The manuscript by Ye et al. presents a comprehensive study on the chemistry of hydrogen peroxide (H2O2) in the rural North China Plain during the summer of 2016. The research addresses a critical gap in understanding the atmospheric oxidation capacity and photochemical pollution in a region known for severe air quality issues. The study combines field measurements with box model simulations to investigate H2O2 concentrations, sources, sinks, and its relationship with other oxidants like ozone (O3) and peroxyacetyl nitrate (PAN). The findings provide valuable insights into the role of heterogeneous uptake by particles, the sensitivity of H2O2 production to various precursors, and implications for O3 formation regimes. Overall, the manuscript is well-structured, with detailed methodology and robust data analysis. I recommend minor revisions for this manuscript before publication. There are areas where clarity, depth, and presentation can be improved to enhance the impact of the work.

Specific comments:

1. Section 3.3: The analysis of O3/H2O2 ratio differences between clean and polluted days provides an interesting preliminary assessment, but the authors should acknowledge potential confounding factors like VOC/NOx ratios that might influence this relationsh
2. While the study effectively demonstrates the need for particle uptake, the sensitivity to the HO2 uptake coefficient (discussed lines 304-309) is important. The manuscript correctly notes this influences the derived H2O2 uptake coefficient. Perhaps briefly reiterate this uncertainty in the conclusion when stating the H2O2 uptake coefficient.
3. The text acknowledges the underestimation of organic peroxides (lines 125-126, 244-245). While H2O2 is shown to dominate, briefly stating why the method underestimates organic peroxides (e.g., lower collection efficiency for some species) could add clarity for readers unfamiliar with the technique.
4. There seems to be a minor discrepancy in the stated contribution of particle uptake to H2O2 loss (69% in Abstract/Conclusions vs. 64% implied by Fig S2 caption/text line 320). Please ensure consistency.
5. Line 192-196: The manuscript highlights an increasing trend in H2O2 concentrations over time in the North China Plain. While comparisons with previous studies are provided, the discussion on potential drivers of this trend (e.g., changes in NOx/VOC ratios due to emission policies) is limited. The authors should expand on this.
6. Line 407: The conclusions summarize the key findings well but could include a forward-looking statement on future research needs (e.g., long-term H2O2 monitoring, improved HO2 uptake parameterization) to guide subsequent studies.

Review of Understanding summertime H₂O₂ chemistry in North China Plain through observations and modelling studies by Can Ye et al.

This study presents a well-executed combination of field observations, chemical box modeling, and a thorough understanding of the literature to explore the dynamics of atmospheric hydrogen peroxide (H₂O₂)—a species that, in my view, remains underexamined in atmospheric chemistry.

The authors investigate H₂O₂ chemistry in the rural North China Plain during summer 2016, using detailed field measurements alongside box model simulations. They identify H₂O₂ as the dominant atmospheric peroxide, showing a clear diurnal pattern consistent with photochemical production. A notable strength of the study is the incorporation of heterogeneous uptake by particles into the model, which markedly improves agreement with observations, reducing an initial overestimate by a factor of 2.7.

The paper also provides a comprehensive budget analysis of H₂O₂ sources and sinks and employs Relative Incremental Reactivity (RIR) analysis to examine how precursor reductions influence H₂O₂ levels. The findings indicate that both VOC and NOₓ reductions are critical for simultaneously mitigating H₂O₂ and ozone pollution, offering practical insights for air quality policy in rural, polluted regions.

There is much to appreciate in this work: the application of RIR and the RACM model, the concrete policy implications, the determination and contextualization of the H₂O₂ uptake coefficient, and the quality of the observational data—Figure 1 being a particularly compelling example.

My comments are minor and peripheral, and I recommend publication following minor revisions.

Scientific Comments

The authors mention unidentified processes that weaken the H₂O₂–O₃ correlation. Could they comment on plausible candidates for these processes, such as aqueous-phase reactions or nighttime chemistry? Exploring these possibilities would help clarify what additional mechanisms may need to be included in future modeling efforts.

The model initially overestimates H₂O₂ by a factor of 2.7. How robust are the RIR conclusions in light of this discrepancy? It would be helpful to discuss whether this modeling bias could influence the inferred sensitivity of H₂O₂ to different precursors. How sensitive are the model results to the assumed uptake coefficient (6×10⁻⁴) for H₂O₂? Is there a justification or uncertainty range?

Does the rural Wangdu site reflect conditions across the North China Plain? How generalizable are the results?

In Figure 3, around 19:00, H₂O₂ accounts for over 90% of total peroxides, while at 5:00, it accounts for only about 25%. Could the authors comment on the causes of this diurnal variation and the differing behavior of organic peroxides versus H₂O₂? This would enrich the interpretation of the peroxide measurements and their photochemical dynamics.

Technical Comments

Line 151: Please change lagrangian to Lagrangian, as it is a proper adjective derived from Joseph-Louis Lagrange (analogous to Watt, Poisson, Newtonian, etc.).

Typographic conventions: According to the IUPAC Green Book (3rd edition, 2007), symbols for physical quantities should be printed in italic type to distinguish them from unit symbols. Please revise:

k in line 158

r² in lines 258, 259, and Figure 10

T, P, and other physical quantities, if applicable elsewhere

Line 174 and elsewhere: Change O1D to O(¹D) to reflect the correct notation for electronically excited oxygen.

Line 177: Use a subscript for O3 — i.e., O₃.

Line 189: Change Hongkong to Hong Kong, the correct spelling in English.

Line 230: Change O3P to O(³P) to properly denote the electronic state of ground-state atomic oxygen.