3.2 Environment - Atmospheric Chemistry (Learning Guide)

Air Pollution Control:

Designing systems to reduce air pollution requires knowledge of the chemical reactions involved in pollutant formation and removal.

Climate Change Mitigation

Engineers play a crucial role in developing technologies to mitigate climate change. This involves understanding the greenhouse effect and the role of atmospheric gases in driving climate change.

Material Science and Corrosion:

Atmospheric conditions, including pollutants and humidity, can significantly impact the durability of materials. Engineers need to consider these factors in designing structures and products.

Environmental Impact Assessment:

Engineers often need to assess the environmental impact of projects, which includes understanding how emissions from these projects might affect air quality and climate change.

Composition of Earth’s Atmosphere

The atmosphere is composed of 78.08% Nitrogen, 20.95% Oxygen, 0.93% Argon, approximately 0.04% trace gases including greenhouse gases (CO2, CH4, N2O, O3), and varying concentrations of Water Vapor.

Major Gases in Earth's Atmosphere

Nitrogen (N2): 78.084%, Oxygen (O2): 20.946%, Argon (Ar): 0.934%, Carbon Dioxide (CO2): 0.042%, Methane (CH4): 1.92 ppm, Nitrous Oxide (N2O): 0.33 ppm, Ozone (O3): 0.07 ppm.

Troposphere

The lowest layer of the atmosphere, where weather occurs, most of the atmosphere's mass is found, and temperature decreases with altitude.

Stratosphere

Layer containing the ozone layer, which absorbs UV radiation and experiences an increase in temperature with altitude due to this ozone.

Mesosphere

Temperature decreases with altitude; this layer is where meteors burn up.

Exosphere

The outermost layer of the atmosphere that gradually merges into space, where satellites orbit.

Types of Air Pollutants

Gaseous pollutants include Sulfur Dioxide (SO2), Nitrogen Oxides (NOx), Carbon Monoxide (CO), Ozone (O3), and Volatile Organic Compounds (VOCs). Particulate Matter (PM) refers to solid or liquid particles less than 10 micrometers in diameter.

Primary vs. Secondary Pollutants

Primary pollutants are emitted directly into the air (such as PM, SO2, CO), while secondary pollutants form through reactions between primary pollutants (e.g., tropospheric ozone)

Sources of Air Pollution

Natural sources include volcanoes and wildfires. Human activities contribute through transportation (cars, trucks, planes) and industrial activities (power plants, manufacturing).

Criteria Pollutants

Includes Particulate Matter (PM), ground-level ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead; each having specific health impacts.

Acid Rain

Formed by emissions of SO2 and NOx reacting with water to create sulfuric and nitric acids, largely from fossil fuel combustion and vehicle emissions.

Greenhouse Effect

The natural greenhouse effect is caused by gases like CO2, CH4, N2O, and fluorinated gases, which trap heat in the atmosphere; the enhanced greenhouse effect increases this warming.

Greenhouse Gas Sources

Major sources of greenhouse gases include Carbon Dioxide (CO2) from natural gas systems and fossil fuel combustion, Methane (CH4) from landfills and agriculture, and Nitrous Oxide (N2O) from fossil fuel combustion and agriculture.

Nitrogen (N2)

78.084%

Oxygen (O2)

20.946%

Argon (ar)

0.934%

Carbon Dioxide (CO2)

0.042%

Particulate Matter (PM)

Respiratory issues are categorized by size (PM10 and PM2.5).

Ground-level Ozone

Formed from reactions between pollutants in sunlight, damaging lungs

Carbon Monoxide

Limits oxygen supply to the body

Sulfur Dioxide

Strong odor, contributes to acid rain.

Nitrogen Dioxide

Irritant to respiratory system, contributes to smog.

Lead

Heavy metal impacting the nervous system.