Aquatic and Terrestrial Pollution

Sources of Pollution

• Pollution sources can be classified as point sources, which discharge pollutants from a single identifiable location, or nonpoint sources, which come from diffuse, widespread areas. APES emphasizes that point sources, like wastewater treatment plants or factory discharge pipes, are easier to regulate under laws such as the Clean Water Act, while nonpoint sources, like agricultural runoff, are harder to control due to their diffuse nature.
• In aquatic systems, agricultural activities are one of the leading contributors to pollution, introducing nutrients like nitrogen and phosphorus that cause eutrophication. Industrial facilities, mining operations, and urban stormwater runoff also release heavy metals, oils, and sediments into waterways, impacting both water quality and aquatic biodiversity.
• Atmospheric deposition is another major source, where pollutants such as mercury or nitrogen oxides travel through the air before settling into water or land ecosystems. This creates a link between Units 7 and 8, as air pollution directly contributes to aquatic contamination.
• Marine pollution often stems from both land-based and ocean-based activities, such as plastic waste entering from rivers and illegal dumping from ships. These pollutants can persist for decades, disrupting marine food webs and threatening human food security through contaminated seafood.
• Understanding pollution sources is critical for designing mitigation strategies. APES students should recognize that tackling pollution requires a combination of local, national, and global policies, along with technological solutions like green infrastructure to manage runoff.

Human Impact on Ecosystems

• Human activities often alter ecosystems in ways that reduce biodiversity and disrupt ecological balance. Deforestation, overfishing, mining, and urbanization can fragment habitats, making it difficult for species to survive and reproduce. APES connects these impacts to ecosystem services, showing how human well-being is tied to ecological health.
• Pollution can cause bioaccumulation and biomagnification, where toxins such as mercury and PCBs build up in organisms and become more concentrated at higher trophic levels. This poses significant risks to apex predators, including humans who consume contaminated fish and meat.
• Invasive species, often introduced accidentally or intentionally by humans, can outcompete native species and alter food webs. Pollution can worsen the problem by stressing native populations, making ecosystems more vulnerable to invasion.
• Climate change, driven by human greenhouse gas emissions, interacts with pollution to amplify ecosystem damage. For example, warmer temperatures can intensify algal blooms caused by nutrient pollution, creating hypoxic zones that devastate aquatic life.
• Sustainable resource management, including marine protected areas, habitat restoration, and pollution reduction policies, is essential for reversing human-caused ecosystem decline. APES stresses evaluating both ecological and economic factors when creating these strategies.

Thermal Pollution

• Thermal pollution occurs when human activities raise water temperatures, often from industrial processes such as power plants discharging heated water into rivers or lakes. This temperature change can lower dissolved oxygen levels, making it harder for aquatic organisms to survive.
• Species adapted to narrow temperature ranges are particularly vulnerable, as even small increases can affect metabolic rates, reproduction, and migration patterns. APES connects this to biodiversity concepts, as thermal pollution can shift competitive balances in ecosystems.
• Thermal pollution can also increase the toxicity of certain pollutants, as chemical reaction rates often rise with temperature. This can exacerbate the effects of nutrient pollution and heavy metal contamination.
• Climate change and thermal pollution can interact, making water bodies even warmer and increasing the risk of large-scale fish kills. This makes addressing thermal pollution more urgent in a warming world.
• Mitigation strategies include cooling towers, artificial wetlands, and shifting industrial operations to closed-loop cooling systems that recycle water rather than discharge it into natural bodies of water.

Aquatic and Terrestrial Pollution (Continued)

Solid Waste Disposal and Waste Reduction Methods

• Solid waste disposal includes landfills, incineration, and open dumping, each with its environmental trade-offs. Landfills are the most common method in the U.S., but they can produce methane emissions and leachate that contaminates groundwater if not managed properly.
• Incineration reduces the volume of waste but releases air pollutants such as dioxins and heavy metals unless advanced filters are used. While energy recovery incinerators can produce electricity, the trade-off is increased air emissions that require strict regulation.
• Open dumping, still prevalent in many developing countries, poses severe environmental and health hazards. These unregulated sites allow hazardous materials to leach into soil and water and attract disease-carrying pests.
• Waste reduction methods in APES include reducing consumption, reusing materials, recycling, and composting organic waste. Recycling conserves raw materials and reduces energy use, but contamination in recycling streams remains a major challenge.
• APES emphasizes integrated waste management strategies, which combine multiple disposal and reduction methods tailored to local conditions to minimize environmental harm while meeting societal needs.

Pollution and Human Health

• Pollution affects human health through exposure to contaminants in air, water, soil, and food. Chronic exposure to low levels of pollutants such as lead, mercury, or particulate matter can cause long-term health problems including neurological damage and respiratory disease.
• Acute exposure events, such as chemical spills or industrial accidents, can lead to immediate, severe health effects or fatalities. APES connects these risks to environmental justice, as marginalized communities often face disproportionate exposure to pollution sources.
• Biomagnification of toxins in the food chain increases human health risks, particularly from consuming high-trophic-level species such as tuna or swordfish, which accumulate heavy metals like mercury.
• Pollution-related health issues often strain public health systems, especially in regions without adequate environmental regulation or healthcare infrastructure. This highlights the intersection of environmental science and public policy.
• Preventing pollution through stricter emissions controls, sustainable agriculture practices, and cleaner energy sources is more effective and less costly than treating pollution-related diseases after exposure has occurred.

Pathogens and Infectious Diseases

• Pathogens, including bacteria, viruses, and parasites, can spread through contaminated water, food, air, or direct contact with infected organisms. APES emphasizes how environmental factors influence pathogen spread, such as poor sanitation or warming climates expanding vector habitats.
• Waterborne diseases like cholera and dysentery remain major global health issues, especially in areas lacking access to safe drinking water. Agricultural runoff and sewage discharge into water bodies are common sources of contamination.
• Vector-borne diseases, such as malaria and dengue fever, are influenced by ecosystem changes and climate patterns. Deforestation, urbanization, and warming temperatures can increase human exposure to disease-carrying insects like mosquitoes.
• Pathogen spread is often linked to pollution events, such as flooding that overwhelms sewage systems or hurricanes that disperse contaminated water across large areas. APES ties these to natural disaster management and infrastructure planning.
• Prevention strategies include improving sanitation infrastructure, controlling vectors through integrated pest management, and ensuring reliable access to clean water. APES stresses that reducing environmental degradation often directly reduces disease risks.

Common Misconceptions

Misconceptions About Solid Waste Disposal

• Students often assume that landfills are sealed perfectly and pose no environmental risk. In reality, even modern sanitary landfills can leak methane gas and leachate if not monitored and maintained over decades, making them a long-term environmental management challenge.
• Another misconception is that recycling automatically results in significant environmental savings. In APES, we emphasize that recycling benefits depend on material type, contamination levels, and transportation energy costs; sometimes, recycling certain materials can use more energy than producing them new.

Misconceptions About Pollution and Human Health

• Some students incorrectly believe that only high-dose or immediate exposure to pollutants is dangerous. APES testing often covers chronic low-level exposure, which can cause subtle but serious health effects over time, such as reduced lung capacity or developmental delays.
• There is also a tendency to overlook the role of environmental justice in pollution impacts. On the AP Exam, many questions require recognizing that certain communities face disproportionately higher exposure due to proximity to industrial facilities or lack of regulatory enforcement.

Misconceptions About Pathogens and Infectious Diseases

• Students sometimes think that infectious disease spread is only a public health issue, not an environmental one. In APES, the exam emphasizes how water quality, sanitation systems, land use changes, and climate patterns are environmental drivers of disease outbreaks.
• Another common misunderstanding is assuming that improving medical treatment alone will stop disease spread. APES stresses that controlling environmental factors — like eliminating standing water to reduce mosquito breeding — is often more effective and sustainable for long-term prevention.