Coastal iodine emissions: part 2. Chamber experiments of particle formation from Laminaria digitata-derived and laboratory-generated I2
Ashu-Ayem, Enowmbi R.
Darby, Steven B.
Smith, Paul D.
Stengel, Dagmar B.
Venables, Dean S.
O'Dowd, Colin D.
American Chemical Society
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 O3mixing ratios of <3 ppbv (R2 = 0.7 and 0.83, respectively for low light levels, and R2 = 0.95 and 0.98, respectively for medium lightlevels). Additional experiments into particle production as a function of laboratory-generated I2, over a mixing ratio range of 1−8ppbv, were conducted under moderate O3 mixing ratios (∼24 ppbv) where a clear, 100-fold or greater, increase in the aeroso lnumber 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 thatproduced from CH2I2 for the same mixing ratios.
Air Pollution and Industrial hygiene , Marine boundary layer , Iodine release
MONAHAN, C., ASHU-AYEM, E. R., NITSCHKE, U., DARBY, S. B., SMITH, P. D., STENGEL, D. B., VENABLES, D. S. & O’DOWD, C. D. 2012. Coastal Iodine Emissions: Part 2. Chamber Experiments of Particle Formation from Laminaria digitata-Derived and Laboratory-Generated I2. Environmental Science & Technology, 46, 10422-10428. doi: 10.1021/es3011805
Copyright © 2012 American Chemical Society. This document is the Accepted Manuscript version of a Published Work that appeared in final form in Environmental Science and Technology, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://pubs.acs.org/doi/abs/10.1021/es3011805