Mémoire
| Résumé : | Remediation of Cd and Zn contaminated soils by phytoextraction with Noccaea caerulescens is largely studied and is expected to deplete bioavailable trace metal soil pools. The aim of our study was to assess the efficiency of Cd and Zn phytoextraction on soils destined for cropping. As human health is concerned by soil-to-crop transfer of trace metals, the leafy vegetable phytometer Diplotaxis tenuifolia (arugula) was used to determine the worst-case scenario bioavailable concentrations. Diplotaxis tenuifolia plants were grown in pots on 14 moderately polluted soils - exceeding the Belgian legal thresholds - that had previously undergone a season of phytoextraction with N. caerulescens. Our results show that, for a specific selection of soils only, trace metal uptake by N. caerulescens decreases Cd and Zn concentrations in arugula leaves. This strongly depended on soil pH and carbonate in the case of Cd phytoextraction whereas an efficient Zn phytoextraction was found on soils with high bioavailable Zn concentrations. Furthermore, root decay of N. caerulescens did not seem to replenish the soil trace metal supply. These observations suggest that phytoextraction with N. caerulescens is possible while highly depending on soil properties and should be studied more thoroughly as a solution to the depollution of potential crop soils. Finally, this study shows that bioavailable Cd and Zn concentrations assessed by ammonium acetate-EDTA are highly linked to the bioavailable Cd and Zn concentrations found in the D. tenuifolia phytometer. This allowed us to suggest maximal Cd and Zn bioavailable concentrations for crop soils to limit human health risks. |
