With reference to soil, consider the following terms and their meanings:
1. Biostimulation ↔ addition of nutrients to soil to stimulate the growth of indigenous microflora
2. Bioventing ↔ addition of gases such as oxygen or methane to stimulate activity of microflora
3. Bioaugmentation ↔inoculation of soil with exogenous microorganisms
4. Soil sealing ↔ mixing toxic soil with healthy soil
Which among the above is / are correct?

Answer: [B] Only 1, 2 & 3

Chemicals present in the soil may be those that are purposefully applied to the soil such as pesticides and fertilizers or those that make an accidental entrance to the soil. Microorganisms present in the soil may use the pollutant as a source of energy for their metabolism or would make it less harmful by changing its composition.

But when certain microorganisms are employed exclusively  for this purpose, it is called bioremediation.

It can be enhanced through the addition of nutrients to soil to stimulate the growth of  indigenous microflora (biostimulation), addition of gases such as oxygen or methane to stimulate activity of microflora (bioventing),  inoculation of soil with exogenous microorganisms (bioaugmentation), mixing toxic soil with healthy soil (landfarming) and use of  plants (phytoremediation). Let’s play our part to raise awareness about the importance of healthy soils. In the coming future, healthy soils will have to sustain food production to meet the needs of the increasing population   Soil sealing Soil sealing occurs through the destruction or covering of soil by buildings, or types of artificial material which may be very slowly permeable to water (e.g. asphalt or concrete). Soil sealing can cause rapid overland flow after precipitation where water cannot soak  away leading to potential flooding.

This question is a part of GKToday's Integrated IAS General Studies Module