This manuscript reported a four-month’s continuous bihourly measurement of various types of secondary organic aerosol (SOA) tracers originated from common specific volatile organic compounds (VOCs). The authors focused on the concentration change of the SOA tracers during high PM_2.5 episodes and found obvious mass increment of the SOA tracers during the episodes especially in summer and fall, suggesting enhanced SOA formation during the episode. Moreover, the chemical formation mechanism and ageing of the biogenic SOA formation during the episodes were examined with the measurement of multiple molecular tracers from single VOC precursor, which provide valuable insight into the formation mechanism under ambient atmosphere similar to this study area. In general, this manuscript is well written, and the dataset is large. The manuscript can be accepted with the following revisions:

1. As the focus of this work is to examine the SOA tracers, while most of which lack authentic standards for the quantification. The authors should elaborate more on how the identification and quantification was achieved (such as the retention time, quantification ions, etc.).
2. The SOA tracers are widely used to estimate the SOC contribution either by the SOA tracer method or by receptor models such as Positive Matrix Factorization (PMF). Since the comprehensive measurement data are available, do the authors plan to conduct such analysis to get a more quantitative estimation of the SOA contribution?
3. Lines 190-194: Why the authors only selected the “before-episode period” to evaluate the evolution of SOA tracers, instead of using all measured data?
4. The date format in the main text and Tables is not consistent. For example, “10 Jul. -7 Oct” in Line 135 vs. “Sep-01 12:00 PM” in Table 1. Please check and unify the format.
5. Figure 1: there are only two sites showing numbers near the column plot in the figure, are they the concentration values stated in the figure caption? How about the other sites?
6. Figures 5-6: the figure numbers “(a)” and “(b)” in the figure are missing.
7. Figure S8: The axis of Figure S8 is not readable.
8. Line 193: “were” should be “are”.
9. Line 230: “in Chow et al. 2016).” should be “in Chow et al. (2016)).”.
10. Lines 297-298: The description is not consistent with the content of Figure 5. At EP6N, isoprene SOA tracer concentrations were higher in the time period before the episode.
11. Lines 374-379: The description is not consistent with Figure 7.
12. Line 403: “2-methyl tetrols” should be “2-methyltetrols”.

The current study has been designed to monitor SOA tracers at a suburban site in Hong Kong for four months. Results showed regional characteristics for anthropogenic and biogenic SOA including for biomass burning SOA. This study also highlights the need of high time resolution organic marker measurement at multiple sites to fully capture the spatial variability and implement control measures. I think such kind of field study should be promoted in future to completely understand the role of SOA formation during haze events.

My suggestions are given below:

Please add reference “PM pollution was observed to have a clear seasonal pattern, with lower concentrations in summer and higher in fall and winter.”

Please add reference” In this work, we define that a PM2.5 pollution episode occurred when the PM2.5 concentration was higher than 35 μg/m3 (24-hour standard)”

Line 220: What about levoglucosan and nitrocatechol correlation in different periods? Have authors also checked other meteorological parameters? Sometimes meteorology could affect the existing correlation.

Line 230: “This likely reflects that 4-nitrocatechol has precursor sources other than BB and joint measurements of potential precursors (e.g., catechol, phenol, benzene) in the future would help to discern the relative importance of precursors from BB versus anthropogenic sources.” Yes, nitrocatechol has other precursors and author should cite those references here. Have author checked nitrocatechol to levoglucosan ratio for different season?

Line 260: Did author suggest the role of ozone in the formation of phthalic acid and DHOPA? I will appreciate if more information can be provided on their formation pathways.