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Objective: To better understand the wetland restoration, the physicochemical property and microbial community in rhizosphere and bulk soil of the living and death Tamarix chinensis covered soil zones were studied. Results: There were differences between growth conditions in the levels of soil pH, salinity, SOM, and nutrient. The living status of T. chinensis exhibited higher capacity of decreasing saline-alkali soil than the death condition of plants, and the living T. chinensis showed higher uptake of N, P, and K as compared with the death samples. Proteobacteria, Bacteroidota, and Chloroflexi were the predominant bacterial communities as revealed via high-throughput sequencing. Conclusions: It is great potential for using halophytes such as T. chinensis to ecological restore the coastal saline-alkali soil. This study could contribute to a better understanding of halophyte growth during the coastal phytoremediation process, and guide theoretically for management of T. chinensis population. [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]

It has become apparent that the threat of an organic pollutant in soil is directly related to its bioavailable fraction and that the use of total contaminant concentrations as a measure of potential contaminant exposure to plants or soil organisms is inappropriate. In light of this, non-exhaustive extraction techniques are being investigated to assess their appropriateness in determining bioavailability. To find a suitable and rapid extraction method to predict phenanthrene bioavailability, multiple extraction techniques (i.e., mild hydroxypropyl- β-cyclodextrin (HPCD) and organic solvents extraction) were investigated in soil spiked to a range of phenanthrene levels (i.e., 1.12, 8.52, 73, 136, and 335 μg g dry soil). The bioaccumulation of phenanthrene in earthworm ( Eisenia fetida) was used as the reference system for bioavailability. Correlation results for phenanthrene suggested that mild HPCD extraction was a better method to predict bioavailability of phenanthrene in soil compared with organic solvents extraction. Aged (i.e., 150 days) and fresh (i.e., 0 day) soil samples were used to evaluate the extraction efficiency and the effect of soil contact time on the availability of phenanthrene. The percentage of phenanthrene accumulated by earthworms and percent recoveries by mild extractants changed significantly with aging time. Thus, aging significantly reduced the earthworm uptake and chemical extractability of phenanthrene. In general, among organic extractants, methanol showed recoveries comparable to those of mild HPCD for both aged and unaged soil matrices. Hence, this extractant can be suitable after HPCD to evaluate risk of contaminated soils. [ABSTRACT FROM AUTHOR]

Laser ablation coupled with inductively coupled plasma-mass spectrometry was used to find Cu and Zn concentration in surface tissue along a longitudinal developmental gradient with meristem, rapidly elongating tissue, and nongrowing tissue in a model system of seedling roots of Cucumis sativus L. (cucumber). Tissue metal accumulation was determined for roots of seedlings growing on cellulosic germination paper treated with nutrient solution (controls), and also treated with concentrations of Zn (40 ppm) and Cu (10 ppm) that reduced growth. Cu content of all roots is highest at the apex and falls sharply to lower values by 2 mm from the root tip. In contrast, at moderate Zn availability (0.07 ppm), Zn content rises from the apex to 2 mm then falls throughout the remainder of the growth zone. At high external Zn the spatial pattern resembles that of Cu. Cucumber root growth zones accumulate more of each metal with higher external availability. Metal deposition rates were calculated using a continuity equation with data on local metal content and growth velocity. Deposition rates of both metals are generally highest in the rapidly elongating region, 1.5–3.5 mm, even where metal concentration is decreasing with position and root age and even when the accumulation is inhibitory to growth. [ABSTRACT FROM AUTHOR]

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]