Environmental Science Chapter: Atmosphere & Pollution

Atmosphere

• Layer of gases surrounding Earth
• Very thin
• Absorbs solar radiation
• Burns up meteors
• Transports and recycles water

Atmospheric Layers

• Troposphere (10-15 km): Air we breathe, weather, warmed by the sun
• Stratosphere (15-48 km): Temperature increases, contains ozone, airplanes fly here
• Mesosphere (48-90 km): Temperature decreases
• Thermosphere (90-500 km): Very thin air

Air Pollutants

• Particulate matter/aerosols: Size matters, affects how long it stays in the atmosphere, how it scatters light, and how it is deposited in lungs
• EPA monitors 190 air pollutants
• Primary pollutants: Released directly into the air (CO, SO2, CFCs)
• Secondary pollutants: Formed through chemical reactions (NO + O2 in sunlight = O3)

Air Pollution Sources

• Point source: Stationary, localized sources (factory smoke stack)
• Non-point source: Diffuse sources, small amounts (automobiles, agriculture, fireplaces)

Ozone

• Troposphere: Harmful
• Stratosphere: Beneficial, protects from UV radiation
• Ozone layer: 12 parts per million in lower stratosphere, enough to absorb UVA light and protect
• Ozone depletion: Detected over Antarctica in 1985, 40-60% decline over a decade
• Cause: Human-made molecules (CFCs) that persist in the stratosphere and split oxygen atoms off ozone (O3) to form oxygen (O2)

Acid Deposition

• Killing N. European forests in the 1950s, reducing biodiversity of lakes and streams
• Very acidic lakes near industrial centers in Europe in the 1960s and 1970s
• Caused by reaction of pollutants (SO2 + NO2)
• Sources: Coal-fired power plants, metal smelters, power plants, vehicle exhaust
• Effects: Nutrient leaching from soil, aluminum becomes available and taken in by plants (damage to roots)

Heavy Metals

• Mercury: 1/3 natural, 1/3 human activity, 1/3 re-emitted
• Lead: Added to gasoline in 1923 to increase power efficiency, catalytic converters required in 1975, leaded fuel banned in 1980

Smog

• Industrial: CO, SO2, soot
• Photochemical: Exhaust + Sun = smog

International Air Pollution Policy

• Geneva Convention on Long-Range Transboundary Air Pollution (1983): Abate acidification, ground-level ozone
• Montreal Protocol on Substances That Deplete the Ozone Layer (1987): Phase out ozone-depleting substances

Earth's Water

• Over 10% of Earth's surface is covered in water
• Same amount of water evaporates as precipitates
• 3 ways precipitation returns to the atmosphere: Evapotranspiration, rivers and streams, groundwater

Hydrologic (Water) Cycle

• Continuous movement of water between Earth's atmosphere, hydrosphere, lithosphere, and biosphere
• Powered by the sun and gravity
• 278,000 cubic miles of water enter the atmosphere daily
• Basic steps: Condensation, precipitation, runoff or infiltration, evaporation

Transpiration

• Process by which plants release water into the atmosphere as water vapor

Evaporation

• Process by which water turns into water vapor

Precipitation Runoff

• Watershed: Area of land being drained by runoff

Infiltration

• Non-renewable resource, we are using it faster than it can recharge
• Gets to air by evaporation/transpiration

Water Pollution

• Point source pollution: Single identifiable source of pollution
• Non-point source pollution: No identifiable source of pollutants

Water Quality

• Clean Water Act: Impaired waters exceed total maximum daily load
• Pathogens: Sewage, septic, stormwater flow
• Nutrients: Agriculture
• Metals: Industry

Effects of Water Pollution on Ecosystems

• Headwaters to the sea: Biodiversity loss, endangered mussels
• Lakes: Eutrophication

Eutriphication

• Excess nutrients (N, P)
• Rapid growth of algae followed by death
• Decomposition leads to low oxygen and biodiversity reduction

Water Pollution Impacts on Ecosystems

• Estuaries: Areas where freshwater meets saltwater, dead zones due to pollution
• Oceans: Dead zones, coral reef decline

Ocean Acidification

• Increasing CO2 inputs from atmosphere, 1/4 absorbed by oceans
• Decreasing pH
• Reduced calcification, slowing coral reef growth

Ocean Garbage

• Plastics are a big problem
• Great Pacific Garbage Patch: > 5 million square miles

Harmful Plastic

• Cannot biodegrade
• Breaks down into smaller pieces
• Toxic chemicals leach out
• Endangers wildlife: mistaking for food, feeding to young, entanglement

Water Management and Conservation

• Dams and diversions: Limit flooding, store water, produce electricity
• Channelization: Widens rivers and streams to make them less prone to flooding
• Levees: Hold back water

Managing and Conserving Water in Agriculture

• 70% of water for human use is for irrigation
• Most evaporates from fields
• Irrigation efficiency: Percentage of water used by crop plants
• Ways to increase irrigation efficiency: Surge irrigation, aerial sprinklers, drip irrigation

Desalination

• Removing salts from water
• Distillation: Boiling water, condensing steam
• Reverse Osmosis: Filtering through selective membrane

Water Pricing

• Agriculture in CA uses >80% of water, farmers pay 5-20% of supply cost, little incentive to invest in conserving technologies
• Residential use: Flat monthly rate, no price change
• Water meters: Changes pricing based on exact usage
• Graduated pricing: Changes pricing based on usage tiers

Agriculture

• Practice of cultivating soil, producing crops, and raising livestock for human use and consumption
• 38% of Earth's surface is used for agriculture
• Croplands and rangelands depend on healthy soil

The Green Revolution

• 1940s-1960s effort to eliminate hunger
• Improved crop performance through use of chemical pesticides, fertilizers, modern irrigation and equipment, and high-yield varieties (HYTs)
• Results: 1000% increase in global food production, 20% reduction in famine
• Trade-offs: Chemical dependence on fertilizers, toxicity threats from pesticides, pest resistance

Agroecosystems

• Humans < 1% of Earth's animal biomass
• Converted 1/3 of ice-free Earth to agriculture
• Production of a few species
• Depend on natural cycles

Energetics

• Agroecosystem includes crops/domestic animals, abiotic and biotic environment
• Producers: Plants
• Consumers: Animals
• Short food chain
• Trophic level efficiency: Fraction of consumed food energy stored as biomass

Agriculture's Environmental Impacts

• Depletes water supply
• Fertilizer and chemical residues carried into waters and streams, leading to eutrophication and mortality of aquatic organisms
• Soil salinization where evaporation rates are high
• Industrialized livestock operations (CAFOs) lead to waste, land use, deforestation, overgrazing, disease transmission (bird and swine flu, E. coli)

Japanese Rice Farmer Takao Furuno

• Avoids pesticides and herbicides
• Works towards an ecology of eating

Food Footprint

• Component of ecological footprint
• Top of food chain
• Land area to produce food
• Exposure to toxins
• Organic food: Limits synthetic fertilizers and pesticides, smaller ecological footprint

Hidden Water

• Water used to produce food

Reduce Food Waste

• 40% of food grown in the US doesn't get eaten
• Trayless dining

Explore the layers of the atmosphere, their functions, and the various air pollutants affecting our environment. This quiz covers essential concepts such as point and non-point sources of pollution, and the role of ozone in different atmospheric layers. Test your knowledge of this critical subject in environmental science!