Unit 7 - Atmospheric Pollution Flashcards
***Write about air pollutants (specific molecules or particles) not just air “pollution” as an idea
Clean Air Act
Clean Air Act (1970) identified 6 criteria air pollutants that EPA is required to set acceptable limits for, monitor, and enforce
- SO2, NOx, CO, PM, O3, Pb
SO2 (sulfur dioxide)
- formed from Coal combustion (electricity)
- Respiratory irritant, smog, acid precipitation
NOx (nitrogen oxides)
- formed from All FF combustion (gas esp.)
- O3 | photochemical smog | acid precip.
CO
- formed from incomplete combustion
- O3, lethal to humans
PM (particulate matter)
- FF / biomass combustion
- respiratory irritant | smog
O3 (tropospheric ozone)
- formed from the Photochemical oxidation of NO2
- Respiratory irritant|smog|plant damage
Pb (lead)
- formed from metal plants, waste incineration
- Neurotoxicant
Air Pollutants vs Greenhouse Gases
- CO2 is NOT one of the 6 criteria pollutants in the Clean Air Act
- CO2 does not directly lower air quality from human standpoint (not toxic to breath, not damaging to ENT, does not lead to smog)
- CO2 is a GREENHOUSE GAS, it leads to earth warming => env. and human health consequences
Coal Combustion
- releases more air pollutants than other FF’s
- 35% of global electricity
Impacts of SO2
- respiratory irritant (inflammation of lungs), asthma, bronchitis
- sulfur aerosols (suspended sulfate particles) block incoming sin, reducing visibility and photosynthesis
- forms sulfurous smog
- combines w water and O2 in atmosphere to form sulfuric acid => acid rain
EPA and Lead
- Before CAA, lead was a common gasoline additive; EPA began phaseout of lead from gasoline in 1974
- vehicles made post 1974 are required to have catalytic converters to reduce NOx and HC emissions (lead damages converters)
- damages nervous system
primary air pollutants
- emitted directly from sources such as vehicles, power plants, factories, or natural sources (volcanoes, forest fires)
- NOx, CO, VOCs, SO2, PM, hydrocarbons
Secondary Air Pollutants
- primary pollutants that have transformed in presence of sunlight, water, O2
- occur more during the day (since sunlight often drives formation)
- tropospheric O3
- sulfuric acid (H2SO4) & sulfate (SO4-2)
- nitric acid and nitrate ion
Photochemical Smog Precursors
~ NO2 - broken by sunlight into NO + O (free O + O2 => O3)
~ VOCs - Volatile Organic Compounds (Hydrocarbons) that bind with NO & form photochemical oxidants
- carbon based compounds that volatize (evaporate) easily (this make them smelly)
- sources: gasoline, formaldehyde, coniferous trees, oil based paints, cleaning fluids
~ O3 - forms when NO2 is broken by sunlight and free O binds to O2
Photochemical Smog Conditions
- Sunlight: drives O3 formation by breaking down NO2 => NO + O; then free O binds with O2
- Warmer: Hotter atmo. temp. speeds O3 formation, evaporation of VOCs and thus smog formation
factors that increase smog formation
- more sunlight (summer, afternoon) = more O3
- higher temp speeds evap. of VOC’s & rxn that leads to O3
- high VOCs emissions (gas stations, laundromats, plastic factories)
- higher vehicle traffic, higher NO2 emissions, and therefore O3 formation
impact of smog
environment - reduces sunlight; limiting photosynthesis
- O3 damages plant stomata and irritates animal resp. tracts
humans - resp. irritant; worsens asthma, bronchitis, COPD; irritates eyes
economic - high healthcare costs to treat asthma, bronchitis, COPD
- lost productivity due to sick workers missing work or dying
- ag. yields due to low sunlight reaching crops and damage to plant stomata
reduction of smog
Vehicles - decreasing the # of vehicles on the road lowers NO2 emissions
- decrease vehicles = low gas = low VOCs
(carpooling, public transport, biking, walking, etc.)
Energy - increased electricity production from renewable sources that don’t emit NOx (solar, wind, hydro)
- natural gas power plants release far less NOx than coal
urban heat island effect
urban areas tend to have higher surface and air temperature than surrounding suburban and rural areas due to:
- lower albedo; concrete and asphalt absorb more of sun’s energy than areas with more vegetation
- less evapotranspiration: water evaporating from surfaces and transpiration from plants carries heat from surface into atmosphere and cools off rural and suburban areas w vegetation
normal convection
- normally, the atmosphere is warmest at earths surface and cools as altitude rises
- because warm air rises, air convection carries air pollutants away from earth’s surface and distributes them higher into the atmosphere
thermal inversion
- because cold air at the surface is trapped beneath the warmer mass above, convection doesn’t carry pollutants up and away
- during a thermal inversion, a cooler air mass becomes trapped near earth’s surface (inverting normal gradient)
- due to a warm front moving in over it
- due to hot urban surfaces cooling overnight while IR radiation absorbed during the day is still being released
effects of thermal inversion
- air pollutants (smog, PM, ozone, SO2, NOx) trapped closer to earth
- respiratory irritant
- decreased tourism revenue
- decreased photosynthetic rate
Natural Sources of Air Pollutants
- Lightning Strikes (Convert N2 in atm. to NOx)
- forest fires (CO, OM, NOx)
- plants (esp. conifers) - emit VOC’s
- volcanoes - SO2, PM, CO, NOx
natural sources of CO2 & PM
- respiration: all living things release CO2
- aerobic decomp: decomp of organic matter by bacteria and decomposers in the presence of oxygen => releases CO2
- anaerobic decomposition: decomp of organic matter by bacteria and decomposers in low or O2 free conditions => releases CH4
- natural PM sources: sea salt, pollen, ash from forest fires, volcanic dust => leads to haze
Particulate Matter
solid or liquid particles suspended in air (also referred to as “particulates”)
PM10
particles or droplets like dust, pollen, ash, pr mold
- too small to be filtered out by nose hairs and trachea cilia; can irritate respiratory tract & cause inflammation
PM2.5
- particles from combustion (esp. vehicles) smaller dust particles
- more likely to travel deep into the lungs due to smaller size
- associated with chronic bronchitis and increased risk of lung cancer
Indoor Air Pollutants: developing nations
- developing nations use more subsistence fuels such as wood, manure, charcoal (biomass)
- these biomass fuels release CO, PM, NOx, VOCs
- often combusted indoors with poor ventilation, leading to high concentrations
- est. 3 billion people globally cook with subsistence fuels, resulting in est. 3.5 - 4.3 million deaths annually
Indoor Air Pollutants: developed nations
- developed nations use more commercial fuels (coal, oil, natural gas) supplied by utilities
- typically burned in closed, well ventilated furnaces, stoves, etc
- come from chemicals in products: adhesives in furniture, cleaning supplies, insulation, lead paint
INDOOR AIR: PM and Asbestos
- PM is a common indoor air pollutant
ex: smoke (from indoor biomass combustion or cigarettes), dust, and asbestos - asbestos is a long, silicate particle previously used in insulation ( since been linked to lung cancer and asbestosis)
- phased out of use, but still remains in older building
- not dangerous until insulation is disturbed and asbestos particles enter air and then resp. tract
- should be removed by trained professionals
INDOOR AIR: CO
- CO is produced by incomplete combustion of basically any fuel
- CO is an asphyxiant = causes suffocation due to CO binding to hemoglobin
how is CO released in developing nations
CO emitted from indoor biomass combustion for heating or cooking
how is CO released in developed nations
CO released into home by malfunctioning natural gas furnace ventilation
VOCs
- chemicals used in variety of home products that easily vaporize, enter air, and irritate eyes, lungs, bronchioles
- adhesives/sealants
- formaldehyde
- cleaners
- plastics and fabrics
Radon Gas
- Radon 222 is a radioactive gas released by decay of uranium naturally found in rocks underground (granite especially)
- usually enters homes through cracks in foundation
- can also seep into groundwater sources and enter body through drinkning water
- 2nd leading caused of lung cancer after smoking
- EPA recommends testing homes with airborne Radon monitor
- seal cracks in foundation to prevent entering
reducing emission = reducing air pollutants
- drive less, walk/bike/bus more
- conserve electricity (smart appliances)
- eat more plants, less meat
- renewable, non-pollution emitting energy (solar, wind, hydro)
clean air act
- allows EPA to set acceptable levels for criteria air pollutants
- monitor emissions levels from power plants and other facilities
- tax/sue/fine corporations that release emissions above levels
pollution credits
- similar to ITQs for fish
- companies that reduce emissions well below EPA-set levels earn pollution credits
- they can sell these to companies that release more than acceptable levels
CAFE Vehicle Standards
- (Corporate Avg Fuel Economy) standards require the entire US “fleet” of vehicles to meet certain average fuel
- requires vehicle manufacturers to work to make more efficient vehicles
- more efficient vehicles burn less gasoline and release less NOx, PM, CO, CO2
vapor recovery nozzle
- capture hydrocarbon VOCs released from gasoline fumes during refueling
- separate tube inside nozzle captures vapors and returns the, to underground storage tank beneath the gas station
- reduces VOCs, which contribute to smog and irritate resp. tracts
- also reduces benzene (carcinogen) released from gasoline vapors
baghouse filter (PM)
- large fabric bag filters that trap PM as air from combustion/industrial process passes through
- shaker device knocks trapped particles loose into collection hopper below
- PM collected and taken to landfill
Catalytic Converter
- required on all vehicles since 1975
- contains metals that bind to NOx and CO
- CC converts NOx, CO, and other hydrocarbons into CO2, N2, O2, & H2O
crushed limestone (SO2)
- used to reduce SO2 from coal power plants
- crushed coal mixed with limestone before being burned in boiler
- limestone combines with SO2 to produce calcium sulfate, reducing the SO2 being emitted
- limestone can be used to make gypsum wallboard or sheetrock for home foundations
fluidized bed combustion
- fluidized jets of air pumped into combustion bed
- jets of air bring more O2 into rxn, making combustion more efficient and bringing SO2 into more contact with limestone
- also allows coal to be combusted at lower temp, which emits less NOx
Wet and Dry Scrubbers
are air pollution control devices that remove particulates and/or gases from industrial
exhaust streams.
urban noise pollution
any noise at great enough volume to cause physiological stress (difficulty communicating, headaches, confusion) or hearing loss
- constructions
- transportation
- industrial activities
- domestic activity
