RAS question
Thermal pollution of water bodies is caused by:
Correct answer: (B) Discharge of heated water from power plants and industries.
Thermal pollution of water bodies is caused by the discharge of heated water from power plants and industries.
Explanation
Thermal pollution occurs when heated effluent from power plants, refineries and factories is released into water bodies. The cited EPA page supports the power-plant part directly: steam electric plants use fossil or nuclear fuels to heat water, and their operations generate wastewater that includes thermal pollution, described as heated water, from water treatment, the power cycle, ash handling and air-pollution control systems. Once such heated wastewater enters a water body, it raises the water temperature, reduces dissolved oxygen and harms aquatic life adapted to specific temperature ranges. That is why the cause is not merely any discharge, but specifically the release of heated water from industrial and power-generation processes.
Why the other options are wrong
- (A) Cold water discharge does not match the given mechanism, because thermal pollution here is tied to warm or heated effluent entering a water body.
- (C) Sound waves cause noise-related disturbance, not the heating of water or the fall in dissolved oxygen described in thermal pollution.
- (D) Light exposure is not the discharge of heated industrial or power-plant wastewater, so it does not explain the temperature rise in the water body.
Concept
This tests the Environment and Ecology concept of water pollution by source and effect. It recurs in RAS because industrial effluents, power plants, dissolved oxygen and aquatic ecosystem stress are standard applied-environment themes.