Pollution

A. Classification of Pollutants:

• Biodegradable Pollutants: Substances that can be naturally decomposed and recycled by biological microorganisms (bacteria/fungi) over time without causing long-term harm (e.g., domestic sewage, animal dung, paper, vegetable peelings).
• Non-Biodegradable Pollutants: Synthetic materials that cannot be broken down by biological processes; persist in the environment for centuries and bioaccumulate / biomagnify up the food chain (e.g., Plastics, DDT, Polythene bags, Lead, Mercury, Arsenic).

B. Major Types of Pollution:

1. Air Pollution:
   • Gaseous Pollutants: Carbon Monoxide ($CO$, highly toxic, combines with blood hemoglobin to form carboxyhemoglobin, suffocating tissues), Sulphur Dioxide ($SO_2$), Nitrogen Oxides ($NO_x$), and $PM_{2.5} / PM_{10}$ particulate soot.
   • Photochemical Smog: Smoke + Fog + Sunlight interacting with hydrocarbons and $NO_x$, causing severe respiratory distress and asthma.
2. Water Pollution & Eutrophication:
   • Agricultural runoff carrying phosphate and nitrate fertilizers washes into water bodies.
   • Eutrophication: Nutrients cause explosive growth of algae (Algal Bloom). When the thick layer of algae dies, aerobic decomposer bacteria multiply exponentially, consuming almost all Dissolved Oxygen ($DO$). This leads to a massive surge in Biological Oxygen Demand ($BOD$), suffocating fish and aquatic organisms to death.
3. Radiation Pollution:
   • Caused by nuclear power plants, weapon testing, uranium mining, and improper radioactive waste disposal. High-energy ionizing rays cause chromosome damage, leukemia, and birth defects.
4. Noise Pollution:
   • Sounds exceeding $85\text{ decibels (dB)}$ cause permanent hearing damage, hypertension, stress, and insomnia.

A. Acid Rain:

Formed when combustion of fossil fuels in power plants and vehicles releases Sulphur Dioxide ($SO_2$) and Nitrogen Oxides ($NO_x$) into the atmosphere. These gases dissolve in atmospheric cloud water droplets to form strong acids:

• Precipitates as rain or snow with a $pH < 5.6$.
• Stone Cancer: Acid rain chemically reacts with marble/limestone monuments ($CaCO_3$), converting it into powdery gypsum ($CaSO_4$), visibly corroding historical structures like the Taj Mahal in Agra: $$\text{CaCO}_3 + \text{H}_2\text{SO}_4 \to \text{CaSO}_4 + \text{H}_2\text{O} + \text{CO}_2$$
• Acidifies lakes and soils, killing fish eggs and leaching toxic aluminium into water reserves.

B. The Greenhouse Effect & Global Warming:

• Mechanism: Greenhouse gases ($CO_2, CH_4$ / Methane, $N_2O$, CFCs, Water vapor) allow incoming short-wave solar radiation to pass through, but trap outgoing long-wave terrestrial infrared radiation, warming the lower troposphere.
• Excessive burning of fossil fuels and deforestation has amplified this effect, causing Global Warming: melting Himalayan and polar glaciers, thermal expansion of oceans, rising sea levels, and extreme weather events.

C. Ozone Layer Depletion:

• Caused by man-made Chlorofluorocarbons (CFCs) used in refrigerants, air conditioners, and aerosol sprays.
• Solar UV radiation breaks down CFCs, releasing active Chlorine atoms ($Cl^\bullet$). A single chlorine atom catalytically destroys up to $100,000$ ozone ($O_3$) molecules: $$\text{CFCl}_3 \xrightarrow{\text{UV}} \text{CFCl}_2 + \text{Cl}^\bullet$$ $$\text{Cl}^\bullet + \text{O}_3 \to \text{ClO} + \text{O}_2$$
• Created an "Ozone Hole" over Antarctica, allowing dangerous UV rays to reach the surface. Phased out globally under the Montreal Protocol (1987).

A. The 3Rs Hierarchy:

1. Reduce: Minimizing waste generation at source by consuming less, avoiding single-use disposable plastics, and using durable goods.
2. Reuse: Using items multiple times instead of discarding them (e.g., refilling glass bottles, using cloth shopping bags).
3. Recycle: Collecting, sorting, and reprocessing discarded waste materials into new useful products (e.g., recycling scrap paper, aluminum cans, glass, and plastic polymers).

B. Safe Waste Disposal Techniques:

• Sanitary Landfills: Deep engineered pits lined with impermeable plastic liners and clay to prevent toxic leachate from seeping into groundwater; waste is spread in thin layers, compacted, and covered with soil daily.
• Composting: Aerobic biological decomposition of biodegradable wet organic waste into nutrient-rich organic manure for agriculture.
• Segregation at Source: Separating waste into Green Bins (Wet Biodegradable) and Blue Bins (Dry Recyclable).