This manuscript investigated the EEM spectra of different types of strong light-absorbing organic compounds and water-soluble organic matter in different aerosol samples. The motivation is to broaden the application of the EEM-PARAFAC method to study atmospheric BrC. This manuscript is thoughtful and well-written. Below are some issues and comments for the authors to consider.

1. Introduction: some more description of WSOC should be involved in the introduction.
2. Line 83: In the water environment, we usually call WSOC as DOM.

The excitation-emission matrix (EEM) fluorescence spectroscopy is a highly sensitive analytical technique for the identification of the chemical characteristics and sources of atmospheric chromophores. However, some explanation may be inaccurate because the identification of fluorescent components is mainly based on aquatic DOM. This study investigated the EEM spectra of different types of strong light-absorbing organic compounds and water-soluble organic matter in different aerosol samples, soil dust, and purified fulvic and humic acids and some novelty findings were obtained. For example, aromatic compounds containing nitro groups, which show strong absorption and are the major component of atmospheric brown carbon, exhibited no significant fluorescence. In addition, the fluorescent component 1 (235, 270/330 nm) is generally considered as protein-like groups, however the results of this study suggested that it is mainly composed of aromatic acids, phenolic compounds, and their derivatives, with only traces of amino acids in ambient WSOM. In all, this manuscript is well-written and the major data and their interpretation are scientifically sound. I have some suggestions for changes that should be made before the manuscript is published, to wit:

The comments and suggestions that need to be addressed:

(L=Line)

1. Abstract: the abstract should include quantitative information on the point that are made.
2. Line 28. “by ..” should be changed to “supplemented by an parallel factor (PARAFAC) modeling”.
3. Line 35. The “fluorescent component 1” is confused. I suggest to add “PARAFAC-derived” to define it.
4. Line 41: The “fluorescent component 3” refer to C3?
5. Line 98. What are “various properties”? The reference here is not appropriate, because it only focused on fluorescence properties of aerosol chromophores. I suggest the authors provide more relevant references.
6. Line 110. Please add “peaks” after “fluorescence”.
7. Section 2.3: Please provide how Raman and Rayleigh scattering was removed from EEM.
8. Line 155. Please give a detailed definition of “IFEs”.
9. Line 163-165. I want to know if all the samples were investigated with the PARAFAC modeling?
10. Line 190-194. I suggest the authors provide some references to support this point.
11. Line 220: Please remove the “and aquatic DOM” from sentence.
12. Line 277. Please add some references to support the similarities to EEM of BB and CC WSOM.
13. Line 310. To support the opinion in L311-312 “Although the fluorescence intensities varied with different sites and seasons, the EEM spectra of WSOM were very similar”, I suggested the authors to add more examples for the EEM fluorescence spectra of aerosols from different sites and seasons.
14. Line 304-315: What is the purpose of the EEM spectrum being divided into five regions in Figure 2, and also have a discussion about them.
15. Also in Line 311-312: “Although the fluorescence intensities varied with different sites and seasons, the EEM spectra of WSOM were very similar”. It may be more appropriate to replace “EEM spectra” with “shape of the EEM spectra”.
16. Line 319-320: “To better explain the various fluorophores in different atmospheric WSOM samples, the EEM spectra were resolved with the EEM–PARAFAC tool”. This sentence is repeated with the meaning expressed above, suggest deleting this sentence.
17. Line 326-328: It is written: “In general, these fluorescent components have been interpreted based on the knowledge of fluorescence characteristics of aquatic DOM.”. However, in Line 329-332, the reference you cited was atmospheric WSOC.
18. Line 334. Please add the “terrestrial” after “aquatic”.
19. Line 351-354: the reference is missing.
20. Line 387-390. Similar questions above. Can these two samples be representative? I suggest the authors summarize more samples in detail.
21. Line 388: Please explain the “HULIS-1” used here. HULIS-1 of what?
22. Line 389: It may be more appropriate to replace “component 2” with corresponding compound.
23. Line 485-487. The conclusion on contributions of fluorophores within CZ WSOM was wrong.

Reviewer: In this study, EEM data of different types of strongly light-absorbing organic compounds, water-soluble organic matter (WSOM), soil dust, and purified xanthic and humic acids from different aerosol samples (combustion source samples and ambient aerosols) were investigated in a comprehensive manner using the EEM-parallel factor method. This work can be recommended for publication in Atmospheric Chemical and Physics after the authors address some issues as follows.

1. Lines 129-130: What is the purpose of setting up soil samples? Please explain it in detail.
2. Lines 134: Additional details whether the blank PM₅ sample was collected, please add this information.
3. Lines 411-412: “The relatively higher C3 content in CZ could be attributed to the comparatively high contribution of soil dust in the suburban region”. Please provide more evidence for the higher contribution of suburban soil dust to atmospheric PM₅
4. Section 3.4. The paper also mentions that some brown carbon fractions have strong absorbance but not fluorescence characteristics, so is it reasonable to analyze the relationship between absorbance and fluorescence using Pearson correlation coefficient?
5. In Introduction part, Section 3.1 and 3.3, some new references associated with WOSM molecular and chemical functional group profiles should be added to support the finding of this study, such as:

1). Light absorption properties and molecular profiles of HULIS in PM_2.5 emitted from biomass burning in traditional "Heated Kang" in Northwest China. Sci. Total Environ. 2021, 776, 146014.;

2). Seasonal and diurnal variation of PM_2.5 HULIS over Xi'an in Northwest China: Optical properties, chemical functional group, and relationship with reactive oxygen species (ROS). Atmos. Environ. 2022, 268, 118782.;

3). Optical properties, chemical functional group, and oxidative activity of different polarity levels of water-soluble organic matter in PM_2.5 from biomass and coal combustion in rural areas in Northwest China. Atmos. Environ., 2022, 283.

4) Optical properties, molecular characterizations, and oxidative potentials of different polarity levels of water-soluble organic matters in winter PM2.5 in six China's megacities. Science of The Total Environment, 2022, 853: 158600

6. Line 451: The conclusion of this part is not prominent enough, suggesting a more in-depth analysis and better conclusions.
7. Figure 3 was lost the legend, please redraw this figure.
8. Please add the necessary comments for Figure 4, what does each line represent?
9. The language overall is acceptable, except for a few places which fail to meet the required level, advice on Grammar from a native writer of English would be helpful.