This manuscript investigated the influences of mixing state on BC light absorption properties, mainly based on simulations. Different scenarios were designed, and the modeling results were constrained using field observational data. Although the topic of this manuscript is within the scope of ACP, I have substantial concerns on the methodologies as well as some results. It needs to be re-reviewed after major revisions. First, the estimation of POC and SOC using the EC-tracer method. In the current manuscript, the minimum OC to EC ratio (1.16) was used to represent primary emissions (Page 4, equation 1). This approach needs to be refined, e.g., by using the lowest 10 % percentile of ambient OC/EC ratios (please refer to https://doi.org/10.1029/2008JD010902; Atmos. Chem. Phys., 15, 2969–2983, 2015; etc.). In addition, the POC and SOC results should be carefully evaluated, e.g., by examining the dependence of SOC on RH, and the relationship between POC and carbon monoxide. Second, the robustness of the measured babs, i.e., the observational constraint. For AE33, the correction factor for multiple scattering effect should be carefully determined (rather than simply using a reported value). In addition, please confirm that similar to results from in-situ techniques (e.g., photoacoustic spectrometer), the AE33-based light absorption coefficients are “sensitive” to BC mixing state, e.g., by examining the relationship between babs and EC mass concentration. Third, based on Figure 6 and Table 2, the performance of the “CSs” scenario (i.e., core-shell mixing) appeared best for reproducing the measured light absorption coefficients. Then I could not understand why the author argued that “Partial internal mixing and partial coating are the closest to reality”. For the same reason, the logic of Sections 3.3 and 3.4 was confusing.

This study uses the APM model combined with observations to discuss the impact of representative schemes of aerosols on optics. The whole study is meaningful and helpful for the experiment and model development. However, excessive use of concepts to represent aerosol mixing states lacks detailed and intuitive introductions, which reduces readability. A minor revision should be added before accepting.

1.     Many excellent concept maps can be referenced to enhance readers' understanding of mixing states, such as Fig. 4 in 10.1038/s41467-018-05635-1, Fig. 1 in 10.1175/bams-d-16-0028.1

2.     Line 40: add references for condensation and coagulation processes: 10.1016/j.isci.2023.108125

3.     Lines 190-192: Fin and Fc are not clear? Number fraction? Mass fraction?

4.     What are the differences between CS-Fin and CS-FinFc? You divided accumulation mode aerosols into 4 types (embedded, partly coated, bare-like BC and BC-free) or 3 types (embedded, bare-like BC and BC-free)? Detailed introductions should be added for mixing states in Table 1.

5.     How to define Partial internal mixing and partial coating?

6.     Line 313: How do you calculate Eabs? Add detailed calculation/inversion process.