L9_Ozone_AirPollution

Ozone Overview

• Ozone (O3) is a significant component of smog and is usually found at ground level.

• Bad Ozone: Affects air quality and is not emitted directly into the air but formed through reactions.

Formation of Ground-Level Ozone

• Ozone is formed when:

  • NOx (Nitrogen Oxides)

  • VOCs (Volatile Organic Compounds)

  • Heat and Sunlight

• Chemical Reaction: NOx + VOC + Heat & Sunlight → Ozone

• Major sources of NOx and VOCs come from:

  • Industrial facilities

  • Vehicle emissions

  • Gasoline vapors

Great Smog of London

• Occurred in December 1952, significant historical event showcasing air pollution.

Temperature Influence on Ozone

• Higher ozone levels observed on warmer days.

• Recorded data from Los Angeles reflecting ozone levels in relation to daily maximum temperatures.

Air Quality Index (AQI) for Ozone

• Different levels of ozone impact health:

  • Good: 0 - 54 ppb

  • Moderate: 55 - 70 ppb

  • Unhealthy for Sensitive Groups: 71 - 85 ppb

  • Unhealthy: 86 - 105 ppb

  • Very Unhealthy: 106+ ppb

• The AQI is based on an 8-hour average concentration of ozone (ppb = parts per billion).

Emissions Impacting Ozone Formation

Breakdown of NOx Sources

• Major source contributions:

  • Transportation: 54%

  • Electric utilities: 22%

  • Industrial combustion: 14%

  • Miscellaneous: 2%

Breakdown of VOC Sources

• Emissions from:

  • Solvent use: 29%

  • On-road vehicles: 28%

  • Non-road equipment: 19%

  • Industrial processes: 11%

  • Other: 13%

Household Contributions to VOCs

• Everyday products significantly contributing to VOC emissions include:

  • Shampoo, hairspray, deodorants, air fresheners, cleaning sprays, laundry detergents, paints, etc.

• Surprising impact of these products; household use contributes to 38% of VOC emissions.

Natural Sources of VOCs

• Trees produce VOCs:

  • Various species such as Maple, Oak, and Pine generate isoprene among other compounds impacting air quality.

Ozone Effects on Plants

• Ozone exposure can significantly reduce plant growth, affecting:

  • Photosynthesis due to chlorophyll damage.

  • Net growth of urban vegetation compared to rural vegetation, influenced by ozone concentration.

Pollution Impact on National Parks

• National parks most affected by air pollution:

  • Sequoia National Park and Kings Canyon National Park received the lowest scores on air quality.

Particulate Matter (PM) Overview

• PM2.5: Most concerning pollutant from wildfires, significantly impacts human health.

• Sources of particulate matter include:

  • Wildfires, wind erosion, agriculture, and vehicle emissions.

Tree Mitigation of Air Pollution

• Urban trees can remove a fraction of various pollutants like CO, NO2, O3, and PM10 from the atmosphere, but the percentage is relatively low (below 1% for each).

COVID-19 Impact on Air Quality

• Notable decreases in pollutant levels observed during the COVID-19 pandemic, comparing March 2020 to averages from 2017-2019 for ozone, carbon monoxide, particulate matter, and nitrogen dioxide.

Summary of Study Points

• Understand how ozone is formed, factors affecting its distribution, its impact on plant life, and the significance of PM10 and PM2.5 pollutants, particularly in California.