Which one of the following is a major environmental issue in eastern Canada?
- (a)Acid precipitation
- (b)Groundwater depletion
- (c)Land degradation
- (d)Desertification
Correct — A, Acid precipitation. Eastern Canada (Ontario, Quebec and the Maritime provinces) is a classic acid-rain region. Sulphur- and nitrogen-oxide emissions from coal-fired power plants and metal smelters — both in the US industrial midwest and in Canada itself — drift north-east and fall as acidic rain, acidifying thousands of lakes and damaging conifer forests and soils.
- (b)Groundwater depletion — Groundwater over-draft is the signature problem of arid and heavily irrigated regions (the US High Plains, north-west India), not humid, water-rich eastern Canada.
- (c)Land degradation — Widespread land degradation is chiefly a dryland and intensively farmed-tropics issue; it is not the headline environmental problem of forested eastern Canada.
- (d)Desertification — Desertification affects semi-arid margins such as the Sahel; the cool, humid climate of eastern Canada makes it irrelevant there.
Acid precipitation forms when sulphur dioxide and nitrogen oxides from burning fossil fuels and smelting react with atmospheric moisture to make sulphuric and nitric acids, lowering rainwater pH. Prevailing winds carry pollutants across borders, so downwind regions like eastern Canada suffer from emissions produced elsewhere.
Each wrong option is a real environmental problem, but each belongs to a dry climate. Match the issue to the climate: cool, wet, industrial-downwind eastern Canada points to acid rain.
- Acid rain is caused mainly by sulphur dioxide (SO2) and nitrogen oxides (NOx).
- Rainwater is treated as 'acid rain' when its pH falls below about 5.6.
- Transboundary pollution from the US midwest is a major source over eastern Canada.
- Effects include acidified lakes, damaged coniferous forests, and corroded buildings and monuments.
- Assuming any famous environmental problem fits — match the issue to the region's climate.
- Forgetting that acid rain crosses borders, so the pollution source may lie outside the affected area.
Asked either as 'the major issue in region X' or directly as 'acid rain is caused by which pollutants'.
Acid rain is caused by the pollution of environment by
- (a) carbon dioxide and nitrogen
- (b) carbon monoxide and carbon dioxide
- (c) ozone and carbon dioxide
- (d) nitrous oxide and sulphur dioxide
Answer(d) nitrous oxide and sulphur dioxide
Same concept — acid rain. UPSC 2013 tests the causative pollutants (nitrogen oxides and sulphur dioxide); this NDA item asks where acid rain is a major regional problem (eastern Canada).
For acid rain, the pH of rain water should be less than
- (a) 7.0
- (b) 6.6
- (c) 5.6
- (d) 8.0
Answer(c) 5.6
Same concept — acid rain. That NDA item fixes the pH threshold (below 5.6); this one identifies eastern Canada as a major acid-rain region.
- practice — not a real PYQ
Acid rain is chiefly caused by atmospheric pollution from which pair of gases?
- (a)Carbon dioxide and methane
- (b)Sulphur dioxide and nitrogen oxides
- (c)Ozone and carbon monoxide
- (d)Chlorofluorocarbons and nitrogen
Answer(b) Sulphur dioxide and nitrogen oxides — they form sulphuric and nitric acids in the atmosphere.
- practice — not a real PYQ
Rainwater is generally classified as 'acid rain' when its pH falls below about
- (a)7.0
- (b)6.5
- (c)5.6
- (d)8.0
Answer(c) 5.6 — the reference pH of clean rain in equilibrium with atmospheric CO2.