Unit 8: Aquatic and Terrestrial Pollution

Human Impact on the Environment

• Human activities often have negative consequences on the environment.
  • Chemical use.
  • Trash release.
  • Air pollution.
• Organisms and the environment have a range of tolerance.

Range of Tolerance

• Optimal vs. Suboptimal conditions.
• Polar bear example:
  • Happy in normal cool weather.
  • Physiological stress occurs when conditions deviate from optimal (changes in growth, reduced reproduction).
  • Outside the range of tolerance leads to:
    • Physiological stress.
    • Limited growth.
    • Possible death.
• Other examples:
  • Acid Rain: Changes pH of soil and water, affecting species like amphibians with narrow pH tolerance.

Specific Examples of Environmental Impact

Coral

• Climate change can cause coral die-off.
• Coral bleaching: Increased ocean temperatures cause coral to turn white and die.

Oil Spills

• Examples: Deepwater Horizon (2011), Exxon Valdez (1980s).
• Effects:
  • Hydrophobic nature causes rapid spreading on the water surface.
  • Problems with bird feathers.
  • Oil can sink, covering the benthic zone and killing species.
  • Toxicity makes fishing unsafe and fish consumption dangerous.

Plastics

• Photo degrade into smaller pieces instead of decomposing.
• Small animals ingest them, mistaking them for food.
• Release toxins as they break apart.

Endocrine Disruptors

• Disrupt hormones by:
  • Competing with hormones.
  • Altering hormones.
  • Preventing hormones from functioning.
• Effects:
  • Birth defects.
  • Developmental and reproductive effects.
  • Immune system problems.

Types of Pollution

Point Source Pollution

• Pollution emitted directly from an identifiable source.
  • Examples: Smokestack, outflow pipe.

Non-Point Source Pollution

• Diffuse or spread out pollution, often runoff-influenced.
• Example: Fertilizer runoff from farm fields.

Nutrient Excess and Eutrophication

• Non-point source pollution leads to nutrient excess (nitrogen and phosphorus) in waterways, often from fertilizers.
• Eutrophication steps:
  1. Runoff carries nutrients into a waterway.
  2. Algae increase dramatically.
  3. Algae block sunlight, preventing photosynthesis in deeper plants.
  4. Algae die in large quantities.
  5. Decomposition uses up dissolved oxygen.
  6. Oxygen levels lower, leading to hypoxic conditions.
  7. Fish and plant die-offs occur.
• Dead zones: Hypoxic areas with extremely low oxygen levels due to excessive nutrient input.
  • Example: Gulf of Mexico dead zone caused by Mississippi River watershed runoff.
  • Stratification in the Gulf prevents mixing of oxygenated and hypoxic water, exacerbating the dead zone.

Oxygen Sag Curve

• Charts how oxygen levels change downstream from a pollution source.
• Biological Oxygen Demand (BOD):
  • Amount of oxygen used up by organisms in the water.
  • Low BOD: Water is full of oxygen, not rapidly used.
  • High BOD: Water is polluted, oxygen is being used rapidly.
• The graph shows the distance downstream away from a pollution source and how the oxygen (red line) and the biological oxygen demand (blue line) have changed. The dissolved oxygen drops where the BOD is high and increases again as the BOD drops off.

Bioaccumulation and Biomagnification

• Mercury released from burning coal settles into waterways and converts to toxic methylmercury.
• Bioaccumulation: Methylmercury accumulates in organism tissues, especially fats, over time.
• Biomagnification: Mercury is passed up the food chain, with top-level predators having very high levels.
• Example: Krill -> Small Fish -> Medium Fish -> Big Fish, with mercury concentration increasing at each level.

Thermal Pollution

• Caused by hot water being dumped into a water body.
• Source: Coal-fired and nuclear power plants use water to cool equipment and release it at a higher temperature.
• Effects:
  • Fish avoid the area.
  • Warmer water holds less oxygen.
  • Physiological stress and lack of oxygen for fish.

Terrestrial Pollution

Solid Waste

• Disposal Methods:
  • Sanitary Landfills:
    • Pits lined with plastic to prevent leaking.
    • Leachate collection systems to manage fluid accumulation.
    • Methane collection for burning and electricity production.
    • Capping and reversion to green space after finalization.
  • Incineration:
    • Reduces volume of trash, but releases air pollution.
  • Recycling:
    • Energy-intensive and expensive.
    • Not all materials are recyclable.

Sewage Treatment

• Three levels of processing plus disinfection:
  1. Primary Treatment (Physical):
     • Removes large objects using grates and screens.
  2. Secondary Treatment (Biological):
     • Uses bacteria to break down wastes (feces, food, soaps, detergents).
     • Aeration to speed up bacteria activity.
  3. Tertiary Treatment (Chemical):
     • Nutrient removal.
• Disinfection methods:
  • Chlorine sterilization.
  • Ozone gas bubbling.
  • UV light.

Human Health

• Climate change expands the range of diseases carried by vectors like mosquitoes (West Nile virus, Zika, Malaria).
• Pathogens spread in areas with poverty, lack of sanitation, and dirty water.
• Lethal Dose 50% (LD50):
  • The dose of a chemical required to kill 50% of a population.
  • Used to determine safe dosing levels.
  • Dosage of 100 mg/kg is deadly to 50% of the population in the graph example.

Laws

• Clean Water Act:
  • Unlawful to discharge pollutants from a point source into navigable waters.
• Safe Drinking Water Act:
  • Protects underground sources of drinking water from contamination.
• Resource Conservation and Recovery Act (RCRA):
  • Monitors hazardous waste from creation to disposal (cradle to grave management).
• Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA or Superfund):
  • Companies are responsible for cleaning up hazardous waste they create.
• Delaney Clause:
  • Bans food additives known to cause cancer in humans or animals.