General comments

This study investigated the WS-BrC from AOSR industrial operations by using the ultraviolet-visible spectroscopy, fluorescence excitation-emission matrix (EEM) spectroscopy, and the Parallel Factor Analysis (PARAFAC). The analysis identified three fluorescent components: one humic-like (C1) and two protein-like (C2, C3). This study indicated that the Increased fluorescence of C1 and C3 was linked to proximity to oil sands facilities and correlated with pollutants indicative of industry emissions. Component C2 was prominent during wildfire smoke events and associated with anthropogenic sources as well. This study proposed that combined EEM-PARAFAC analysis would be an effective and accessible method for monitoring WS-BrC in the AOSR. Overall, this paper is within the scope of ACP and would be of great interest to the broad atmospheric science community. I recommend that this paper can be accepted after minor revision.

My main comment is to explicitly highlight the significance and novelty of this study in the context of climate change. Section 1, 2.1, and 4.1 collectively imply that, given the large area of AOSR and the high BrC light absorption capacity, WS-BrC in this area may exhibit indispensable influence on the global climate. Can the authors summarize the information and explicitly discuss the potential global impact in the Conclusion section?

Specific comments:

1. Please clarify why the pH of sample extracts was adjusted to ~6.5 prior to the optical analysis.
2. Please briefly explain the principle of how the fluorescence analyses combined with the PARAFAC can identify WS-BrC in the first paragraph of Section 2.4.
3. Line 195: “refer1ence” should be “reference”.
4. Lines 308-310: Does this information suggest the uniqueness of organic aerosol composition within the oil sands region?
5. Lines 456-463: According to the information in this paragraph, can the authors discuss what kind of further research is required to understand the more detailed emissions profiles of C1 and C3 in relation to regional industrial activities?
6. Lines 485-486: Is there any approach to quantify the contribution of wildfires to the C2 fluorescence?