unit 7 (atmospheric pollution)

sulfur dioxide (SO₂)

released largely by coal combustion; a respiratory irritant that can cause acid rain

can worsen bronchitis and asthma; creates sulfur aerosols, which blocks incoming sunlight and reduces visibility or photosynthesis; forms sulfurous smog; can form sulfuric acid in the atmosphere

nitrogen oxides (NO & NO₂)

refers to nitric oxide (NO) and nitrogen dioxide (NO₂); caused by fossil fuel and biomass combustion, with the leading anthropogenic source being the combustion of gasoline in cars and coal

forms tropospheric ozone, which later leads to photochemical smog; combines with water and oxygen in the atmosphere to form nitric acid, a component of acid rain

carbon monoxide (CO)

produced by the incomplete combustion of various fuels; lethal to humans

lead (Pb)

released when metals are smelted and when waste is incinerated; it is a neurotoxicant, and can damage the nervous system of humans and animals

ozone (O₃)

specifically tropospheric ozone; a respiratory irritant that can also damage plants and lead to smog

particulate matter (PM)

refers to suspended particles in the air; caused by combustion and various different events; a respiratory irritant that can lead to the formation of smog and the thickening of smog

coal combustion

releases CO, CO₂, SO₂, NO_x, toxic metals, and PM

primary air pollutants

air pollutants that are emitted directly from a source (vehicles, power plants, factories, volcanoes, forest fires, etc.)

examples: CO, CO₂, SO₂, NO_x, PM, VOCs, hydrocarbons

secondary air pollutants

air pollutants that have undergone a transformation in the presence of sunlight, water, and oxygen; more prevalent during the day

examples: O₃, H₂SO₄ (sulfuric acid), HNO₃ (nitric acid)

precursors of photochemical smog

nitrogen oxides and volatile organic compounds (VOCs) that react with heat and sunlight to form various pollutants, like ozone and nitric oxide

environmental conditions of photochemical smog

accessible sunlight, which breaks down nitrogen dioxide to form ozone, and large amounts of warmth, which speeds up the evaporation of VOCs

ozone formation

nitrogen dioxide levels peak in the early morning, as a result of commutes, and when the Sun rises the light and warmth will break the nitrogen dioxide into nitric oxide and an oxygen atom; the oxygen atom will bind with oxygen gas (O₂), which will form ozone (O₃)

ozone concentrations peak in the afternoon, and are higher in the summer, because of the accessibility of sunlight and warmth

volatile organic compounds (VOCs)

hydrocarbons that sublimate or evaporate at room temperature; trees are sources for these compounds

examples: gasoline, formaldehyde

photochemical smog in urban areas

have more photochemical smog as a result of larger amounts of nitrogen dioxide being released, since there are larger traffic numbers, and hotter average temperatures

human health effects of photochemical smog

can cause eye irritation and irritate respiratory tracts, and thus worsen asthma and bronchitis

methods to reduce photochemical smog

decreasing the number of vehicles, since it reduces the nitrogen dioxide emissions and emits less VOCs from gasoline

• encourage carpooling, improve or construct public transportation methods

utilizing renewable energy sources that don’t emit nitrogen dioxide

thermal inversion

a phenomenon where the traditional temperature gradient of the atmosphere (warm air closest to the Earth’s surface) is altered, and thus a warm air layer is trapped between two cooler and cold layers of air

effects of thermal inversion

limits the traditional convection cell process, and thus traps pollutants, such as smog and PM, closer to the Earth’s surface, leading to respiratory irritation

natural sources of nitrogen oxides

lightning strikes, forest fires, volcanoes

natural sources of carbon monoxide

forest fires, volcanoes

natural sources of particulate matter

forest fires and volcanoes (ash), sea salt, pollen, dust

leads to haze (scattering of sunlight and reduced visibility)

natural sources of VOCs

plants, especially coniferous trees

natural sources of sulfur dioxide

volcanoes

natural sources of carbon dioxide

respiration (not a major source), aerobic decomposition, volcanic eruptions

anaerobic decomposition

the decomposition of organic matter by bacteria and decomposers in low or oxygen-free conditions, releasing methane as a byproduct

particulate indoor air pollutants

asbestos, smoke, and dust

asphyxiant

a nontoxic, or minimally toxic, gas that can cause suffocation by displacing the concentration of oxygen that is received during respiration by an animal or human

example: carbon monoxide (indoor air pollutant)

natural source indoor air pollutants

radon, dust, and mold

human-made indoor air pollutants

insulation; VOCs from furniture, paneling, and carpets; formaldehyde from building materials, furniture, upholstery, and carpeting; and lead from paints

combustion indoor air pollutants

carbon monoxide, sulfur dioxide, nitrogen oxides, particulates, and tobacco smoke

radon-222

a naturally occurring, radioactive gas that is produced by the decay of uranium found in common rocks and soils in or under the foundation of houses

enters homes via cracks in the walls or foundation and can also possibly leak into groundwater sources, which is harmful for homeowners that use well water

effects of radon-222

can cause lung cancer, and it is the second-leading cause for lung cancer in the United States

methods to reduce air pollutants

regulatory practices (laws and regulations), conservation practices, and alternative fuels

clean air act

allows the EPA to set acceptable criteria levels for certain air pollutions, and thus monitor emissions levels and issue consequences

CAFE vehicle standards

also called the “Corporate Average Fuel Economy”; standards that require the entire US “fleet” of vehicles to meet a certain average fuel consumption rate (fuel economy)

raising these standards would promote more efficient vehicles by forcing manufacturers to create them, in order to sell in the US

pollution credits

rewards given to companies that reduce emissions below the EPA-set levels and are able to sell them to companies, who are forced to buy them because they release more than EPA-set levels

vapor recovery nozzle

an air pollution control device that prevents VOCs from being released into the atmosphere from gasoline fumes, by attaching to the gasoline pump, when refueling a motor vehicle

catalytic convertor

an air pollution control device that is required on all internal combustion engine vehicles, and it converts harmful air pollutants (CO, NO_x) to less harmful molecules (H₂O, CO₂, N₂, O₂)

dry scrubbers

large columns that are filled with chemicals that absorb or neutralize oxides from emissions

wet scrubbers

mist droplets absorb and neutralize various air pollutions and possibly trap particulate matter, before falling to the bottom of the scrubber and being removed

electrostatic precipitator

used to reduce air pollution from coal-burning power plants by passing emissions through a device that gives particles a negative charge, before trapping them to positively charged plates that discharge, forcing the particles to fall into a collection hopper

effects of acid rain

can lead to the acidification of soil and water, most commonly in environments downwind from coal-burning power plants

• can slow the growth or kill plants and animals living in the soil and water, as toxic metals are also more likely to be soluble in acidic environments

can corrode human-made structures

solutions to mitigating acid rain

utilizing limestone to neutralize acid rain as the rock’s calcium carbonate reacts with the hydrogen ions of acid rain (acidic water/soil) to neutralize it

• this can be a natural mitigation technique as regional differences in soil and bedrock could lead to higher concentrations of limestone in certain environments

noise pollution

sound at levels high enough, a volume loud enough, to cause physiological stress (difficulty communicating, headaches, confusion) or hearing loss

sources of noise pollution

transportation (cars, busses); construction (jack hammers, trucks); industrial activity (manufacturing plants); domestic activity (neighbor’s music, home projects)

noise from ship engines, military sonar, and seismic air blasts from oil/gas surveying ships

ecological effects of noise pollution

physiological stress, the masking of animal sounds used for hunting or communicating, damaged hearing, and changes to migratory routes