No abstract

Cr(VI) represents an environmental challenge in both soils and waters as it is soluble and bioavailable over a wide range of pH. In previous investigations, Portulaca oleracea (a plant local to the UAE) demonstrated particular ability for the phytoextraction of Cr(VI) from calcareous soils of the UAE. In this publication, the results of the evaluation of P. oleracea phytoextraction of Cr(VI) from UAE soil at higher concentrations are reported. P. oleracea was exposed to nine different concentrations of Cr(VI) in soil from 0 to 400 mg kg -1 . The uptake of Cr(VI) increased as its concentration in soil increased between 50 and 400 mg kg -1 , with the most efficient removal in the range from 150 to 200 mg kg -1 . The total chromium concentrations exceeded 4600 mg kg -1 in roots and 1400 mg kg -1 in stems, confirming the role of P. oleracea as an effective Cr(VI) accumulator. More than 95% of the accumulated Cr(VI) was reduced to the less toxic Cr(III) within the plant.

Local soil from the Emirate of Abu Dhabi, United Arab Emirate is investigated for its efficiency in removing heavy metals from industrial wastewater. Eight different industrial water effluents from different industries were treated. Pb, Zn, Fe, Cu and Mn were removed from industrial wastewaters yielding treated water with heavy metal concentrations well below the maximum limits enforced by environmental protection agencies.

Phytoextraction is an effective and environment-friendly approach for remediation of soil polluted with toxic metals. Portulaca oleracea is a potential hyperaccumulator of Cr(VI) from polluted soil. In this study, the effect of soil organic content, pH, and sulphate concentration on phytoextraction of Cr(VI) using Portulaca oleracea was investigated. Seedlings of Portulaca oleracea were grown in soils with (i) three organic content compositions, (ii) six levels of pH, and (iii) six concentrations of sulphate salts; all were irrigated with Cr(VI) solutions at 200 ppm concentration. Chromium concentration in different tissues of plants was monitored under the variant conditions. Results indicated that the uptake of Cr(VI) by Portulaca oleracea is favoured at (i) low organic content soil (0.42%), (ii) slightly alkaline pH range (∼8), and (iii) with sulphate concentration in the range of 300–600 ppm.