Showing papers by "Shengguo Xue published in 2021"

Arsenic biomineralization by iron oxidizing strain (Ochrobactrum sp.) isolated from a paddy soil in Hunan, China

Abstract: The biogeochemistry of iron (Fe) could affect arsenic (As) fate and change its availability. Fe(II) oxidation mediated by Fe oxidizing bacteria (FeOB) has the potential for As contamination remediation due to the formation of biogenic minerals. However, microbial Fe(II) oxidation coupled with the immobilization of As and the effect of FeOB on As remediation in soils has not been thoroughly investigated. In this study, a FeOB was isolated from a paddy soil and identified as Ochrobactrum sp. EEELCW01. The kinetics reactions were used to investigate how biological and chemical reactions were involved in the Fe(II)‐NO₃⁻‐FeOB system. Microbial Fe(II) oxidation coupled As mineralization, as well as its application in As contaminated paddy soils was studied. The results suggested that biological pathway contributed to the Fe(II) oxidation and NO₃⁻ reduction in the whole process, in which the chemical Fe(II) oxidation by biogenic NO₂⁻ was involved. Meanwhile, Fe(II) facilitated the reduction of NO₂⁻ while inhibited the reduction of NO₃⁻. Adding 2% or more bacteria led to a significant removal effect for aqueous As, resulting in the formation of lepidocrocite and two As‐containing minerals (angelellite, loellingite). With the simultaneous application of FeOB and NO₃⁻, the available As content in soils decreased by 37.6% and stabilized at 0.80 mg kg⁻¹ finally. In addition, the immobilization showed long‐term effect compared to the treatment with Fe(II) or NO₃⁻ alone. The study proved that the isolated FeOB had a significant ability for As mineralization and immobilization, which provided theoretical and application basis for the remediation of As contaminated soils.

Long term natural restoration creates soil‐like microbial communities in bauxite residue: A 50‐year filed study

Abstract: Ecological reconstruction on bauxite residue disposal areas is regarded as an effective approach to eliminate potential environmental risks. Establishment of microbial communities and associated functions may improve physical and chemical properties, and may stimulate soil formation in bauxite residue. Spontaneous colonization at a disposal area in Shandong Province, China, over 50 years, indicated that natural weathering can ameliorate residues, and in turn, support the establishment of vegetation communities. Residue samples were collected from unrestored, poorly restored and well restored areas to investigate the development of microbial communities and associated functions. Microbiota significantly developed after long term natural restoration. Microbial biomass, respiration and enzyme activities significantly increased in restored bauxite residue, whereas the metabolic quotient significantly decreased. In addition, the long‐term natural restoration significantly shaped the microbial structure from alkalophilic and halophilic assemblages (Firmicutes and Actinobacteria) to neutrophilic assemblages (Acidobacteria and Planctomycetes). Both microbial communities and associated functions in well restored residue had high similarity with that in natural soil, indicating that long term restoration created diverse soil‐like microbial communities and functions. Redundancy analysis (RDA) revealed that TN, followed by Na+, ESP, SOC, AP and pH were the major influence factors in the development of microbial communities in bauxite residue. These findings provide us a biogeochemical perspective to reveal soil formation in bauxite residue and suggest that nutrient supplement and regulation of salinity‐alkalinity may benefit for the establishment of microbial communities and functions in bauxite residue.

Arsenic availability and transportation in soil-rice system affected by iron-modified biochar

Abstract: Iron-modified biochar (FeOS) is known to be effective at immobilization of arsenic (As) in soils. A pot experiment was conducted to investigate the effects of FeOS on As availability and ttransportation in the soil-rice system at different growth stages of rice with different pollution levels. The results showed that Fe concentration decreased and As concentration increased in paddy soils with the FeOS addition, especially in 120 mg/kg As treatment, the As concentration decreased by 16.46% and 30.56% at the maturity stage with 0.5% and 1% FeOS additions, respectively. Compared with the control, the application of FeOS reduced the arsenic content in rice tissues and increased the biomass, with the root biomass increased by 12.68% and the shoot biomass was increased by 8.94% with the addition of 1% FeOS. This may be related to the promotion of iron plaque formation and the transformation of microbial community structure in FeOS treatments, in accordance with the result of gene abundance and Fe/As contents of iron plaque in the study. This study is expected to provide further support and theoretical basis for the application of FeOS in the remediation of As contaminated paddy soil.

Evaluating aggregate stability, surface properties and disintegration behaviour of bauxite residue induced by Ca/Na

Abstract: Bauxite residue, a typical industrial solid waste which contains a large amount of Na+, is usually physically degraded Understandings of aggregate formation, which is a critical process in soil development, are essential to facilitate ecological rehabilitation on the disposal areas However, few studies have investigated the aggregation behavior and mechanisms of key salt ions (Ca2+ and Na+) in residue aggregates Therefore, an integrated method of Le Bissonnais’ method, the combined determination method, and laser diffraction measurements was applied to evaluate aggregate stability, surface properties and disintegration behavior of bauxite residue following Ca/Na additions With increasing Ca2+ addition, mean weight diameter (MWD) increased, indicating improved resistance to dispersion Ca2+ had a positive effect on flocculation of silt‐size microaggregates, whilst disintegration was induced following Na+ addition Repeated laser diffraction analysis of residue samples circulating in 50 mmol L‐1 electrolyte solution (Ca2+/Na+) provided a detailed view of the changes in particle size distribution as aggregates fragmented The visualized three‐dimensional surface map revealed that Na+ promoted the disintegration of >250 μm aggregates into finer dispersed particles, whilst Ca2+ protected the microaggregates from fragmenting into smaller particles Variation in electrochemical properties of aggregate surfaces affected the micro‐morphology significantly The findings provide a new approach to specify pedogenic aggregate behavior of bauxite residue, whilst revealing the effects of Ca2+/Na+ on aggregate stability, surface electrochemical properties and its micromorphology The results will provide a detailed understanding of aggregate behavior during soil formation process in bauxite residue