Assessing the potential for zinc and cadmium phytoremediation with the hyperaccumulator Thlaspi caerulescens

Thlaspi caerulescens is a Zn and Cd hyperaccumulator, and has been tested for its phytoremediation potential. In this paper we examine the relationships between the concentrations of Zn and Cd in soil and in T. caerulescens shoots, and calculate the rates of Zn and Cd extraction from soil. Using published data from field surveys, field and pot experiments, we show that the concentrations of Zn and Cd in the shoots correlate with the concentrations of Zn and Cd in soils in a log-linear fashion over three orders of magnitude. There is little systematic difference between different populations of T. caerulescens in the relationship between soil and plant Zn concentrations. In contrast, populations from southern France are far superior to those from other regions in Cd accumulation. Bioaccumulation factors (plant to soil concentration ratio) for Zn and Cd decrease log-linearly with soil metal concentration. Model calculations show that phytoremediation using T. caerulescens is feasible when soil is only moderately contaminated with Zn and Cd, and the phytoremediation potential is better for Cd than for Zn if the populations from southern France are used. Recent progress in the understanding of the mechanisms of Zn and Cd uptake by T. caerulescens is also reviewed.