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Your search keyword '"Chan, Chak Keung"' showing total 19 results
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19 results on '"Chan, Chak Keung"'

4. Distinct Photochemistry in Glycine Particles Mixed with Different Atmospheric Nitrate Salts

Author

Liang, Zhancong, Cheng, Zhihao, Zhang, Ruifeng, and Chan, Chak Keung

Abstract

Particulate Free amino acids (FAAs) are essential components of organonitrogen that have critical climate impacts, but they are usually considered stable end products from protein degradation. In this work, we investigated the decay glycine (GC) as a model FAA under photolysis of different particulate nitrate salts using an in-situ micro-Raman system. Upon changes of the relative humidity (RH) cycle between 3 and 80 % RH, ammonium nitrate (AN)+GC mixed particles did not exhibit any phase change, whereas sodium nitrate (SN)+GC mixed particles crystallized at 60 % and deliquesced at 82 % RH. Under light illumination at 80 % RH, AN+GC particles showed almost no spectral changes, while rapid decays of glycine and nitrate were observed in SN+GC particles. The interactions between nitrate and glycine in AN+GC particles suppressed crystallization, but also hindered nitrate photolysis and glycine decay. On the other hand, glycine formed a complex with Na+ in deliquescent SN+GC particles and allowed unbonded nitrate to undergo photolysis and trigger glycine decay, though nitrate photolysis was greatly hindered upon particle crystallization. Our work provides insights into how FAAs may interact with different nitrate salts under irradiation and lead to distinct decay rates, which facilitates further investigations on their atmospheric lifetime estimation.

Published
2023

6. Supplementary material to "Sulfate formation via aerosol phase SO2 oxidation by model biomass burning photosensitizers: 3,4-dimethoxybenzaldehyde, vanillin and syringaldehyde using single particle characterization"

Author

Zhou, Liyuan, primary, Liang, Zhancong, additional, Mabato, Beatrix Rosette Go, additional, Cuevas, Rosemarie Ann Infante, additional, Tang, Rongzhi, additional, Li, Mei, additional, Cheng, Chunlei, additional, and Chan, Chak Keung, additional

Published
2023
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16. Investigation into the Phase–Activity Relationship of MnO 2 Nanomaterials toward Ozone‐Assisted Catalytic Oxidation of Toluene (Small 50/2021)

Author

Yang, Ruijie, primary, Guo, Zhongjie, additional, Cai, Lixin, additional, Zhu, Rongshu, additional, Fan, Yingying, additional, Zhang, Yuefeng, additional, Han, Pingping, additional, Zhang, Wanjian, additional, Zhu, Xiangang, additional, Zhao, Qitong, additional, Zhu, Zhenye, additional, Chan, Chak Keung, additional, and Zeng, Zhiyuan, additional

Published
2021
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17. Simultaneous Formation of Sulfate and Nitrate via Co-uptake of SO2 and NO2 by Aqueous NaCl Droplets: Combined Effect of Nitrate Photolysis and Chlorine Chemistry.

Author

Zhang, Ruifeng and Chan, Chak Keung

Subjects
PHOTOLYSIS (Chemistry), PARTICULATE nitrate, SULFATES, NITRATES, HYDROLYSIS, SALT, CHLORIDE ions
Abstract

SO2 and NO2 are the critical precursors in forming sulfate and nitrate in ambient particles. We studied the mechanism of sulfate and nitrate formation during the co-uptake of NO2 and SO2 into NaCl droplets at different RHs under irradiation and dark conditions. A significant formation of nitrate attributable to NO2 hydrolysis was observed during the NO2 uptake under all conditions, and its formation rate increases with decreasing RH. The averaged NO2 uptake coefficient, γNO2, from the unary uptake of NO2 into NaCl droplets under dark are 1.6 × 10-5, 1.9 × 10-5, and 3.0 × 10-5 at 80 %, 70 %, and 60 % RH, respectively. Chloride photolysis and nitrate photolysis play a crucial role in sulfate formation during the co-uptake. Nitrate photolysis generates reactive species (e.g., OH radicals, NO2, and N(III)) that directly react with S(IV) to produce sulfate. The generated OH radicals from nitrate photolysis can also react with chloride ions to form reactive chlorine species and then sulfate. To parameterize the role of nitrate photolysis and chloride photolysis in forming sulfate, the SO2 uptake coefficient, γSO2, as a function of nitrate photolysis rate, P NO3- (= j NO3- × [NO3-]), and chloride photolysis rate, P Cl- (= j Cl- × [Cl-]), as γSO2 = 0.41 × P NO3- + 0.34 × P Cl- was derived. Our findings open up new perspectives on the formation of secondary aerosol from the combined effect of nitrate photolysis and chlorine chemistry. [ABSTRACT FROM AUTHOR]

Published
2023
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