Atmospheric chemistry of mercury and sulfur induced by sunlight: Quantum-chemical modelling and environmental implications

• Main Author: Carmona García, Javier
• Other Authors: Roca Sanjuán, Daniel, Saiz López, Alfonso, Institut de Ciència Molecular
• Format: Doctoral or Postdoctoral Thesis
• Language: English; Spanish
• Published: 2024
• Subjects: química atmosférica; mercurio; azufre; química cuántica; fotoquímica; química física; espectroscopía; UNESCO::QUÍMICA::Química física; UNESCO::FÍSICA::Química física::Espectroscopía molecular; UNESCO::FÍSICA::Química física::Fotoquímica; UNESCO::CIENCIAS DE LA TIERRA Y DEL ESPACIO::Ciencias de la atmósfera ::Química atmosférica; Arctic; Mercurio; Azufre; Global warming
• Online Access: https://hdl.handle.net/10550/99935

Sunlight chemistry plays a key role in the global dynamics of atmospheric compounds. Understanding the photochemical processes that these species may undergo is mandatory to evaluate their role and fate in the atmosphere of our planet. In this regard, atmospheric models can simulate the atmospheric cycle of these species and analyze their dispersion and accumulation around the globe. However, the limited information on the photochemical properties of specific atmospheric compounds sometimes leads to models and simulations that do not align with observational data. Taking that into account, the present Thesis aims to deepen the understanding of the chemistry induced by solar light absorption of atmospheric mercury and sulfur compounds, species of interest in the fight against air pollution and global warming, respectively, by means of quantum chemical methods. The results are presented in three chapters. Chapter 4 examines the gas-phase photolytic reactivity of oxidized mercury compounds and its impact on the tropospheric and stratospheric cycles of this neurotoxin. The results obtained indicate that these species can undergo photolytic reduction, increasing the atmospheric lifetime of the metal. In Chapter 5, the absorption and photochemical properties of brominated mercury compounds which can be present in the Arctic environment during atmospheric mercury depletion events are studied. The findings from this theoretical assessment suggest that their photoreduction can contribute to the observed mercury reemissions from the snowpack in this environment. Chapter 6 focuses on the photochemical properties of sulfur species involved in stratospheric sulfate aerosol generation, a process of interest in solar geoengineering plans to reduce global temperatures. For the sulfur radicals studied (cis-HOSO and HOSO2), the results obtained show that they can photolyze in the stratosphere, although this reactivity is not competitive over their reaction with molecular oxygen. In contrast, the photostability of sulfur trioxide ...