General Comments:

Optical apportionment of carbonaceous aeroso" is an important process in the measurement of aerosol absorption properties. This manuscript presents an improved model without initial assumptions of parameters for distinguishing the composition and sources of light-absorbing carbonaceous aerosols based on the traditional optical apportionment model used for multi-wavelength absorption coefficient detection. From a scientific perspective, this study lacks significant innovation. Additionally, the deployment and application of this improved model toolkit holds some technical value. Therefore, it is recommended to reconsider the acceptance of this study after the following issues have been well solved.

Specific Comments:

1) The algorithm presented in this paper requires at least one additional independent measurement result (e.g., Levoglucosan), which significantly limits the application of this method. In Equations 1 and 2 within the text, each of them has four unknowns. In theory, the detection results from five wavelengths are sufficient to solve these unknowns. Why didn't the authors use the results from a multi-wavelength absorption analyzer for independent calculations?

2) In the algorithm described in this paper, α_BC, α_FF, and α_WB remain constant over a certain period of time (such as during a field experiment), while α_BrC varies with time. This is not reasonable. For example, in the observation example in Milan, α_BrC clearly varies with time, while α_WB is assumed to be a constant value in this period. This can introduce significant errors into the calculations. For example, in Figure 6, the trends of BrC and BC_WB are nearly identical, while in Figure 7, there is a significant difference between them. This distinction may be a result of the algorithm rather than the environmental conditions themselves.

3) In Figure 3, in the left panel, α_BC has a higher R² value around 0.93, while in the right panel, α_WB has a higher R² value around 1.67. Why not use these two values as fitting results?

4) In P6L178, the author mentioned that the Milan campaign had 20 samples, but in Figure 5, there are 25 samples. Why is that?

5) The abbreviations BC, BrC, FF, and WB should only be introduced with their full names the first time they appear, and there's no need to reintroduce them later (e.g., as in P3L90). Similarly, EC should be introduced with its full name the first time it appears.