Unit 7 PPT: Air Pollutants

7.1 Introduction to Air Pollution (Pollutants) 7.2 Photochemical Smog 7.3 Thermal Inversion 7.4 Atmospheric CO2 & PM 7.5 Indoor Air Pollutants 7.6 Reduction of Air Pollutant 7.7 Acid Rain 7.8 Noise Pollution

Regarding FRQs about air pollution, what must be included to receive points?

Specific molecules and particles about air pollutants, and not pollution as a general idea

Clean Air Act (1970)

identified 6 criteria air pollutants that the EPA is required to set acceptable limits for, monitor, and enforce
-monitor emissions levels from power plants and other facilities
-tax/sue/fine corporations that release emissions above levels

sulfur dioxide

SO2

where is sulfur dioxide released from?

coal combustion (electricity)

consequences of sulfur dioxide

respiratory irritant, smog, acid precipitation

carbon monoxide

CO

where is nitrogen oxides released from?

All FF combustion-gas especially (FFs and biomass)

consequences of nitrogen oxides

leads to O3, photochemical smog, acid precipitation

nitrogen oxides

(NOx)- NO & NO2

where is carbon monoxide released from?

incomplete combustion

consequences of carbon monoxide

leads to O3, lethal to humans

particulate matter

PM
solid or liquid particles suspended in air (particulates)

where is PM released from?

FF/biomass combustion

consequences of particulate matter

respiratory irritant, smog

ozone (tropospheric)

O3

where is tropospheric ozone released from?

photochemical oxidation of NO2

consequences of tropospheric ozone

respiratory irritant, smog, plant damage

lead

Pb

where is lead released from?

metal plants, waste icineration

consequences of lead

neurotoxicant

Why is CO2 NOT one of the 6 criteria pollutants described in the Clean Air Act of 1970?

-CO2 does not directly lower air quality from a human health standpoint
-not toxic to organisms to breath
-not damaging to lungs/eyes
-does not lead to smog, decreased visibility

why is CO2 bad?

it is a greenhouse gas that leads to earth warming and environmental/human health consequences

Why shouldn't you include CO2 as a air pollutant in FRQs?

In APES, CO2 is not typically included on FRQ scoring guides (do not take the risk; stick to SO2, NOx, O3, PM)

coal combustion

Releases more air pollutants than other FFs; ~35

what air pollutants does coal combustion lead to?

releases CO, CO2, SO2, NOx, toxic metals (mercury, arsenic, lead), and PM (often carried in toxic metals)

Impacts of SO2 (detailed)

-respiratory irritant (inflammation of bronchioles, lungs), worsens asthma and bronchitis
-sulfur aerosols (suspended sulfate particles) block incoming sun, reducing visibility and photosynthesis
-forms sulfurous (grey) smog
-combines with water and O2 in atmosphere to form sulfuric acid to acid precipitation

What does NOx refer to?

nitrogen oxides (both NO and NO2)

How does NO form?

N2 in atmosphere combines with O2 (especially during combustion)

what can NO become?

NO2 by reacting with O3 or O2

what does sunlight do to NO2?

convert NO2 back into NO + O

environmental and human health impacts of NOx

-respiratory irritant
-leads to tropospheric ozone (O3) formation, which leads to photochemical smog
-combines with water and O2 in the atmosphere to form nitric acid to acid precipitation

before CAA, what was lead used for?

gasoline additive

when did EPA begin phaseout of lead from gasoline?

1974
-vehicles after required to have catalytic converters to reduce NOx, CO and hydrocarbon emissions (lead damages catalytic converters)

Primary Air Pollutants

-emitted directly from sources such as vehicles, power plants, factories, or natural sources (volcanoes, forest fires)
-NOx, CO, CO2, 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 (ozone)
-sulfuric acid (H2SO4) and sulfate
-Nitric acid (HNO) and nitrate (NO3)

what happens to the free oxygen molecule released from NO2 after sunlight breaks it up?

O binds to O2 to make O3
-respiratory irritant in troposphere (at earth's surface)
-damaging to plant stomata, limiting growth

Volatile organic compounds

VOCs- (hydrocarbons) that bind with NO and form photochemical oxidants
-carbon baed compounds that volatize (evaporate) easily makes them smelly
-sources: gasoline, formaldehyde, cleaning fluids, oil-based paints, even coniferous trees (pine smell)

What conditions drive atmospheric pollution?

sunlight and warmth

how does warmth affect air pollution?

hotter atmospheric temperature speeds O3 formation, evaporation of VOCs and thus smog formation

What happens to O2 at night?

reacts with NO to form NO2 and O2 again; O2 levels drop overnight

When does O3 formation peak?

afternoon when sunlight is most direct and NO2 emissions from morning traffic have peaked

How does photochemical smog form?

without NO to react with, O2 builds up overnight and combines with photochemical oxidants (NO + VOCS) to form photochemical smog

What leads to more O3?

more sunlight (summer/afternoon), warmer temperature speeds evaporation of VOCs and rxn that leads to O3

Why do urban areas for more smog?

-more traffic leads to more NO2
-hotter temperature due to low albedo of blacktop
-more VOCs due to gas stations and factories
-more electricity demand, more NOx emissions from nearby power plants

Impacts of Smog

Environmental: reduces sunlight, limiting photosynthesis, O3 damages plant stomata and irritates animal respiratory tracts

Humans:
Respiratory irritant, worsens asthma, bronchitis, COPD; irritates eyes

Economic:
Increased health care costs to treat asthma, bronchitis, COPD, lost productivity due to sick workers missing work or dying, decreased agricultural yields due to less sunlight reaching crops and damage to plant stomata

reduction of smog

vehicles:
decreasing the number of vehicles on the road decreases NO2 emissions; fewer vehicles leads to less gas and fewer VOCs; carpooling, public transport, biking, walking, working from home

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

why do urban areas tend to have higher surface and air temperature than suburban and rural areas?

-lower albedo due to concrete and asphalt (absorb sun's energy more than areas with vegetation and gives off heat)
-less evapotranspiration (water evaporating from surfaces and transpiration from plants that carry heat from surface to atmosphere)

thermal inversion

atmosphere is warmest at earth's surface and cools as attitudes rise, but sometimes cold air at the surface is trapped beneath the warmer mass above so convection doesn't carry pollutants up and away

why does thermal inversion occur?

warm front moving over cooler air, or due to hot urban surfaces cooling overnight with 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 irritation: asthma flare ups leading to hospitalization, worsened COPD, emphysema
- Decreased tourism revenue
- Decreased photosynthetic rate

natural sources of air pollutants

-lightning strikes: converting N2 in atmosphere
-forest fires: CO, PM, NOx from combustion of biomass also release CO2 and H2O vapor (GHG)
-plants (esp. conifers) emit VOCs (ex. Smoky Mountains)
-volcanoes: SO2, PM, CO, NOx

Natural sources of CO2 and PM

-respiration: all living things (plants included) release CO2 through respiration
-Natural PM sources: sea salt, pollen, ash from forest fires and volcanoes dust (windborne soil); leads to haze (scattering of sunlight and reduced visibility)
-aerobic decomposition: decomposition of organic matter by bacteria and decomposers in the presence of oxygen to release CO2
-Anaerobic decomposition: decomposition of organic matter by bacteria and decomposers in low or oxygen-free conditions to release CH4 (methane)

PM10

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PM2.5

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how do developing nations release air pollutants?

-use more subsistence fuels such as wood, manure, charcoal (biomass)
-these biomass fuels release CO, PM, NOx, VOCs (cause deforestation)
-often combusted indoors with poor ventilation, leading to high concentrations

how do developed nations release air pollutants?

-use commerical fuels (coal, oil, natural gas) supplied by utilities
-typically burned in closed, well ventilated furnaces, stoves, etc.
-major indoor pollutants in developed nations come from chemicals in products (adhesives in furniture, cleaning supplies, insulation, lead paint)

what is a common indoor air pollutant?

PM (particulates)
ex: smoke (biomass combustion or cigarettes), dust, and asbestos

asbestos

long, silicate particle previously used in insulation (linked to lung cancer and asbestosis)
-still found in older buildings
-not dangerous in insulation until disturbed and particles enter air and respiratory tract
-should be removed by trained professionals w/ respiratory equipment, ventilation and plastic to seal off area from the rest of the building

What does it mean for CO to be an asphyxiant?

causes suffocation due to CO binding to hemoglobin in blood, displacing O2

How is CO released in developed nations?

released into home by malfunctioning natural gas furnace ventilation (can be detected by CO detectors)

how is CO released in developing nations?

CO emitted from indoor biomass combustion for heating/cooking

VOCs

(Volatile organic compounds)
-chemicals used in variety of home products that easily vaporize, enter air, and irritate eyes, lungs and bronchioles
-ex: adhesives/sealants, formaldehyde, cleaners, plastics and fabrics

formaldehyde

common adhesive in particle board and carper glues (new carpet smell)

radon gas

radioactive gas released by decay of uranium naturally found in rocks underground (granite esp)

how does radon gas enter the house?

cracks in the foundation and then disperses up from basement/foundation through home (can also seep into groundwater sources and enter body through drinking water)

what is the second leading cause of lung cancer after smoking?

radon gas

how to treat radon gas?

testing homes with airborne Radon monitor, sealing cracks in foundation, increasing ventilation

dust and mold

Natural indoor air pollutants that can worsen asthma, bronchitis, COPD, emphysema

how does mold develop?

in areas that are dark and damp and aren't well ventilated (sinks/showers, behind panels in walls and ceilings)
-black mold releases spores in air (esp harmful to respiratory system)

how can mold be removed?

physically cleaning mold out and fixing water leak or ventilation issue that lead to mold forming

where is lead found typically?

in paint of old homes (EPA banned lead paint in 1978)

how does lead get in children?

paint chips off walls/windows and is eaten by small children (due to curiosity and sweet taste) or inhaled as dust
-lead water pipes release lead to drinking water

how does lead affect children?

damages central nervous system due to smaller size and still developing brain

how can lead by removed?

stripping lead paint and replacing with non-lead paint, and lead pipes can be replaced by cities with copper pipes

how to reduce emissions/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)

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 Average 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, and CO2

reducing vehicle air pollutants

vapor recovery nozzle and catalytic converter

vapor recovery nozzle

-capture hydrocarbon VOCs released from gasoline fumes during refueling
-separate tube inside nozzle captures vapors and returns them to underground storage tank beneath the gas station
-reduce VOCs, which contribute to smog and irritate respiratory tracts
-also reduce benzene (carcinogen) released from gasoline vapors

catalytic converts (CC)

-required on all vehicles after 1975
-contain metals (platinum and palladium) that bind to NOx and CO
-CC convert NOx, CO, and other hydrocarbons into CO2, N2, O2, and H2O

Reducing SOx

crushed limestone
-used to reduce SO2 from coal power plants
-crushed coal mixed with limestone (calcium carbonate) before being burned in boiler
-calcium carbonate in limestone combines with SO2 to produce calcium sulfate, reducing the SO2 being emitted
-calcium sulfate can be used to make gypsum wallboard or sheetrock for home foundations
fluidized bed combustion

reducing NOx

fluidized bed combustion
-fluidizing jets of air pumped into combustion "bed"
-jets of air bring more O2 into rxn, making combustion more efficient and brining SO2 into more contact with calcium carbonate in limestone
-allows more coal to be combusted at lower temperature which emits less NOx

Dry Scrubbers (NOx, SOx, VOCs)

-Large column/tube/pipe filled with chemicals that absorb or neutralize oxides (NOx, SOx, VOCs) from exhaust streams (emissions)
-Calcium oxide is a common dry scrubber additive which reacts with SO2 to form calcium sulfite

Wet Scrubbers (NOx, SOx, VOCs + PM)

-May involve chemical agents that absorb or neutralize NOx, SOx, VOCs, but also include mist nozzles that trap PM in water droplets as well
-Mist droplets with pollutants and PM trapped in them fall to bottom of scrubber or get trapped @ top by mist eliminator
-Sludge collection system traps polluted water for disposal

Reducing PM

electrostatic precipitator, baghouse filter

electrostatic precipitator

-Power plant/factory emissions passed through device with a neg. charged electrode, giving particles a neg. Charge
-Neg. charged particles stick to pos. charged collection plates, trapping them
-Plates discharged occasionally so particles fall down into collection hopper for disposal in landfills

baghouse filter

-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

what are the primary pollutants that cause most acid precipitation?

NOx and SO2

major sources of SO2

Coal fired power plants, metal factories, vehicles that burn diesel fuel

major sources of NOx

vehicle emissions, diesel generators, coal power plants

how to limit acid rain

-reducing NOx and SO2 emissions reduces acid deposition
-higher CAFE standards
-more public transit
-renewable energy sources
-more efficient electricity use

how did CAA affect acid deposition?

Clean Air Act decreased acid deposition significantly

how does SO2 and NOx create negative consequences?

-NOx and SO2 reacts with O2 and H2O in the atmosphere, forming nitric acid and sulfuric acid
-both acids dissociate in presence of water into sulfate and nitrate ions and hydrogen ions
-acidic rain water decreases soil water pH; can limit tree growth in forests down wind from major SO2 and NOx sources

acidity

higher H+ ion concentration, lower pH

environmental effects of acid rain

soil/water acidification, pH tolerance

soil/water acidification

-H+ ions displace or leech other pos. charged nutrients (Ca2+, K+) from soil. -H+ ions also make toxic metals like aluminum and mercury more soluble in soil and water
(slow growth or kill plants and animals)

pH tolerance

-As pH decreases (more acidic) outside optimal range for a species, pop. declines
-When pH leaves range of tolerance, they cannot survive at all, due to:
-Aluminum toxicity
-Disrupted blood osmolarity (Na+/Cl- balance disrupted at low pH)

indicator species

can be surveyed and used to determine conditions of an ecosystem (soil, water, etc)
-ex: high whitemoss/filamentous algae population indicates pH < 6.0
-high crustacean population indicates pH \> 6.0

mitigating acid rain

limestone (calcium carbonate- CaCO3) is a natural base that can neutralize acidic soil/water
-reacts with H+ ions forming HCO3, and giving CA2+ to move water/soil closer to pH of 7
-regions with limestone have natural buffering of acid rain
-humans can add crushed limestone to soil/water
-acid rain can corrode human structures, esp those made from limestone

noise pollution

any noise that causes physiological stress or has the potential to damage human health (difficulty commuting, headaches, confusion or hearing loss)