The manuscript has made marked improvement from the last time, as suggested by the referees. I would like to see a few additional areas made clearer, however, before publication. I've uploaded a document with some individual/minor comments written in-place, and I've added some more substantive comments separately.

Please process the changes appropriately and upload two versions: one clean manuscript, and a separate file with all changes from the current version with tracked changes so I can review quickly and efficiently. Feel free to add a cover letter with any discussion/explanation necessary.

Thank you for your details response to the the last edits and all referee comments. The publication is acceptable for publication in current form. There are a number of typos in the re-written sections (starting e.g. Line 366). Before publication be sure to carefully check for typos in the paragraphs following this point.

Congratulations, and thank you for choosing to publish your work in Atmospheric Chemistry and Physics.

Alex Huffman

Two minor points to change in addition to the typos involving spacing and punctuation:
Line 368: change “amino acids concentration” to “amino acid concentration”
Line 369: change “fraction percent” to “percent”