Environmental Science
Environmental Science tests pollution, environmental chemistry, impact assessment, waste management and environmental law. Definitional and numerical questions are common.
Core rules
- Air pollutants are primary (SO2, NOx, CO, particulates) or secondary (ozone, PAN, smog). PM2.5 penetrates deep into the alveoli.
- Water quality: DO, BOD, COD, pH and turbidity. High BOD indicates organic pollution; COD measures chemically oxidisable matter.
- EIA stages: screening, scoping, baseline, impact prediction, environmental management plan, public hearing and appraisal. EIA Notification 2006 classifies projects as Category A or B.
- Waste hierarchy: reduce–reuse–recycle; landfill, composting, vermicomposting and incineration; biomedical and e-waste have separate rules.
- Law: Environment (Protection) Act 1986; Air Act 1981; Water Act 1974; NGT Act 2010.
- Ozone depletion involves CFCs and halons, controlled by the Montreal Protocol. Greenhouse gases include CO2, CH4, N2O and F-gases.
Worked example
A river sample has DO 3 mg/L and BOD 12 mg/L. Reasoning: low DO plus high BOD means heavy organic load and microbial oxygen consumption; the river is stressed. The BOD/DO ratio is high; check sewage ingress and require effluent treatment.
Traps
- Confusing BOD with COD; COD is not a biological measure.
- Treating EIA as a one-time clearance rather than a process with monitoring.
- Mixing global warming with ozone depletion.
- Forgetting public hearing where it applies.