In situ measurements of molecular iodine in the marine boundary layer: the link to macroalgae and the implications for O3, IO, OIO and NOx
Item
Title (Dublin Core)
In situ measurements of molecular iodine in the marine boundary layer: the link to macroalgae and the implications for O3, IO, OIO and NOx
Description (Dublin Core)
Discrete in situ atmospheric measurements of molecular iodine (I<sub>2</sub>) were carried out at Mace Head and Mweenish Bay on the west coast of Ireland using diffusion denuders in combination with a gas chromatography-mass spectrometry (GC-MS) method. I<sub>2</sub>, IO and OIO were also measured by long-path differential optical absorption spectroscopy (LP-DOAS). The simultaneous denuder and LP-DOAS I<sub>2</sub> measurements were well correlated (<i>R</i><sup>2</sup>=0.80) but the denuder method recorded much higher concentrations. This can be attributed to the fact that the in situ measurements were made near to macroalgal sources of I<sub>2</sub> in the intertidal zone, whereas the LP-DOAS technique provides distance-averaged mixing ratios of an inhomogeneous distribution along the light-path. The observed mixing ratios of I<sub>2</sub> at Mweenish Bay were significantly higher than that at Mace Head, which is consistent with differences in local algal biomass density and algal species composition. Above algal beds, levels of I<sub>2</sub> were found to correlate inversely with tidal height and positively with the concentrations of O<sub>3</sub> in the surrounding air, indicating a role for O<sub>3</sub> in the production of I<sub>2</sub> from macroalgae, as has been previously suggested from laboratory studies. However, measurements made ~150 m away from the algal beds showed a negative correlation between O<sub>3</sub> and I<sub>2</sub> during both day and night. We interpret these results to indicate that the released I<sub>2</sub> can also lead to O<sub>3</sub> destruction via the reaction of O<sub>3</sub> with I atoms that are formed by the photolysis of I<sub>2</sub> during the day and via the reaction of I<sub>2</sub> with NO<sub>3</sub> radicals at night. The results show that the concentrations of daytime IO are correlated with the mixing ratios of I<sub>2</sub>, and suggest that the local algae sources dominate the inorganic iodine chemistry at Mace Head and Mweenish Bay.
Creator (Dublin Core)
Huang, R.-J.
Seitz, K.
Buxmann, J.
Pöhler, D.
Hornsby, K. E.
Carpenter, L. J.
Platt, U.
Hoffmann, T.
Date (Dublin Core)
2018-01-15
Type (Dublin Core)
Text
Format (Dublin Core)
application/pdf
Identifier (Dublin Core)
10.5194/acp-10-4823-2010
https://acp.copernicus.org/articles/10/4823/2010/
Source (Dublin Core)
eISSN: 1680-7324
Language (Dublin Core)
eng
