This is a synthesis study on Aerosol Iron fractional solubility, compiling all available soluble Al and Fe data over the Atlantic and Pacific oceans. This study has high scientific significance, improving our current understanding of aerosol iron solubility. This paper improves the understanding of the traditional hyperbolic relation between soluble iron and dust/Aluminum. The scientific quality and presentation quality of the paper are excellent and need minimal improvement. The synthesis of a relationship diagram between the EF T-Fe and [d-Fe]/[d-Al] ratio over a large geographical area has global significance. This study will also motivate atmospheric geochemists to make concordant observations of dissolved iron and aluminum. Before the publication of this manuscript, the author should address the few major corrections, which will improve the manuscript. In general, all axis labels for similar plots should be consistent and align with the text description.

The authors have assembled an impressive dataset of aerosol concentration data from previous studies as well as unpublished data of their own. Focusing on total and soluble aerosol iron, along with supporting data that includes total and soluble aluminum, they have attempted to better understand the long recognized inverse relationship between the amount of aerosol iron and its solubility. They explain the data using a previously published framework that associates the calculated enrichment factor of aerosol iron relative to the upper continental crust and the ratio of soluble iron to soluble aluminum. Based on this analysis, they conclude that observed increases in aerosol iron solubility are indicative of atmospheric processing during transport rather than simple mixing of high abundance, low solubility mineral aerosol with low abundance, high solubility anthropogenic aerosol.

The question of what processes and factors control aerosol iron solubility has bedeviled the research community and hampered progress in our ability to model this important input to the surface ocean. The methodology applied in this study shows promise, though its broad applicability is not clear. The soluble aerosol observations utilized in this study are biased toward ‘mild’ leaching techniques which may not be indicative of the ultimate aerosol solubility, and more so, the bioavailability of these aerosol derived trace elements. This comment is not an indictment of the study and certainly does not place it out of step with the current state of the art in the field. The work is an important contribution that could be improved with revision as detailed in the comments to follow.