General comments

The paper “Modeling the drivers of fine PM pollution over Central Europe: impacts and contributions of emissions from different sources“ presents a detailed and comprehensive comparison of a source apportionment modelling study based on both brute force and tagging methods.

The paper provides a lot of quantitative results reported in terms of maps and tables that help the reader to evaluate the role of the different sources as well as to understand the differences among the methods.

Therefore, the paper fits the scope of ACP. The paper is also well written, with concise and clear statements, and it does not require any substantial review of syntax and language.

The paper could be published considering just a couple of integrations:

• The model performance evaluation could be supported by a few additional analysis (also in terms of reference) that should consider:
  1. PM precursors (e.g. NOX, NO2, SO2,…)
  2. PM chemical composition (EC, OC, NH4, NO3, SO4,…)
  3. Meteorological variables

This would allow to better investigate the reason of CAMx underestimation, particularly during the summer season

• The analysis at the receptor shown in table S1-6 could be extended to a few PM compounds both primary and secondary to better highlight which compounds and which processes give rise to corresponding discrepancies between contributions and impacts shown for PM2.5.

Such analysis could represent an interesting complement to all the maps and could maybe allow to remove some maps (for example some maps with relative contributions that are not so informative)

Specific comments and Technical corrections

P8 – R250 – which are the differences respect to the setup of “SOAP base case” and “PSAT simulations”?

P10-R301- Figure 2 – standard deviation bars for modelled results are almost not visible, is it correct?

P10-R302 – SOAP base case and PSAT should provide the same result, isn’t it?

P10 – Validation – Which are, according to the authors, the main reason of the discrepancies between modelled and observed PM2.5 values, taking place particularly during the summer season? Are they related to meteorology, lacking in emission inventories?

Authors provide some discussion in the final section but keeping it rather generic.

P11-R292-293 – Did authors expect a larger difference in solvents contribution, with respect to SOAP when applying VBS?

P13-R393 – Did author also perform a simulation where “all remaining sources “(and boundary conditions, maybe) are removed? This would allow to check if the sum of all impacts is equal or not to the total concentration of the base case (probably not…)

P13-R426 – This was expected because impacts and contributions are identical for primary non-reactive compounds.

P15 -R492-496 – from Figure 12 captions and title it seems that maps show the relative fraction with respect to total PNH4 and not to total PM2.5, where the latter seems more reasonable, looking at the maps

P22 -R718-721 – This statement is reasonable, but it would require additional analysis for example a comparison of modelled and observed PM chemical composition