Unit 8: Aquatic and Terrestrial Pollution Study Guide

Sources of Pollutants (8.1)

• Point Source Pollution:     * Definition: A point source refers to a single, identifiable source of a pollutant. It is a pollutant that enters the environment from an easily identified and confined place where one can physically "point" to the origin.     * Examples:         * A specific smokestack from a coal power plant releasing emissions such as $CO_2$, $NO_x$, $SO_2$, and particulate matter (PM).         * A waste discharge pipe from a factory.         * Animal waste runoff from a Concentrated Animal Feeding Operation (CAFO), which typically contains ammonia ($N$) and fecal coliform bacteria.         * The BP Oil Spill, which released hydrocarbons and benzene.

• Nonpoint Source Pollution:     * Definition: Nonpoint sources are diffused pollutants that enter the environment from many places at once. They are difficult to identify as a single individual source and are often described as being difficult to "point" to.     * Examples:         * Urban runoff, which collects motor oil, nitrate fertilizer, road salt, and sediment from various city surfaces.         * Pesticides sprayed on agricultural fields that are carried by the wind or washed off large regions into water bodies.         * Estuaries and bays are frequently polluted by various nonpoint sources originating from the vast watersheds that empty into them.

• Pollutants vs. Pollution for FRQs:     * Pollutants: This term refers to specific chemicals or groups of chemicals from specific sources with defined environmental and human health effects. Using specific pollutant names is required for FRQ credit.     * Pollution: This is a vague, nondescript term for any substance harmful to the environment and is generally not acceptable on an AP Environmental Science FRQ.     * Required Specifics: On pollution-related FRQs, students must identify specific pollutant names, their sources, their environmental and human health effects, and mitigation strategies. Exceptions include categorical terms like Thermal pollution, Noise pollution, and Sediment pollution.

Human Impacts on Ecosystems (8.2)

• Range of Tolerance:     * Organisms have a range of tolerance for abiotic conditions in their habitat, including $pH$, temperature, salinity, sunlight, and nutrient levels (such as ammonia or phosphate).     * Organisms maintain an optimum range where they can maintain homeostasis.     * Physiological Stress: Outside the optimum range, organisms experience limited growth, reduced reproduction, and difficulty respiring (asphyxiation/suffocation).     * Hormonal Disruption: High concentrations of pollutants can disrupt endocrine functions or lead to death.

• pH Tolerance and Indicator Species:     * As $pH$ decreases (becomes more acidic) outside the optimal range, populations decline.     * Survival failure at low $pH$ is often due to Aluminum toxicity and disrupted blood osmolarity ($Na^+/Cl^-$ balance).     * Whitemoss/Filamentous Algae: High populations indicate pH < 6.0.     * Crustaceans: High populations indicate pH > 6.0.

• Coral Reef Ecosystems:     * Mutualism: Corals have a relationship with photosynthetic algae called zooxanthellae. The algae provide sugar, and the coral provides $CO_2$ and detritus.     * Temperature Sensitivity: Algae have a narrow temperature tolerance. When temperatures rise, algae leave the reef, causing Coral Bleaching, where coral loses color and becomes vulnerable to disease.     * Human Impacts:         * Greenhouse Gas Emissions: Lead to ocean warming and bleaching.         * Sediment Pollution: Runoff makes water turbid, reducing sunlight and photosynthesis.         * Toxicants: Chemicals from sunscreen, roadway oil, and agricultural pesticides.         * Nutrient Pollution: Ammonia from animal waste and nitrates/phosphates from lawn or agricultural fertilizers.         * Overfishing: Decreases fish populations; bottom trawling destroys reef structures.

• Oil Spills:     * Biological Effects: Hydrocarbons are toxic and can be ingested or absorbed through gills/skin. Oil coats the feathers of birds and the fur of marine mammals, leading to loss of insulation or flight.     * Bottom-Dwellers: Sinking oil components can suffocate or poison organisms on the ocean floor.     * Economic Consequences: Damage to fishing and tourism industries; oil in mangroves or salt marshes can kill grasses, leading to coastline erosion.     * Cleanup Methods:         * Booms: Floating barriers to contain surface spread.         * Vacuums/Skimmers: Siphoning oil from the surface.         * Physical Removal: Using towels, soaps, and shovels on beaches.         * Chemical Dispersants: Chemicals used to break up oil so it sinks (may be harmful to bottom-dwellers).         * Burning: Igniting oil directly off the water surface.

Endocrine Disruptors and Heavy Metals (8.3)

• Endocrine Disruptors:     * Mechanism: These chemicals bind to cellular receptors meant for hormones, either blocking the signal or amplifying its effect.     * Atrazine: A broad-spectrum herbicide that can contaminate groundwater. In male frogs, it binds to receptors that convert estrogen into testosterone, leading to low sperm counts or feminization (egg development in testes).     * DDT: A phased-out insecticide that persists in the environment.     * Phthalates: Used in plastics and cosmetics; enter water via dumping, trash, or landfill leaching.     * Human Medications: Pass through urine into sewage or are flushed, disrupting animal hormones.

• Heavy Metals:     * Mercury ($Hg$):         * Sources: Coal combustion, trash incineration, medical waste burning, and cement production (heating limestone).         * Methylmercury: Bacteria in water convert elemental mercury into highly toxic methylmercury, a neurotoxicant that damages the central nervous system.         * Effects: Inhibits estrogen and insulin; acts as a teratogen (harmful to fetuses).     * Arsenic: Naturally occurring in rocks; worsens with mining. Anthropogenic sources include old pesticides and wood treatment chemicals. It is carcinogenic (lungs, bladder, kidneys).     * Lead ($Pb$):         * Sources: Old paint, old water pipes, and vehicle exhaust (pre-$1970s$ phase-out).         * Effects: Neurotoxicant that damages the central nervous system, especially in children.     * Coal Ash: A significant source of mercury, lead, and arsenic. It is stored in ponds that can leach into groundwater or overflow into surface waters.

Watersheds and Human Impact (4.6 & 8.4)

• Watershed Characteristics:     * Definition: All land that drains into a specific body of water, divided by ridges.     * Factors: More vegetation increases infiltration and groundwater recharge. Greater slopes increase runoff velocity and erosion. Soil permeability determines the balance between runoff and infiltration.     * Chesapeake Bay Case Study: A six-state region draining into an estuary. Provides ecosystem services like tourism, water filtration, habitats for fish/crabs, and storm protection.

• Wetlands and Mangroves:     * Wetlands: Areas submerged/saturated for part of the year with emergent plants (cattails, reeds).         * Provisioning: Habitat for foods.         * Regulating: Groundwater recharge, flood absorption, and $CO_2$ sequestration.     * Mangroves: Specifically valued for wood, livelihoods ($120 ext{ million}$ people nearby), and massive carbon storage ($3 ext{ to } 5 imes$ higher than tropical upland forests).     * Economic Value: Mangrove ecosystem services are worth between $US ext{\$} 33,000$ and $US ext{\$} 57,000$ per hectare per year.     * Threats: Commercial development (filling/draining), dam construction (restricting water/sediment), overfishing, and pollutants.

Eutrophication (8.5)

• The Process:     1. Extra input of Nitrates ($N$) and Phosphates ($P$) (limiting nutrients).     2. Algal Bloom: Rapid growth covers the surface, blocking sunlight.     3. Die-off: Plants below surface and algae eventually die.     4. Decomposition: Bacteria break down dead organic matter via aerobic respiration, using up Dissolved Oxygen ($DO$).     5. Hypoxia: Low $DO$ leads to a "dead zone."     * Positive Feedback Loop: Less $DO$ leads to more dead organisms, which leads to more decomposition, further lowering $DO$.

• Waterway Classifications:     * Oligotrophic: Low nutrient levels, stable algae, and high $DO$.     * Eutrophic: High nutrient levels, algal blooms, and low $DO$.     * Natural Succession: Ponds shift from oligotrophic to mesotrophic to eutrophic over time due to sediment/nutrient buildup.     * Cultural Eutrophication: Human-caused nutrient pollution from sewage treatment, CAFOs, and synthetic fertilizers.

Thermal Pollution (8.6)

• Physical Principles:     * There is an inverse relationship between water temperature and oxygen solubility. As water temperature increases, $DO$ decreases.     * Thermal Shock: Heat increases the respiration rate of aquatic organisms while oxygen levels are simultaneously dropping, potentially leading to suffocation.

• Sources:     * Power plants (especially nuclear) use cool water to condense steam back into water.     * Manufacturing (steel and paper mills) uses water to cool machinery.     * Urban stormwater runoff heating up on blacktop/asphalt.

• Solution: Cooling Towers or cooling ponds are used to dissipate heat before returning water to the environment.

Persistent Organic Pollutants - POPs (8.7)

• Properties:     * Persistent: Do not easily break down because they are synthetic and carbon-based.     * Fat-Soluble: They accumulate in fatty tissues (bioaccumulation) rather than being excreted in urine.     * Transport: POPs travel long distances via wind and water.

• Examples:     * DDT: Insecticide.     * PCBs: From industrial wastewater; toxic to fish.     * PBDEs: Fire-proofing chemicals.     * BPA and Phthalates: Plastic additives.     * Dioxins: Byproducts of fertilizer production and biomass/waste combustion. $90 ext{ percent}$ of human exposure comes from animal fats.     * Perchlorates: From rockets and fireworks; remains in soil and leaches into groundwater.

Bioaccumulation and Biomagnification (8.8)

• Bioaccumulation: The absorption and concentration of compounds (especially fat-soluble ones like POPs and methylmercury) in the cells and fat tissues of a single organism over its lifetime.

• Biomagnification: The increase in concentration of substances per unit of body tissue at successively higher trophic levels.     * The 10% Rule: Because only $10 ext{ percent}$ of energy is transferred up, predators must eat massive amounts of biomass, concentrating all the toxins from those prey.

• Case Studies:     * DDT and Birds: Caused eggshell thinning in predatory birds like eagles and osprey. This led to the passage of the Endangered Species Act (1973).     * Methylmercury: Biomagnifies in tuna, sharks, and whales. It is a neurotoxicant damaging the central nervous system.

• Questions & Discussion

• Practice FRQ 8.1: Describe the difference between point and nonpoint pollution. Identify sources for $NO_x$.     * Draft Answer: Point source is identifiable (smokestack); nonpoint is diffused (urban runoff). A point source of $NO_x$ is a coal power plant; a nonpoint source is the collective exhaust from all cars in a city.

• Practice FRQ 8.2 (Math): ANWR contains $10 ext{ billion}$ barrels of oil. US uses $20 ext{ million}$ barrels/day. How many days of supply?     * Calculation: $\frac{10,000,000,000 ext{ barrels}}{20,000,000 ext{ barrels/day}} = 500 ext{ days}$.

• Practice FRQ 8.3: Identify a toxic metal other than mercury.     * Draft Answer: Lead ($Pb$). It is introduced via old water pipes or lead-based paint.