A Study of the Use of Alfalfa (Medicago sativa L.) for the Phytoremediation of Organic Contaminants in Soil

Abstract

This article presents the results of a study that was conducted to determine the effectiveness of using alfalfa (Medicago sativa L.) to enhance the phytoremediation of three different types of chemical contaminants. The chemicals studied were trinitrotoluene (TNT), the polycyclic aromatic hydrocarbon (PAH) pyrene, and the polychlorinated biphenyl (PCB) Aroclor 1248. Experiments were conducted using soils that contained high and low organic matter content. The results indicated that recoveries of pyrene and TNT from soil were highly dependent on the soil organic matter content, while the recovery of PCB was not. Significantly low levels of pyrene and TNT were recovered from all treatments in the soil with 6.3 percent organic matter content compared to recovery levels found in soil with 2.6 percent organic matter. The presence of alfalfa plants had a significant effect on the transformation of TNT and PCB in the low organic matter content soil only and had no effect on the fate of pyrene. In the low organic matter soil, only 15 percent and 17 percent of the initial TNT and PCB levels, respectively, were transformed in the unplanted control soils compared to 66 percent and 77 percent in the alfalfa planted pots. In both soil types, pyrene dissipation could not be attributed to the presence of alfalfa plants. Overall, it was concluded that under high soil organic matter conditions, adsorption and covalent binding to the soil organic matter appeared to be the dominant force of pyrene and TNT removal. The effectiveness of using alfalfa to enhance PCB and TNT transformations was more significant in the lower organic matter soil; thus phytoremediation had a greater effect in soils with lower organic matter content. © 2001 John Wiley & Sons, Inc.

Influence of Rhizobium meliloti on phytoremediation of polycyclic aromatic hydrocarbons by alfalfa in an aged contaminated soil

“…The efficiency of phytoremediation relies on the establishment of active plants with sufficient biomass growth, active root proliferation and/or root activities that can support a flourishing microbial consortium assisting phytoremediation in the rhizosphere [3,40,41]. Legumes, including alfalfa, have been identified as strong candidates for remediation of contaminated sites [22,23,42,43]. In the present study planted soil did show significantly lower concentrations of PAHs suggests that alfalfa in this experiment played a role in the remediation of PAH-contaminated soil.…”

Assessing the Phytoremediation Potential of Tall Fescue and Sericea Lespedeza for Organic Contaminants in Soil

“…Although recovery levels were markedly better in the low-OM soil, planting sericea and tall fescue did not have any significant effect on the transformation of Pyrene. The lack of plant effect on Pyrene transformations in soil has been repeatedly shown in other similar studies (Chekol & Vough, 2001;Chekol et al, 2002).…”

Impact of the plant rhizosphere and augmentation on remediation of polychlorinated biphenyl contaminated soil

“…A previous report demonstrated removal of 77% of Aroclor 1248 in a pot experiment containing eight Medicago sativa L. (alfalfa) using a low organic matter soil, whereas unplanted controls removed only 18% [7]. The same authors conducted a PCB transformation study with two other plants, tall fescue (Festuca arundinacea Schreb.)…”

“…Despite nearly 30 years of research on enhancing in situ PCB biodegradation [1,2], the most common method for remediating PCB-contaminated soil still involves excavation, followed by landfilling or incineration [3,4]. In light of the dearth of available remediation options for PCB-contaminated soils, it is surprising that only a few studies have investigated the potential for plants to assist in its removal [5][6][7][8].…”