 |
| Titel |
Observations of Coastal IO Emissions on the Southern Hemisphere and Emission Potential of Different Seaweed Species |
| VerfasserIn |
Martin Horbanski, Stefan Schmitt, Udo Frieß, Denis Pöhler, Paul Johnston, Karin Kreher, Andrew D. Robinson, Alan Thomas, Neil R. P. Harris, Ulrich Platt |
| Konferenz |
EGU General Assembly 2014
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250092028
|
| Publikation (Nr.) |
 EGU/EGU2014-6353.pdf |
|
|
|
|
|
| Zusammenfassung |
| At coastal sites reactive iodine species emitted by seaweed in the intertidal zone during low
tide are known to have an important influence on the atmospheric chemistry. However, many
underlying mechanisms are presently not understood. Also coastal studies were focused on a
few locations on the northern hemisphere and their predominant seaweed species laminaria
digitata and ascophyllum nodosum. Therefore the spatial emission and extent of the
areas where halogen chemistry is of importance needs to be much better quantified.
Especially in the mid latitudes of the southern hemisphere RHS measurements are very
sparse.
Here we report the first observations of coastal iodine monoxide (IO) in the southern
hemisphere during the HALMA/MAORI campaign which was carried out in February to
March 2013 on the east coast of New Zealand’s South Island at Shag Point located north of
Dunedin. To detect IO we used a mobile Open Light Path Cavity Enhanced Differential
Optical Absorption Spectroscopy (CE-DOAS) instrument and a stationary Long Path
(LP)-DOAS Instrument, which was furthermore used to measure BrO, O3 and I2.
The measurement path was positioned over the water and mainly measured air
masses that only passes over submerged seaweed forests. With the CE-DOAS placed
close to exposed seaweed patches (mainly Macrocystis Pyrifera) we were able to
observe high IO mixing ratios of up to 50 ppt (2ppt detection limit). However, the
LP-DOAS did not detect IO above the detection limit of 0.7 ppt. This is consistent with
previous observations which found that seaweed only emits halogens when exposed to
air.
To further investigate the emission potential of the seaweed species we setup a Teflon
chamber around the CE-DOAS and measured the emissions of five different species for
several hours. Additionally the air in the chamber was probed by a compact gas
chromatograph (μDIRAC) for measurements of halocarbons and a TEI Ozone monitor.
We found very high IO mixing ratios of up to 500 ppt for four seaweed species
which correlated with high levels of halocarbons (CH3I, CH2Br2, CH2BrI and
CH2BrCl up to 100ppt, CHBr3 up to 600ppt). These results, the similarities and
differences in the emission behavior and implications for atmospheric chemistry are
discussed. |
|
|
|
|
|
|