The manuscript by Wang et al. provides a comprehensive analysis of the physicochemical properties of black carbon (BC)-containing particles over the Tibetan Plateau, with an emphasis on the impacts of anthropogenic emissions. The authors conduct detailed field observations, which contribute valuable data to this field of study. Their findings represent a noteworthy advancement in elucidating the impact of anthropogenic emissions on the properties of BC, especially within the environmentally sensitive Tibetan Plateau region. See my detailed comments below.

Major Comments:

1. Addressing Seasonality and Expanding Temporal Scope: The manuscript effectively outlines how regional transport influences the BC characteristics over the plateau. This is particularly evident in the comparison between the northeast and southeast regions. Yet, the study seems to focus predominantly on the spring season (Table 1). It would be valuable if the authors could discuss the potential seasonality of these findings or provide reasons for the focus on this particular season, including how the results might vary in other seasons.
2. Lack of Detailed Model Evaluation：The manuscript utilizes the WRF-Chem model to simulate the atmospheric processes and black carbon (BC) characteristics over the Tibetan Plateau. However, there seems to be a lack of detailed evaluation or validation of the model simulations against observational data. Without proper validation, the reliability of the model results and the subsequent conclusions drawn from them may be questionable.

Minor Comments:

• Line 155: According to my understanding, the study by Cui et al. (2022) only provides BC concentrations in urban areas of Shanghai, and does not directly provide the number 25%. Please directly provide the BC concentrations mentioned in Cui et al. (2022)'s study and explain how the calculation for obtaining 25% is done. In addition, although EC is sometimes used as a substitute for BC in some cases due to the lack of BC observations, it should not be said that they are equivalent
• Line 158: The sentence suggests that the intermediate position of the concentration within the TP region may be due to anthropogenic emissions in the surrounding area. However, it does not explain why it is not in a high concentration position.
• Line 175: Is this difference statistically significant? Are there any indicators for testing the significance of differences that can be reported?
• Line 192: The sentence could be improved by providing citations to support the claim that C2H3O+ is a typical biomass burning (BB) tracer.
• Line 222: 17.3% cannot be reflected in Fig. 5b, but only in Fig. 5a, and there is no particular reason to switch from two decimal places to one decimal place in the figure.
• Line 240: The statement "The abundant NO3- was closely associated with anthropogenic sources" is mentioned here, but it should be referenced in line 222 to support the conclusion that "indicating that anthropogenic..."

The manuscript provides observational evidence of the spatial discrepancies in the physicochemical properties of black carbon (BC)-containing particles within the Tibetan Plateau region. It emphases the significant impacts of elevated anthropogenic emissions from surrounding low-altitude areas on BC, altering its concentration and chemical composition, as well as enhancing its light absorption ability. The manuscript is well written, and the topic is of interest and fits the scope of ACP. I recommend a minor revision before publication. The detailed comments or suggestions are shown below:

1. In this study, there are three factors identified using PMF, which is a little less than the usual number (normally 4 or 5 factors can be resolved by PMF for HR-AMS data). It is better to provide the explanation of why the 3-factor result is chosen in the main text or SI.

2. Line 131: what refractive index did you use for the core-shell Mie model? Please add the numbers you adopted and reference here.

3. Line 154: It is suggested to clarify the different measuring instruments corresponding to different BC definitions before comparing BC concentrations in Table 1.

4. In Table 1, the description “BC (EC)” is not very precise here. Please revise them.

5. Table 1: Please add a note illustrating the meaning of the numbers in “BC concentration” column, i.e., is it a mean or median value? What does the range stand for in the parenthesis?

6. Line 106: please add abbreviation of light absorption coefficients (b_abs) here.

7. Figure 7: the color of CL2 in subplot (b) overlaps with the background map. It is better to change it to ensure the visibility.

8. Please check and ensure that the number of significant digits are consistent throughout the manuscript.

Black carbon (BC) is one of the most important aerosol species affecting climate, glaciers and hydrology in Tibetan Plateau (TP). However, large uncertainties still exist in the estimation of BC DRF over the TP, which is related to the mixing states of BC. This study presents multi-point observations of BC mixing states, especially the chemical composition of BC-containing particles, and combines model simulation to reveal the causes of spatial differences and the impacts of transported emission sources. It provides valuable results which may support the future evaluation of BC climate and environmental effects over the TP region. The coupling mechanism between the planetary boundary layer, topography, and pollution mentioned in the text is also interesting. Overall, it is a well-organized manuscript. Thus, I suggest publishing after minor revisions. The detail comments are shown below:

1.    My main suggestion is that the model configuration and validation need to be more detailed, which can be described in 2.3 part. Additional figures of model validation can be added into the SI (e.g. meteorological parameters, gaseous pollutants). Furthermore, a brief setup of the chemical transport model should be elucidated within the main text, in addition to its inclusion in the Supplementary Information.

2.    As I commented earlier in the discussion process, the authors should pay careful attention to the use of significant figures in both the main text and figures. For instance, in Figure 5, the fractions should be reported with 2 significant digits, not 4. Additionally, it is important that the number of significant figures is consistent across all panels in Figures 3 and 7.

3.    Line 27: the term “self-elevated” is typically associated with plume uplift due to the absorption of solar radiation by black carbon. However, as the uplift in question may not be solely attributed to this mechanism, it is recommended to replace the term.

4.    Line 36: The expression “2,500,000 km2” appears twice in a sentence. Please remove one instance to ensure clarity and conciseness.

5.    Line 150, too many digitals for wind speed and gaseous pollutant concentrations

6.    Line 175, a t-test is needed when comparing RBC between Xinhan and Lulang

7.    Line 199-200, “MO-OOA had very high O:C (0.84), while the O:C of LO-OOA was only 0.49.” 

It is better to be rephrased to in Xinhai “MO-OOA exhibited higher O:C ratio (0.84) than LO-OOA (0.49) ”

8.    Line 201 “Therefore, this POA factor was identified as biomass burning OA (BBOA) in Lulang.”

Since f60 from this factor is not as high as those from biomass burning source test, likely caused by aging process, it is better to state that this factor is likely associated with biomass burning activities.

9.    Figure 6, in the figure caption, it is better to explain how the grid of x-axis is calculated since RBC equals 0 meaning externally mixed BC.

10.    Line 191: “The POA factor had higher signal of C4H7+ and C4H9+ in its mass spectrum…”. Please explain the major sources of C4H7+ and C4H9+ and add proper references here.

11.    Line 214: “OA was the dominant component of BC coating (Fig. 5b) at both sites”. Here it should refer to Fig. 5a rather than Fig. 5b.

12.    Line 219: “The dominance of MO-OOA in BC coating was resulted from strong atmospheric oxidizing capacity in TP and fast aging process during transport.”. Based on Fig. 5, I don’t think there is information about the atmospheric oxidation capacity and aging rates during transport. If this discussion is located in the latter part of the article, it is suggested to place this sentence in a more appropriate location.

13.    Line 305: is there any observed MAC in TP region? If yes, it is recommended to compare the results in this study with previous observations (references need to be added accordingly).

14.    The abbreviations of CL 1,2,3 should be defined in the main text.