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The distribution and mobility of manganese (Mn) in the hyperaccumulator plant species Phytolacca acinosa Roxb. (Phytolaccaceae) were investigated in a hydroponic system. The plants were exposed to 2 or 5 m M Mn for up to 28 days. For any given plant, the Mn content in the mature leaves (nos. 5–9) was always higher than that in the old (nos. 1–4) and young leaves (nos. 10–14). Within the different parts of a leaf, Mn was preferentially accumulated in the leaf marginal area, where the observed level was threefold higher than that in the midrib. Cross-sectional analysis of the leaf revealed that the concentration of Mn was higher in the leaf epidermis than in the mesophyll. Cell fractionation analysis with P. acinosa leaves showed that most of the Mn (78.4%) was present in the final supernatant fraction (following centrifugation at 20,000 g for 45 min). The distribution of Mn in the leaves of P. acinosa was controlled mainly by the transpiration rate. Our investigation demonstrated that Mn was readily transported from the roots to shoots of P. acinosa but that it could not be remobilized readily after it reached leaves. [ABSTRACT FROM AUTHOR]

Passivation of nanoscale zerovalent iron hinders its efficiency in water treatment, and loading another catalytic metal has been found to improve the efficiency significantly. In this study, Cu/Fe bimetallic nanoparticles were prepared by liquid-phase chemical reduction for removal of hexavalent chromium (Cr(VI)) from wastewater. Synthesized bimetallic nanoparticles were characterized by transmission electron microscopy, Brunauer–Emmet–Teller isotherm, and X-ray diffraction. The results showed that Cu loading can significantly enhance the removal efficiency of Cr(VI) by 29.3% to 84.0%, and the optimal Cu loading rate was 3% (wt%). The removal efficiency decreased with increasing initial pH and Cr(VI) concentration. The removal of Cr(VI) was better fitted by pseudo-second-order model than pseudo-first-order model. Thermodynamic analysis revealed that the Cr(VI) removal was spontaneous and endothermic, and the increase of reaction temperature facilitated the process. X-ray photoelectron spectroscopy (XPS) analysis indicated that Cr(VI) was completely reduced to Cr(III) and precipitated on the particle surface as hydroxylated Cr(OH)3 and CrxFe1−x(OH)3 coprecipitation. Our work could be beneficial for the application of iron-based nanomaterials in remediation of wastewater. [ABSTRACT FROM AUTHOR]

As the biogeochemical cycling of S in soil is closely associated with the mobility and bioavailability of heavy metals, in this study, we investigated the influence of S fertilization (S and SO) in paddy soils on rice growth, iron plaque formation over root surface, and Cu speciation of rice rhizosphere soil under flooding conditions. The dry weight and height of rice plants increased significantly after S fertilization, indicating that S fertilization of Cu-contaminated paddy soils can enhance rice growth. Sulfur fertilization (less than 500 mg/kg) promoted the formation of iron plaque, thus sequestering a large amount of Cu on root surface and decreasing the bioavailability of Cu by inducing transformation of Cu bioavailable fractions (exchangeable, carbonate oxides, or iron and manganese oxide bound to Cu) to Cu bound to organic matter. Copper K-edge X-ray absorption near-edge structure (XANES) revealed that S fertilization increased the percentage of Cu present as CuS and Cu-cysteine in rice rhizosphere soil, thus reducing Cu mobility. As Cu concentration in rice plants decreased and the biomass of rice plants increased after S fertilization, it can be suggested that S fertilization may be an effective approach for managing Cu-contaminated paddy soils. [ABSTRACT FROM AUTHOR]