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

• Autores: Javier Carmona García
• Directores de la Tesis: Daniel Roca Sanjuán (dir. tes.), Alfonso Saiz López (codir. tes.)
• Lectura: En la Universitat de València ( España ) en 2024
• Idioma: español
• Tribunal Calificador de la Tesis: Joseph S. Francisco (presid.), Begoña Milián Medina (secret.), Lara Martínez Fernández (voc.)
• Programa de doctorado: Programa de Doctorado en Química Teórica y Modelización Computacional/Theoretical Chemistry and Computational Modelling por la Universidad Autónoma de Madrid; la Universidad Complutense de Madrid; la Universidad de Barcelona; la Universidad de Cantabria; la Universidad de Extremadura; la Universidad de las Illes Balears; la Universidad de Murcia; la Universidad de Oviedo; la Universidad de Sevilla; la Universidad de Vigo; la Universidad del País Vasco/Euskal Herriko Unibertsitatea; la Universida
• Materias:
  • Física
    • Química física
      • Espectroscopia molecular
      • Fotoquímica
  • Ciencias de la tierra y del espacio
    • Ciencias de la atmósfera
      • Química atmosférica
• Enlaces
  • Tesis en acceso abierto en: TESEO
• Resumen

  • 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 field observations and experimental 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 allows its reaction with nitric acid, generating a relatively photostable product that may be relevant to the partitioning of sulfur in the stratosphere in the presence of abundant sulfur trioxide. The results and conclusions derived from this Thesis shed light on the importance of light-induced reactivity in the atmospheric cycling of mercury and sulfur compounds. They demonstrate that future modeling assessments must consider the new photochemistry presented for a complete understanding of the evolution of these compounds in their respective atmospheric contexts.