Environmental Pollution: Air, Water, Soil, Noise and Solid Waste
What this domain tests
Environmental Pollution: Air, Water, Soil, Noise and Solid Waste tests pollutant types, sources, effects and control, and the indicators used to measure pollution. Expect numerical questions on BOD, noise addition, and waste composition, and definitional questions on primary versus secondary pollutants.
Core rules and concepts
- Primary pollutants are emitted directly (SO₂, NOₓ, CO, PM); secondary pollutants form in the atmosphere (ozone, PAN, sulphuric and nitric acid).
- Air pollution control: cyclone separators, electrostatic precipitators, bag filters, scrubbers, catalytic converters.
- Water pollution indicators: DO, BOD, COD, pH, turbidity, coliforms. High BOD means high biodegradable organic load and low DO.
- Eutrophication: nutrient enrichment → algal bloom → oxygen depletion → fish kill.
- Biomagnification increases concentration of persistent fat-soluble substances (e.g., DDT, mercury) up the food chain.
- Noise is measured in decibels (dB), a logarithmic scale; 80 dB is ten times the intensity of 70 dB, not 10% more.
- Solid waste: segregation at source, 3R hierarchy (reduce, reuse, recycle), composting, sanitary landfill; e-waste and biomedical waste need separate handling.
Worked example
Two machines each produce 60 dB. Combined intensity doubles, so the level rises by about 3 dB to 63 dB, not 120 dB. Reasoning: dB = 10 log₁₀(I/I₀); doubling I adds 10 log₁₀2 ≈ 3 dB. For n identical sources, add 10 log₁₀n dB. This is why many small sources can breach a limit.
Traps
Adding dB arithmetically; saying BOD measures all organic matter (it measures biodegradable organic matter; COD is chemical); confusing biomagnification with bioaccumulation; assuming dilution is a treatment. Check whether a question asks for source, effect or control.