ARS | Publication request: PHYTOEXTRACTION OF ZINC BY OAT (AVENA SATIVA), BARLEY (HORDEUM VULGARE) ANDINDIAN MUSTARD (BRASSICA JUNCEA)

Submitted to: Journal of Environmental Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 1, 1998
Publication Date: N/A

Interpretive Summary: Heavy metal (Pb, Zn, Cd, Cu, Cr and Ni) contamination of soils poses serious problems to both human health and agriculture in the U.S. Current engineering-based technologies used to remediate soils (e.g., removal of top soil for storage in landfills) are quite costly, and often dramatically disturb the landscape. Recently, there has been considerable interest focused on the use of terrestrial plants to absorb heavy metals from the soil and concentrate them in the easily harvestable shoot tissues as an alternative remediation technology. However, little is currently understood about the traits that would make certain plant species the best candidates for phytoremediation of contaminated soils. In this study, we looked at the effectiveness of grass species in terms of their ability to extract Zn from solution and from a contaminated soil in comparison with a plant species, Indian mustard, that has been identified as a potential heavy metal accumulator. Twenty two different grass species were screened by growing them on nutrient solution that had high levels of Zn. This study indicated that oat and barley were the best performing grass species, and were comparable to Indian mustard in terms of tolerating and extracting Zn from the growth solution. A pot study carried out on Zn contaminated soil obtained from a Zn smelter site verified the potential of these two species for phytoremediation. These findings should broaden the range of plant species that could be used for phytoremediation.

Technical Abstract: The success of phytoremediation hinges on the selection of plant species and soil amendments that maximize contaminant removal. Indian mustard (Brassica juncea) has been shown to be effective in phytoextracting Zn, particularly after the synthetic chelate EDTA has been applied to the soil. However, the effectiveness of grass species for phytoremediation has not been addressed in great detail. A hydroponic screening of 22 grass species indicated that oat (Avena sativa) and barley (Hordeum vulgare) tolerated the high Cu, Cd and Zn concentrations present in the solution and also accumulated elevated concentrations of these metals in the shoots. A hydroponic experiment comparing these two grasses to Indian mustard indicated that although shoot Zn concentrations were greater for Indian mustard, the grasses were considerably more tolerant. A pot experiment conducted using a Zn-contaminated soil showed that the addition of EDTA to the soil significantly increased Zn accumulation by B. juncea but not oat or barley. Nonetheless, barley accumulated >2 mg Zn/plant, which was 2-4 times more Zn than what was accumulated in Indian mustard in the presence of EDTA. The results of this experiment suggest that barley has a phytoremediation potential equal to, if not greater than that for B. juncea.