Phyto stabilization

Figure 5.3. Different mechanisms for phytoremediation.

PAHs in Terrestrial Environment and their Phytoremediation 77

5.3.1.2 Phyto Stabilization

In phyto stabilization, the contaminants are immobilized in the root system through adsorption

on roots, adsorption and accumulation by roots or precipitation in the rhizosphere. The process

supresses the pollutants mobility, preventing their migration by leaching, erosion or dispersion

along with soil, water or air and thus attenuate their bioavailability in the food chain (Radziemska

et al. 2017, Zgorelec et al. 2020). Phyto stabilization does not physically eliminate the pollutants

from the soil, but rather causes the deactivation and immobilization of their potential ions, thereby

preventing further migration to the food chain. For an effective phyto stabilization process, selection

of suitable plants that offer certain characteristics is necessary. Plants should grow rapidly under

field conditions, possess high tolerance to the soil conditions and vast root system. Moreover, the

plants must be easy to maintain under site-specific conditions and must have a relatively long life

(Muthusaravanan et al. 2018). The efficiency of the phyto stabilization process is generally affected

by various factors such as contaminant to be removed, soil cover, rhizosphere modification and root

system of the plant. Vegetation cover interrupts the direct impact of wind and rain, increases the

soil compaction thus reducing the velocity of runoff, and acts as an insulator against temperature

variation. Rhizosphere induces changes such as acidification, microbial activity and release of

organic acids alter the soil properties and thus the transformation, bioavailability and mobility of

contaminants which affects the phyto stabilization of contaminated sites. The plant root anatomy is

a critical factor for potential application of this technique. The higher root biomass producing plants

with dense and deep roots are desirable for phyto stabilization as they can exploit larger volumes

of contaminated soils. Fibrous roots provide greater surface area for contaminant absorption and

plant–microbe interactions. Remediation potential of black locust (Robinia pseudoacacia Nyirsegi)