Table 4.
Hypothetical remediation times (years) of best performing clones/mutant of tested species to reduce 1 mg of Cd, Zn and Pb kg-1 DW soil for high or moderate field Cd, Zn and Pb concentrations to remediation thresholds (2 mg Cd, 282 mg Zn and 200 mg Pb kg-1 DW soil).
| Hypothetical remediation times (years) | Contamination level: | ||||
|---|---|---|---|---|---|
| High | Moderate | ||||
| Species | Clone/mutant | 7 mg Cd kg-1 DW | 429 mg Zn kg-1 DW | 217 mg Pb kg-1 DW | 4 mg Cd kg-1 DW |
| Poplar | D × (T × M) | 336 | 320 | n.d. | 134 |
| Willow | Zwarte Driebast | 150 ± 90 | 181 ± 107 | n.d. | 60 ± 36 |
| Tobacco | NBCu-10-8 | 401 ± 211 | 657 ± 345 | 1,864 ± 1,145 | 160 ± 84 |
| Sunflower | 15-35-190-04 | 744 ± 407 | 250 ± 152 | 4,250 ± 2,380 | 298 ± 163 |
Assumptions made were: (i) species’ extraction potentials are independent of soil metal concentrations, (ii) total soil metal content decreases linearly due to a constant yearly extraction, (iii) contamination and rooting depth are 0.5 m, and (iv) soil density is 1,250 kg m-3.