2. Release of nutrients, oxidants or electron donors into the environment to stimulate naturally occurring microorganisms to degrade a contaminant, is referred to as
(1) biostimulation.                                           (2) phytoremediation.
(3) bioaugmentation.                                       (4) bioremediation

Concept and option-wise explanation

Release of nutrients, oxidants or electron donors specifically to stimulate naturally occurring microorganisms fits the definition of biostimulation, so option (1) is correct for the description and hence the correct choice among the given terms.

(1) Biostimulation – matches the definition

• Biostimulation means modifying the environment (e.g., adding nitrogen, phosphorus, oxygen, or organic electron donors) so that indigenous microbes grow faster and degrade contaminants more efficiently.

• The key idea is: no new microbes are added; instead, native communities are “fed” or supplied with needed electron acceptors/donors to enhance degradation of pollutants.

(2) Phytoremediation

• Phytoremediation uses plants (with or without associated microbes) to remove, stabilize, or transform contaminants through processes such as phytoextraction, rhizofiltration, and phytodegradation.

• It is not defined by nutrient/oxidant addition, but by the central role of plants, so it does not match the given description.

(3) Bioaugmentation

• Bioaugmentation is the addition of selected microbial strains or consortia (often high‑performing degraders) into a contaminated site.

• While it is also a bioremediation strategy, its hallmark is introducing microbes, not just adding nutrients or electron donors to stimulate those already present, so it does not fit the description.

(4) Bioremediation

• Bioremediation is the broad umbrella term for any use of living organisms (microbes, plants, etc.) to detoxify or remove pollutants.

• Biostimulation, bioaugmentation, and phytoremediation are specific types of bioremediation.

• Because the question asks for the specific term for nutrient/electron‑donor addition, this general word is too broad.

Therefore, the process described—adding nutrients, oxidants, or electron donors to stimulate native microbes to degrade contaminants—is correctly called biostimulation (option 1).