Unit 8: Aquatic and Terrestrial Pollution
AP Environmental Science: 51 practice questions with detailed explanations.
Unit Study Guide
Executive Summary
Unit 8 follows pollution into water and land: sources, effects on ecosystems and health, and how societies clean up.
Point vs nonpoint
Point sources are identifiable pipes (factory outfall); nonpoint sources are diffuse (fertilizer runoff, urban stormwater). Nonpoint is harder to regulate and is now the leading water-quality problem.
Water pollution
Nutrients (N, P) cause eutrophication — algal blooms, then oxygen-depleted dead zones. Pathogens (fecal coliform) sicken swimmers. Heavy metals (mercury, lead, arsenic) and endocrine disruptors (BPA, phthalates, atrazine) accumulate in food chains. Oil spills coat and poison wildlife.
Waste
Municipal solid waste goes to landfills (lined, capped, methane-captured) or incinerators. The waste hierarchy: reduce, reuse, recycle, compost — source reduction beats recycling. E-waste is the fastest-growing stream, often exported to LDCs.
Sewage treatment
Primary: physical settling. Secondary: bacteria digest organics. Tertiary: nutrient removal and disinfection. Treated effluent still adds nutrients; septic systems treat on-site.
Health and dose
LD50 measures acute toxicity — the dose lethal to 50% of test animals; lower LD50 = more toxic. Bioaccumulation builds within an organism; biomagnification multiplies up the food chain (mercury in tuna). Cholera, dysentery, and malaria spread with poor sanitation.
Exam traps
Bioaccumulation is within one organism; biomagnification is across trophic levels — don't confuse them. Eutrophication starts with nutrient ADDITION, not toxicity. Lower LD50 means more toxic. Landfills capture methane but still leak leachate.