the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 22 Oct 2024
A novel formation mechanism of NH2SO3H and its enhancing effect on methanesulfonic acid-methylamine aerosol particle formation in agriculture-developed and coastal industrial areas
Abstract. Sulfamic acid (SFA) significantly impacts atmospheric pollution and poses potential risks to human health. Although traditional source of SFA and its role on sulfuric acid-dimethylamine new particle formation (NPF) has received increasing attention, the formation mechanism of SFA from HNSO2 hydrolysis with CH3SO3H and its enhancing effect on methanesulfonic acid-methylamine APF has not been studied, which will limit the understanding for the source and loss of SFA in agriculture-developed and coastal industrial areas. Here, the gaseous and interfacial formation of SFA from HNSO2 hydrolysis with CH3SO3H was investigated using quantum chemical calculations and BOMD simulations. Furthermore, the role of SFA in CH3SO3H-CH3NH2 system was assessed using the Atmospheric Cluster Dynamics Code kinetic model. Our simulation results indicate that the gaseous SFA formation from the hydrolysis of HNSO2 with CH3SO3H can be competitive with that catalyzed by H2O within an altitude of 5–15 km. At the air-water interface, two types of reactions, the ions forming mechanism and the proton exchange mechanism to form NH2SO3-•••H3O+ ion pair were observed on the timescale of picosecond. Considering the overall environment of sulfuric acid emission reduction, the present findings suggest that SFA may play a significant role in NPF and the growth of aerosol particle as i) SFA can directly participate in the formation of CH3SO3H-CH3NH2-based cluster and enhance the rate of NPF from these clusters by approximately 103 times at 278.15 K; and ii) the NH2SO3- species at the air-water interface can attract gaseous molecules to the aqueous surface, and thus promote particle growth.
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Status: final response (author comments only)
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RC1: 'Comment on egusphere-2024-2638', Anonymous Referee #2, 11 Nov 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-2638/egusphere-2024-2638-RC1-supplement.pdf
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RC2: 'Comment on egusphere-2024-2638', Anonymous Referee #1, 12 Nov 2024
The manuscript egusphere-2024-2638, “A novel formation mechanism 1 of NH2SO3H and its enhancing effect on methanesulfonic acid-methylamine aerosol particle formation in agriculture-developed and coastal industrial areas”. The work studied the formation of sulfamic acid via HNSO2 hydrolysis in the gas phase and at the air-water interface by using theoretical methods. Then, the author investigated the new particle formation for the role of sulfamic acid in CH3SO3H-CH3NH2 system. The work is very interesting for understanding the chemical processes of sulfamic acid in the atmosphere. However, there are some issues that should be addressed before publication.
(1) In Line 39, “the concentration of NH2SO3H was expected to reach up to108 molecules⸱cm-3”, the concentration of sulfamic acid was only estimated by theoretical method, not measured by field observations. Therefore, it is required to elucidate this point.
(2) Lines 41-42, “the sources of NH2SO3H in the atmosphere have been well investigated (Lovejoy and Hanson, 1996; Pszona et al., 2015; Li et al., 2018; Larson and Tao, 2001; Manonmani et al., 2020; Zhang et al., 2022).” In fact, sulfamic acid has been not investigated by field measurements. Therefore, it is not well investigated in the atmosphere.
(3) Lines 46-47, “for the hydrolysis of SO3 assisted by water molecule (10-11-10-10 cm3 molecule-1 s-1) (Kim et al., 1998; Hirota et al., 1996; Shi et al., 1994).” Some important references are missing such as J. Am. Chem. Soc. 2023, 145, 19866-19876. and J. Am. Chem. Soc. 1994, 116, 10314−10315.
(4) What is the concertation of HNSO2 in the atmosphere? This is very necessary for determining the importance of HNSO2 in the atmosphere.
(5) The reliability of the chosen methods should be clarified in the HNSO2 + CH3SO3H reaction. Although the traditional method CCSD(T)//M06-2X has been widely used for atmospheric reactions, it should be noted that there are quite large uncertainties for estimating barrier height. This should clearly tell the potential readers.
(6) In kinetics calculations, it is unclear. There are lots of issues that must be addressed. Provide the details of VRC calculations. For example, how to set pivot points and what is the electronic structure method for VRC-TST calculations? The author should provide the input files for VRC-TST and MESMER calculations in Supporting information to help the potential readers to understand the computational details.
(7) According to the authors' previous research (Phys. Chem. Chem. Phys., 2022, 24, 4966-4977), the reaction of HNSO2 with nH2O also has a sufficiently low free energy barrier, which implies that HNSO2 can undergo hydrolysis or decomposition directly at the gas-liquid interface or in the bulk phase. This seems to contradict the explanation on line 228 (page 8), given that the concentration of water is sufficiently high.
(8) Why did the authors not consider a third access channel in the gas phase, that is, the reaction pathway of HNSO2… CH3SO3H + H2O? Considering the reactions at the gas-liquid interface, it seems more plausible that HNSO2… CH3SO3H would first form a complex before reacting with water molecules.
(9) In Section 3.3, the authors examined the impact of MSA-MA-SFA clusters on nucleation. Interestingly, DMA, which has a stronger nucleation capability, and NH3, which has a higher concentration, were excluded. I would like the authors to provide some appropriate justifications for this.
(10) Since the ammonolysis of SO3 is the primary pathway for SFA formation, the authors could have compared it with the current pathway, which would be necessary for accurately assessing the atmospheric significance of the current reaction.
(11) In Fig. 6b and Fig. 7b, it is necessary for the authors to carefully examine whether the significant abrupt changes caused by the concentrations of SFA and MA are reasonable.
Citation: https://doi.org/10.5194/egusphere-2024-2638-RC2
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