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Title: NiO(s) (Bunsenite) is not Available to Alyssum species

item Fellet, Guido
item Centofanti, Tiziana
item Chaney, Rufus
item Green, Carrie

Submitted to: Plant and Soil
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/11/2008
Publication Date: 1/17/2009
Citation: Fellet, G., Centofanti, T., Chaney, R.L., Green, C.E. 2009. NiO(s) (Bunsenite) is not Available to Alyssum species. Plant and Soil Journal. 319:219-223.

Interpretive Summary: Phytoextraction of soil contaminants is conducted with plants which hyperaccumulate heavy metals such as Ni. Because metals can occur as different compounds in soils, it is important to know if common forms of the metal in contaminated soils can be dissolved and hyperaccumulated by the plants selected for phytoextraction. Further, understanding the limitations of these plants to dissolve particular soil metal chemical forms will help understand what is possible with these plants. In the present study, a nickel (Ni) hyperaccumulator, Alyssum corsicum, was grown in nutrient solution without and with the addition of powdered crystalline NiO (the crystalline mineral bunsenite). The NiO was comprised of micron sized particles of the green oxide which has very slow dissolution kinetics. At pH 7, the half time for dissolution of NiO is over 20 years, so a phytoextraction plant would need to be able to attack the compound and alter its natural dissolution rate in order to achieve phytoextraction from this compound in soil. Prior research has shown that NiO does persist in soils near Ni smelters after the NiO is emitted at high temperature. The plants were grown for 4 weeks with 1.34 mmol Ni per L as NiO and then analyzed compared to a control. Supply of this high level of NiO did not harm the plants, nor was Ni hyperaccumulated. Shoots contained 19 mg Ni/kg while plants supplied a soluble Ni source at 0.32 mmol/L accumulated over 12,000 mg Ni/kg dry matter shoots. The roots were coated with the NiO particles, with over 3% Ni after water rinsing. Thus the natural Ni hyperaccumulator, Alyssum corsicum, cannot hyperaccumulate Ni from NiO (bunsenite) in soils, and cannot practically phytoremediate smelter contaminated soils rich in NiO. The hyperaccumulator, Alyssum species, remain highly effective in phytoextracting normal forms of Ni in soils including serpentine soils which are naturally mineralized with Ni and can be phytomined as a new economic farming technology.

Technical Abstract: AIMS: To determine if the Ni-hyperaccumulator Alyssum corsicum can absorb Ni from the kinetically inert crystalline mineral NiO(s) (bunsenite). METHODS: A. corsicum and A. montanum plants were grown for 30 days in a serpentine Hoagland solution. NiO was provided at 0 or 0.1 g L-1 (1.34 mmol L-1) as reagent grade NiO particles <1 µm diameter, continuously mixed by aeration. RESULTS: A. corsicum and A. montanum shoots contained 19.4 and 5.2 mg Ni kg-1 DW with NiO, and 3.0 and 1.1 mg Ni kg-1 DW shoots, respectively in the control treatment. A. corsicum normally absorbs over 10 g Ni kg-1 shoots when supplied 300 µM soluble Ni. Roots were coated with the NiO particles and contained 3-5% Ni at harvest. CONCLUSION: Despite the small Ni accumulation in the NiO treatment above control, A. corsicum is not capable of dissolving and hyperaccumulating Ni from NiO.