Pollution — Ecology & Environment

Q.1

WBCS Prelims 2023

The main source of methane gas in India —

A. Floriculture gardens

B. Orchards

C. Tea gardens

D. Paddy fields

Explanation

Why Correct: Paddy fields (rice cultivation) are India's largest anthropogenic source of methane due to anaerobic decomposition of organic matter in flooded soils.
Distractor Analysis: Floriculture gardens involve flower cultivation with minimal methane emissions. Orchards are fruit tree plantations with dry soil conditions unsuitable for methane production. Tea gardens are typically on well-drained slopes where aerobic decomposition produces CO2 rather than methane.
Takeaway: Methane emissions from agriculture also come significantly from livestock enteric fermentation and manure management.

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Q.2

WBCS Prelims 2020

The greenhouse gas that is a product of the contribution of fossil fuels is

A. CO2

B. CH4

C. O3

D. N2O

Explanation

Why Correct: Burning fossil fuels (coal, oil, natural gas) releases carbon dioxide (CO2) as the primary greenhouse gas through combustion, accounting for about 76% of global anthropogenic greenhouse gas emissions.
Distractor Analysis: Methane (CH4) primarily comes from agriculture (livestock digestion, rice paddies), landfills, and natural gas leaks. Ozone (O3) forms in the lower atmosphere from photochemical reactions involving nitrogen oxides and volatile organic compounds. Nitrous oxide (N2O) mainly originates from agricultural soil management (fertilizer use) and industrial processes.
Takeaway: CO2 has the highest absolute contribution to global warming, but methane has 28-36 times the global warming potential of CO2 over 100 years.

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Q.3

WBCS Prelims 2010

The toxic chemical element that caused Minamata disease in Japan was

A. Uranium

B. Mercury

C. Cadmium

D. Arsenic

Explanation

Why Correct: Minamata disease resulted from industrial methylmercury poisoning in Minamata Bay, Japan, during the 1950s-60s, causing severe neurological damage.
Distractor Analysis: Uranium causes radiation poisoning and kidney damage. Cadmium causes Itai-itai disease through bone and kidney damage. Arsenic causes arsenicosis with skin lesions and cancers.
Takeaway: Itai-itai disease in Japan was caused by cadmium contamination from mining in Toyama Prefecture.

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Q.4

WBCS Prelims 2001

The erosion of soil by winds can be best controlled by

A. afforestation

B. removal of vegetation

C. dry farming

D. creation of wind breaks

Explanation

Why Correct: Wind breaks are physical barriers like trees, shrubs, or fences that reduce wind speed at ground level, directly preventing soil particle detachment and transport.
Distractor Analysis: Afforestation helps long-term but takes years to establish effective protection. Removal of vegetation exposes soil to wind, increasing erosion. Dry farming conserves moisture but doesn't directly control wind erosion.
Takeaway: For water erosion control, contour plowing and terracing are primary methods, while windbreaks and shelterbelts specifically target wind erosion.

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