Which of the following is not a source of pollution in soil ?

Question

Accepted Answer

Correct answer: D — Concept — what makes an activity a source of soil pollution Soil pollution is the addition of solid, liquid or chemical residue to land in quantities that alter the soil's physical, chemical or biological quality. An activity is therefore a source of soil pollution only when it actually discharges such material onto or into the ground — ash, sludge, spilled hydrocarbons, heavy metals, salts, agro-chemicals or solid waste. An activity that merely converts energy from one form into another, releasing no material to the land, is not a soil-pollution source, however large its other environmental effects may be. Applying the test to each activity Activity Material it adds to the soil Transport sector Lead, zinc and hydrocarbons from exhaust and from fuel and lubricant spills, together with tyre and brake-lining dust, settle on roadside land. Agriculture sector Nitrates and phosphates from chemical fertilisers, pesticide residues, and salts left behind by irrigation return-flow accumulate in the crop root zone. Thermal power plants Fly ash and bottom ash from burning pulverised coal are stored in ash ponds and dykes, from which arsenic, mercury and other heavy metals pass into the surrounding land. Hydropower plants None. Falling water drives the turbine and leaves it chemically unchanged, so no combustion product or chemical residue is discharged onto the land. Cross-check A hydroelectric project is not free of environmental cost: the reservoir submerges forest and farmland, people are displaced, silt that would have enriched downstream fields is trapped behind the dam, and fish migration is disrupted. These are land-use and hydrological effects, not the addition of a pollutant to the soil. Transport, agriculture and coal-fired generation each leave a measurable chemical residue in the ground, so among the four activities listed the one that is not a source of soil pollution is hydropower plants.

Answer

A. Transport sector

Answer

B. Agriculture sector

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C. Thermal power plants

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D. Hydropower plants

Activity	Material it adds to the soil
Transport sector	Lead, zinc and hydrocarbons from exhaust and from fuel and lubricant spills, together with tyre and brake-lining dust, settle on roadside land.
Agriculture sector	Nitrates and phosphates from chemical fertilisers, pesticide residues, and salts left behind by irrigation return-flow accumulate in the crop root zone.
Thermal power plants	Fly ash and bottom ash from burning pulverised coal are stored in ash ponds and dykes, from which arsenic, mercury and other heavy metals pass into the surrounding land.
Hydropower plants	None. Falling water drives the turbine and leaves it chemically unchanged, so no combustion product or chemical residue is discharged onto the land.