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Flux chamber study of particle formation from Durvillaea potatorum

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Cainey, JM and Keywood, M and Bigg, EK and Grose, MR and Gillett, RW and Meyer, M (2007) Flux chamber study of particle formation from Durvillaea potatorum. Environmental Chemistry, 4. pp. 151-154. ISSN 1448-2517

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Abstract

Brown kelp, in particular Laminaria digitata at Mace Head, Ireland, has been shown to emit iodine when under
stress, resulting in new particle formation. The Cape Grim Baseline Air Pollution Station, Tasmania, is surrounded by
rocky reefs that support large colonies of the brown kelp Durvillaea potatorum. During an intensive campaign in February
2006 at Cape Grim, levels of IO, OIO and methyl iodide remained at background levels and no particle formation events
could be associated with locally generated precursor iodine species.
In order to better understand the limitations of the local kelp to provide a source of precursor species, samples of
Durvillaea potatorum were collected from the beach below the Cape Grim Station and tested for their capacity to initiate
particle formation using a flux chamber technique. Particles were observed only when the kelp was exposed to both very
high levels (>100 ppb) of ozone and natural solar radiation. There was a high correlation between ozone level and particles
produced. The particles resulting from exposure to high levels of ozone were aromatic and volatile.
Durvillaea potatorum appears to plays a very limited role in contributing to particle formation at Cape Grim, but it
does represent a source of atmospheric iodine under photo-oxidative stress, of 18 pmol g−1 (fresh weight) min−1 and is
likely to have a significant role in atmospheric chemistry at this site.
The role of the brown kelp, Laminaria digitata, in providing
the necessary precursors to nucleation events at Mace Head,
Ireland, has been well studied,[1–3] and it had been expected that
the brown kelp, Durvillaea potatorum, at Cape Grim, Australia,
would also provide a source of iodine and iodated gases that
would initiate particle formation.
Previous measurements at the Cape Grim Baseline Air Pollution
Station of a range of alkyl halides, including IO andOIO, had
shown that these gases were either at low levels or below detection
limits,[4–6] and this was suggested to be the result of the
distance of the Cape Grim Station from the source region on the
beach 94m below.[7] Measurements of particle numbers, both at
the Station and on the beach below had previously shown that
beach cast Durvillaea potatorum was a source of particles[8,9]
and at the same magnitude as observed at Mace Head, 20 000
and 57 000 respectively.[1,9]
During the Precursors to Particles Campaign 2006 (P2P
2006),[10] the expected nucleation events due to the local
macroalgae, Durvillaea potatorum, were not observed, suggesting
differences between the processes at Cape Grim and at Mace
Head. Initial tests during P2P 2006 showed that beach cast
Durvillaea potatorum produced particles only when exposed to
high levels of ozone (>450 ppb) and light. To better understand
the possible role of the local kelp as a source of particles, a limited
assessment of Durvillaea

Item Type: Article
Journal or Publication Title: Environmental Chemistry
Publisher: CSIRO Publishing
Page Range: pp. 151-154
ISSN: 1448-2517
Identification Number - DOI: 10.1071/EN07006
Additional Information:

Copyright © 2007 CSIRO.

Date Deposited: 07 Apr 2008 14:41
Last Modified: 18 Nov 2014 03:36
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