Concept and option-wise explanation

Phytoremediation is, by definition, plant‑based remediation. Recognized mechanisms include phytoextraction/phytoaccumulation, phytodegradation, phytovolatilization, phytostabilization, rhizofiltration, and the use of hyperaccumulator plants; the driving agent is always the plant system.

(1) Phytodegradation – phytoremediation

• Also called phytotransformation.

• Plants (and root-associated microbes) enzymatically break down organic contaminants within roots, shoots, or rhizosphere.

• This is a classic phytoremediation mechanism.

(2) Phyto‑mining – phytoremediation

• A special case of phytoextraction where metal‑accumulating plants are grown on metal‑rich soils, the biomass is harvested, burned, and the metal is recovered from ash.

• It is a plant-based removal and resource‑recovery strategy; hence a phytoremediation approach.

(3) Continuous removal through hyperaccumulators – phytoremediation

• Hyperaccumulator species repeatedly take up metals/metalloids from contaminated soil into shoots; plants are harvested each cycle, gradually lowering contaminant levels.

• This is essentially phytoextraction with hyperaccumulators, a core phytoremediation strategy.

(4) Chelate mediated extraction of pollutants – not a primary phytoremediation strategy

• Chelate-mediated extraction usually refers to adding synthetic chelating agents (e.g., EDTA, EDDS) to soil to solubilize metals and remove them by soil washing or leaching.

• While mild chelation can sometimes be combined with phytoextraction to increase bioavailability, the phrase as given describes a chemical extraction process, not a direct plant mechanism.

• Therefore, it is the option that does not itself represent a phytoremediation strategy.

So, the process that does not represent a phytoremediation strategy is chelate mediated extraction of pollutants (option 4).