Effects of Plants for Reduction and Removal of Hexavalent Chromium from a Contaminated Soil

The comparative effectiveness for hexavalent chromium reduction and removal from irrigation water, using three selected plant species (Phragmites australis, Salix viminalis, and Ailanthus altissima) planted in soil contaminated with hexavalent chromium, has been studied in the present work. The above plant species were irrigated, in a continuous mode, with water, contaminated with 10 mg/L of hexavalent chromium. Hexavalent chromium and total chromium have been measured in all plant tissues species and in the drainage water. Total chromium removal from water was ranging from 56 % (Phragmites) to 70 % (Salix). After 360 days of growth, the chromium content of the contaminated soil dropped from 70 (initial) to 32, 36, and 41 mg Cr/kg(dry soil), for Salix, Phragmites, and Ailanthus, respectively. Salix and Phragmites accumulated the highest amount of chromium in the roots (2,029 and 1,800 mg Cr/kg(dry tissue), respectively), compared with 358 mg Cr/kg(dry tissue) for Ailanthus roots. Most of chromium was found in trivalent form in all plant tissues. Ailanthus had the lowest affinity for CrVI reduction in the root tissues. Phragmites indicated the highest chromium translocation potential, from roots to stems, while Salix indicated the highest chromium translocation from roots to leaves. Toxicity effects, expressed as root growth rate inhibition, indicated that Salix is the most chromium-tolerant species, with Ailanthus in the antipode.