| Title | Bioremediation of a PCB historically contaminated soil in presence of the leguminous Medicago sativa |
| Abstract | Plant-assisted bioremediation is emerging as one of the most effective means by which plants and their associated rhizosphere microorganisms can degrade organic contaminants in soils. Among biostimulation approaches, vegetation of different contaminated matrices with plant species found applications for accelerating the depletion of recalcitrant contaminants comprising Polychlorinated biphenyls (PCBs). This process is mainly due to the stimulation of organic contaminant biodegradation by natural occurring microorganisms through root exudates that can eventually increase the bioavailability of the contaminants and induce a natural selection of the microbial community. However, the efficiency of a phytoremediation process depends mainly on the presence and activity of plant-associated microorganisms carrying degradation genes required for the enzymatic breakdown of contaminants. In case the plant is growing in presence of contaminants, there is an interaction between contaminant, soil, and plant species that determines the structure and the metabolic activity of the plant associated microbial communities. The knowledge of this interaction is far from being complete, even though it is essential for designing an efficient plant based biostimulation of contaminants biodegradation. PCBs are ubiquitous and persistent organic pollutants (POPs), generated exclusively from human sources. They are found in the environment as a mix of several congeners (e.g. Apirolio, produced in Italy and used for electrical transformers). PCB biodegradation can potentially occur through aerobic and anaerobic microbial processes, but their poor bioavailability and the requirement for an inducer in anaerobic conditions may hinder microbial degradation.
In this work the results of pot studies conducted in a greenhouse for 8 months for investigating the effect of the forage species Medicago sativa on PCBs degradation are reported. Soil samples were collected from a historically contaminated soil and used for setting-up different microcosms in presence/absence of the plant and/or of municipal solid waste compost. An additional amount of Apirolio was added to half microcosms. Finally, eight different experimental conditions were set-up.
Microbiological and chemical analysis were performed at different experimental times in order to evaluate the changes in the structure and functioning of microbial populations in relation to the different experimental conditions and the PCB degradation. The microbial community was studied in terms of abundance (DAPI counts), viability (live/dead methods), diversity (Fluorescent In Situ Hybridization) and activity (dehydrogenase activity). PCBs decreased in all conditions 8 months after the microcosm set-up. Each treatment acted in a different way and times on transformation/degradation of the various congeners. The addition of Apirolio not only did not affect negatively the microbial community, but it also stimulated their degradation activity particularly towards the low chlorinated congeners (28 and 52). Apirolio being freshly added PCBs degraded faster than the pre-existing ones, according with the fact that PCB molecules adsorbed on soil for a long time become progressively less bioavailable. PCB degradation of most congeners analysed (28, 52, 105, 167, 156, 157, 101, 118) was higher in the conditions in which Apirolio was added together with plant and compost. These results are supported by a significant shift at 224 days in the microbial community groups. In particular, Beta-Proteobacteria, initially the dominant group of the bulk soil, decreased significantly while at the same time Alpha-Proteobacteria become the dominant one. |
| Source | 6th European Bioremediation Conference (ebc-vi 2015), Chania, Crete, Greece, June 29-July 2 2015, Chania, Crete, Greece, June 29-July 2 2015 |
| Keywords | Plant-assisted bioremediationstructure and functioning of microbial populations |
| Year | 2015 |
| Type | Abstract in atti di convegno |
| Authors | Barra Caracciolo A, Grenni P, Di Lenola M, Ancona V, Massacci A |
| Text | 340787 2015 Plant assisted bioremediation structure and functioning of microbial populations Bioremediation of a PCB historically contaminated soil in presence of the leguminous Medicago sativa Barra Caracciolo A, Grenni P, Di Lenola M, Ancona V, Massacci A Barra Caracciolo A, Grenni P, Di Lenola M, Ancona V IRSA CNR Massacci A IBAF CNR 6th European Bioremediation Conference ebc vi 2015 , Chania, Crete, Greece, June 29 July 2, BOOK OF ABSTRACTS N. Kalogerakis, F. Fava, E. Manousaki 978 960 8475 23 6 Published version 6th European Bioremediation Conference ebc vi 2015 , Chania, Crete, Greece, June 29 July 2 2015 Chania, Crete, Greece June 29 July 2 2015 Internazionale Contributo Plant assisted bioremediation is emerging as one of the most effective means by which plants and their associated rhizosphere microorganisms can degrade organic contaminants in soils. Among biostimulation approaches, vegetation of different contaminated matrices with plant species found applications for accelerating the depletion of recalcitrant contaminants comprising Polychlorinated biphenyls PCBs . This process is mainly due to the stimulation of organic contaminant biodegradation by natural occurring microorganisms through root exudates that can eventually increase the bioavailability of the contaminants and induce a natural selection of the microbial community. However, the efficiency of a phytoremediation process depends mainly on the presence and activity of plant associated microorganisms carrying degradation genes required for the enzymatic breakdown of contaminants. In case the plant is growing in presence of contaminants, there is an interaction between contaminant, soil, and plant species that determines the structure and the metabolic activity of the plant associated microbial communities. The knowledge of this interaction is far from being complete, even though it is essential for designing an efficient plant based biostimulation of contaminants biodegradation. PCBs are ubiquitous and persistent organic pollutants POPs , generated exclusively from human sources. They are found in the environment as a mix of several congeners e.g. Apirolio, produced in Italy and used for electrical transformers . PCB biodegradation can potentially occur through aerobic and anaerobic microbial processes, but their poor bioavailability and the requirement for an inducer in anaerobic conditions may hinder microbial degradation. In this work the results of pot studies conducted in a greenhouse for 8 months for investigating the effect of the forage species Medicago sativa on PCBs degradation are reported. Soil samples were collected from a historically contaminated soil and used for setting up different microcosms in presence/absence of the plant and/or of municipal solid waste compost. An additional amount of Apirolio was added to half microcosms. Finally, eight different experimental conditions were set up. Microbiological and chemical analysis were performed at different experimental times in order to evaluate the changes in the structure and functioning of microbial populations in relation to the different experimental conditions and the PCB degradation. The microbial community was studied in terms of abundance DAPI counts , viability live/dead methods , diversity Fluorescent In Situ Hybridization and activity dehydrogenase activity . PCBs decreased in all conditions 8 months after the microcosm set up. Each treatment acted in a different way and times on transformation/degradation of the various congeners. The addition of Apirolio not only did not affect negatively the microbial community, but it also stimulated their degradation activity particularly towards the low chlorinated congeners 28 and 52 . Apirolio being freshly added PCBs degraded faster than the pre existing ones, according with the fact that PCB molecules adsorbed on soil for a long time become progressively less bioavailable. PCB degradation of most congeners analysed 28, 52, 105, 167, 156, 157, 101, 118 was higher in the conditions in which Apirolio was added together with plant and compost. These results are supported by a significant shift at 224 days in the microbial community groups. In particular, Beta Proteobacteria, initially the dominant group of the bulk soil, decreased significantly while at the same time Alpha Proteobacteria become the dominant one. Abstract in atti di convegno anna.barracaracciolo BARRA CARACCIOLO ANNA paola.grenni GRENNI PAOLA valeria.ancona ANCONA VALERIA angelo.massacci MASSACCI ANGELO TA.P04.005.011 Vulnerabilita degli ecosistemi delle acque sotterranee e attenuazione naturale degli inquinanti nel suolo e nel sottosuolo |
