2.1. Definitions
Aerosol iodine quantities are defined as in (Gómez Martín et al., 2021).
Total iodine (TI) is given by the sum of total soluble iodine (TSI) and
non-soluble iodine (NSI): TI = TSI + NSI. Total soluble iodine
encompasses total inorganic iodine (TII = [I-] +
[IO3-]) and SOI. Note that except
for one recent organic speciation work (Yu et al., 2019), the only
individual species reported in the majority of field measurement (Tables
S1 and S2) are iodide (I-) and iodate
(IO3-). SOI is determined from the
TSI, I- and IO3-observations: SOI = TSI - [I-] -
[IO3-]. The soluble speciation is
the set of three ratios of the concentrations of I-,
IO3- and SOI to TSI.
Iodine in bulk aerosol and in the fine and coarse aerosol fractions are
noted respectively as Xbulk, Xfine,
Xcoarse (X = TI, TSI). Particulate matter with diameterd < x μm is noted as PMx, and TI and
TSI for diameter d < x μm are noted as
TIx and TSIx. Usually the cut-off
between fine and coarse aerosol is stablished operationally at a
particle diameter of 1 μm. This reflects approximately the usual size
classification of marine aerosol, characterized by the nuclei (d< 0.1 μm), the accumulation mode (0.1 μm < d< 0.6 μm) and the coarse mode (d > 0.6 μm)
(Seinfeld & Pandis, 1998). PM1 encompasses the nuclei
and the accumulation mode and is composed mostly of sulfate aerosol (low
pH), while coarse marine aerosol consists of sea-salt aerosol produced
by bubble bursting and wave breaking.