Uptake of Cadmium by Hydroponically Grown, Mature Eucalyptus Camaldulensis Saplings and the Effect of Organic Ligands

Abstract

The potential suitability of Eucalyptus camaldulensis for Cd phytoextraction was tested in a hydroponic study. Saplings were exposed to 4.5 and 89 μM Cd for one month, with and without EDTA and s,s-EDDS at 0.1, 1, and 5 mM. The saplings’ growth was not affected at the 4.5 μM Cd concentration, yet it decreased 3-fold at 89 μM, and almost all the Cd taken up was immobilized in the roots, reaching 360 and 5300 mg Cd kg⁻¹, respectively (approximately 75% of which was non-washable in acid). The respective Cd root-to-shoot translocation factors were 0.14 and ≈5*10⁻⁴. At 0.1 mM concentration, EDTA and EDDS had no effect or even a positive effect on the saplings growth. This was reversed at 1 mM, and the chelants became lethal at the 5 mM concentration. At 89 μM Cd in the growth medium, 0.1 mM EDTA increased Cd translocation into the shoots by almost 10-fold, however it strongly reduced Cd content inside the roots. This hydroponic study indicates the feasibility of E. camaldulensis use for cleanup Cd-contaminated soils at environmental concentrations, both for site stabilization (phytostabilization) and gradual remediation (phytoextraction). EDTA was shown to be much more efficient in enhancing Cd translocation than s,s-EDDS.

KEY WORDS:

• EDDS
• EDTA
• phytoextraction
• phytostabilization
• root-shoot Cd translocation

ACKNOWLEDGMENTS

The authors would like to acknowledge the Ministry of Human Resource Development, Government of India and the Ministry of Foreign Affairs, Government of Israel for granting a scholarship to support this research. Special thanks to Dr. Nir Atzmon and Mr. Yossi Moshe for their invaluable help throughout the study. The work was partially funded by the Italian Ministry of the Environment, Territory and Sea, within the Italian-Israeli Cooperation on Environmental Technologies – Project 5.