Reduced arsenic accumulation in indica rice (Oryza sativa L.) cultivar with ferromanganese oxide impregnated biochar composites amendments.

The effects of biochar (BC) and ferromanganese oxide biochar composites (FMBC1 and FMBC2) on As (Arsenic) accumulation in rice were determined using a pot experiment. Treatments with BC or FMBC improved the dry weights of rice roots, stems, leaves, and grains in soils containing different As contamination levels. Compared to BC treatment, FMBC treatments significantly reduced As accumulation in different parts of the rice plants (P < 0.05), and FMBC2 performed better than FMBC1 did. Furthermore, exposure to 2% FMBC2 decreased the total As concentration in the grain by 68.9-78.3%. The addition of FMBC increased the ratio of essential amino acids in the grain, decreased As availability in the soil, and significantly increased the Fe and Mn plaque contents. The reduced As accumulation in rice can be attributed to As(III) to As(V) oxidation by ferro - manganese binary oxide, which increased the As adsorbed by FMBC. Furthermore, Fe and Mn plaques on the rice root surface decreased the transport of As in rice. Taken together, our results demonstrated the applicability of FMBC as a potential measure for reducing As accumulation in rice, improving the amino acid content of rice grains, and effectively remediating As-polluted soil.

Lin L ，Gao M ，Qiu W ，Wang D ，Huang Q ，Song Z ... -  《-》

Effects of manganese oxide-modified biochar composites on arsenic speciation and accumulation in an indica rice (Oryza sativa L.) cultivar.

A pot experiment was used to investigate arsenic (As) speciation and accumulation in rice, as well as its concentration in both heavily contaminated and moderately contaminated soils amended with manganese oxide-modified biochar composites (MBC) and biochar alone (BC). In heavily As-contaminated soil, application of BC and MBC improved the weight of above-ground part and rice root, whereas in moderately As-contaminated soil, the application of MBC and low rate BC amendment increased rice root, grain weight and the biomass of the plant. Arsenic reduction in different parts of rice grown in MBC-amended soils was greater than that in plants cultivated in BC-amended soils. Such reduction can be attributed to the oxidation of arsenite, As(III), to arsenate, As(V), by Mn-oxides, which also had a strong adsorptive capacity for As(V). MBC amended to As-contaminated soil had a positive effect on amino acids. The Fe and Mn levels in the iron-manganese plaque that formed on the rice root surface differed among the treatments. MBC addition significantly increased Mn content (p < 0.05); the application of 2.0% MBC increased Mn content 36- and 10-fold compared to the control in heavily and moderately As-contaminated soils, respectively. The results indicate that application of Mn oxide-modified biochar to As-contaminated paddy soil could effectively remediate contaminated soil and reduce As accumulation in edible parts of rice.

Yu Z ，Qiu W ，Wang F ，Lei M ，Wang D ，Song Z ... -  《-》

Capacity and mechanism of arsenic adsorption on red soil supplemented with ferromanganese oxide-biochar composites.

Lin L ，Zhou S ，Huang Q ，Huang Y ，Qiu W ，Song Z ... -  《-》

Mitigating arsenic accumulation in rice (Oryza sativa L.) from typical arsenic contaminated paddy soil of southern China using nanostructured α-MnO(2): Pot experiment and field application.

Manganese oxides are naturally occurring powerful oxidants and scavengers, which can control the mobility and bioavailability of arsenic (As). However, the effect of synthetic nanostructured manganese oxides on the mobilization and transportation of As at actual paddy soils are poorly understood, especially in soils with low or medium background Mn concentration. In the present study, a novel nano manganese oxide with superior reactivity and surface area has been synthesized. A 90-d soil incubation experiment combined with pot and field rice cultivation trials were designed to evaluate the effectiveness of exogenous α-MnO2 nanorods on the mobilization and transportation of As in soil-rice systems. Our results proved that the addition of α-MnO2 nanorods can effectively control the soil-to-solution partitioning of As under anaerobic conditions. After treatment with different amounts of α-MnO2 nanorods, the content of effective As decreased, offset by an increase in residual As and insoluble binding As (Ca-As and Fe-As). Enhancing the oxidation of As(III) into As(V), the α-MnO2 nanorods increased the adsorption of As onto indigenous iron (hydr)oxides which greatly reduced the soil porewater As content. In addition, pot experiments and field applications revealed that the influx of As into the aerial parts of rice plants (stems, husk and leaves) was strictly prohibited after treatments with different amount of α-MnO2 nanorods; more interestingly, significantly negative correlations have been observed between As and Mn in rice, which indicated that as Mn is increased in soil, As in brown rice decreases. Our results demonstrated that the use of α-MnO2 nanorods in As polluted paddy soil containing low levels of background Mn oxides can be a promising remediation strategy.

Li B ，Zhou S ，Wei D ，Long J ，Peng L ，Tie B ，Williams PN ，Lei M ... -  《-》

Effects of Fe-Mn modified biochar composite treatment on the properties of As-polluted paddy soil.

This study aimed to determine the effects of FeMn modified biochar composite (FMBC) treatment on the pH, redox properties, enzyme activities, and bacterial communities of As-polluted paddy soil. The two utilized FMBCs (FMBC1 and FMBC2) exhibited markedly different effects on soil pH, and treatment with biochar (BC) or FMBCs increased the soil redox potential and reduced the content of available As, facilitating the conversion of originally present non-specifically sorbed and specifically bound As forms to residual, amorphous hydrous oxide-bound, and crystalline hydrous oxide-bound ones. In general, the activities of soil enzymes increased after the above treatments, with the exception of that of alkaline phosphatase, which decreased upon supplementation with FMBC2. Supplementation with BC or FMBCs increased the abundance of Proteobacteria and Firmicutes, decreasing that of Bacteroidetes. Notably, FMBC1 and FMBC2 affected soil properties in different ways, although the mechanisms of the corresponding influence were similar. Thus, treatment with BC-based materials changed the distribution of As and the activities of soil enzymes, additionally affecting a variety of other physicochemical soil properties to make it suitable for microbial growth.

Lin L ，Li Z ，Liu X ，Qiu W ，Song Z ... -  《-》