5. Conclusions
There are some uncertainties regarding the different analytical methods
employed in the determination of iodine speciation in aerosol (see
supplementary text ST2 and (Yodle & Baker, 2019)), and we recommend
that future work considers carefully the problems associated with the
combination of cellulose filters and long time (and/or high power)
ultrasonic extraction. However, the correspondence between the spatial
trends of ocean productivity variables and the SOI fraction in marine
aerosol determined from the global iodine speciation dataset compiled in
this work, and the correlations between iodine speciation ratios and
major ions concurrently measured in seven cruises indicate that the two
acidity regimes and the availability of organics are major controlling
factors of the iodide-iodate-SOI variability, as summarized in the
chemical scheme in Figure 7. Future laboratory and modelling work needs
to address the underlying chemical and photochemical reactions of this
system, especially regarding the reactions between DOM and HOI and the
photochemical processes linking SOI and iodide.