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Orientador(es)
Resumo(s)
Phytoremediation technologies based on the combined
action of plants and the microbial communities that they support
within the rhizosphere hold promise in the remediation of land
and waterways contaminated with hydrocarbons but they have
not yet been adopted in large-scale remediation strategies. In this
review plant and microbial degradative capacities, viewed as a
continuum, have been dissected in order to identify where bottlenecks
and limitations exist. Phenols, anilines and polyaromatic
hydrocarbons (PAHs) were selected as the target classes of molecule
for consideration, in part because of their common patterns
of distribution, but also because of the urgent need to develop
techniques to overcome their toxicity to human health.
Depending on the chemical and physical properties of the pollutant,
the emerging picture suggests that plants will draw pollutants
including PAHs into the plant rhizosphere to varying extents
via the transpiration stream. Mycorrhiz.osphere-bacteria arid -fungi
may play a crucial role in establishing plants in degraded ecosystems.
Within the rhizosphere, microbial degradative activities
prevail in order to extract energy and carbon skeletons from
the pollutants for microbial cell growth. There has been little
systematic analysis of the changing dynamics of pollutant degradation
within the rhizosphere; however, the importance of
plants in supplying oxygen and nutrients to the rhizosphere via
fine roots, and of the beneficial effect of microorganisms on
plant root growth is stressed.
In addition to their role in supporting rhizospheric degradative
activities, plants may possess a limited capacity to transport some
of the more mobile pollutants into roots and shoots via fine
roots. In those situations where uptake does occur (i.e. only
limited microbial activity in the rhizosphere) there is good evidence
that the pollutant may be metabolised. However, plant
uptake is frequently associated with the inhibition of plant
growth and an increasing tendency to oxidant stress. Pollutant
tolerance seems to correlate with the ability to deposit large
quantities of pollutant metabolites in the 'bound' residue fraction
of plant cell walls compared to the vacuole. In this regard,
k,
particular attention is paid to the activities of peroxidases,
laccases, cytochromes P450, glucosyltransferases and ABC trans- il
porters. However, despite the seemingly large diversity of these B
proteins, direct proof of their participation in the metabolism B
of industrial aromatic pollutants is surprisingly scarce and little
is known about their control in the overall metabolic scheme. ]]
Little is known about the bioavailability of bound metabolites;
however, there may be a need to prevent their movement into
wildlife food chains. In this regard, the application to harvested
plants of composting techniques based on the degradative capacity
of white-rot fungi merits attention.
Descrição
Palavras-chave
Anilines Bound residues Cytochromes P450 Gluco- M Syl transferases Oxidant stress Peroxidases Phenols Phytoremediation Polyaromatic hydrocarbons Rhizosphere
Contexto Educativo
Citação
HARVEY, Patrícia J....[et al] - Phytoremediation of Polyaromatic Hydrocarbons, Anilines and Phenols. Environmental Science and Pollution Research International. ISSN 0944-1344. Vol. 9, n.º 1 (2002), p. 29-47
Editora
Springer