A Mathematical Model of Phytoremediation for Petroleum Contaminated Soil: Sensitivity Analysis

Abstract

Phytoremediation is an attractive treatment technology for many contaminated sites due to its cost effectiveness and public acceptance. We present a sensitivity analysis of important parameters from a screening level model for phytoremediation by grass species of weathered petroleum-contaminated sites. The conceptual framework is that root movement through contaminated soil will enhance contaminant biodegradation by providing a local environment more favorable for petroleum degrading microorganisms--the so-called rhizosphere effect. Common questions in phytoremediation are, "What species should be planted?" and "What management practices should be followed?" These choices may affect degradation kinetics, root biomass (and therefore rhizosphere volume), and the root turnover. Important model parameters are the rate constants, rhizosphere volume, and the rate of root turnover. We present a sensitivity analysis with the aim of identifying the most important factors for improving phytoremediation effectiveness. For simulations of the phytoremediation of weathered diesel range organics, our results indicate that annual species, with higher root turnover, are preferred over perennial species with the caveat of equal degradation rate constants, that is, no species-dependent effects. In addition, the results suggest that the management of nonrhizosphere soil could play an important role in the overall effectiveness of phytoremediation. Finally, the effect of increasing root biomass or increasing the rhizosphere thickness is approximately equivalent with respect to the ultimate removal of the contaminants.

Future Prospects

“…Estimated costs for hydraulic control of an unspecifi ed contaminant in a 20-foot-deep aquifer at a 1-acre site were $660,000 for conventional pump and treat and $250,000 for phytoremediation (EPA/600/R-99/107). Studies indicate that phytoremediation is competitive with other treatment alternatives, as costs are approximately 50-80 % of the costs associated with physical, chemical or thermal techniques at applicable sites (Thomas et al 2003 ). Some more actuarial studies need to be carried out to give an estimate of the perceived costs of remediation works that will be useful for project sanctioning authorities or decision-makers.…”

Phytodegradation of organic compounds

“…Developing effective models may help to address these limitations and might help the research community to understand the interactions among the many processes that contribute to phytoremediation. Thoma and colleagues [49,50] developed a model for screening grass species for the phytoremediation of weathered petroleum. Models for calculating hydraulic control based on transpiration and groundwater characteristics have been discussed and evaluated, with the suggestion that field measurements be used to verify model predictions whenever possible [51].…”

The Potential ofChromolaena Odorata(L) to Decontaminate Used Engine Oil Impacted Soil Under Greenhouse Conditions

“…Thus for a plant species to qualify for application in phytoremediation it has to posses characteristics such as strong adaptive features, resistance to adverse conditions, grow rapidly under normal conditions and probably have high germination rates. Although mathematical models have been developed to determine the appropriateness of a plant species (Thoma et al, 2003) for remediation of soil impacted by organics, the actual selection is empirical and based on laboratory or greenhouse trials (Kirkpatrick et al, 2006;Liste and Prutz, 2006;Euliss et al, 2007;Muratova et al, 2008).…”