Dear authors,

I am happy to accept your paper " Oxygen isotope mass balance of atmospheric nitrate at Dome C, East Antarctica, during the OPALE campaign” for publication in ACP subject to minor, mostly technical corrections. The requested changes are listed below and I ask you to implement them in the final version.

In your reply you were not sure how to interpret and answer to the comment from B. Alexander on the shift in timing between the maximum in the effect of photochemistry in spring relative to the highest SZA in summer. I think that in your answer you do actually answer this point (the argumentation on the reservoir effects) and I would like you include this in the final manuscript.

The major points of the anonymous referee have been adequately addressed, namely
a) why only selected points are analyzed in detail (duration of OPALE campaign)
b) that unknown systematic effects (even if unidentified) may contribute to the discrepancy between observed and modeled D17O of O3
c) that unknown mass independent fractionations in established reactions could contribute as well
These effects are now shortly discussed, which is adequate given that no independent information is available. However, the additional text L554-576 is poorly written and has numerous grammatical errors. Please check thoroughly and rewrite this section!
Some suggestions:
554: I would replace “we can question the accuracy” by something like: …the discrepancy may originate from an error in the D17O value assigned to tropospheric O3, specifically at Dome C….
555 the ones -> the values for
558: delete “application of”
559: will → would
560: techniques
561: Given…
564: techniques
565: reformulate “such demonstration”
566: Reword “wrong 17Oexcess transfer”
the O3 D17O → the D17O of O3
568: Replace “strange” by a more suitable word and try to formulate this point more generally, namely that an unknown MIF process occurs in known (i.e. well established) chemical reactions, where one example could be the CO + OH reaction (although no evidence is presently available for this to occur).
574: will → would, also remove “conclusions”, or replace by “interpretation”
575/6: add: above the Antarctic ice sheet

Also, the new sentences that were added at the end of the conclusions section 635 ff are not very strong and not well formulated. Consider reformulating them, and/or placing them before the last sentence.

Minor issues:
271: replace “is continue” by “is continuing” or “continues”
1010: leave out “conditions”