Ch 10: Environmental Chemistry

📋 Types of Environmental Pollution

💨

Air Pollution

Contamination by harmful gases, particulates and chemicals. Greenhouse gases, Smog, Acid Rain, Ozone depletion.

💧

Water Pollution

Contamination by industrial, agricultural and domestic waste. BOD, Eutrophication, heavy metals.

🪨

Soil Pollution

Contamination by pesticides, heavy metals, industrial waste. DDT is a persistent soil pollutant.

🔊

Sound Pollution

Excessive noise causing harm to living organisms. >85 dB harmful to humans.

☢️

Radiation / Radioactive Pollution

Pollution caused by radioactive substances and nuclear waste.

⚠️ Exam Trap

DDT = Dichloro Diphenyl Trichloroethane — persistent pollutant (stays in environment)
PCBs = Polychlorinated Biphenyls = carcinogenic industrial pollutant

🌡️ Global Warming & Greenhouse Effect

📘 Greenhouse Effect

Greenhouse gases trap heat in Earth's atmosphere → increases Earth's temperature → Global Warming.

GREENHOUSE GASES:

CO₂

CH₄ (Methane)

N₂O

CFC (Freon)

SO₂

⚠️ Exam Trap — Greenhouse Gases

Main greenhouse gas = CO₂ (most contribution to warming)
Most potent greenhouse gas = CH₄ (methane — 25× more potent than CO₂)
CFC is both greenhouse gas AND ozone depleter

🌫️ Smog

General Smog

Reducing mixture

Composition: Smoke + Fog + SO₂
Nature: Reducing
Common in industrial areas with coal burning

Photochemical Smog

Oxidative nature

Formed from: Oxides of Nitrogen + Hydrocarbons (in sunlight)
Nature: Oxidative
Components: Ozone, Nitric Oxide, PAN

📘 PAN (Peroxy Acetyl Nitrate)

Key component of photochemical smog. Causes eye irritation and plant damage. Formula: CH₃CO·O₂NO₂

⚠️ Exam Trap — Smog

PAN = Peroxy Acetyl Nitrate (NOT Peroxy Acyl Nitrate — similar but note spelling)
Photochemical smog = Oxidative; General smog = Reducing
Components of photochemical smog: Ozone + NO + PAN

🌧️ Acid Rain

📘 Acid Rain

Rainwater with pH below 5.6. Normal rain has pH 5.6 (slightly acidic due to dissolved CO₂).

Normal Rain pH

5.6

Acid Rain pH

< 5.6

Responsible Gases

SO₂ + NO₂

Responsible gases: SO₂ and NO₂ (from industrial emissions, vehicles)
Damages historic monuments (marble/limestone buildings)
Harms soil, water bodies, forests
Marble cancer = acid rain eroding Taj Mahal

⚠️ Exam Trap — Acid Rain

Acid rain pH = below 5.6 (NOT below 7)
Caused by SO₂ and NO₂ (NOT CO₂)
CO₂ makes normal rain slightly acidic (pH 5.6) but that is NOT acid rain

🌐 Ozone Depletion

📘 Ozone Layer

Present in the Stratosphere. Protects Earth from harmful UV radiation. CFC destroys ozone molecules.

Location: Stratospheric pollution
Main cause: CFC (Chlorofluorocarbon) and Halogens
CFC = also called Freon
CFC composition: Compounds of C, Cl and F
CFC used in: Refrigerators and AC (Air Conditioners)
Each CFC molecule can destroy thousands of ozone molecules

⚠️ Exam Trap — Ozone

CFC = Chlorofluorocarbon = Freon = depletes ozone
CFC used in refrigerators and AC
Ozone depletion = Stratospheric pollution (NOT tropospheric)
Ozone hole first discovered over Antarctica
CFC is also a greenhouse gas (dual effect)

💧 Water Pollution — BOD

📘 BOD — Biochemical Oxygen Demand

Amount of oxygen consumed by aerobic bacteria to decompose organic matter in polluted water. Higher BOD = More polluted.

5 ppm

BOD — Clean Water ✅

17 ppm

BOD — Highly Polluted Water ⚠️

🌿 Eutrophication

📘 Eutrophication

Process where excess nutrients (nitrates, phosphates from fertilisers) enter water bodies → Algal bloom → Algae consume dissolved O₂ → Depletion of O₂ in water → Fish and aquatic life die.

Caused by excess nitrates and phosphates (from agricultural runoff, sewage)
→ Algal bloom (rapid growth of algae)
→ Dissolved O₂ depleted
→ Death of aquatic life (fish kill)

⚠️ Exam Trap — Eutrophication

Eutrophication = depletion of dissolved O₂ (NOT increase). Caused by EXCESS nutrients (nitrates, phosphates), NOT pollution directly. Algae consume O₂ when they decompose.

🧪 Maximum Metal Limits in Drinking Water

Metal	Symbol	Max Concentration (ppm)	Risk if Exceeded
Iron	Fe	0.2 ppm	Rust taste, staining
Manganese	Mn	0.05 ppm	Neurological effects
Aluminium	Al	0.2 ppm	Possible link to Alzheimer's
Copper	Cu	3.0 ppm	Liver, kidney damage
Zinc	Zn	5.0 ppm	Nausea at high levels
Cadmium	Cd	0.005 ppm	Kidney damage, Itai-Itai disease

⚠️ Exam Trap — Metal Limits

Cadmium (Cd) = 0.005 ppm (LOWEST limit — most toxic)
Zinc (Zn) = 5.0 ppm (HIGHEST limit — least toxic)
Fe and Al both = 0.2 ppm
PCBs (Polychlorinated Biphenyls) = carcinogenic industrial pollutant in water

☠️ Bhopal Gas Tragedy — 3 December 1984

3 Dec 1984

Date of Tragedy

Bhopal, MP

Location

Union Carbide

Company

MIC

Gas Leaked

Gas leaked: Methyl Isocyanate (MIC) — formula: H₃C–N=C=O
Company: Union Carbide Limited, Bhopal
MIC was a product used in pesticide manufacturing
One of the worst industrial disasters in history
Thousands of people killed and injured

⚠️ Exam Trap — Bhopal

Date = 3 December 1984 (NOT 1986 which is Chernobyl)
Gas = Methyl Isocyanate (MIC) — NOT CO or CH₄
Company = Union Carbide Limited (NOT Union Carbon or Union Carbonate)
MIC is used in making pesticides

♻️ Green Chemistry

📘 Green Chemistry

Design of chemical products and processes that reduce or eliminate chemical hazards to humans and the environment.

Uses water as solvent — cost-effective, non-flammable, non-carcinogenic
Aim: reduce pollution at the source (prevention over cure)
12 principles of Green Chemistry

Old Zapper Technology

Developed by TERI

TERI = The Energy and Resource Institute
Old Zapper is an environment-friendly technology

📋 Key Environmental Terms Summary

Term	Full Form / Key Fact
DDT	Dichloro Diphenyl Trichloroethane — persistent pollutant
CFC	Chlorofluorocarbon (Freon) — depletes ozone; used in AC & refrigerators
PAN	Peroxy Acetyl Nitrate — component of photochemical smog
BOD	Biochemical Oxygen Demand; clean water = 5 ppm; polluted = 17 ppm
PCBs	Polychlorinated Biphenyls — carcinogenic industrial pollutant
TERI	The Energy and Resource Institute — developed Old Zapper
MIC	Methyl Isocyanate — Bhopal Gas Tragedy (3 Dec 1984)

🎯 High-Frequency BPSC/BSSC Exam Points

DDT = Dichloro Diphenyl Trichloroethane — persistent pollutant
5 types of pollution: Air, Water, Soil, Sound, Radioactive
Greenhouse gases: CO₂, CH₄, N₂O, CFC, SO₂
General smog = Reducing (Smoke + Fog + SO₂)
Photochemical smog = Oxidative (NOx + Hydrocarbons + sunlight)
PAN = Peroxy Acetyl Nitrate — in photochemical smog
Acid rain: pH < 5.6; caused by SO₂ and NO₂
Ozone depletion: CFC = Freon; used in refrigerators & AC
Ozone depletion = Stratospheric pollution
Bhopal Tragedy: 3 December 1984 | Gas = MIC (Methyl Isocyanate) | Company = Union Carbide Limited
BOD clean water = 5 ppm; highly polluted = 17 ppm
Eutrophication = depletion of dissolved O₂ due to algal bloom (nitrates/phosphates)
Cadmium (Cd) max limit = 0.005 ppm (lowest — most toxic)
Zinc (Zn) max limit = 5.0 ppm (highest)
Fe and Al both max = 0.2 ppm
PCBs = Polychlorinated Biphenyls = carcinogenic
Green Chemistry: uses water as solvent — non-toxic, non-flammable
TERI = The Energy and Resource Institute; Old Zapper technology

📋 Abbreviations Quick Reference

Abbreviation	Full Form
DDT	Dichloro Diphenyl Trichloroethane
CFC	Chlorofluorocarbon (Freon)
PAN	Peroxy Acetyl Nitrate
BOD	Biochemical Oxygen Demand
PCBs	Polychlorinated Biphenyls
MIC	Methyl Isocyanate
TERI	The Energy and Resource Institute

⚠️ Most Common Exam Traps

Acid rain pH = below 5.6 (NOT 7)
Acid rain caused by SO₂ & NO₂ (NOT CO₂)
Photochemical smog = Oxidative; General = Reducing
Ozone = Stratospheric (NOT tropospheric)
Bhopal gas = MIC (NOT CO or H₂S)
Bhopal date = 3 Dec 1984 (NOT 1986)
BOD high = more polluted (Higher BOD = worse)
Cd has LOWEST limit (0.005 ppm) — most toxic
Eutrophication = O₂ decreases in water
CFC = ozone depleter + greenhouse gas (both)

🌍 Environmental Chemistry