Resource manipulation in uranium and arsenic attenuation by Lemna gibba L. (duckweed) in tailing water of a former uranium mine

Abstract

Influences of phosphorus and nitrogen on uranium and arsenic accumulation in Lemna gibba L. were investigated in the laboratory hydroponic cultures and in the field pot experiments. The initial uranium and arsenic concentrations in solutions for the hydroponic cultures were 1000 µg l −1 each, while in situ trials used tailing water containing 198.7 ± 20.0 µg U l −1 and 75.0 ± 0.4 µg As l −1 at a former uranium mine in eastern Germany. A test of three PO 3− 4 concentrations (0.01, 13.6 and 40.0 mg l −1 ) in the hydroponic cultures, highest uranium accumulated in L. gibba under the culture with highest PO 3− 4 . Significant differences in uranium accumulation were between 0.01 mg l −1 and 13.6 mg l −1 PO 3− 4 cultures only (ANOVA p = 0.05). In the field, addition of 40.0 mg l −1 PO 3− 4 increased the bioaccumulation of uranium significantly. Contrary, high PO 3− 4 concentrations suppressed the bioaccumulation of arsenic in both the laboratory and the field. The bioaccumulation of both uranium and arsenic increased slightly with the increase of NH + 4 concentration. However, high NH + 4 concentrations reduced the yield in the control experiments. The concentration of uranium rose temporarily to 856.0 ± 294.0 µg l −1 , while the concentration of arsenic sunk slightly and temporarily immediately after amending the tailing waters with 40 mg l −1 PO 3− 4 . The speciation of uranium in the tailing water was modelled with geochemical code PhreeqC, which predicted that uranyl carbonate species dominated before addition of phosphates, but after increasing the PO 3− 4 concentrations, uranyl phosphates species became dominant. Addition of NH + 4 to the tailing water had negligible influence on free available uranium and arsenic concentrations. Thus, manipulations to enhance uranium and arsenic attenuation by L. gibba has limitation when the amendments interact with other elements including the contaminants in the milieu, and when the target contaminants have antagonistic behaviour in the tailing water.

Selecting Appropriate Forms of Nitrogen Fertilizer to Enhance Soil Arsenic Removal byPteris Vittata: A New Approach in Phytoremediation

“…A similar phenomenon was reported by Huang et al (2004) in As-hyperaccumulating ferns. Mkandawire et al (2005) observed that As accumulation in duckweed increased slightly with an increase in NH 4 + concentration. The increase in As accumulation in plants supplied with NH 4 -N fertilizer is probably due to the enhancement of uptake and/or accumulation of AsO 4 3− by an ion synergistic effect of NH 4 + .…”

Biogeochemistry of uranium in the soil-plant and water-plant systems in an old uranium mine

“…ex Hensch. (Overall and Parry, 2004), Lemna gibba L. (Mkandawire et al, 2004(Mkandawire et al, , 2005Sasmaza and Obek, 2009), Spirodela punctata (G.Mey.) C.-H.Thomps.…”

Characterization and remediation of soils contaminated with uranium

“…The transfer of radionuclides from soils to plants is dependent on three classes of factors [129,214,314]:…”

“…Considering the effects of various soil amendments on uranium desorption from soil to soil solution, a number of authors investigated the physiological characteristics of uranium uptake and accumulation in plants, and developed techniques to trigger uranium hyperaccumulation in plants [313,314]. Their studies indicate that soil organic matter sequestered uranium, rendering it largely unavailable for plant uptake [265].…”