Environmental Science Fundamentals: Pollution, Resources, and Management

1. Global Concepts & Protocols

Problems and Global Issues

• Resource Depletion: Finite resources, renewable resources, and resource degradation.
• Environmental Pollution: Air, water, and soil pollution, including causes and mitigation methods.
• Global Climate Change (全球气候变化)
  • Key Substances (GHGs): Primarily $\text{CO}_2$ (Carbon Dioxide), $\text{CH}_4$ (Methane), $\text{N}_2\text{O}$, and CFCs.
  • Mechanism (Greenhouse Effect): Solar shortwave radiation enters Earth $\rightarrow$ Ground heats up and emits longwave infrared radiation $\rightarrow$ GHGs absorb this heat in the atmosphere $\rightarrow$ Global warming.
  • Consequences: Sea level rise, extreme weather, loss of biodiversity.
  • Corresponding Conventions: Kyoto Protocol & Paris Agreement.
• Ozone Layer Depletion
  • Key Substances (ODS): CFCs (Chlorofluorocarbons - used in refrigerators/sprays) and Halons (fire extinguishers).
  • Mechanism: CFCs reach the stratosphere $\rightarrow$ UV light breaks down CFCs, releasing Chlorine (Cl) atoms $\rightarrow$ Cl atoms rapidly destroy $\text{O}_3$ molecules ($\text{Cl} + \text{O}_3 \rightarrow \text{ClO} + \text{O}_2$).
  • Consequences: Increased UV radiation reaching the ground, leading to skin cancer and cataracts.
  • Corresponding Convention: Montreal Protocol.
• Acid Rain
  • Key Substances: Acidic Gases ($\text{SO}_2$ from coal power plants; $\text{NO}_x$ from vehicles/high-temperature combustion).
  • Mechanism: Gases react with atmospheric water ($\text{H}_2\text{O}$) $\rightarrow$ Formation of strong acids ($\text{H}_2\text{SO}_4$ and $\text{HNO}_3$) $\rightarrow$ Precipitation.
  • Consequences: Corrosion of buildings, acidification of lakes, damage to forests.
• Ecological Overshoot: Consumption exceeds Earth's biocapacity (regeneration rate).
• Ecological Tipping Point: The threshold beyond which an ecosystem cannot cope with environmental changes (e.g., pollution, climate change).
• Reducing Ecological Footprint (Suggestions):
  • Transportation: Use public transport more often.
  • Diet: Reduce meat consumption (especially beef); eat locally and seasonally (reduce carbon mileage).
  • Energy/Waste: Save electricity (turn off lights/AC when not in use) and implement the 3R principle (Reduce, Reuse, Recycle), such as reducing disposable plastics.
• Tragedy of the Commons: Individuals acting in self-interest deplete shared resources (e.g., oceans, air), causing collective ruin. Solution: Privatization or Regulation.
• IPAT Model: Impact = Population $\times$ Affluence $\times$ Technology.

Key Protocols (Must Memorize)

• Montreal Protocol: Targets Ozone Depletion. Goal: Phase out CFCs.
• Kyoto Protocol: Targets Climate Change. Goal: Reduce GHG emissions.
• Paris Agreement: Limit global warming to well below $2^{\circ}\text{C}$ (aim for $1.5^{\circ}\text{C}$).

Environmental Management

• Environmental Management System (ISO 14001): P - Plan $\rightarrow$ D - Do $\rightarrow$ C - Check $\rightarrow$ A - Act (Continuous Improvement).

2. Air Pollution

Pollutant Classification

• Primary Pollutants: Emitted directly from sources (e.g., $\text{CO}$, $\text{SO}_2$, $\text{NO}$, PM).
• Secondary Pollutants: Formed by chemical reactions in the atmosphere.
  • Ozone ($\text{O}_3$): Formed by $\text{NO}_x + \text{VOCs} + \text{Sunlight}$ (Photochemical smog).
  • Photochemical Smog: Contrast with Industrial Smog (London-type: $\text{SO}_2 + \text{PM}$).
  • Acid Rain: $\text{SO}_2/\text{NO}_2$ react with water $\rightarrow \text{H}_2\text{SO}_4/\text{HNO}_3$.

Criteria Pollutants

• Nitrogen Dioxide ($\text{NO}_2$): Reddish-brown gas from vehicle exhaust and power plants. Key cause of acid rain and photochemical smog.
• Carbon Monoxide (CO): Colorless, odorless gas from incomplete fuel burning. Binds strongly with hemoglobin, causing oxygen shortage.
• Sulfur Dioxide ($\text{SO}_2$): Mainly from coal burning. Causes acid rain, damages buildings, and harms the respiratory system.
• Particulate Matter (PM10, PM2.5): Tiny particles. PM2.5 is more harmful as it can enter the lungs and blood.
• Lead (Pb): Mainly from old leaded gasoline and paint. A neurotoxin harmful to children’s brain development.
• Ozone ($\text{O}_3$): Ground-level ozone. A strong oxidant that irritates the lungs.

Effects and Monitoring

• Air Quality Monitoring: Involves monitoring stations, instruments, and the Air Quality Index (AQI).
• Photochemical Smog: A typical brown smog in cities.
  • Formation Formula (to memorize): $\text{NO}_x + \text{VOCs} + \text{sunlight} \rightarrow \text{Ozone} (\text{O}_3) + \text{smog}$. This explains why ozone pollution peaks in summer.
• Indoor Air Pollution: Often more serious than outdoor pollution.
  • Radon: Radioactive, odorless gas from soil/granite. Second leading cause of lung cancer after smoking.
  • Sick Building Syndrome: People feel ill indoors but recover after leaving the building.

Particulate Control Methods (去除颗粒物方法)

• Cyclones / Mechanical Collectors (旋风分离器):
  • Principle: Uses centrifugal force to throw heavy particles to the wall.
  • Features: Cheap and simple, but only removes large particles; ineffective for PM2.5.
• Electrostatic Precipitators (ESP) (静电除尘器):
  • Principle: Particles are charged by high voltage and attracted to oppositely charged plates.
  • Features: Very high efficiency (over 99%); widely used in power plants; can remove fine particles.
• Baghouses (袋式除尘器):
  • Principle: Dirty air passes through fabric filters, trapping dust.
  • Features: Highest efficiency (about 99.9%), but filters can be damaged by high temperature or moisture.

B. Gaseous Pollutant Control (去除气体污染物)

• Flue Gas Desulphurization (FGD):
  • Target: Remove $\text{SO}_2$.
  • Principle (Wet scrubber): Spray limestone slurry ($\text{CaCO}_3$) into flue gas.
  • Reaction: $\text{SO}_2 + \text{limestone} \rightarrow \text{gypsum} (\text{CaSO}_4)$. Gypsum can be reused.
• Catalytic Converters (催化转换器):
  • Target: Used in car exhausts to treat $\text{NO}_x$, $\text{CO}$, and $\text{HC}$.
  • Principle: Use catalysts (platinum, palladium, rhodium) to convert harmful gases into harmless $\text{N}_2$, $\text{CO}_2$, and $\text{H}_2\text{O}$.

3. Solid Waste

Waste Management Principles

• Waste Hierarchy: Reduce $>$ Reuse $>$ Recycle $>$ Treatment $>$ Disposal.
• Source Reduction: Design, manufacturing, and lifestyle changes.

Landfill By-products and Open Dumps

• Leachate: Toxic liquid formed by rainwater filtering through waste. Control: Impermeable Liners + Collection System.
• Landfill Gas: Methane ($\text{CH}_4$) + $\text{CO}_2$ from anaerobic decomposition. Control: Collection for energy or Flaring (to prevent explosion).
• Daily Cover: A layer of soil applied after waste disposal to prevent smell, pests/rats, and fires.

Treatment Methods

• Incineration:
  • Pros: Volume Reduction, Waste-to-Energy.
  • Cons: Air Pollution, Toxic Ash, NIMBY (Not In My Back Yard).
• Composting (堆肥):
  • Definition: Aerobic biological decomposition of organic matter.
  • Requirements: Oxygen, Moisture, and Bacteria.
  • Product: Fertilizer / Soil Conditioner. It is a form of material recycling.
• Recycling: Involves technical difficulties and potential rebound effects.

Hazardous Waste

• Characteristics: Ignitability, Corrosivity, Reactivity, Toxicity.
• Treatment: Neutralization, biodegradation, absorption, etc.
• Disposal: Incineration and land disposal (deep well injection, surface impoundments, landfills).

Radioactive Pollution

• Definition: Radioactive material and harmful ionizing radiation; damages DNA.
• Radioactive Disposal:
  • On-site: Transuranic wastes (require geological isolation); mining/milling waste (require covering); high-level radioactive waste (stored in Spent Fuel Pools, then potentially Dry Casks awaiting Deep Geological Disposal).
  • Off-site (Low-level waste): Compressed, encapsulated, and disposed of via Shallow Land Burial.

4. Water Pollution

Water Resources & Cycle

• Scarcity: Only 2.5% of Earth's water is fresh, and most of that is frozen. Usable fresh water is extremely limited.
• Impact on Cycle (Human Activities):
  • Urbanization: Concrete surfaces prevent infiltration, increasing surface runoff and flood risk.
  • Agriculture and Dams: Alter evaporation rates and natural river flow.

Water Use Classification

• Consumptive Use (消耗性用水): Water is not returned to the source (evaporated or incorporated into products).
  • Examples: Agricultural irrigation (the largest consumer), lawn watering.
  • Agricultural Mitigation: Reduce fertilizer/pesticide use; create buffer zones; improve irrigation efficiency.
• Non-consumptive Use (非消耗性用水): Water is treated and returned to the source (though quality may decrease).
  • Examples: Industrial cooling water, toilet flushing, bathing.
• Virtual Water: The 'hidden' water consumed to produce food or products (e.g., 1kg of beef requires about 15,000 liters).

Sources and Pollutants

• Point Source: Distinct pipe or outfall (e.g., factory, sewage plant). Easy to monitor/regulate.
• Non-point Source: Diffuse runoff (e.g., agricultural fertilizer, urban runoff). Difficult to control.
• Major Pollutants & Effects:
  • Pathogens: Bacteria, viruses causing waterborne diseases (cholera, typhoid).
  • Eutrophication Process:
    1. Excess Nutrients ($ ext{N}, \text{P}$) from fertilizer runoff, detergents, or sewage.
    2. Algae Bloom $\rightarrow$ Sunlight blocked.
    3. Algae die & decompose $\rightarrow$ Bacteria consume Oxygen $\rightarrow$ Hypoxia (Oxygen depletion) $\rightarrow$ Fish Kill.
  • Thermal Pollution: Caused by cooling water from power plants. Increased water temperature lowers Dissolved Oxygen (DO), suffocating fish and accelerating bacterial growth.

Water Quality Indicators

• DO (Dissolved Oxygen): Higher is better; indicates healthy water.
• BOD (Biochemical Oxygen Demand): Represents the oxygen microbes need to decompose organic matter. High BOD means severe organic pollution.

Water Treatment Stages (Sewage Treatment)

• Primary Treatment: Physical process (Screening + Settling) to remove suspended solids.
• Secondary Treatment: Biological process (Use bacteria to break down organic matter).
• Tertiary Treatment: Chemical/Advanced process (Remove nutrients ($ ext{N}, \text{P}$), toxins, viruses).

5. Noise Pollution

Sound Fundamentals

• Definition: Sound is a pressure wave generated by vibrating objects, requiring a medium for propagation.
• Characteristics: Wavelength, frequency, period, speed, amplitude, pressure.
• Units:
  • dB (Decibel): Physical unit; logarithmic scale.
  • dBA (A-weighted Decibel): Measurement scale mimicking human ear sensitivity; used for environmental sound measurement.

Health Effects

• Auditory: TTS (Temporary Threshold Shift) and PTS (Permanent Threshold Shift).
• Non-auditory: Stress, hypertension, sleep disturbance.

Control Strategies

• Source Control: Use quiet equipment (QPME), limit piling hours, use absorbing materials, employ vibration isolators, and lubricate machinery.
• Path Control: Install Noise Barriers, use Enclosures, integrate controls into building design, and increase the distance between the source and the receiver (sound attenuates with distance).
• Worker Protection: Job Rotation, Earplugs.
• Building Protection: Setbacks, Architectural fins, Insulated windows.

Patterns of Noise

• Continuous; Intermittent; Impulsive.

6. Energy Resources

Energy Sources Classification

• Renewable: Naturally replenished (Hydropower, geothermal, biomass, solar, wind).
• Non-renewable: Limited supply (Fossil fuels: coal, oil, gas; Nuclear fuel: uranium).

Hydropower (水能) – Most Mature Renewable Energy

• Principle: Uses the water cycle.
• Energy Conversion (Key): Potential energy $\rightarrow$ Kinetic energy $\rightarrow$ Mechanical power $\rightarrow$ Electricity.
• Technologies:
  • Impoundment (蓄水式): Traditional dams with reservoirs.
  • Pumped Storage (抽水蓄能): Acts like a large battery: pump water uphill during off-peak; release water to generate power during peak.
• Pros: High efficiency, reliable, flexible.
• Cons: Ecosystem damage, land flooding, population relocation.

Solar Energy – Largest Potential

• Key Features:
  • Solar Constant: Solar radiation outside the atmosphere.
  • Variability (变异性): Spatial (stronger near the equator) and Temporal (intermittent due to day/night and weather).
• Technologies:
  • Photovoltaics (PV): Light $\rightarrow$ electricity (photoelectric effect).
  • Solar Thermal (CSP): Light $\rightarrow$ heat $\rightarrow$ mechanical $\rightarrow$ electricity.
• Pros: Abundant, low operating cost, no noise.
• Cons: Intermittent, low energy density, requires large land area.

Wind Energy – Fastest Growing

• Principle: Wind is moving air caused by uneven solar heating.
• Energy Conversion: Kinetic energy of air $\rightarrow$ blade motion $\rightarrow$ electricity.
• Wind Farms (风力发电场): Turbines require spacing due to the wake effect.
• Pros: Low cost, strong offshore potential.
• Cons: Intermittent, noise and visual impact (NIMBY), bird deaths.

Energy Solutions

• Solutions for Intermittency: Energy Storage (Pumped Hydro Storage, Smart Grid & Storage, Thermal Storage), Hybrid Systems, Improved Forecasting.
• Nuclear Energy: Clean (Low Carbon) but Non-renewable (relies on finite Uranium). Major concerns: Radioactive waste and Safety.

7. HK Strategy Bank (Environmental Management Examples)

• Waste Management:
  • Implement the Waste Charging Scheme (Polluter-pays principle).
  • Develop I-PARK (Integrated Waste Management Facilities / Incinerator).
  • Manage WEEE (E-waste recycling) as it contains lead and mercury and cannot be landfilled; enhance recycling infrastructure and education.
• Air Quality:
  • Promote EVs and phase out old vehicles (One-for-One Replacement Scheme).
  • Tighten Fuel and Emission Standards (Install advanced exhaust gas processors).
  • Improve Public Transport & Traffic Management.
  • Require Vessel Fuel Switch at berth (switching from high-$ ext{SO}_2$ Bunker Fuel to Low Sulphur Fuel) and regulate VOCs content.
• Water Management:
  • Use Seawater Flushing to conserve fresh water.
  • Utilize HATS (Harbour Area Treatment Scheme) for chemical primary or secondary treatment before discharge.
  • Implement Tiered Water Pricing & promote Water Saving Devices.
• Noise Control:
  • Use Low-noise Road Surfacing (Porous material absorbs sound).
  • Install Noise Barriers/Enclosures.
  • Improve Urban Planning & Building Design (Positioning noise-insensitive areas facing roads).
• Fossil Fuel Reliance & $\text{CO}_2$ Emissions:
  • Change the fuel mix: Replace Coal with Natural Gas.
  • Develop Renewable Energy (e.g., solar panels utilizing Hong Kong's geography).
  • Increase the import of Nuclear/Zero-carbon Energy.