the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
A new smog chamber system for atmospheric multiphase chemistry study: design and characterization
Taomou Zong
Zhijun Wu
Junrui Wang
Kai Bi
Wenxu Fang
Yanrong Yang
Xuena Yu
Zhier Bao
Xiangxinyue Meng
Yuheng Zhang
Yang Chen
Chunshan Liu
Yue Zhang
Shao-Meng Li
Abstract. Multiphase chemistry is an important pathway for the formation of secondary organic aerosols in the atmosphere. In this study, an indoor 2 m3 Teflon chamber system (Aerosol multIphase chemistry Research chamber, AIR) was developed and characterized to specifically simulate atmospheric multiphase chemistry processes. The temperature and humidity controls, diurnal variation simulation, and seed particle generation unit in this chamber system were designed to meet the needs of simulating multiphase atmospheric chemical reactions. The AIR chamber is able to accurately control temperature (2.5 ~ 31 ± 0.15 ℃) and relative humidity (RH < 2 % ~ > 95 % ± 0.75 %) over a relatively broad range. In addition, an RH regulation module inside the chamber was designed to simulate the diurnal variation of ambient atmospheric RH. The aerosol generation unit is able to generate pre-deliquescent seed particles with an organic-coating across a wide range of phase states or morphologies. The organic coating thickness of the aerosols within the chamber can be precisely controlled through adjusting the condensation temperature, further helping to elucidate the roles of seed particles in multiphase chemical reactions. The inner walls of the AIR chamber are passivated to reduce the wall loss rates of reactive gases. Yield experiments of α-pinene ozonolysis with and without seed particles combined with a box model simulation demonstrate the high-quality performance of secondary aerosol formation simulation using the AIR chamber.
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Taomou Zong et al.
Status: final response (author comments only)
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RC1: 'Comment on amt-2023-34', Anonymous Referee #2, 26 Apr 2023
The manuscript by Zong et al., titled “A new smog chamber system for atmospheric multiphase chemistry simulation: design and characterization” characterized the 2 m3 indoor smog chamber (AIR) and conducted a series of characterization experiments. The characterization results, as well as the yield experiments of α-pinene ozonolysis combined with a box model simulation, supported that the AIR chamber could be used to simulate multiphase atmospheric chemical reactions. The manuscript was well written and organized, but the reviewer thinks that detail characterizations related to new designs for multiphase chemistry may be further strengthened.
Specific comments:
- Figure 2: the conditions of the test should be listed, such as the fan condition. Is it batch mode? Will irradiation affect the temperature? Can water molecules permeate the FEP film? If so, the RH should decrease with time due to the water permeation.
- What is the size distribution of the particles before and after condensing organics on the particles? Is it efficient to introduce monodisperse seeds (number concentration and size distribution)? Is there homogeneous nucleation?
- For the pinene ozonolysis experiments, is there homogeneous nucleation with the high concentrations of pinene and ozone. I think the experimental conditions should be optimized for multiphase chemistry. For example, SOA is generated on the seed surfaces as much as possible.
- Section 4: The vapor wall loss can have significant influence on SOA formation. How this will affect the SOA formation and SOA yield in this study, especially for different systems in the absence or presence of seed aerosols?
Citation: https://doi.org/10.5194/amt-2023-34-RC1 -
RC2: 'Comment on amt-2023-34', Anonymous Referee #1, 03 May 2023
The authors show their results about a newly constructed smog chamber for multiphase chemistry studies. The facility and characterization results have been demonstrated. This work is well organized and presented. It is publishable after the following questions have been well addressed.
- The novelty of this work should be demonstrated based on a good review of previous studies.
- Line 105, the uncertainty of RH measurement is ±75%. What is the uncertainty for the RH sensor?
- Lines 223-225, is the coating system stable enough for generating organic coated particles? In my experience, the coating efficiency might decrease with time at high temperatures.
- How long does it take for introducing around 5000 cm-3 OA-coated seeds into the chamber?
- Figure 4, why is the SOA yield higher than those reported values at high OA mass loading?
- When calculating SOA yields, the wall loss of LVOCs should be accounted for. The low SOA yield might be related to the high wall loss rate of LOVCs.
- I am wondering why the authors do not evaluate the photochemical performance here.
Citation: https://doi.org/10.5194/amt-2023-34-RC2 -
RC3: 'Comment on amt-2023-34', Anonymous Referee #3, 11 May 2023
Comments on “A new smog chamber system for atmospheric multiphase chemistry study: design and characterization” by Zong et al.
This study designed and characterized a new smog chamber that can be used to study atmospheric multiphase chemistry. The smog chamber system can achieve precise control of temperature and humidity to generate seed particles at different phases states. Some key parameters for the new chamber, including leak proofness, mixing performance, the wall losses for gas and particle phases etc, were systematically characterized. The new smog chamber system shows its ability to simulate secondary aerosol formation and atmospheric multiphase processes like other chambers. Overall, the manuscript is well organized. Some questions shall be clarified before publication:
Major comments:
1: Line 138-140: Have the authors measured the temperature differences in different positions of the chamber? The sensor was set in the bottom now. How about the spatial distribution of the sensor.
2: Line 442-443: Are there any other studies about NaCl seed found the same conclusion? Is the dry NaCl seed not competitive with sorption of organic vapors onto the chamber wall? Or the condensing SOA compounds form a separate phase from the seed?
3: Line 372-373：How to determine the segmentation of the shift and whether the results of the shift accurately represent the actual wall loss of the substance in different experiments?
Technical comments:
4: Line 239-240: Please note the use of subscripts (SO2 and O3).
5: The description of figures should be more accurate.
- Line 259-261: “more than 25 hours” could not be seen in Fig. S2a.
- Line284-285: Most of the mixing time to uniformity for gas showed in the figure is longer than 1minute with the fans on.
6: Line 321-323: The number of lights of scheme ‘left and right’ is 20 but not 40, and is 10 lights for ‘only left’ and ‘only right’.
7: Line 378-380: Please note the use of operational symbol (* and Í).
Line 198: The format of unit shall be checked through, e.g., should be no ‘space’ before %. The same unit with different format such as cm-3 and μg/m3 were used.
8: Please unify the format of the graphs and optimize the graphs. For example, the font size is different in Fig. 3a and 3b. There should be a ‘space’ between 20 and ℃ for Fig. 3b. And we could even see some grey lines outside the graphs, it seems that the graphs were simply pasted from other software and combined together. Please redraw these figures and unify the format.
9: Please doublecheck the citation of references. For example,
Line 85, the citation of “Ravishankara, 97” should be 1997 but not 97.
Line 762-764, the year was missing for this citation.
Citation: https://doi.org/10.5194/amt-2023-34-RC3
Taomou Zong et al.
Taomou Zong et al.
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