Atmospheric Pollution: Types and Sources

• These notes cover atmospheric pollution, photochemical smog, thermal inversion, carbon dioxide and particulates, indoor air pollutants, global change, and noise pollution.

Introduction to Air Pollutants

• The EPA regulates pollutants like NOx, SOx, CO, lead, and PM.
• SOx is naturally produced by volcanoes and forest fires.
  • SOx is anthropogenically produced by the combustion of coal.
  • SOx can cause acid rain.
• NOx is naturally produced by volcanoes and lightning.
  • NOx is anthropogenically produced by cars (if incompletely combusted).
  • NOx can cause respiratory irritation, smog, and acid rain.
• CO is naturally produced by volcanoes and forest fires.
  • CO is anthropogenically produced by incomplete combustion.
  • CO can cause hypoxia (oxygen starvation).
• PM is naturally produced by dust storms, wildfires, and volcanoes.
  • PM is anthropogenically produced by soot, ash, combustion, fossil fuel use, smoking, and construction.
  • PM causes respiratory irritation, heart/lung disease, and haze.
• Tropospheric Ozone exists naturally in the stratosphere
  • Tropospheric Ozone exists anthropogenically in the troposphere.
  • Tropospheric Ozone is a respiratory irritant.
• Lead exists naturally in the lithosphere.
  • Lead is anthropogenically produced by paint, gas, and pipes.
  • Lead causes neurological issues in babies

Air Pollutants

• Carbon dioxide is not typically considered an air pollutant because it does not cause direct human harm or respiratory illness, even though it causes the earth to warm.
• Primary air pollutants enter the atmosphere as is (no chemical reaction).
  • An example of a primary air pollutant is CO2.
• Secondary air pollutants form from a chemical reaction between a primary pollutant and UV/O2.
  • Smog is a secondary air pollutant.

Photochemical Smog

• Photochemical smog is created with NOx + VOCs + O2 + UV, forming O3 + PANs in the atmosphere.
• Photochemical smog forms more easily during high sunlight exposure and heavy traffic hours (morning/afternoon).
• Tropospheric ozone forms as part of photochemical smog (see above).
• Tropospheric ozone levels usually decline overnight due to a lack of UV radiation to catalyze chemical reactions.
• PANs harm plant tissues.
• Photochemical smog is a respiratory irritant.

Thermal Inversion

• Normal temperature-altitude relationships in the troposphere mean that as altitude increases, temperature decreases.
• This relationship exists because warm air rises and disperses pollutants.
• Thermal inversion is a natural event where cold air traps warm air.
• Thermal inversion traps ground-level air pollutants over a city.
• The urban heat island effect makes cities hotter than nearby rural areas because cold, dense air does not rise, preventing convection currents.

Atmospheric CO2 and Particulates

• Natural sources of carbon dioxide include cellular respiration, decomposition, and volcanoes.
• Decomposition can produce both CO2 and CH4, depending if it occurred aerobically or anaerobically.
• Smaller PM sizes correlate with an increased human health hazard because they get lodged deep into the lungs.
• Natural sources of particulate matter (PM) include forest fires, soil/dust carried by the wind, and pollen/ash.

Indoor Air Pollutants

• The major source of indoor air pollution in developing countries is indoor biomass combustion for heating/cooking, which releases CO, PM, VOCs, and NOx.
• The human health impacts of indoor biomass combustion include respiratory irritation, COPD, and headaches.
• Solutions to reduce the impacts of indoor air pollutants include ventilation (chimneys, open windows, fans, vents) and cooking outdoors.
• Asbestos comes from old insulation (attic, ceiling tiles) and causes lung cancer.
  • Mitigation include professional removal.
• Faulty furnace ventilation produces CO and causes hypoxia/suffocation.
  • Mitigation includes repairing ventilation.
• Cleaners, wood, and adhesives release VOCs and cause lung irritation.
  • Mitigation include organic cleaners and ventilation.
• Radioactive decay of uranium in bedrock (enters through cracks) produces Radon, which causes lung cancer (and is a leading cause).
  • Mitigation include sealing cracks and ventilation.
• Mold, dust, and smoke produce PM, causing lung irritation.
  • Mitigation include disinfectant and ventilation.
• Old paint chips and lead pipes contain lead, causing neurotoxic learning disabilities in kids.
  • Mitigation include professional removal/replacement of pipes.

Global Change

• Sunscreen is most effective against UV-A.
• Stratospheric O3 protects against UV-B and UV-C by absorbing it and breaking into O2 and a free oxygen radical, which reforms into O3 later.
• UV-B and UV-C radiation exposure can cause DNA mutation, cancer, and cataracts.
• The Montreal Protocol banned CFCs and led the U.S. to transition towards using HFCs.
• Transitioning from CFCs to HFCs leads to less O3 depletion and less contribution to climate change.
• Greenhouse gasses warm Earth's atmosphere, infrared radiation (heat) released/emitted from Earth's surface is absorbed by GHGs and then re-radiated/emitted back towards Earth's surface, thus warming the atmosphere
• Water is considered a greenhouse gas, but not a major contributor to climate change because it traps radiation but has a short residence time (lifespan) in the atmosphere as it constantly condenses and is cycled as liquid/solid.
• Greenhouse Warming Potential (GWP) measures a GHG's ability to contribute to climate change relative to CO2.
  • GWP depends on residence time and the ability to absorb radiation.
• Methane is more powerful compared to CO2.

Increase in Greenhouse Gases

• Sea levels rise as global atmospheric temperature increases due to thermal expansion (H2O molecules spread apart, adding to water volume and raising sea level) and glacial ice melting (runoff adds to the water volume and raises sea level).
• An ecologic consequence of sea-level rise for coastal ecosystems is flooding, increased salinity in fresh H2O areas, and decreased light penetration.
• An economic consequence of sea-level rise for coastal communities is property damage, increased insurance costs, and increased costs of building sea walls.
• Global warming may increase the impacts of infectious disease by increasing the range where mosquitoes can breed, reproduce, and spread disease.
• Earth has experienced a fairly consistent pattern of global climate change over the past 800,000 years with periods of direct and indirect solar radiation causing cool and warm periods.
• Scientists measure historic temperature and CO2 concentrations of Earth's atmosphere using ice core data; CO2 bubble concentration can be measured within the ice.
• Melting polar ice generates a positive feedback loop that causes more warming because more heat is absorbed causing sea ice to melt.
  • Darker surfaces are exposed and Albedo increases.
• Ecological consequences of rising sea level in coastal regions include increased erosion, decreased photosynthesis as biodiversity is lost, increased salinity in fresh H2O areas, and increased habitat loss.

Reduction of Air Pollutants

• Individual-scale methods for reducing air pollutants include carpooling and walking.
• Government-scale methods for reducing air pollutants include taxes, regulations, and emission caps.
• Vapor-recovery fuel nozzles reduce VOCs.
• Catalytic converters convert CO and NOx into CO2, N2, O2, and H2O.
• Wet and dry scrubbers reduce air pollutants from factory/power plant emissions.
  • Wet scrubbers: Liquid chemicals are misted into a VAT that traps PM, SOx, NOx, and VOCs and combines them with pollutants to form sludge that is later disposed of.
  • Dry scrubbers: Solid chemical agents bind to pollutants and trap them in a filter.
• Additional methods for reducing PM from power plant or industrial emissions include baghouse filters or electrostatic precipitators.
  • Baghouse filter: traps pollutants in a filter bag.
  • Electrostatic precipitator: uses electric current to trap pollutants.

Acid Deposition

• The two primary pollutants that lead to acid deposition are SOx (from coal) and NOx (from cars).
• SOx and NOx react with H2O + O2 in the atmosphere to form sulfuric and nitric acid, which contribute to acid deposition.
• Acids dissociate (break down) into sulfate + nitrate, releasing H+ ions, which decreases pH (increases acidity).
• An environmental consequence of acid deposition is that plants and aquatic life die off.

Noise Pollution

• Sources of noise pollution include traffic, construction, ships, and seismic survey ships.
• Specific effects of noise pollution on organisms include migratory disruption, predator-prey disruption, and communication disruption.