General comments:

1. The authors refer to size bins of the PSM in nm size with 2 digit precision (e.g. line 1471.34-1.39 nm) and further refer to J rates and GR for 1.34 nm particles. I would suggest to round this number, as other studies show, that there is e.g. an uncertainty of 0.1 nm for the calibration of the PSM (Kangasluoma et al., 2015) and also other particle instruments, such as CPCs have an uncertainty for the cut-off size of 0.2 nm (e.g. stated in Dada et al., 2020). I am not sure the PSM can distinguish the sizes down to 0.01 nm difference in diameter.
2. In section 2.2.3 the authors mention measurements with an ACSM, however I did not find any data shown from this instrument in this measurement report. Was the data used for the study? If so, could it support the NPF mechanism assumptions of the study?
3. Do I interpret this correctly from Fig. 2 that there are NPF events at the GC site almost every day, but they seem to be transported? And on certain days, such as the example in Fig. 3, there is NPF in the range of 1.3-3.7 nm and further a growth is visible in the larger particles, measured by SMPS? Could the authors be more precise regarding the NPF event classification? In Fig. 2 it seems like most events are transported events, since there are barely any paritcles below approx. 18 nm.
4. The authors mention several measurements of tracehouse gases, the proxy of sulfuric acid and ACSM data, however only show a fraction or mean of it. I would suggest to add those measurements in the time series plot of figure 2 or potentially in the supplementary, so that the reader gets a clearer idea of the behaviour of the various parameters.
5. Figure 5 is not mentioned anywhere in the text. Please include or remove the figure if irrelevant for the study.

Specific remarks:

Language remarks:

Supplementary material:

Hong et al. presents a measurement report on wintertime new particle formation (NPF) in the rural area of North China Plain, exploring its influencing factors and possible formation mechanism. While NPF in urban cities of China are relatively well investigated, measurements in the rural areas are rather not enough to understand its underlying mechanisms. This manuscript is of great interest to readers of general aerosol formation, particularly in the NPF research. However, the following issues/concerns need to be addressed before it can be accepted for publication in the journal.

1. The sulfuric acid (SA) concentration in this study was calculated according to proxy proposed by Petaja et al. (2009). However, Lu et al. (2019) proposed a better proxy for estimating SA concentration in urban Beijing. It would be beneficial to compare both proxies for their performance since Petaja et al.’s proxy is based on measurements in boreal environments while Lu et al’s one might be more applicable to the current study.
2. This study measured only particle number size distribution and no potential nucleating precursors (e.g., sulfuric acid, amines, carboxylic acids) were measured. A SA-DMA mechanism was proposed based on the similarity of correlations of the particle formation rate with sulfuric acid concentration for this study and for the Cloud studies. It seems that proposing such a mechanism based solely on this similarity does not make any sense, providing no any measured DMA concentration in this area. In addition, how can the authors ensure the base is DMA rather than any other amines?
3. The exclusion of SA-acid mechanism was based on Figure S1 which show a bad correlation between J and SA*diacids. However, the rationale needs to be validated since concentrations of both SA and diacids varied in the correlation plot, leading to violation of thermodynamic roles. This approach is not convincing.
4. The authors conclude that the controlling factor for NPF is the condensational sink which is based on qualitative comparison of CS characteristics between the measurement site and urban Beijing. However, some quantitative representations are needed to make sure the CS indeed is the most important factor for determining the occurrence of NPF at the site.
5. Below are rather minor:

• There are lots of typos, ill-sentences through the manuscript which need to be corrected.
• L39, at an urban site
• L61 and throughout the text, H2SO4 needs subscript for 2 and 4. There are lots of such typos in the text for H2SO4 and other molecular formula
• L61, sulfuric acid molecules, follow a plural form
• L67, newly form
• L73-74, I don’t think the chemical composition of 1-3 nm particles has been speciated thus far.
• L80, important contributors to atmospheric nucleation
• L84, formation
• L137-138, I think 3080 include DMA inside
• L188&198, where, ???
• L203, particles in new mode? What does this mean?
• L207, discussion
• L208, section 3.1.
• L215, at the current site
• L222 & others, lower than, not “compared to”
• L226, what are they referred to?
• L253&others, “Note that” is simple than “It has to be noted that”
• L256-257, it is hard to understand this sentence
• L262, formation rates vs those
• L266, in those polluted atmospheres
• L288-289, that clause is ambiguous here

Reference

Lu, Y., Yan, C., Fu, Y., Chen, Y., Liu, Y., Yang, G., et al. (2019). A proxy for atmospheric daytime gaseous sulfuric acid concentration in urban Beijing. Atmospheric Chemistry and Physics, 19(3), 1971–1983. https://doi.org/10.5194/acp-19-1971-2019