Heterogeneous Chemistry of CaCO <subscript>3</subscript> Aerosols with HNO <subscript>3</subscript> and HCl.
In: The journal of physical chemistry. A, Jg. 124 (2020-05-14), Heft 19, S. 3886-3895
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Zugriff:
Calcite (CaCO 3 ) aerosols often serve as an idealized proxy for calcium-rich mineral dust. Their use has also previously been proposed for stratospheric solar radiation management (SSRM). Little is known about the heterogeneous chemistry of calcite aerosols with trace gases HNO 3 and HCl and therefore their potential impact on stratospheric ozone (O 3 ). Here we report the results of an experimental study of the uptake of HNO 3 and HCl onto submicron CaCO 3 particles in two different flow reactors. Products and reaction kinetics were observed by impacting aerosolized CaCO 3 onto ZnSe windows, exposing them to the reagent gases at a wide range of concentrations, at 296 K and under dry conditions, and analyzing the particles before and after trace gas exposure using Fourier transform infrared spectroscopy (FTIR). A Ca(OH)(HCO 3 ) termination layer was detected in the form of a HCO 3 - peak in the FTIR spectra, indicating a hydrated surface even under dry conditions. The results demonstrate the reaction of HNO 3 with Ca(OH)(HCO 3 ) to produce Ca(NO 3 ) 2 , water, and CO 2 . HCl reacted with Ca(OH)(HCO 3 ) to produce CaCl 2 and also water and CO 2 . The depletion of the Ca(OH)(HCO 3 )/Ca(CO 3 ) signal due to reaction with HNO 3 or HCl followed pseudo-first-order kinetics. From the FTIR analysis, the reactive uptake coefficient for HNO 3 was determined to be in the range of 0.013 ≤ γ HNO3 ≤ 0.14, and that for HCl was 0.0011 ≤ γ HCl ≤ 0.012 within the reported uncertainty. The reaction of HCl with airborne CaCO 3 aerosols was also studied in an aerosol flow tube coupled with a quadrupole chemical ionization mass spectrometer (CIMS) under similar conditions to the FTIR study, and γ HCl was determined to be 0.013 ± 0.001. Following previous modeling studies, these results suggest that the reactions of HCl and HNO 3 with calcite in the stratosphere could ameliorate the potential for stratospheric solar radiation management to lead to stratospheric ozone depletion.
Titel: |
Heterogeneous Chemistry of CaCO <subscript>3</subscript> Aerosols with HNO <subscript>3</subscript> and HCl.
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Autor/in / Beteiligte Person: | Huynh, HN ; McNeill, VF |
Zeitschrift: | The journal of physical chemistry. A, Jg. 124 (2020-05-14), Heft 19, S. 3886-3895 |
Veröffentlichung: | Washington, D.C. : American Chemical Society, c1997-, 2020 |
Medientyp: | academicJournal |
ISSN: | 1520-5215 (electronic) |
DOI: | 10.1021/acs.jpca.9b11691 |
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