., Molloy S.B., Klekociuk A.R., Johnston P.V., Kreher K., Thomas A.J., Robinson A.D., Harris N.R.P., Johnson R., Wilson S.R. (2015) Boundary layer new particle formation over East Antarctic sea ice – possible Hg-driven nucleation?, Atmospheric Chemistry and Physics 15. 13339-13364; [Ref: 15738]

Humphries R.S., Klekociuk A.R., Schofield R., Keywood M., Ward J., Wilson S.R. (2016) Unexpectedly high ultrafine aerosol concentrations above East Antarctic sea ice, Atmospheric Chemistry and Physics 16. 2185-2206; [Ref: 15752]

Gionfriddo C.M., Tate M.T., Wick R.R., Schultz M.B., Zemla A., Thelen M.P., Schofield R., Krabbenhoft D.P., Holt K.E., Moreau J.W. (2016) Microbial mercury methylation in Antarctic sea ice, Nature Microbiology 1. Article number 16127; [Ref: 15941]

Category 3: Conference paper

Humphries R.S., Schofield R., Keywood M.D., Ward J.P., Pierce J.R., Gionfriddo C.M., Tate M., Krabbenhoft D., Galbally I.E., Molloy S.B., Klekociuk A.R., Johnston P.V., Kreher K., Thomas A.J., Robinson A.D., Harris N.R.P., Johnson R., Wilson S.R. (2015) Atmospheric aerosol formation over East Antarctic sea ice – possible Hg catalysed nucleation?, Atmospheric Composition & Chemistry Observations & Modelling Conference incorporating the Cape Grim Annual Science Meeting 2015, South Durras, Australia, 11-13 November 2015 .; [Ref: 15735]

Category 3: Poster

Humphries R., Klekociuk A., Schofield R., Keywood M., Ward J., WIlson S., Murphy C. (2014) Tropospheric entrainment as a source of ground level aerosols within the polar Antarctic cell, International Symposium on Sea Ice in a Changing Environment, Hobart, Australia, 10-14 March 2014 .; [Ref: 15272]

Humphries R., Klekociuk A., Schofield R., Keywood M., Ward J., Wilson S., Murphy C. (2013) Tropospheric entrainment as a source of ground level aerosols within the polar Antarctic cell, American Geophysical Union (AGU) Fall Meeting, San Francisco, USA, 9-13 December 2013 .; [Ref: 15273]

Humphries R., Schofield R., Keywood M., Ward J., Wilson S., Galbally I., Kreher K., Johnston P., Thomas A., Robinson A., Harris N., Klekociuk A., Murphy C. (2013) Measurements of Aerosols and Precursors over East Antarctic melting spring sea ice, Strategic Science in Antarctica Conference, Hobart, Australia, 24-26 June 2013 .; [Ref: 15276]

Schofield R., Humphries R., Gionfriddo C., Kreher K., Johnston P., Harris N., Robinson A., Gordon A., Tate M., Krabbenhoft D., Moreau J., Molloy S., Galbally I., Keywood M., Wilson S., Alexander S., Klekociuk A., Bowie A., Lannuzel D. (2013) Atmospheric chemistry measurements over the East Antarctic during the SIPEX II cruise in polar spring 2012, Strategic Science in Antarctica Conference, Hobart, Australia, 24-26 June 2013 .; [Ref: 15277]

Gionfriddo C., Tate M., Krabbenhoft D., Humphries R., Molloy S., Galbally I., Klekociuk A., Kreher K., Johnston P., Meiners K., Bowie A., Lannuzel D., Schofield R. (2013) Mercury Cycling over the Southern Ocean during Polar Spring: Results from SIPEX II, Strategic Science in Antarctica Conference, Hobart, Australia, 24-26 June 2013 .; [Ref: 15278]

Category 3: Thesis, higher degree

Gordon A. (2013) Measurements of Tropospheric Halogen Compounds in New Zealand and the Southern Ocean, University of Cambridge, United Kingdom, Department of Chemistry Part III Research Project dissertation .; [Ref: 15102]

Humphries R. (2015) Aerosol formation in the Antarctic Sea-Ice Region, PhD Thesis, University of Wollongong, Wollongong, Australia .; [Ref: 15757]

Gionfriddo C.M. (2016) Biogeochemical mercury cycling in sea ice and geothermal springs, PhD Thesis, University of Melbourne, Melbourne, Australia .; [Ref: 15942]

Category 3: Verbal presentation

Humphries R., Gionfriddo C., Moreau J., Tate M., Krabbenhoft D., Keywood M., Wilson S., Galbally I., Kreher K., Johnston P., Thomas A., Robinson A., Harris N., Klekociuk A.R., Alexander S., Schofield R. (2013) Atmospheric measurements over East Antarctic melting spring sea ice during SIPEX II, Australian Meteorological and Oceanographic Society (AMOS) National Conference, Melbourne, Australia, 11-13 February 2013 .; [Ref: 14974]

Schofield R., Humphries R., Gionfriddo C., Kreher K., Johnston P., Harris N., Robinson A., Gordon A., Tate M., Krabbenhoft D., Moreau J., Molloy S., Galbally I., Keywood M., Wilson S., Alexander S.P., Klekociuk A.R., Bowie A., Lannuzel D., Meiners K. (2013) Atmospheric chemistry measurements over the East Antarctic during the SIPEX II cruise in polar spring 2012, Davos Atmosphere and Cryosphere Assembly 2013, Davos, Switzerland, 8-12 July 2013 .; [Ref: 15128]

Schofield R., Humphries R., Gionfriddo C., Kreher K., Johnston P., Harris N., Robinson A., Gordon A., Tate M., Krabbenhoft D., Moreau J., Molloy S., Galbally I., Keywood M., Wilson S., Alexander S., Klekociuk A., Fisher J., Yang X., Bowie A., Lannuzel D., Meiners K. (2014) Bromine Explosion events Driving Mercury Deposition over the East Antarctic during the SIPEX II cruise in Polar Spring 2012, International Symposium on Sea Ice in a Changing Environment, Hobart, Australia, 10-14 March 2014 .; [Ref: 15271]

Schofield R., Humphries R., Gionfriddo C., Kreher K., Johnston P., Harris N., Robinson A., Gordon A., Tate M., Krabbenhoft D., Moreau J., Molloy S., Galbally I., Keywood M., Wilson S., Alexander S., Klekociuk A., Fisher J., Yang X., Bowie A., Lannuzel D., Meiners K. (2013) Understanding mercury and ozone depletion events over East Antarctic sea-ice, Atmospheric Composition and Chemistry Observations and Modelling Conference incorporating the Cape Grim Annual Science Meeting, Aspendale, Victoria, Australia 27-29 November 2013 .; [Ref: 15274]

Gionfriddo C., Tate M., Krabbenhoft D., Humphries R., Molloy S., Galbally I., Klekociuk A., Kreher K., Johnston P., Meiners K., Bowie A., Lannuzel D., Schofield R., Moreau J.W. (2013) Mercury Cycling over the Southern Ocean during Polar Spring: Results from SIPEX II, International conference on Mercury as a Global Pollutant, Edinburgh, Scotland, 28 July–2 August 2013 .; [Ref: 15275]