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Identifier

000453749

Title

Κλιματική παρέμβαση και αναστροφή κλιματικής αλλαγής : ετερογενής αλληλεπίδραση αέριων HCl και SO2 με νανοσωματίδια CaCO3, υπό στρατοσφαιρικές συνθήκες

Alternative Title

Climate intervention and climate change inversion: heterogeneous interactions of gaseous HCl and SO2 with CaCO3 nanoparticles, under stratospheric conditions

Author

Τέλλιου, Παντάνασσα Α.

Thesis advisor

Κανακίδου, Μαρία

Reviewer

Μήλιος, Κωνσταντίνος
Παπαδημητρίου, Βασίλειος

Abstract

In this work, the kinetics and the mechanism for the heterogeneous interaction of calcium carbonate nanoparticles (CaCO₃, 100 – 150 nm, calcite polymorph) with gaseous hydrogen chloride (HCl) and sulfuric dioxide were studied, aiming to investigate their impact on stratospheric photochemistry. The present study is part of the interdisciplinary research project, Climate Intervention, based on which it was recently proposed to inject CaCO₃ in the Stratosphere (Stratospheric Aerosol Injection, SAI), pointing to reduce the amount of the incoming solar radiation into Earth’s Atmosphere and to counterbalance the Global Warming. In this framework, the adsorption efficiency of HCl and SO₂ gases onto calcite nanoparticles, as well as the potent CaCO₃ chemical transformation, were measured, since it is likely to impact on both Earth’s energy balance and stratospheric photochemistry. More specifically, initial, γ₀, and steady state, γ_ss, uptake coefficients were determined for the gaseous ΗCl adsorption on CaCO₃ nanoparticles surface, under very low pressure conditions (2 – 10 mTorr), using a continuous flow system, equipped with a specially modified Knudsen reactor (Kn-R). Kn-R coupling with quadrupole mass spectrometry (QMS) detection technique allows the real-time identification and the quantitative determination of the adsorbed gases as well as of the possible volatile products. In addition, the time-profile shape of the mass spectral intensity recorded during the gases adsorption on/desorption from CaCO₃, provides with significant mechanistic information about the nature and the involved processes of the interaction, such as physisorption, diffusion, accommodation, chemisorption and desorption. Further, the potent chemical transformation of calcite, during its interaction with gaseous HCl and SO₂ was also investigated. For that purpose, independent measurements were carried out employing the static technique of the thermostated reactor (Static Thermostated Reactor, STR), as a function of temperature, 240 – 296 K and pressure, 100 – 760 Torr, in absence and presence of controlled levels of water vapors. In these measurements, CaCO₃ nanoparticles samples were exposed to the gases mentioned above for long-time periods (1 – 4 days), and they were further characterized using the ex-situ techniques of powder X-Ray Diffraction (p-XRD), Energy dispersive X-ray Spectroscopy (EDS) and X-Ray Photoelectron Spectroscopy (XPS). The combined data analysis of the results obtained using the two independent experimental techniques, i. e., Kn-R and STR, showed that the initial physisorption of HCl and SO₂ gases on CaCO₃ samples is followed by diffusion/accommodation and chemisorption, with the latter leading to permanent chemical transformation of the nanoparticles. The observed chemical transformation, will not only affect the chemistry of the Stratosphere, but also alter the optical properties of the particles and impact the radiation balance of the region. The utilization of this work results on properly designed photochemical models of Earth’s Stratosphere could provide with key-information about the impact of CaCO₃ injection on Earth’s Climate and Global Warming and assist the policy-makers to proceed with informed decisions about their use- terms.

Language

Greek

Subject

Aerosol

Chemical transformation

Climate intervention

Stratosphere

Uptake

Αερόλυμα

Κλιματική παρέμβαση

Προσρόφηση

Στρατόσφαιρα