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Communication Dans Un Congrès Année : 2023

Uptake of glyoxal on natural gobi desert dust under simulated atmospheric conditions

Résumé

Mineral dust represents the highest emission source of particles in the atmosphere. Saharan and Gobi deserts contribute around 70% of global annual emissions. Once emitted, dust particles can travel thousands of kilometers, and provide active surface area for the adsorption and transport of atmospheric pollutants. Glyoxal (GL) is a key atmospheric pollutant of anthropogenic and biogenic origin. It is a ubiquitous atmospheric compound and an important precursor of Secondary organic aerosols (SOA). GL participates in a series of homogeneous and heterogeneous photochemical reactions that affect air quality and climate. Interestingly, once adsorbed, GL can undergo oligomerization, hydration, and hemi-/acetal formation and thus it can drastically alter the physical (size, shape, viscosity) and chemical (hygroscopicity, oxidation state) properties of the particles on which it is taken-up. Therefore, the adsorption of GL and these subsequent reactions will likely alter the interactions of mineral dust with radiation and clouds. As a result, dust/organic interactions will likely affect both the global SOA budget and global/regional cloud formation potential. In the framework of the current study, we investigated the uptake of glyoxal onto natural Gobi Desert dust under simulated atmospheric conditions of pressure, relative humidity (RH), GL concentration, light radiation, and temperature (T). Laboratory experiments were performed in a coated wall flow tube reactor coupled to a soft ionization mass spectrometer (SIFT-MS) for real-time monitoring of the gas phase. To quantify the GL-dust interaction, we determined the uptake coefficients (γ) and the surface coverages (Ns) of GL. The uptake coefficient was found to strongly depend on the concentration of GL and was parametrized according to the following expression: (4.3±0.3)×10-5×[GL]-0.69. Under atmospheric relevant concentrations of a few ppt, the uptake coefficient is in the order of 10-3 to 10-4, indicating that the heterogeneous loss on dust particles is an important process, that has never been considered in models yet. In addition, under humid conditions (30% RH and higher) and long exposition experiments, we observed that the uptake proceeds beyond monolayer formation, leading to the coverage of the dust particle with SOA. Besides uptake, the desorption of GL from mineral particles was evaluated. At 298 K, and atmospheric relevant relative humidity levels, GL is reversibly taken up. On the contrary at temperatures below 278 K, the uptake is completely irreversible.
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Dates et versions

hal-04641922 , version 1 (09-07-2024)

Identifiants

  • HAL Id : hal-04641922 , version 1

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Antonia G Zogka, Frederic Thevenet, Manolis N. Romanias. Uptake of glyoxal on natural gobi desert dust under simulated atmospheric conditions. International conference on mineral dust, May 2023, Bari (IT), Italy. ⟨hal-04641922⟩
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