In the last two decades there has been a growing interest in
bioremediation technologies which use plants and microorganisms to
degrade organic chemicals such as Polychlorinated Biphenyls (PCBs) in
contaminated sites. These techniques represent a good alternative to
traditional remediation technologies, being cheaper, not disruptive and
more suitable for large contaminated areas. Different studies have been
conducted to investigate the potential of plant-microbe interactions in
the remediation of organic chemical contaminated soils with respect to
natural attenuation, providing useful data such as chemical degradation
rates (K
D
) or half lives (HL). Such a type of data can be used to predict
soil concentration temporal trend, as well as the time needed to achieve
legal limit when using plants and their associated rhizosphere microbe to
remediate contaminated sites. In the present work, rhizoremediation
experiment derived KD or HL for PCBs will be used as input parameters
in an existing dynamic air-plant-litter-soil model (SoilPlusVeg) to
estimate PCB concentration temporal trend in the soil of a National
Relevance Site (SIN) for remediation located in Northern Italy (SINBrescia
Caffaro). Analyses of sample collected in this area have shown
the presence of a high spatial variability of PCB concentrations with
values varying up to 3-4 orders of magnitude. Therefore it could be
interesting to understand if rhizoremediation might be a suitable
technique for the entire site. A number of long term simulations were
run with SoilPlusVeg model for some PCBs and results were used to 1)
compare the influence of natural attenuation vs. plant/microbe
interactions on soil concentrations, 2) evaluate the effectiveness of
rhizoremediation when a complex contamination gradient is present.
Simulations results showed that although the importance of natural
attenuation vs plant/microbe interactions depends on PCB physical
chemical properties, when considering rhizoremediation experiment
derived degradation rates the time requested to achieve legal limits
decrease. However, rhizoremediation must be accurately implemented
(in terms of species to be selected, their density, etc) to account for
effective remediation, especially when complex patterns of contaminant
are present