PHYTOEXTRACTION OF Pb AND Cd FROM A SUPERFUND SOIL: EFFECTS OF AMENDMENTS AND CROPPINGS

Abstract

In a growth chamber, maize (Zea mays) and Indian mustard (Brassica juncea) were grown over two croppings in soil from a Superfund site (Pb_Total = 65,200 mg/kg and Cd_Total = 52 mg/kg). Soil treatments consisted of ethylenediaminetetraacetic acid, sodium citrate and composted sewage sludge, each at two rates (EDTA .05%, EDTA .2%, citrate .05%, citrate .2%, CSS 5% and CSS 10%, respectively). In most cases, the EDTA and citrate treatments were superior in terms of solubilizing soil Pb for root uptake and translocation into above-ground biomass. In the first maize crop, the EDTA .2% treatment resulted in 2435 and 9389 mg/kg Pb in shoot and root tissues, respectively. The CSS treatments typically resulted in lowest Pb and Cd removal efficiencies. Lead remaining in the soil after two croppings was mainly associated with the carbonate, organic, and residual fractions, which represent the less bioavailable forms. Soil Cd was generally more mobile for plant uptake than soil Pb. The EDTA .2% and citrate treatments were most successful in promoting Cd uptake by both maize and mustard. Although Pb concentrations (mg/kg tissue) were lower for maize than mustard, the former removed more total Pb (0.2 mg per pot, mean over all treatments), compared to mustard (0.03 mg), by virtue of its higher biomass production.

Keywords:

• Biosolids
• Brassica juncea
• Citric acid
• EDTA
• Hyperaccumulator
• Phytoremediation
• Zea mays

ACKNOWLEDGMENTS

The study reported herein was supported by the Indiana Academy of Science and the Ball State University Internal Grants Program.