Summary:

Naphthalene (Nap) and its derivatives are important intermediate volatile organic compounds (IVOCs) contributing to the formation of secondary organic carbon (SOC). This manuscript uses the CMAQ model to investigate the impacts of Nap and methylnaphthalene (MN) on the formation of SOC and other secondary pollutants in the YRD region. Overall, the manuscript is well written and easy to follow. The results are interesting and meaningful. I recommend accepting this manuscript after some minor revisions.

Minor comments:

1. Lines 29-30: Does the 3.1% contribution refer to total methylnaphthalene?
2. Lines 154-156: Why only the anthropogenic emissions of Nap and MN were scaled in the emis-adjust case? According to Figure S3, the Nap and MN emissions in the YRD regions are much lower than those in other regions. Could you please show the difference between the MEIC and the YRD emission inventories, and add a brief discussion about such uncertainty?
3. Lines 160-161: Is the total Nap and MN emission rate over the YRD region 0.9 kg day^-1? Please verify the numbers.
4. Lines 195-196: Could you clarify the meaning of "the original settings" mentioned here?
5. Lines 199-200: It is recommended to change the units for 1.40E-2 ppb and 1.50E-2 ppb to ppt.
6. Lines 201-202: According to Figure 1, the simulated concentrations of OC and PM₅ were nearly identical for both cases. Therefore, the term "improved" may not be appropriate here.
7. Lines 269-272: There is no significant difference in the simulated OC concentrations between case-1product and case-2products.
8. Lines 294-302: I’m curious about the diurnal variations in O₃ and radicals. Could you provide more details?
9. Figure 4: Please check the line length in the colorbar ticks.