Detailed Notes on Air Quality and Stratospheric Ozone

Section 1: Housekeeping

  • Course information: ENV100 The Environment Atmospheric Science III - Damian Maddalena - University of Toronto Mississauga Fall-Winter 2024-2025.
  • Important announcements regarding syllabus adjustments and exam details.

Section 2: Indoor and Outdoor Air Quality

Topics Covered:

  • Air quality trends
  • Factors affecting air quality
  • The Air Quality Health Index (AQHI)
  • Sources and types of indoor air pollution
  • Health effects of common indoor pollutants

Air Quality Trends:

  • Significant improvements in pollutant levels since the 1970s:
    • Sulphur oxides (SOx)
    • Carbon monoxide (CO)
    • Nitrogen oxides (NOx)
    • Volatile organic compounds (VOCs)
    • Lead
  • Example data on emissions from the US and Canada from 1990 to 2021.

History of Atmospheric Lead:

  • Lead was used in gasoline, causing severe health impacts before it was phased out globally from 1990 to 2002.
  • Lead exposure, particularly in children, correlated with significant drops in IQ.

Current Air Quality Challenges:

  • Ground-level ozone (O3) and other pollutants have shown less improvement.
  • Total emissions data from 1990-2021 highlight declines and ongoing issues with pollutants like PM and GHGs.
  • The urban heat island effect exacerbates pollution issues in cities.

Health Impacts:

  • Air quality leads to approximately 4.2 million premature deaths per year globally.
  • Particularly harmful pollutants: PM and Ground-level ozone (O3).

Air Quality Technology and Policy Improvements:

  • Introduction of scrubbers, clean technologies, and pollutant trading programs help in air quality management.
  • Current status of emissions significantly lower than 2005 levels (e.g., for SOx, NOx, VOCs).

Air Quality Health Index (AQHI):

  • Measures air quality risk from 1 to 10 based on common pollutants.
  • Provides customized health messages to various populations based on AQHI levels.

Section 3: Stratospheric Ozone

Topics Covered:

  • Importance of the ozone layer
  • Natural production and destruction of ozone
  • Measurement of ozone
  • Ozone depletion and the role of CFCs

Importance of Stratospheric Ozone:

  • The ozone layer, located 25-35 km above Earth's surface, absorbs harmful UV radiation and protects life.
  • Ozone concentrations are measured in Dobson Units (DU), which quantify the density of ozone in the atmosphere.

Ozone Measurement and Chemistry:

  • Dobson Unit: 1 DU = a layer of pure ozone 0.01 millimeters thick at standard temperature and pressure.
  • Chapman Cycle: Describes the processes of ozone formation and destruction through UV radiation.

Ozone Depletion:

  • First noticed in the 1970s, particularly severe in polar regions leading to the phenomenon known as the "ozone hole".
  • Chlorofluorocarbons (CFCs) are significant contributors to ozone depletion, releasing chlorine which can degrade many ozone molecules.
  • Measures taken include the Montreal Protocol to phase out ozone-depleting substances globally.

Future Outlook:

  • Signs of ozone layer recovery by 2040 if current policies are sustained, with the Montreal Protocol being cited as a model for international environmental agreements.

Takeaway Messages:

  • Improvement in some air quality measures but challenges remain, especially with indoor pollutants.
  • Understanding urban effects and transboundary pollution is crucial for effective air quality management.
  • The connection between stratospheric ozone depletion and public health demonstrates the urgency of international cooperation in environmental policies.