Intro to Air Pollutants Notes - 7.1 to 7.3

What pollutants did the Clean Air Act (1970) identify as criteria pollutants?

Sulfur Dioxide - coal combustion; respiratory irritant, smog, acid precipitation

Nitrogen Oxides - all fossil fuel combustion; photochemical smog and acid precipitation

Carbon Monoxides - incomplete combustion; O3, lethal

PM - fossil fuel/biomass combustion

Ozone - photochemical oxidation; respiratory irritant, smog, damaging to plants

Lead - metal plants, waste incineration, neurotoxin (damages nerve system)

Air pollutants vs GHG’s

Not all greenhouse gases are air pollutants; they harm human health and the environment as they contaminate the air. GHGs, like CO2, don’t directly lower air quality from the human health standpoint, but it does lead to warming.

Coal Combustion

releases more CO2 than any other fossil fuel (35% of global electricity). Coal Combustion releases CO, CO2, SO2, NOx, toxic metal (mercury, arsenic, lead), and PM (usually carries the metals)

Impacts of SO2 (Sulfur Dioxide)

respiratory irritant; worsens asthma and bronchitis.

Sulfur aerosols block sun which reduces visibility and effects photosynthesis.

forms smog

Combines with water + O2 in atmosphere which creates acid rain.

Nitrogen Oxides (NOx)

released by combustion of anything, especially, fossil fuels and biomass. The acronym, NOx, can refer to both NO or NO2

N2 + 02 –> 2NO (nitric oxide)

2NO + 02 –> 2NO2 (Nitrogen dioxide)

Health effects of Nitrogen Oxides

respiratory irritant, leads to tropospheric ozone formation (photochemical smog), and acid precipitation.

EPA and Lead

Before the Clean Air Act, Lead was common in gasoline. The EPA phased out lead from gas in 1974 to reduce NOx, CO2, and hydrocarbon emissions.

Vehicles made after 1974 are required to have catalytic converters.

Primary pollutants

Pollutants directly from the source, such as vehicles, power plants, factories, or natural sources such as volcanoes or forest fires

Releases NOx, CO, CO2, VOCs (Volatile organic compounds), SO2, PM, and hydrocarbons

Secondary Pollutants

formed from chemical reactions between primary pollutants. These chemical reactions occur during the day in the presence of sun, water, and O2

Examples include Ozone (O3), Sulfuric Acid(H2SO4), Sulfate (SO2−4), nitric acid (HNO3), and nitrite (NO3-)

Photochemical Smog precursors

NO2 is broken by sunlight into NO + O, leaving a free O to bind with O2 to form O3. VOC bines with NO and forms photochemical oxidants

Carbon based compounds react (evaporate) easily, and are found in formaldehyde, cleaning fluids, oil based paints, and coniferous trees (all known for their smell)

respiratory irritant in troposphere and damages plant stomata with limits growth

Photochemical Smog conditions

sunlight drives O3 formation by breaking down NO2 into NO and O. The warmer it is, the easier it is for this to occur.

Normal O3 formation

Morning commutes can release high NOx emissions from car exhaust, as the sunlight breaks down NO2 into NO and O (O binds with O2 to make O3)

O3 levels drop at night due to lack of sunlight, and peak in the afrernoon as both sunlight and traffic emissions peak.

Without NO to react with O3, it builds up instead of returning.

Impacts of Smog

Env - limits photosynthesis by reducing light, damages plant stomata and irritates animal respiratory tracts.

Human - respiratory irritant, eye irritant, worsens asthma + bronchitis, and COPD (Chronic Obstructive Pulmonary Disease)

Economic - increased health care costs to treat health effects, loss of productivity from sick/dying workers, and decreased agricultural yields from lack of sunlight.

Smog reduction

Decrease the amount of vehicles on the road by carpooling, working from home, using public transport, biking, and walking.

Increase renewable sources for electricity production that don’t emit NOx such as natural gas

Therman Inversion

a meteorological phenomenon where a layer of warm air traps cooler air near the Earth's surface, preventing normal air circulation.

Air convections can carry air pollutants away from earths surface and distributes them higher into the atmosphere. Because the cold air is trapped, convections cant carry air pollutants away from the earth

Effects of Thermal Inversion

air pollutants such as smog, PM, ozone, SO2, and NOx are trapped closer to earth.

Respiratory irritant, decreased tourism, and decreased photosynthesis,