Chemistry Masterclass: The Science of Sustainability

Phase 1: Advanced Atmospheric Chemistry

The atmosphere is a giant chemical reactor. Even small changes in composition lead to global impacts.

1. The Ozone Cycle (Chapman Cycle)

• Formation: UV light splits $O_2$ into two $O$ atoms, which react with $O_2$ to form $O_3$ (Ozone).
• Depletion: CFCs release Chlorine atoms which acts as a Catalyst. One Cl atom can destroy 1,00,000 ozone molecules.
• Montreal Protocol (1987): International treaty to phase out Ozone-depleting substances.

2. Acid Rain (The pH Logic)

• Normal rain $pH approx 5.6$ (due to $CO_2$).
• Acid rain $pH < 5$ (due to $H_2SO_4$ and $HNO_3$).
• Effect on Heritage: Taj Mahal "Marble Cancer" due to $SO_2$ from Mathura refinery.

Phase 2: Water & Soil Contamination

1. Biological Impact Terms

• Bio-magnification: Concentration of toxic substances (like Mercury, DDT) increases up the food chain. (Why big fish have more toxins).
• Eutrophication: Excess nutrients $ightarrow$ Algal bloom $ightarrow$ Oxygen depletion $ightarrow$ Fish death.
• Minamata Disease: Caused by Mercury poisoning.
• Itai-Itai Disease: Caused by Cadmium poisoning.

Phase 3: Modern Waste & Remediation

1. The Plastic & E-waste Crisis

• Microplastics: Particles $< 5 mm$. Found in ocean and even human blood.
• E-waste Rules (India): Mandatory "Extended Producer Responsibility" (EPR). Manufacturers must collect back old gadgets.

2. Bio-remediation (The Solution)

• Using organisms (Bacteria, Fungi) to clean up polluted sites.
• Oil Zapper: Bacteria developed by TERI to "eat" oil spills.
• Phyto-remediation: Using plants to remove heavy metals from soil.

Phase 4: The Exam Edge (High-Yield Facts)

• BOD vs COD: Biological Oxygen Demand (BOD) vs Chemical Oxygen Demand (COD). COD is always higher than BOD.
• PAN (Peroxyacetyl Nitrate): A secondary pollutant found in Photochemical Smog.
• Fly Ash: Waste from coal power plants. Used in cement and bricks.

[!IMPORTANT]
Greenhouse Potential: $SF_6$ (Sulfur Hexafluoride) is thousands of times more potent as a GHG than $CO_2$, but its concentration is very low.