Point and Nonpoint Pollution Sources

A point source refers to a single, identifiable source of a pollutant. Examples of point sources include:

1. A particular factory that buries its waste underground.

2. A sewage treatment plant that discharges its wastewater from a pipe into the ocean.

3. A smokestack that releases harmful chemicals into the air.
   

8.1 Sources of Pollutants

Point vs. Nonpoint Pollution Sources

Point sources of pollution have single locations, while nonpoint sources have diffuse locations. Nonpoint sources of pollution are diffused and can therefore be difficult to identify.
Examples of nonpoint sources include:

1. A suburban community with many lawns and septic systems.

2. Storm runoff from a large number of parking lots.

3. Pesticide spraying.

4. Urban runoff.
   While each cow makes a small contribution of manure that can release excess nutrients that are carried to the stream, collectively, the thousands of cattle spread across a large area represent a nonpoint source of pollution.
   

FRQ Practice 8.1

Describe the difference between a point and nonpoint source of pollution.

A point source pollutant enters the environment from an easily identifiable and confined place, while nonpoint source pollutants enter from diffuse, difficult to pinpoint sources.

Identify ONE point source of NOx emissions and ONE nonpoint source of NOx emissions.

• Nonpoint NOx Sources: Manure lagoons, agricultural fertilizer use, traffic, forest fires.

• Point NOx Sources: A single coal-fired power plant, a single vehicle, a specific coal mine.

8.2 Human Impacts on Ecosystems

Range and Tolerance

Living under the ideal range of conditions allows organisms to maintain homeostasis.
Homeostasis: The ability of organisms to experience relatively stable internal conditions in their bodies. Within this range of conditions, an organism can survive, grow, and reproduce. Outside of this range, organisms can no longer maintain homeostasis, leading to physiological stress, limited growth, reduced reproduction, and in extreme cases, death.

The performance of individuals begins to decline as the concentration of a pollutant increases. Initial increases in pollutant concentrations can impact the physiology and behavior of an individual, while higher concentrations can impede its growth and survival.

The Cascade of Neurotoxicity

An example of neurotoxicity involves low concentrations of a pesticide impacting an animal's nervous system, causing their movement to be slower and less coordinated. At moderate concentrations, the pesticide more strongly impairs nerve transmission and muscle movement, making it difficult for the animal to find food and grow. At even higher concentrations, the pesticide can cause the nervous system to stop stimulating heart contractions, leading to the animal's death.

Coral Reefs and Environmental Stressors

Coral reefs are suffering damage due to a variety of factors, including:

1. Increasing ocean temperature.

2. Sediment runoff.

3. Destructive fishing practices.

Coral Bleaching

Coral Bleaching: A phenomenon in which algae inside corals die, causing the corals to turn white.
Coral reefs are particularly harmed by several simultaneous challenges:

1. Pesticides impacting the homeostasis of corals combined with sediment runoff from human activities.

2. An increase in atmospheric CO2 leading to warmer ocean temperatures and loss of the algal symbiont, which causes coral bleaching.

3. Higher atmospheric CO2 dissolving into the water, lowering pH and causing exoskeletons to dissolve.

4. Destructive fishing practices, including tourists removing corals for souvenirs.

Changes in Ocean pH

Changes in pH in the world's oceans pose a risk to many marine organisms, particularly those with calcium carbonate shells or exoskeletons.

Explanation of Threats

A decrease in pH levels can have the following effects:

1. Shells and coral exoskeletons may dissolve.

2. The growth of new corals/shells may be prevented.

3. Renewal and maintenance of existing corals/shells may be hindered.

Impacts on Organisms

Organisms such as mollusks and coral face threats like:

1. Reduced fitness and decreased number of offspring.

2. Increased predation risk.

3. Increased threat of disease.

Oil Spill Effects

Oil spills in marine waters cause organisms to die from the hydrocarbons in oil. Oil that floats on the surface of the water can coat the feathers of birds and fur of marine mammals. Some components of oil sink to the ocean floor, killing bottom-dwelling organisms.

Effects of Oil Spills

The effects that an oil spill can have in coastal areas and on marine organisms include:

1. Birds may lose their buoyancy or ability to fly if their feathers are coated with oil.

2. Degradation of nursery grounds, feeding grounds, and habitats may lead to a loss of biodiversity.

3. Disruption of food webs when populations of specific organisms suffer negative health impacts.

4. Decreased sunlight reaching photosynthetic organisms in water due to oil coverage.

5. Bottom-dwelling organisms may be killed by smothering or by ingesting, inhaling, or absorbing oil.

Economic Impact of Oil Spills

Positive Economic Impact

1. Financial aid brought into local economies through grants, disaster relief, and settlements.

2. Increase in jobs and revenue during cleanup and monitoring of oil spills.

Negative Economic Impact

1. Cost of cleanup efforts.

2. Loss of revenue from tourism.

3. Loss of revenue from commercial fishing.

4. Monetary value of lost crude oil.

Famous Oil Spills

Deep Water Horizon Oil Spill

The Deep Water Horizon oil spill occurred when a pipe broke on the ocean floor nearly 1.6 km (1 mile) below the surface of the ocean. From April until the well was sealed in August 2010, the broken pipe released an estimated 780 million liters (206 million gallons) of crude oil into the Gulf of Mexico.

Exxon Valdez Oil Spill

In 1989, the oil tanker ran aground, spilling millions of liters of crude oil onto the shores of Alaska, killing thousands of animals and harming many others. Cleanup efforts went on for 2 decades.

Remediating Oil Pollution (Oil Spill Clean-Up)

Cleanup Methods

1. Physical Methods:
      - Burning oil on the surface of the water.
      - Dredging and vacuuming to remove oil.
      - Physical washing of rocks/organisms.
      - Use of absorbent materials to remove oil or contain the spill.
      - Using booms to contain oil on the surface and skimmers to separate oil from water.

2. Chemical Dispersants:
      - Advantages:
        - Easy to apply quickly.
        - Less costly than shoreline cleaning.
        - Minimize spreading of surface oil.
      - Disadvantages:
        - Oil is only dispersed, not removed.
        - May be toxic to organisms.
        - May increase the toxicity of the oil.

3. Biological Method:
      - Introduction of microbes that degrade oil spills. Scientists discovered a naturally occurring bacterium that obtained its energy by consuming oil emerging from natural seeps.

Oxygen Sag Curve

Oxygen Sag Curve: The relationship of oxygen concentration to the distance from a point source of decomposing sewage or other pollutants.
BOD (Biochemical Oxygen Demand): Measure of the amount of oxygen required to break down organic matter in water during the process of decomposition by aerobic bacteria. It refers to organic pollution such as leaves, litter, excess nutrients, storm drains, and debris.

Impacts on Wildlife

Organic pollution can create intestinal blockage and choking hazards for wildlife, as well as introduce toxic substances into the food chain.

FRQ Practice 8.2

The Alaskan National Wildlife Refuge (ANWR) on Alaska's North Slope is frequently in the news because petroleum geologists estimate that there are billions of barrels of economically recoverable oil beneath the surface of its frozen tundra. According to a 1998 United States Geological Survey (USGS) estimate, ANWR could contain up to 10 billion barrels of technically recoverable oil. Oil company officials advocate opening the refuge to oil exploration and subsequent development of its petroleum resources. Environmentalists argue that oil exploration and development will damage this fragile ecosystem and urge Congress to protect ANWR by designating it as a wilderness area.

U.S. Oil Consumption

The United States uses approximately 20 million barrels of oil per day. Based on the USGS estimate, for how many days would the technically recoverable oil resource in the ANWR supply the total United States demand for oil?

• Calculation:
    - Total oil estimated in ANWR: $10 imes 10^9$ barrels.
    - Daily U.S. consumption: $20 imes 10^6$ barrels/day.

• Solution:
  $rac{10 imes 10^9}{20 imes 10^6} = 500 ext{ days}$

Conclusion

The interplay of point and nonpoint sources of pollution reveals the complexities and challenges inherent in managing environmental impacts, especially as they relate to human activities and the resilience of ecosystems.