These lecture notes by Dr Marcellin Adon for a Master 2 course provide a comprehensive physico‑chemical overview of atmospheric pollution. The material begins with a broad definition of atmospheric pollution and a description of atmospheric structure, dynamics, and the Earth’s energy budget. It reviews major greenhouse gases, their radiative properties, and trends. Detailed sections compare stratospheric and tropospheric ozone chemistry, enumerate trace gases and volatile organic compounds, and discuss aerosols and hydrometeors. Temporal and spatial scales of pollutant lifetimes, drivers of planetary change, and the determinants of atmospheric composition are presented, followed by biogeochemical cycles of carbon and nitrogen. The core of the lecture focuses on ozone: altitude‑dependent stratospheric ozone production‑loss balance, the heterogeneous chemistry on polar stratospheric clouds that creates the Antarctic and Arctic ozone holes, and observational evidence from satellite, Dobson‑unit, and balloon measurements. Tropospheric ozone photochemistry is explained through the NO₂ photolysis cycle, the concept of a photostationary state, and the shift toward net ozone production in polluted air. Interactions between NOx and VOCs are examined, defining NOx‑limited and VOC‑limited regimes and their impact on urban‑rural ozone patterns. Oxidation pathways of CO and CH₄ are detailed, showing how they feed radical pools and enhance ozone formation. VOC oxidation mechanisms, formation of peroxy radicals, PAN, aldehydes, and secondary ozone are described. Catalytic ozone‑destruction cycles (HOx, NOx, ClOx, BrOx) are presented with kinetic equations, rate constants, and lifetimes. Finally, the non‑linear sensitivity of photochemical smog to emission reductions is discussed, emphasizing the need for targeted mitigation strategies. Throughout, quantitative tables, reaction schemes, and diagrams support the instructional narrative.
Topics
Atmospheric Pollution: Definition, Drivers, and Impacts
A comprehensive definition of atmospheric pollution encompassing greenhouse warming, ozone depletion, photochemical smog, acid rain, trans‑boundary pollutants, and accidental releases, together with the main anthropogenic drivers (fossil‑fuel combustion, biomass burning, industry, agriculture, waste) and the resulting environmental and health impacts.
Atmospheric Structure, Dynamics, and Energy Balance
Description of the vertical layering of the atmosphere, temperature profile, major circulation cells, mixing scales, and the Earth’s radiative budget (solar constant, albedo, greenhouse effect) that governs atmospheric motion and temperature.
Greenhouse Gases: Properties, Radiative Forcing, and Trends
Presentation of the major greenhouse gases (H₂O, CO₂, CH₄, N₂O, O₃, CFCs), their absorption spectra, radiative‑forcing formulas, atmospheric concentrations, and historical trends.
Trace Gases, VOCs, and Aerosols: Sources, Sinks, and Chemical Roles
Enumeration of key trace species (CO, NOx, NH₃, SO₂, halogenated compounds) and classification of VOCs (alkanes, alkenes, aromatics, etc.) together with primary and secondary aerosol formation, sources, sinks, and their influence on atmospheric chemistry and radiation.
Temporal and Spatial Scales of Atmospheric Species
Matrix linking pollutant lifetimes—from seconds to centuries—with the spatial extent of their influence, illustrating how lifetime controls mixing homogeneity and regional versus global impact.
Biogeochemical Cycles of Carbon and Nitrogen
Illustration of the carbon and nitrogen reservoirs, natural and anthropogenic fluxes, pre‑industrial versus modern budgets, and their contribution to atmospheric CO₂ and N₂O levels.
Fundamentals of Atmospheric Photochemistry
Coverage of solar spectral distribution, actinic flux at different altitudes, photodissociation thresholds for O₂, O₃ and other species, and the generation of radicals that drive atmospheric chemistry.
Stratospheric Ozone Chemistry and the Ozone Hole
Altitude‑dependent ozone production‑loss balance, Chapman mechanism, catalytic destruction cycles (HOx, NOx, ClOx/BrOx), heterogeneous chemistry on polar stratospheric clouds that creates Antarctic/Arctic ozone holes, and observational evidence from satellites, Dobson‑unit records, and balloon sondes.