The Chemistry of the Environment

Earth's Atmosphere Overview

  • The Earth's atmosphere is a layer of gases surrounding the planet.

  • Reaches over 560 kilometers from the surface.

  • Functions:

    • Absorbs energy from the Sun.

    • Recycles water and other chemicals.

    • Protects from high-energy radiation and frigid vacuum of space.

    • Supports life.

Composition of Earth's Atmosphere

  • Major components:

    • Nitrogen (N): 78%

    • Oxygen (O2): 21%

    • Argon (Ar): Approximately 0.9%

    • Trace gases including:

      • Carbon Dioxide (CO2): 0.03%

      • Water vapor (H2O): Up to 10,000 parts per million by volume (ppmv)

      • Ozone (O3): Near zero at the surface, up to 10 ppmv in stratosphere

      • Methane (CH4): 1.7 ppmv

Nitrogen Cycle

  • Nitrogen is crucial for protein synthesis in living organisms.

  • Nitrogen is cycled through the soil, taken up by plants, consumed by animals, and returned to the soil upon decay.

  • Bacteria play a key role in the nitrogen cycle, facilitating conversion processes.

Atmospheric Pressure

  • Atmospheric pressure is the force per unit area exerted by the weight of air above a surface on Earth.

  • At sea level, approximately 9,800 Newtons (2,200 pounds) acts on an area, equivalent to a small car's weight.

  • Pressure decreases with altitude.

    • Gas molecules are tightly packed closer to Earth's surface, leading to higher pressure.

Layers of the Atmosphere

Troposphere

  • Lowest and thinnest layer (16 km at the equator, 8 km at poles).

  • Contains 90% of the atmosphere's mass.

  • Temperature decreases with altitude (6°C per kilometer).

  • Weather occurs here.

Stratosphere

  • Extends from 10 km to 50 km.

  • Less dense, higher ozone concentration.

  • Temperature increases with altitude (ozone absorbs UV radiation).

Mesosphere

  • Extends up to nearly 80 km.

  • Gases are less dense and temperatures drop as altitude increases.

  • Minimal UV radiation absorption.

Thermosphere

  • Extends to nearly 600 km.

  • Temperatures rise drastically as altitude increases due to solar radiation absorption.

  • This layer reflects radio waves.

Ozone Layer and its Importance

  • The ozone layer absorbs harmful UV radiation from the Sun.

  • Thinning of the ozone layer caused by chlorofluorocarbons (CFCs), which were previously used widely in various applications.

  • International agreements like the London Agreement (1991) have reduced CFC production to protect the ozone layer.

Greenhouse Effect

  • Greenhouse gases trap heat, maintaining Earth’s temperature.

  • Naturally occurring gases: Water vapor, carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), ozone (O3).

  • Human activities increase concentrations of greenhouse gases, leading to global warming.

Effects of Global Warming

  • Increased average global temperatures.

  • Consequences include rising sea levels (1.6 ft predicted by 2100), extreme weather events, and shifting agricultural zones.

  • Around 51 trillion lbs (23 trillion kg) of CO2 are released annually.

  • Strategies for mitigation include promoting energy efficiency, reducing emissions, and using eco-friendly products.

Indoor Air Pollution

  • Indoor air contains higher pollution levels than outdoors due to various sources including smoking, cooking, building materials, and cleaning products.

  • Poor indoor air quality (IAQ) leads to health problems and discomfort.

  • Common indoor pollutants include volatile organic compounds (VOCs), carbon monoxide (CO), and particulate matter.

Health Effects of Indoor Air Pollution

  • Can cause respiratory issues, headaches, and long-term illnesses like lung cancer.

  • Symptoms of poor IAQ include irritation of eyes, nose, and throat, as well as fatigue.

  • Reduction of indoor pollutants is beneficial and often involves improving ventilation and using less toxic products.