Basics of Environment and Pollution Control
This domain tests the vocabulary of pollution control and the Indian legal framework you will apply when inspecting water sources, waste sites and mosquito-breeding grounds.
Core areas
- Air pollution: primary versus secondary pollutants, particulate matter (PM10, PM2.5), carbon monoxide, sulphur and nitrogen oxides, greenhouse gases and the greenhouse effect.
- Water pollution: organic load measured by BOD and COD, eutrophication from nitrates and phosphates, biological contamination and indicator organisms such as coliforms.
- Noise: measured in decibels on a logarithmic scale; ambient limits are stricter at night than by day and stricter in silence zones.
- Waste and law: Water Act 1974, Air Act 1981, Environment (Protection) Act 1986, solid waste and biomedical waste rules; CPCB at national level, SPCB at state level.
- Ecology: food chains, biomagnification of pesticides, biodiversity and conservation.
Worked example
A drain sample has a high BOD but the water looks clear. What does this indicate? Reasoning: BOD measures the dissolved oxygen consumed by microbes breaking down organic matter over five days at 20 °C. High BOD means plenty of biodegradable organic matter and active microbial decomposition, which strips oxygen from the water and kills fish. Clarity is misleading - clear water can carry a heavy organic and microbial load. A high BOD therefore points to sewage or organic effluent contamination, and to a possible health risk if the water is used for drinking.
Traps that cost marks
- Swapping BOD and COD definitions, or thinking high BOD means good quality.
- Forgetting that noise limits differ by zone and by day/night.
- Attributing state-level enforcement to CPCB.
- Confusing biomagnification (concentration up a food chain) with bioaccumulation in one organism.