AP Environmental Science: Pollution, Climate and Nutrient Cycles

Primary: emitted directly (CO, SO₂, NOx, particulate matter). Secondary: formed in the air from primary pollutants (ground-level ozone, sulfuric and nitric acid).

Carbon monoxide, lead, nitrogen dioxide, ozone, particulate matter (PM10 and PM2.5), sulfur dioxide

NOx and VOCs (mostly from vehicles) react in sunlight to form ground-level ozone and other oxidants. It peaks on hot, sunny afternoons.

A layer of warm air sits above cooler surface air, trapping pollutants near the ground.

Fine particles (2.5 micrometers or smaller) reach deep into the lungs and the bloodstream, causing respiratory and cardiovascular disease.

SO₂ (mainly from burning coal) and NOx (vehicles, power plants) react with water in the air to form sulfuric and nitric acids.

Lowers the pH of lakes and soils, leaches nutrients, releases toxic aluminum, harms forests and aquatic life, and erodes limestone and marble buildings.

Stratospheric ozone absorbs harmful UV radiation (good). Tropospheric (ground-level) ozone is a lung-damaging secondary pollutant in smog (bad).

CFCs and other halogenated gases: UV light frees chlorine atoms that destroy ozone in a chain reaction. The Montreal Protocol (1987) phased them out.

Radon (the second leading cause of lung cancer after smoking), carbon monoxide, asbestos, formaldehyde, secondhand smoke, mold.

Sunlight warms Earth's surface, which gives off infrared radiation. Greenhouse gases absorb and re-emit that infrared energy, warming the lower atmosphere.

Water vapor, carbon dioxide, methane, nitrous oxide and fluorinated gases (CFCs, HFCs).

CO₂ = 1 Methane ≈ 25–30 Nitrous oxide ≈ 265–300

Sea level rise (thermal expansion and melting ice) More extreme heat, drought and storms Ocean acidification and coral bleaching Species range shifts Thawing permafrost releasing methane

The ocean absorbs CO₂, forming carbonic acid and lowering pH. This reduces the carbonate that corals and shellfish need to build shells and skeletons.

Point source: a single identifiable source (factory pipe, sewage outfall). Nonpoint source: diffuse sources (farm runoff, urban stormwater); harder to regulate.

Excess nitrogen and phosphorus (fertilizer runoff, sewage) cause algal blooms; when the algae die, decomposers use up dissolved oxygen, creating hypoxic dead zones.

The amount of dissolved oxygen microbes use to decompose organic matter in water; high BOD signals pollution and low oxygen.

Species whose presence or absence reflects ecosystem health, e.g. mayfly and stonefly larvae indicate clean streams.

Clean Water Act (1972): regulates pollutant discharges into surface waters. Safe Drinking Water Act (1974): sets standards for public drinking water.

Primary: physical settling of solids. Secondary: bacteria break down organic matter. Tertiary: extra steps that remove nutrients like N and P. Then disinfection (chlorine, UV or ozone).

Bioaccumulation: a toxin builds up in one organism over its lifetime. Biomagnification: the concentration increases at each higher trophic level.

Biomagnified DDT (broken down to DDE) thinned eggshells, which cracked during incubation, causing declines in bald eagles, peregrine falcons and brown pelicans.

Small-scale gold mining and coal burning are the largest human sources. In water, bacteria convert it to methylmercury, which biomagnifies in large predatory fish such as tuna and swordfish.

The dose of a substance that kills 50% of a test population; a lower LD50 means a more toxic substance.

Clay and plastic liners, a leachate collection system, daily soil cover, methane collection and groundwater monitoring wells.

Reduce → reuse → recycle → waste-to-energy → landfill

Fixation: N₂ → NH₃ (bacteria, lightning) Nitrification: NH₄⁺ → NO₂⁻ → NO₃⁻ Assimilation: plants take up NH₄⁺ and NO₃⁻ Ammonification: decomposers return NH₄⁺ Denitrification: NO₃⁻ → N₂

The phosphorus cycle has no gas phase. Phosphorus is released slowly by weathering rock, so little is available to organisms.

The largest stores are sedimentary rock (and fossil fuels) and the deep ocean. Burning fossil fuels moves long-stored carbon into the atmosphere far faster than it is removed.