Environmental Science Exam Notes

Demographic Transition Model

• Phase 1: Pre-industrial Stage

  • Characterized by high Crude Birth Rate (CBR) and Crude Death Rate (CDR).
  • Population is stable.

• Phase 2: Transitional Stage

  • High CBR persists but CDR begins to decrease.
  • Leads to rapid rise in human population, marking the most significant population growth.

• Phase 3: Industrial Stage

  • Low CDR and a declining CBR.
  • Population continues to grow, but at a slower rate, moving towards stabilization.

• Phase 4: Post-industrial Stage

  • Characterized by low CBR and CDR.
  • Population stabilizes or begins to decline.

Air Pollution

• Indoor vs. Outdoor Pollution

  • Indoor air pollution: more severe and deadly, often from burning fuels in rural areas.
  • Modern buildings can also have significant indoor air pollution issues.

• Primary Pollutants: Directly emitted into the troposphere, e.g.,

  • Carbon Dioxide (CO₂), Nitric Oxide (NO), Sulfur Dioxide (SO₂).

• Secondary Pollutants: Formed from reactions between primary pollutants and other substances, e.g.,

  • Sulfur Trioxide (SO₃), Sulfuric Acid (H₂SO₄), Ozone (O₃).

• Key Reactions to Know:

  • Tropospheric Ozone Formation:
  • NO + O2 → NO2
  • NO2 + UV → O + O2 + O_3
  • Formation of Sulfuric Acid:
  • SO2 + O2 → SO_3
  • SO_3 + H₂O → H₂SO₄
  • Formation of Nitric Acid:
  • NO_2 + H₂O → HNO₃

Water Quality

• Water Basics: Majority of Earth's water is saline or frozen.
• Estuaries and Wetlands: Highest average Net Primary Production (NPP), while the open ocean has the highest total NPP.
• Cultural Eutrophication: Excessive nutrient addition leading to toxic algal blooms.
• Pollutants:
  • Nitrates (NO₃⁻) & Phosphates (PO₄³⁻): from fertilizers.
  • Mercury (Hg): from coal-burning power plants.
  • Crude Oil: from drilling spills.

Toxicity and Waste

• Toxicology Definitions:
  • LD50: Lethal Dose-50, amount needed to kill 50% of population.
  • Threshold Level: Dose at which effects begin; some toxins like oxygen are threshold toxins.
• Types of Toxins:
  • Carcinogens: Cause cancer (e.g., nicotine, asbestos).
  • Persistent Organic Pollutants (POPs): Bioaccumulative and biomagnifying (e.g., DDT).

Energy Sources

• Nonrenewable Energy:

  • Coal: Most polluting, releases CO₂, SO₂, mercury.
  • Oil: Major risk of spills, produced from conventional and unconventional sources.
  • Natural Gas: Cleaner but harder to transport; mainly methane.

• Renewable Energy:

  • Wind and Solar: Minimal direct emissions but require land/resources for infrastructure.
  • Geothermal: Effective in seismic zones but may cause groundwater pollution.
  • Biomass: Renewable but has public health implications from indoor pollution.

Climate Change

• Key Concepts:

  • Climate change driven by anthropogenic CO₂ emissions.
  • Keeling Curve: Measurement of CO₂ concentrations over time.

• Effects of Climate Change:

  • Rising temperatures and ice melting impacting ecosystems.
  • Changes in chronic animal behavior and weather patterns.
  • Increased prevalence of invasive species and disease vectors (e.g., mosquitoes).

Environmental Policies

• Clean Air Act (1973): Established standards for air quality and regulated emissions.
• Safe Drinking Water Act (1974): Protects drinking water sources from harmful pollutants.
• Montreal Protocol (1987): Aimed to reduce substances that deplete the ozone layer.
• Paris Climate Accord (2016): International agreement to limit global warming and greenhouse gas emissions.