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MODELING VADOSE ZONE CONTAMINANT TRANSPORT AND ROOT SOLUTE UPTAKE IN A PHYTO-EXTRACTION PROCESSES

Lugli, F.; Mahler, C. F.;

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Phyto-extraction is an in situ remediation technique involving the uptake of contaminants by plant roots and their subsequent accumulation in plant tissues. It stands out for its simplicity and low costs but nevertheless it is not widely used because of difficulties in estimating its efficiency and the required remediation time. Results depend on a complex set of interactive soil, plant, contaminant and atmospheric processes and parameters. Thus, the objective of this research was to numerically estimate the effectiveness of phytoextraction, varying some project parameters. Remediation of Cd2+, Pb2+ and Zn2+ contaminants by Chrysopogon zizanioides (Vetiver grass) was simulated using the Hydrus-1D software package. Variably-saturated flow was described using the standard Richards’ equation, and solute transport using the advection-dispersion equation. Sink terms in the governing flow and transport equations accounted for root water and solute uptake, respectively. Sorption of metals by the solid phase was described using linear isotherms. Two models for contaminant uptake by the roots were used: passive uptake in which uptake is proportional to the solution concentration, and active uptake as described with a Michaelis-Menten kinetic equation. All the applied models were adjusted on greenhouse remediation experiments in previous study. Dynamic field conditions (data from the coastal lowlands of the municipality of Rio de Janeiro) were considered. Several scenarios were tested, including different planting densities and irrigation schemes. The sensitivity analysis permitted to identify several trends in the simulations. It was found that the efficiency of phyto-extraction decreased significantly when contaminant sorption increased (higher retardation factors). By comparison, phyto-extraction was more efficient in time for more mobile contaminants, depending upon the advective contaminant transport velocity in the root zone, the potential transpiration rate, and prevailing water stress conditions in the soil root zone. While more elaborate calibrations may be needed using long-term field data, this study provided useful insight into the phyto-extraction process important for the design of future experiments.

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Palavras-chave: Non-saturated soil, Richard equation, contaminant transport, plant solute uptake,

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DOI: 10.5151/meceng-wccm2012-20146

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Como citar:

Lugli, F.; Mahler, C. F.; "MODELING VADOSE ZONE CONTAMINANT TRANSPORT AND ROOT SOLUTE UPTAKE IN A PHYTO-EXTRACTION PROCESSES", p. 4924-4932 . In: In Proceedings of the 10th World Congress on Computational Mechanics [= Blucher Mechanical Engineering Proceedings, v. 1, n. 1]. São Paulo: Blucher, 2014.
ISSN 2358-0828, DOI 10.5151/meceng-wccm2012-20146

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