Coastal Iodine Emissions: Part 2. Chamber Experiments of Particle Formation from Laminaria digitata-Derived and Laboratory-Generated I^sub 2

Laboratory studies into particle formation from Laminaria digitata macroalgae were undertaken to elucidate aerosol formation for a range of I2 (0.3-76 ppbv) and O3 (<3-96 ppbv) mixing ratios and light levels (EPAR = 15, 100, and 235 µmol photons m^-2 s^-1). No clear pattern was observed for I2 or...

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Bibliographic Details
Published inEnvironmental science & technology Vol. 46; no. 19; p. 10422
Main Authors Monahan, Ciaran, Ashu-Ayem, Enowmbi R, Nitschke, Udo, Darby, Steven B, Smith, Paul D, Stengel, Dagmar B, Venables, Dean S, O'Dowd, Colin D
Format Journal Article
LanguageEnglish
Published Easton American Chemical Society 02.10.2012
Subjects
Aerosols
Algae
Boundary layer
Chemical compounds
Emissions
Environmental science
Experiments
Laboratories
Ratios
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Summary:Laboratory studies into particle formation from Laminaria digitata macroalgae were undertaken to elucidate aerosol formation for a range of I2 (0.3-76 ppbv) and O3 (<3-96 ppbv) mixing ratios and light levels (EPAR = 15, 100, and 235 µmol photons m^-2 s^-1). No clear pattern was observed for I2 or aerosol parameters as a function of light levels. Aerosol mass fluxes and particle number concentrations, were, however, correlated with I2 mixing ratios for low O3 mixing ratios of <3 ppbv (R^2 = 0.7 and 0.83, respectively for low light levels, and R^2 = 0.95 and 0.98, respectively for medium light levels). Additional experiments into particle production as a function of laboratory-generated I2, over a mixing ratio range of 1-8 ppbv, were conducted under moderate O3 mixing ratios (~24 ppbv) where a clear, 100-fold or greater, increase in the aerosol number concentrations and mass fluxes was observed compared to the low O3 experiments. A linear relationship between particle concentration and I2 was found, in reasonable agreement with previous studies. Scaling the laboratory relationship to aerosol concentrations typical of the coastal boundary layer suggests a I2 mixing ratio range of 6-93 pptv can account for the observed particle production events. Aerosol number concentration produced from I2 is more than a factor of 10 higher than that produced from CH2I2 for the same mixing ratios. [PUBLICATION ABSTRACT]
ISSN:0013-936X