Abstract
Many polluted sites are typically characterized by contamination with multiple heavy metals, drought, salinity, and nutrient deficiencies. Here, an Australian native succulent halophytic plant species, Carpobrotus rossii (Haw.) Schwantes (Aizoaceae) was investigated to assess its tolerance and phytoextraction potential of Cd, Zn, and the combination of Cd and Zn, when plants were grown in soils spiked with various concentrations of Cd (20-320 mg kg(-1) Cd), Zn (150-2,400 mg kg(-1) Zn) or Cd + Zn (20 + 150, 40 + 300, 80 + 600 mg kg(-1)). The concentration of Cd in plant parts followed the order of roots > stems > leaves, resulting in Cd translocation factor (TF, concentration ratio of shoots to roots) less than one. In contrast, the concentration of Zn was in order of leaves > stems > roots, with a Zn TF greater than one. However, the amount of Cd and Zn were distributed more in leaves than in stems or roots, which was attributed to higher biomass of leaves than stems or roots. The critical value that causes 10% shoot biomass reduction was 115 μg g(-1) for Cd and 1,300 μg g(-1) for Zn. The shoot Cd uptake per plant increased with increasing Cd addition while shoot Zn uptake peaked at 600 mg kg(-1) Zn addition. The combined addition of Cd and Zn reduced biomass production more than Cd or Zn alone and significantly increased Cd concentration, but did not affect Zn concentration in plant parts. The results suggest that C. rossii is able to hyperaccumulate Cd and can be a promising candidate for phytoextraction of Cd from polluted soils.
Highlights
Phytoremediation that uses plants to clean up polluted soils/waters (Cunningham &Berti 1993) is generally considered as a cost-effective and environment-friendly technique (Salt et al 1998)
Many polluted sites are typically characterized by contamination with multiple-heavy metals, drought, salinity and nutrient deficiencies
An Australian native succulent halophytic plant species, Carpobrotus rossii (Haw.) Schwantes (Aizoaceae) was investigated to assess its tolerance and phytoextraction potential of Cd, Zn and the combination of Cd and Zn, when plants were grown in soils spiked with various concentrations of Cd (20-320 mg kg-1 Cd), Zn (150-2400 mg kg-1 Zn) or Cd+Zn (20+150, 40+300, 80+600 mg kg-1)
Summary
Phytoremediation that uses plants to clean up polluted soils/waters (Cunningham &Berti 1993) is generally considered as a cost-effective and environment-friendly technique (Salt et al 1998). As one of important phytoremediation approaches, phytoextraction utilizes some plants to take up heavy metals from contaminated soils or waters, and translocate them into shoots which are harvested to get heavy metals recycled and soil/water cleaned through further processing methods (Salt et al 1998). Some plant species (defined as hyperaccumulators) can accumulate extraordinarily high (10-100 times) concentrations of heavy metals in shoots than do most plants, they are often not suitable for practical application to phytoextraction due to their specificity to a particular heavy metal and low biomass production (Hassan &Aarts 2011). It is crucial for successful phytoextraction to use plants that could accumulate relatively high amounts of heavy metals and have other tolerant traits
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