🌱 Chapter 05 · Topic 03 · Environmental Pollution

Soil Pollution — Pesticides, Land Degradation & Remediation

Causes of soil pollution, pesticides, heavy metals, desertification, land degradation, and soil remediation techniques — complete UPSC & PSC notes.

🌱 What is Soil Pollution?

Soil pollution is the presence of toxic chemicals, heavy metals, or other harmful substances in soil at concentrations that are harmful to living organisms and disrupt normal soil functions.

🌱 Causes of Soil Pollution

Cause	Pollutants	Effects
Pesticides & herbicides	DDT, BHC, organochlorines, organophosphates	Bioaccumulation, kills soil organisms, groundwater contamination
Excess fertilisers	Nitrates, phosphates	Soil acidification, nitrate leaching to groundwater
Industrial waste	Heavy metals (Pb, Cd, Hg, Cr, As), acids, solvents	Toxic to plants and soil organisms, enters food chain
Mining	Heavy metals, acid mine drainage, tailings	Destroys soil structure, heavy metal contamination
Solid waste dumping	Plastics, e-waste, organic waste	Leachate contaminates soil and groundwater
Acid rain	H₂SO₄, HNO₃	Acidifies soil, leaches nutrients, releases toxic aluminium
Sewage sludge	Pathogens, heavy metals	Pathogen contamination, heavy metal buildup

🌱 Pesticides — Key Facts

Organochlorines (DDT, BHC, Aldrin, Dieldrin) — persistent; bioaccumulate; banned in many countries; regulated under Stockholm Convention
Organophosphates (Malathion, Parathion) — less persistent; more acutely toxic; inhibit acetylcholinesterase enzyme
Carbamates — similar to organophosphates; less persistent
Pyrethroids — synthetic version of natural pyrethrin; less persistent; toxic to fish
DDT was banned in India in 1989 for agricultural use (still used for malaria control)
Silent Spring (1962) — book by Rachel Carson that exposed the dangers of DDT and launched the modern environmental movement

⭐ Rachel Carson’s Silent Spring: Published in 1962, this book documented how DDT and other pesticides were killing birds (hence “silent spring” — no birdsong). It led to the ban of DDT in the USA (1972) and is credited with launching the modern environmental movement. It directly influenced the creation of the US EPA and the Stockholm Conference (1972).

🌱 Land Degradation in India

India has approximately 120 million hectares of degraded land (about 36% of total land area)
Types of land degradation:
- Soil erosion — by water (most common) and wind; removes topsoil
- Waterlogging — excess water in soil; common in canal-irrigated areas
- Salinisation — salt accumulation in soil due to improper irrigation; makes soil infertile
- Alkalisation — increase in soil pH; common in arid regions
- Desertification — degradation of dryland ecosystems
States most affected: Rajasthan, Gujarat, Maharashtra, Jharkhand, Odisha

🌱 Desertification

Desertification = land degradation in arid, semi-arid, and dry sub-humid areas due to human activities and climate change
India has ~30% of land under desertification/land degradation
Causes: overgrazing, deforestation, unsustainable agriculture, climate change, over-extraction of groundwater
Thar Desert — India’s largest desert; spreading eastward (desertification)
UNCCD (UN Convention to Combat Desertification) — 1994; India is a party
India’s commitment: restore 26 million hectares of degraded land by 2030 (Land Degradation Neutrality target)

🌱 Soil Remediation Techniques

Technique	Method	Best For
Phytoremediation	Plants absorb/degrade/immobilise pollutants	Heavy metals, organic pollutants; e.g., sunflower absorbs lead, cadmium
Bioremediation	Microorganisms (bacteria, fungi) degrade pollutants	Organic pollutants, oil spills; e.g., oil-eating bacteria
Soil washing	Washing contaminated soil with water/chemical solvents	Heavy metals, organic contaminants
Incineration	Burning contaminated soil at high temperatures	Organic pollutants; destroys them completely
Stabilisation/Solidification	Mixing with cement/lime to immobilise pollutants	Heavy metals; prevents leaching
Electrokinetic remediation	Electric current moves pollutants to electrodes for removal	Heavy metals in fine-grained soils
Mycoremediation	Fungi (mushrooms) degrade pollutants	Organic pollutants, petroleum products

📌 Phytoremediation Types: Phytoextraction (plants absorb metals — used after Chernobyl); Phytodegradation (plants break down organics); Phytostabilisation (plants immobilise pollutants); Rhizofiltration (roots absorb from water). Sunflower was used at Chernobyl to absorb radioactive caesium and strontium.

🌱 Solid Waste Management

India generates ~62 million tonnes of municipal solid waste (MSW) per year
Only ~20% is processed; rest goes to open dumps or landfills
Hierarchy of waste management (3R + 2R): Reduce → Reuse → Recycle → Recover → Dispose
Solid Waste Management Rules 2016 — segregation at source (wet/dry/hazardous); EPR for producers
Swachh Bharat Mission — launched 2014; aims for open defecation free India; solid waste management
Landfill — engineered disposal site; lined to prevent leachate; produces landfill gas (methane)
Composting — biological decomposition of organic waste; produces manure
Waste-to-Energy (WtE) — burning waste to generate electricity; controversial due to air pollution

✅ Revision Checklist — Soil Pollution

✅ Organochlorines (DDT, BHC) = persistent = bioaccumulate = banned = Stockholm Convention
✅ DDT banned in India 1989 for agriculture; still used for malaria control
✅ Silent Spring (1962) = Rachel Carson = exposed DDT dangers = launched environmental movement
✅ India = ~120 million hectares degraded land = ~36% of total land
✅ Salinisation = salt accumulation = improper irrigation = infertile soil
✅ Desertification = dryland degradation = India ~30% land affected
✅ UNCCD = 1994 = UN Convention to Combat Desertification
✅ India target = restore 26 million hectares by 2030 (LDN target)
✅ Phytoremediation = plants absorb pollutants; sunflower absorbs heavy metals
✅ Bioremediation = microorganisms degrade pollutants; oil-eating bacteria
✅ Mycoremediation = fungi degrade pollutants
✅ India generates ~62 million tonnes MSW per year; only ~20% processed
✅ SWM Rules 2016 = segregation at source = wet/dry/hazardous
✅ Swachh Bharat Mission = 2014 = solid waste management + ODF India