APES Unit 7: Atmospheric Pollution

clean air act (1970)

identified 6 criteria air pollutants that the EPA is required to set acceptable limits for, monitor, and enforce

6 criteria air pollutants in the clean air act

• SO₂

• NO_x

• CO

• PM

• O₃

• Pb

SO₂ source

coal combustion (electricity), vehicles that burn disease fuel

NO_x source

All FF combustion (gas especially), vehicles emissions

negative effects of NO_x

• respiratory irritant

• leads to smog

• combines with H₂O & O₂ = acid rain

CO source

incomplete combustion, O₃

PM Source

FF/biomass combustion, respiratory irritant, smog

O₃ source

photochemical oxidation of NO₂, respiratory irritant, smog, plant damage

Pb source

metal plants, waste incineration, neurotoxicant

Is CO₂ an air pollutant or GHG?

GHG

• does not directly lower air quality from a human health standpoint

coal combustion

releases more air pollutants than other FFs ~ 35% of global electricity

• releases CO, CO₂. SO₂, NO_x, PM, toxic metals (mercury, arsenic, lead)

negative impacts of coal combustion

• respiratory irritant

• sulfur aerosols block incoming sun

• combines with water and O₂ = acid precipitation (rain)

impacts of SO_x

• respiratory irritant (inflammation of bronchioles, lungs), worsens asthma & bronchitis

• sulfur aerosols (suspended sulfate particles) block incoming sun, reducing visibility and photosynthesis

• forms sulfurous (grey) smog

• combines with water & O² in atmosphere to form sulfuric acid → acid precipitation

NO_x → NO & NO₂

released by combustion of anything, especially FFs and biomass

• NO forms when N₂ combines with O₂ (esp. during combustion)

• NO can become NO₂ by reacting with O₃ or O₂

• sunlight converts NO₂ back into NO

NO_x impacts

• respiratory irritant

• leads to tropospheric ozone (O₃) formation, which leads to photochemical smog

• combines with water & O₂ in atm. to form nitric acid → acid precipitation

VOC’s source/def.

chemicals used in variety of home products

VOC’s impacts

• irritate eyes, lungs

• respiratory diseases

VOC: Cleaners

Common household cleaners and deodorizers such as Febreze

VOC: Plastics and fabrics

both can release VOCs themselves, or from adhesives used in production

VOC: Adhesives/sealants

chemicals used to glue carpet down, hold furniture together, seal panels

• Formaldehyde is a common adhesive in particle board and carpet glues (new carpet smell)

EPA and lead

before CAA, lead was a common gasoline additive; EPA began phaseout of lead from gasoline in 1974\

• Vehicles made after 1974 are required to have catalytic converters to reduce NO_x, CO, and hydrocarbons emissions (lead damages catalytic converters_

  • also known as neurotoxicant (damages NS of humans)

primary air pollutant

• Emitted directly from sources such as vehicles, power plants, factories, or natural sources (volcanoes, forest fires)

• NO_x, CO, CO₂*, VOCs, SO₂, PM, hydrocarbons

secondary air pollutant

• 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) & sulfate (SO₄^2-)

• Nitric acid (HNO₃) & nitrate (NO₃^-) 

impacts of PM

impact of CO

• lethal to humans

impact of O₃

SO_x

sulfur dioxide

NO_x

nitrogen oxides

CO

carbon monoxide

PM

particulate matter

VOC’s

volatile organic compounds

CO₂

carbon dioxide

Pb

lead

Hg

mercury

what are vehicles made after 1974 required to have and why?

catalytic converters

photochemical smog precursors

• broken by sunlight in NO

• VOC’s + NO = photochemical oxidants

• forms when NO₂ is broken by sunlight and free O binds to O₂ = O₃ (ozone)

photochemical smog conditions

• sunlight

• warmth = hotter atmosphere speeds up O₃ formation, evaporation of VOC’s → smog formation

• high traffic (afternoon)

why do urban areas have more smog?

• more traffic

• hotter temp. due to low albedo

• more VOC’s due to gas stations and factories

• more electricity demand = more NO₂ emissions from nearby powerplants

how does smog impact the environment?

• reduces sunlight = limits photosynthesis

• O2 damages plant stomata and irritates animal resp. tracts

how does smog impact humans?

• resp. irritant = worsens asthma, bronchitis, COPD, irritates eyes

how does smog impact the economy?

• increased health care costs

• lost productivity due to sickness

• decreased agriculture yields

how to reduce smog caused by vehicles?

• decrease # of vehicles on the road

• fewer vehicles = less gas = fewer VOCs

• carpooling, biking, public transport., walking

how to reduce smog caused by energy use?

• increased electricity production from renewable sources that don't emit NO2

• Nat. Gas power plants release for less NO than coal

urban heat island effect

urban = higher surface and air temp

• lower albedo (concrete and asphalt absorb suns energy than areas with more vegetation)

• less Evo transpiration

thermal inversion

cooler air mass is trapped under a warm front near earth’s surface

what happens to air pollutants in thermal inversion?

• cold air is trapped beneath the warmer mass = convection doesn’t carry pollutants up and away

• warm air rises = convection carries air pollutants away from earths surface and distributes them higher into the atmosphere

effects of thermal inversion

• air pollutants trapped closer to earth

• respiratory irritation

• decreased tourism revenue

• decreased photosynthetic rate

natural sources of air pollutants

• lightning strikes

• forest fires

• volcanoes

• plants

natural sources of CO₂ and PM

• respiration

• natural PM sources

• aerobic decomposition

• anaerobic decomposition

PM₁₀

Particles or droplets like dust, pollen, ash, or mold

PM_2.5

Particles from combustion (especially vehicles) smaller dust particle

developing countries

• subsistence fuels ( wood, manure, charcoal)

• biomass release CO, PM, NO, VOCs

• combusted indoors with high concentration = high concentrations

developed nations

• commercial fuels (coal, oil, natural gas)

• burned in closed, well-ventilated furnaces

asbestos

long silicone particle used in insolation

radon gas

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

how does radon gas enter homes?

• through cracks in the foundation, disperses up from basement through home

• seep into groundwater and enter through drinking water

what is the 2nd leading cause of lung cancer after smoking?

radon gas

how to monitor/ protect against radon gas?

• testing homes with airborne Radon monitor

• sealing cracks in foundation

how does dust enter air?

settles in homes -> disturbed by movement -> enters air

How does a mold form?

formed in areas that are dark and damp and not well ventilation

black mold

class of mold that releases spores into air

how to prevent mold?

removal by cleaning mold out, fixing water leaks/ ventilation issues

where is lead found in homes?

paint in old homes

how does lead come in contact with the human body?

• paint chips off the walls/ windows and is eaten or inhaled as dust

• found in water sources from the lead pipes

what does lead do to the human body?

• damages central nervous system of children due to their small size and still developing brain

how can lead be removed

• stripping lead paint

• replacing lead pipes with copper pipes

how to reduce emissions?

• drive less, walk/bike/bus more

• conserve electricity

• eat more plants, less meat

• renewable, non-pollution emitting energy

pollution credits

companies that keep their levels below EPA's set levels earn pollution points

CAFE

CAFE = corporate average fuel economy

• require U.S. fleet of vehicles to meet certain average fuel

• requires vehicle manufacturers to make more efficient vehicles

• more efficient vehicles burn less gasoline and release less NO4, PM, CO, and CO2

Vapor recovery nozzle

capture hydrocarbon VOCs released from gas fumes during refueling

how do vapor recovery nozzles reduce vehicle air pollutants?

• Reduces VOCs, which contribute to smog & irritate resp. tracts

• Also reduces benzene (carcinogen) released from gasoline vapors

Catalytic converter

converts harmful gases into less harmful gases and water

crushed limestone

used to reduce SO₂ from coal power plants

calcium sulfate

CaSO₄

calcium carbonate

CaCO₃

how does crushed limestone work?

• 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

fluidized bed combustion

reduces SO and NO

dry scrubbers

Large column/tube/pipe filled with chemicals that absorb or neutralize oxides (NOx, SOx, VOCs) from exhaust streams (emissions)

wet scrubbers

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

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

what does the electrostatic preceptor reduce?

PM

what does the baghouse filter reduce?

PM

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 & taken to landfill

how to limit acid rain

• reduce SO and NO emissions

• higher CAFE standards

• more public transport

• renewable energy sources

• more efficient electricity use

what has decreased the acid deposition?

clean air act

what happens with NO and SO2 in the atmosphere?

react with O2 and H2O and forms sulfuric acid

sulfuric acid

SO₂ + O₂ + H₂O → H₂SO₄

what dissociates in the presence of water and what does it create?

sulfuric acid and nitric acid and create sulfate and nitrate ions and hydrogen ions

nitric acid

NO₂ + H₂O → HNO₃

what does acidic rainwater decrease?

soil and water pH, limits tree growth in forests down wind

environmental effects of acid rain

• soil and water acidification

• as pH decreases pop declines

indicator species

if they die, something is wrong

• (pH levels are too acidic)

Mitigating acid rain

• limestone is a natural base that can neutralize acidic water/ soil

• limiting SO₂ and NO

urban noise pollution

Any noise at great enough volume to cause physiological stress (difficulty communicating, headaches, confusion) or hearing loss

examples of urban noise pollution

construction, transportation, industrial activity, domestic activity

effects of urban noise pollution on wildlife on land

• can disrupt animal communication, migration, damage hearing

• physiological stress = caterpillar hearts beat faster when exposed to simulated highway noise pollution

• hearing = prevent predators from hearing their prey, mates from finding each other, prey hearing their predators

effects of urban noise pollution on aquatic wildlife

physiological stress = hearing loss, disrupted communication, mating calls, predator and prey navigation

seismic surveying = ships send huge air blasts down into the water searching for oil (incredibly loud)

What is CO?

asphyxiant = suffocation

what are the two culprits of acid rain?

H₂SO₄

HNO₃

what is the BIGGEST culprit of acid rain?

H₂SO₄