Rhizoremediation half-lives of PCBs: Role of congener composition, organic carbon forms, bioavailability, microbial activity, plant species and soil conditions, on the prediction of fate and persistence in soil

Microcosm Experiment to Assess the Capacity of a Poplar Clone to Grow in a PCB-Contaminated Soil

“…This result could be presumably ascribed to the microbial-root association effect of stimulating the desorption of some non-analysed PCBs, which were attached to the historically contaminated soil, favouring their transformation to the six PCB markers analysed in this work (i.e., 28, 52, 101, 138, 153 and 180), as also found by other authors [6,11,21,70]. Another possibility could be the transformation of higher chlorinated PCBs to the PCB markers analysed, as also found in other studies [1,9] The quantity of PCB markers detected in the roots (Figure 3) was ascribable to the wide growth of the root system ( Figure 1, Table 2), which filled the pots and acts as a strong bioconcentrator. Plant exudates can act as surfactants, forming hydrophilic complexes with PCBs and making possible their transportation into roots [71].…”

“…Watering the soil can be an occasional strategy to improve the anaerobic degradation of PCBs. We cannot exclude a subsequent long-term decrease in PCBs in this historically contaminated soil, as reported in recent review papers [1,9]. However, knowledge of plant-microbe interactions in PCB degradation is far from complete and further studies are necessary to better investigate the chemical dialogue between plant and microbes in the rhizosphere.…”

“…However, plants in this condition showed a higher stress level than the other microcosms, producing higher amounts of phenolic, flavonoid and ascorbate contents, as a defence mechanism.2 of 17 several countries since 1979, there is still much environmental contamination. Their elimination from contaminated areas is therefore a challenge [1].Natural restoration strategies are preferred since they use existing flows of energy and matter, take advantage of local solutions and follow seasonal and climatic changes in ecosystems [2,3]. Among natural-based remediation strategies, the use of plants to promote PCB degradation in the rhizosphere (plant assisted bioremediation, [4]) can be an effective, cost-competitive and environmentally friendly alternative to the most traditional remediation techniques [5].Despite the high chemical stability and low bioavailability of PCBs, they can potentially undergo biological degradation.…”

“…Anaerobic reductive dechlorination happens when PCBs serve as electron acceptors, thus being turned into less chlorinated congeners, and aerobic transformation involves the lower-halogenated congeners (<5 Cl) and leads to the breakdown of the biphenyl structure [6]. Numerous studies have in this context shown an increase in degradation of PCBs, involving mostly the low-halogenated congeners in vegetated soil as compared with non-vegetated soil [1,[7][8][9]; this is the so-called plant-assisted bioremediation [4]. In the rhizosphere, the plant-microorganism association can increase the degradation of PCBs due to synergic exchanges between the natural soil microbial community and roots [9][10][11][12].…”

“…2 of 17 several countries since 1979, there is still much environmental contamination. Their elimination from contaminated areas is therefore a challenge [1].…”