A comparison between phragmites australis and helianthus annuus in chromium phytoextraction

A comparison of chromium abatement from irrigation water, by the use of two selected plant species, Phragmites australis and Helianthus annuus, planted in chromium-contaminated soil, was studied in the present work. The above plant species were irrigated, in a continuous mode, with 10 mg Cr-VI/L contaminated tap water. More than 90 % of hexavalent chromium was reduced to trivalent chromium, from both plant species, as measured in the drainage water. Moreover, total chromium removal ranged from 54 % (Phragmites) to 70 % (Helianthus). After 90 days, the total chromium content of the contaminated soil dropped from 70 to 32 and 34 mg Cr/kgdry soil, for Helianthus and Phragmites, respectively. Helianthus accumulated higher amount of chromium in the roots (2,730 mg Cr/kg(dry tissue)) as compared to 1,800 mg Cr/kg(dry tissue) for Phragmites. Most of Cr-VI was reduced to Cr-III in all plant tissues, with Phragmites showing lower affinity for Cr-VI reduction in the root tissues but higher chromium translocation potential from roots to stems, while Helianthus showed higher chromium translocation from roots to leaves. Toxicity effects, expressed as root growth rate inhibition, indicated that Phragmites were the most tolerant specie to chromium effects. Both plant species showed high potentialities to be used in phytoremediation installations for chromium removal.