unit 7 apes

• Air pollutants


  • Coal combustion (electricity)
  • FF/biomass combustion
  • SO2
  • Nitrogen Oxides (NO & NO2)
  • Carbon Monoxide
  • Particulate Matter
  • Ozone (tropospheric)
  • Lead
• Coal combustion (electricity) causes respiratory irritation, smog, and acid precipitation
• FF/biomass combustion causes respiratory irritation and smog
• SO2


  Sulfur dioxide
• NOx


  Nitrogen oxides (NO & NO2)
• CO


  Carbon monoxide
• PM


  Particulate matter
• O3


  Ozone (tropospheric)
• All FF combustion (gas especially) leads to ozone, photochemical smog, and acid precipitation
• Incomplete combustion leads to ozone and is lethal to humans
• Photochemical oxidation of NO2 leads to particulate matter, respiratory irritation, smog, and plant damage
• Metal plants and waste incineration lead to lead emissions, which is a neurotoxicant
• CO2 is not one of the 6 criteria air pollutants in the Clean Air Act, although it is a greenhouse gas
• CO2 does not directly lower air quality from a human health standpoint

  
• Coal combustion releases more air pollutants than other fossil fuels, including CO, CO2, SO2, NOx, toxic metals, and particulate matter
• SO2 from coal combustion is a respiratory irritant, forms sulfate aerosols that block sunlight and reduce photosynthesis, forms sulfurous smog, and combines with water and oxygen to form sulfuric acid leading to acid precipitation
• NOx refers to nitrogen oxides (NO and NO2) and is released by the combustion of anything, especially fossil fuels and biomass
• NO forms when N2 combines with O2, and NO can become NO2 by reacting with O3 or O2
• NOx is a respiratory irritant, leads to tropospheric ozone formation and photochemical smog, and combines with water and oxygen to form nitric acid leading to acid precipitation
• Before the Clean Air Act, lead was a common gasoline additive, but vehicles made after 1974 are required to have catalytic converters to reduce NOx, CO and hydrocarbon emissions as lead damages catalytic converters
• Lead is also a known neurotoxicant that damages the nervous system
• Primary air pollutants are emitted directly from sources, while secondary air pollutants are formed through chemical reactions in the presence of sunlight, water, and oxygen

  
• NO2


  Broken by sunlight into NO + O, which then binds with O2 to form O3
• VOCs


  Volatile organic compounds (hydrocarbons) that bind with NO and form photochemical oxidants
• O3


  Forms when NO2 is broken by sunlight and the free O binds to O2
• Sunlight


  Drives O3 formation by breaking down NO2 into NO + O
• Warmth


  Speeds up O3 formation, evaporation of VOCs, and thus smog formation
• Photochemical smog forms when VOCs bond with NO to form photochemical oxidants, which then combine with O3
• Factors that increase photochemical smog formation include higher VOC emissions, increased vehicle traffic (more NO2), more sunlight, and warmer temperatures
• Urban areas have more smog due to more traffic, hotter temperatures, more VOCs from gas stations and factories, and more electricity demand leading to more NOx emissions
• Photochemical smog reduces sunlight and limits photosynthesis, is a respiratory irritant that worsens asthma and bronchitis, and leads to economic impacts from increased healthcare costs and lost productivity
• Reducing photochemical smog involves decreasing the number of vehicles on the road, increasing renewable energy sources that don't emit NOx, and using natural gas power plants that release less NOx than coal
• Urban areas tend to have higher surface and air temperatures than surrounding areas due to lower albedo and less evapotranspiration
• During a thermal inversion, a cooler air mass becomes trapped near the earth's surface, preventing air pollutants from being carried away by convection
• The effects of a thermal inversion include respiratory irritation, decreased photosynthesis, and decreased tourism revenue
• Natural sources of air pollutants include lightning strikes, forest fires, volcanoes, and plants
• Natural sources of CO2 include respiration, aerobic decomposition, and anaerobic decomposition
• Natural sources of particulate matter include sea salt, pollen, ash, and dust
• PM10


  Particles or droplets too small to be filtered out by the nose and trachea, can irritate the respiratory tract
• PM2.5


  Smaller particles from combustion that can travel deeper into the lungs, associated with chronic bronchitis and lung cancer