Environmental Pollution — Revision Notes

⚡ 30-Second Revision

Air Pollutants: — $SO_x$ (acid rain, respiratory), $NO_x$ (acid rain, smog, respiratory), $CO$ (carboxyhemoglobin, toxic), $CO_2$ (greenhouse gas), $O_3$ (tropospheric: smog, respiratory; stratospheric: UV protection), CFCs (ozone depletion).
Acid Rain: — $SO_2, NO_x$ react with $H_2O$ to form $H_2SO_4, HNO_3$. pH < 5.6.
Photochemical Smog: — $NO_x +$ Hydrocarbons + Sunlight $ightarrow O_3 +$ PAN. Oxidizing.
Ozone Depletion: — CFCs release $cdot Cl$ in stratosphere; $cdot Cl$ catalytically destroys $O_3$.
Water Pollutants: — Organic waste (high BOD), Pathogens, Heavy metals (Pb, Hg, Cd), Nitrates ($NO_3^-$).
BOD: — Biochemical Oxygen Demand. High BOD = high organic pollution = low DO.
Eutrophication: — Nutrient enrichment ($NO_3^-, PO_4^{3-}$) $ightarrow$ algal bloom $ightarrow$ DO depletion.
Blue Baby Syndrome: — Caused by excess $NO_3^-$ in drinking water.
Minamata Disease: — Mercury (Hg) poisoning. Itai-Itai Disease: Cadmium (Cd) poisoning.
Greenhouse Gases: — $CO_2, CH_4, N_2O$, CFCs, $H_2O$ vapor. Trap heat, cause global warming.
Primary Pollutants: — Directly emitted ($CO, SO_2$). Secondary Pollutants: Formed in atmosphere ($O_3$, PAN).

2-Minute Revision

Environmental pollution involves the introduction of harmful substances into air, water, or soil. Air pollution includes tropospheric and stratospheric issues. Tropospheric pollutants like sulfur oxides ($SO_x$) and nitrogen oxides ($NO_x$) cause acid rain, while carbon monoxide ($CO$) is toxic due to carboxyhemoglobin formation.

Photochemical smog, a mixture of $NO_x$, hydrocarbons, and ozone ($O_3$), forms in sunny conditions. Stratospheric ozone depletion, caused by CFCs releasing chlorine radicals, leads to increased UV radiation.

Water pollution is often indicated by high Biochemical Oxygen Demand (BOD), signifying organic waste and oxygen depletion. Eutrophication, driven by excess nutrients like nitrates and phosphates, causes algal blooms and harms aquatic life.

Heavy metals (e.g., mercury causing Minamata disease, cadmium causing Itai-Itai disease) and nitrates (causing blue baby syndrome) are significant water contaminants. Soil pollution arises from pesticides, fertilizers, and industrial waste.

The enhanced greenhouse effect, due to increased $CO_2$, methane, and $N_2O$, contributes to global warming. Remember the distinction between primary (directly emitted) and secondary (formed in atmosphere) pollutants, and biodegradable vs.

non-biodegradable waste for effective waste management.

5-Minute Revision

Environmental pollution is the degradation of our natural surroundings by harmful agents. Air pollution can be categorized into tropospheric and stratospheric. In the troposphere, major pollutants include $SO_x$ (from fossil fuels, causing acid rain and respiratory issues), $NO_x$ (from combustion, contributing to acid rain and photochemical smog), $CO$ (from incomplete combustion, highly toxic due to carboxyhemoglobin formation), and particulate matter.

Photochemical smog, prevalent in warm, sunny climates, is an oxidizing mixture of $NO_x$, hydrocarbons, and secondary pollutants like ozone ($O_3$) and peroxyacetyl nitrate (PAN), causing eye irritation and plant damage.

In the stratosphere, the protective ozone layer is depleted by chlorofluorocarbons (CFCs). CFCs release chlorine radicals ($cdot Cl$) under UV light, which catalytically destroy ozone molecules, leading to increased harmful UV radiation reaching Earth.

Water pollution is assessed by parameters like Biochemical Oxygen Demand (BOD). A high BOD indicates significant organic pollution, as microorganisms consume dissolved oxygen to decompose waste, harming aquatic life.

Eutrophication, the nutrient enrichment of water bodies (e.g., by phosphates from detergents, nitrates from fertilizers), causes excessive algal growth (algal blooms), which then deplete oxygen upon decomposition.

Specific water pollutants include heavy metals like mercury (causing Minamata disease) and cadmium (causing Itai-Itai disease), and nitrates (causing methemoglobinemia or 'blue baby syndrome' in infants).

Soil pollution is often due to overuse of pesticides and fertilizers, industrial waste, and non-biodegradable plastics.

The greenhouse effect, a natural process, is enhanced by anthropogenic emissions of greenhouse gases ($CO_2, CH_4, N_2O$), leading to global warming. Control strategies include source reduction, waste treatment (e.g., catalytic converters, sewage treatment), recycling, and promoting renewable energy. Always differentiate between primary pollutants (directly emitted, e.g., $CO, SO_2$) and secondary pollutants (formed in atmosphere, e.g., tropospheric $O_3$, PAN).

Prelims Revision Notes

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Air Pollution:

* Tropospheric Pollution: * Gaseous Pollutants: * $SO_x$ ($SO_2, SO_3$): Sources - fossil fuel combustion. Effects - acid rain ($H_2SO_4$), respiratory issues. Precursor to secondary particulates.

* $NO_x$ ($NO, NO_2$): Sources - high-temp combustion. Effects - acid rain ($HNO_3$), respiratory, photochemical smog. * $CO$: Sources - incomplete combustion. Effects - carboxyhemoglobin, toxic (binds to Hb 200-250x stronger than $O_2$).

* $CO_2$: Sources - fossil fuels, deforestation. Effect - major greenhouse gas, global warming. * Hydrocarbons: Sources - unburnt fuels. Effects - carcinogenic, photochemical smog. * Particulate Pollutants: Dust, smoke, mist, fumes.

Effects - respiratory, reduced visibility. * Smog: * Classical (London) Smog: Smoke + Fog + $SO_2$. Cool, humid. Reducing. * Photochemical (Los Angeles) Smog: $NO_x$ + Hydrocarbons + Sunlight $ightarrow O_3$ + PAN.

Warm, dry, sunny. Oxidizing. Effects - eye irritation, plant damage. * Stratospheric Pollution: * Ozone Depletion: Ozone layer ($O_3$) in stratosphere protects from UV. Caused by CFCs ($CF_2Cl_2, CFCl_3$).

* Mechanism: $CF_2Cl_2 xrightarrow{hv} cdot Cl + cdot CF_2Cl$; $cdot Cl + O_3 \rightarrow ClO cdot + O_2$; $ClO cdot + O \rightarrow cdot Cl + O_2$. $cdot Cl$ is a catalyst. * Effects: Increased UV, skin cancer, cataracts, immune suppression.

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Water Pollution:

* Sources: Sewage, industrial effluents, agricultural runoff. * Pollutants: * Organic Wastes: Measured by BOD (Biochemical Oxygen Demand). High BOD = high organic pollution = low dissolved oxygen (DO).

Clean water BOD < $5,\text{ppm}$. * Pathogens: Bacteria, viruses from sewage. Cause diseases (cholera, typhoid). * Chemical Pollutants: * Heavy Metals: Pb (neurological), Hg (Minamata disease), Cd (Itai-Itai disease).

Bioaccumulate, biomagnify. * **Nitrates ($NO_3^-$): From fertilizers. Cause Methemoglobinemia (Blue Baby Syndrome)** in infants. * **Phosphates ($PO_4^{3-}$): From detergents, fertilizers. Cause Eutrophication** (algal bloom $ightarrow$ DO depletion).

* Pesticides: DDT, BHC. Persistent, bioaccumulate, biomagnify. * Thermal Pollution: Hot water discharge. Decreases DO solubility.

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Soil Pollution:

* Sources: Pesticides, fertilizers, industrial waste, plastic. * Effects: Reduced fertility, groundwater contamination, food chain contamination.

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Greenhouse Effect & Global Warming:

* Greenhouse Gases (GHGs): $CO_2, CH_4, N_2O$, CFCs, $H_2O$ vapor. Trap heat. * Enhanced Greenhouse Effect: Anthropogenic increase in GHGs leads to global warming.

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Pollutant Classification:

* Primary: Directly emitted ($CO, SO_2$). * Secondary: Formed in atmosphere ($O_3$ (tropospheric), PAN, $H_2SO_4$). * Biodegradable: Decomposed by microbes (sewage). Non-biodegradable: Not easily decomposed (plastics, heavy metals).

Vyyuha Quick Recall

CFCs are Catalytic Foe to Celestial Shield (Ozone Layer).