Precursors to Particles (P2P) at Cape Grim 2006: campaign overview
Jill M. Cainey A I , Melita Keywood B , Michael R. Grose C , Paul Krummel B , Ian E. Galbally B , Paul Johnston D , Rob W. Gillett B , Mick Meyer B , Paul Fraser B , Paul Steele B , Mike Harvey E , Karin Kreher D , Torsten Stein F , Ossama Ibrahim F , Zoran D. Ristovski G , Graham Johnson G , Cathie A. Fletcher G , E. Keith Bigg H and John L. Gras BA Cape Grim Baseline Air Pollution Station, Bureau of Meteorology, 159 Nelson Street, Smithton, Tas. 7330, Australia.
B CSIRO Marine and Atmospheric Research, Aspendale, Vic. 3195, Australia.
C Institute of Antarctic and Southern Ocean Studies, University of Tasmania, Hobart, Tas. 7001, Australia.
D National Institute of Water and Atmospheric Research, Lauder, New Zealand.
E National Institute of Water and Atmospheric Research, Greta Point, Wellington, New Zealand.
F Institute of Environmental Physics, University of Heidelberg, Heidelberg D-69120, Germany.
G ILAQH, Queensland University of Technology, Brisbane, Qld 4001, Australia.
H Castle Hill, NSW 2154, Australia.
I Corresponding author. Email: j.cainey@bom.gov.au
Environmental Chemistry 4(3) 143-150 https://doi.org/10.1071/EN07041
Submitted: 11 May 2007 Accepted: 6 June 2007 Published: 22 June 2007
Environmental context. Understanding the role of clouds in assessing the impact of climate change is a challenging issue. It is thought that plankton and seaweed contribute to the formation of clouds by emitting gases that lead to the particle production necessary for cloud formation. Macroalgae (kelp) at Mace Head, Ireland, produce large quantities of iodine when exposed to sunlight at low tide and this iodine results in the rapid production of particles. Cape Grim, Tasmania, also has large colonies of kelp and the role of Bull Kelp (Durvillaea potatorum) in particle production was assessed.
Abstract. Iodine emissions from coastal macroalgae have been found to be important initiators for nucleation events at Mace Head, Ireland. The source of this iodine is the large beds of the brown kelp Laminaria digitata, which are significantly exposed at low tide.
On the coast around Cape Grim, Tasmania, there are beds of the brown kelp Durvillaea potatrum. The Precursors to Particles 2006 (P2P 2006) campaign at the Cape Grim Baseline Air Pollution Station in late summer (February) 2006 focused on the role of this local kelp in providing precursor gases to particle formation.
Durvillaea potatorum does not produce iodated precursor gases at the levels observed at Mace Head. IO was measured at 0.5 ± 0.3 ppt, while OIO was below detection limits (9 ppt). The dominant atmospheric iodated species was methyl iodide and the average concentration measured at the Cape Grim Station was 1.5 ± 0.3 pptv in baseline conditions, but showed significant variation in discrete samples collected immediately above the ocean surface.
Nucleation events were not detected at the Cape Grim Station, except for one period where the plume of a local bushfire interacted with air of marine origin. The passage of four fronts did not result in nucleation bursts and measurements on the beach 94 m below the Cape Grim Station suggested that Durvillaea potatorum was only a weak source of new particles.
Additional keywords: iodine, kelp, methyl iodide, particle formation.
Acknowledgements
We would like to thank the staff of the Cape Grim Baseline Air Pollution Station who provided support to all those involved in the campaign, in particular Chris Rickard who assisted with the radiosonde flights. The staff of the Bureau of Meteorology Field Operations Unit who provided a radiosonde system for the campaign and in particular Ken Barker who visited Cape Grim to train staff in the use of the system. We would like to thank Paul Viney, who skippered his boat for the transect work of Cape Grim and Claire Reeves of the University of East Anglia for the long-term loan of the GC-ECD for the methyl halide work. We would like to thank Nada Derek, CSIRO, for producing the figures.
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