Soil Pollution

 Definition

Soil pollution refers to the addition of toxic substances (chemicals, salts, radioactive materials, pathogens) into soil, adversely affecting its physical, chemical and biological properties, thereby reducing productivity.

 Causes & Sources

1. Plastic Waste

• Non-biodegradable → remains for centuries
• Prevents seed germination
• Burning releases:
  • Dioxins
  • Furans
  • Phosgene
  • CO, CO₂
• Blocks soil porosity → reduces groundwater recharge

2. Industrial Sources

• Fly ash
• Heavy metals: Lead, Mercury, Cadmium, Chromium
• Acids, alkalis, cyanides
• Nuclear wastes

3. Pesticides & Fertilisers

• Chlorohydrocarbons (DDT, Endosulfan, Heptachlor)
• Cause biomagnification
• Excess fertilisers:
  • Reduce soil microbes
  • Increase salinity & alkalinity
  • Reduce nitrogen fixation

4. Other Sources

• Acid rain
• Weathering of toxic rocks
• Radioactive leakage

Effects of Soil Pollution

• Reduced fertility
• Increased salinity & alkalinity
• Loss of nitrogen-fixing bacteria
• Soil erosion
• Siltation in reservoirs
• Health hazards
• Ecological imbalance

Solid Waste

Definition

Municipal Solid Waste (MSW) includes:

• Paper
• Plastics
• Food waste
• Glass
• Metals
• Rubber
• Textiles

Problems with Solid Waste

1. Open Dumps

• No segregation
• Disease breeding grounds
• Groundwater contamination

2. Landfills

• Risk of leaching
• Methane emission
• Limited space

3. Sanitary Landfills

• Lined with impermeable materials
• Expensive but safer

Waste Treatment Methods

1. Incineration

• Burning at high temperature
• Produces toxic ash
• Last resort (used for biomedical waste)

2. Pyrolysis

• Combustion in the absence of oxygen
• Produces fuel gas, charcoal, and tar

3. Composting

• Aerobic decomposition
• Produces nutrient-rich humus

4. Vermiculture

• Earthworms convert waste into compost

Plastic Waste Issues

• Releases dioxins (POPs)
• Blocks drains
• Causes animal deaths
• Reduces soil fertility

Dioxins are part of “Dirty Dozen” under: Stockholm Convention on Persistent Organic Pollutants

Plastic in Road Construction

• Polyblend + Bitumen
• Improves water resistance
• Increases road life 3×
• Example of circular economy

Waste Minimization Circles (WMC)

• For SMEs
• Assisted by World Bank
• Implemented via National Productivity Council
• Based on 1992 Policy Statement for Abatement of Pollution

Hazardous Waste

Definition

Waste exhibiting:

• Toxicity
• Ignitability
• Corrosivity
• Reactivity

Sources:

• Industry
• Hospitals
• Agriculture
• Construction
• Power plants

Important International Conventions

Stockholm Convention on Persistent Organic Pollutants

• Eliminates/restricts POPs
• Includes DDT, Aldrin, PCBs

Basel Convention

• Controls transboundary movement of hazardous waste
• Prevents dumping in developing countries

Rotterdam Convention

• Prior informed consent for hazardous chemicals trade
• Promotes information sharing

Electronic Waste (E-Waste)

Definition

Discarded electronic products:

• Computers
• TVs
• Mobiles
• Appliances

Safe if:

• Scientifically recycled

Hazardous if:

• Informally dismantled

Major Toxic Components

E-Waste in India

• ~18.5 lakh MT annually (older data; rising trend)
• Major states:
  • Maharashtra
  • Tamil Nadu
  • Andhra Pradesh
  • UP
  • Delhi

Major cities:
Mumbai, Delhi, Bengaluru, Chennai, Kolkata

Challenges:

• Informal recycling sector
• Worker exposure
• Export dumping

Heavy Metal Toxicity

Lead

• Source: Petrol (TEL), batteries
• Causes:
  • Neurological damage
  • Developmental disorders
  • Lung & kidney cancer

Mercury

• Example: Minamata Disease (Japan)
• Causes:
  • Brain damage
  • Foetal deformities

Arsenic

• Found in groundwater
• Causes:
  • Melanosis
  • Keratosis
  • Skin cancer

Cadmium

• Itai-Itai disease (Japan)
• Causes:
  • Brittle bones
  • Kidney damage