Journal of Central South University最新文献

The long-term operation of the lead smelter has brought serious heavy metal pollution to the surrounding soil. The microbial community structure and composition of heavy metal contaminated soil is important for the risk assessment and pollution remediation. In this study, a lead smelter operating for more than 60 years was used to investigate the effects of heavy metal pollution on soil microbial community structure and composition in vertical profile. The results showed that the heavy metal content decreases gradually with increasing vertical depth of the soil. The diversity of soil microbial community with moderate pollution was higher than that with low pollution. Regardless of the pollution level, the diversity of soil microbial community was higher in the surface layer than in the bottom layer. The dominant relative abundance genera include Perlucidibaca, Limnobacter, Delftia, Hydrogenophaga, Thiobacillus, Sulfurifustis and Sphingopyxis, showing a higher abundance of sulfur-oxidizing bacteria (SOB). XRD results showed the presence of PbSO₄ in soil, may be due to the enrichment of SOB for the oxidation of sulfur. This sulfur cycle characteristic may be potential for the stabilization and remediation of lead (Pb) into PbSO₄.

Emitted dust is the major contributor of heavy metal(loid)s in soils located near lead (Pb) smelters, but the mechanisms for transfer of the heavy metal(loid)s in dust are uncertain. The study systematically investigated the geochemical behaviors and liberation mechanisms of heavy metal(loid)s in this process. The results show that Pb, Zn, Cd, and As in two types of dust samples exceeded the allowable standards, and about 80% of Pb and Zn were present in mobile and bioavailable fractions. More than 70% of arsenic in bottom-blowing furnace dust existed in an acid-soluble fraction, while 60% of cadmium in reducing and fuming dust existed in the acid-soluble fraction. Pb isotope results showed that 97.12% of the Pb in the topsoil came from dust emitted during the smelting process. XRD and MLA results illustrated that PbSO₄, ZnSO₄, and CdSO₄ were the major minerals in the dust, while the mineral phases of the topsoil were mainly quartz, calcite, dolomite, and muscovite. Based on a combination of mineralogical investigations and geochemical modelling, our findings suggest that liberation of the Pb, Zn, and Cd was primarily dependent on sulfate minerals under acidic conditions, whereas the liberation of As was related to adsorption by iron hydroxide.

To improve the remediation and antioxygenic properties of ferrous sulfide (FeS) nanomaterials toward heavy metals is the focus of current research. This study employed a combination of sodium carboxymethylcellulose (CMC) and sodium dodecyl benzene sulfonate (SDBS) for the modification of FeS nanomaterials supported by porous silicon (SiO₂/FeS) to serves as an efficient amendment for cadmium pollution. The optimized slurry with the mass ratio of CMC/SDBS to be 1:3 showed enhanced dispersion and antioxidant effects on SiO₂/FeS (the mass ratio of surfactant to FeS was 1:1). This formulation exhibited the smallest particle size (D₅₀ = 0.66 µm) and the highest absolute Zeta potential values exceeding 30 mV. Also, the obtained products demonstrated effective remediation of cadmium-contaminated solutions, with Cd(II) primarily forming stable CdS and CdSO₄ products through ion exchange and chemical precipitation. The adsorption capacity of SiO₂/FeS-CMC/SDBS 1:3 for cadmium in air and nitrogen was remained during 30 d, reaching about 158 mg/g. Notably, under low concentration Cd contamination, the adsorption capacity of SiO₂/FeS-CMC/SDBS 1:3 exceeded that of SiO₂/FeS-CMC and SiO₂/FeS-SDBS without acidification risk. In summary, this research highlights the improved remediation and antioxygenic properties achieved through CMC and SDBS co-modification of SiO₂/FeS, providing a new amendment for Cd remediation.

Heavy metal composite pollution is becoming increasingly serious. In this study, CaAl-layered double hydroxide (CaAl-LDH) was prepared using the facile co-precipitating method, and was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). Lead(II), Cd(II), and As(V) were selected as the representative heavy metals to evaluate the adsorption capability of the synthesized CaAl-LDH by the batch experiments. The maximal adsorption capability of CaAl-LDH for Pb(II), Cd(II), and As(V) was 786.6, 437.2 and 72.9 mg/g, respectively. The adsorption mechanism of Pb, Cd and As may be surface precipitation, isomorphic substitution and ion exchange within the interlayer spaces of LDH, respectively. In conclusion, this experiment provides a LDH material with fast and efficient adsorption performance for both anionic and cationic metals, indicating its potential for practical application in the remediation of heavy metal composite pollution.

Chromium (Cr) contamination in soil is one of the most severe environmental issues, which poses significant health hazards to humans. In this study, the stabilization mechanism of Cr-contaminated soil by polysulfide-supported nZVI@biochar (PS-nZVI@BC) and the resultant bioavailability of Cr was studied. The addition of PS-nZVI@BC is capable of decreasing 92.0% of leachable Cr(VI) in the soil after 30 days of treatment. According to sequential extraction analysis, the exchangeable Cr in soil decreased drastically from 20.8% to 4.0% after PS-nZVI@BC addition, which was mostly converted to Fe-Mn oxided and organic matter-bound forms. The stabilization mechanisms include electrostatic adsorption, redox reaction, surface complexation, and precipitation. The soil fertility of Cr-contaminated soil was effectively improved by PS-nZVI@BC, and the toxicity of Cr in soil to maize seedlings was reduced. These results demonstrated the great potential of utilizing PS-nZVI@BC for the remediation of Cr-contaminated soils.

Cadmium (Cd) is a biologically non-essential and toxic heavy metal that enters the environment through natural emissions or anthropogenic activities, posing threats to human health. The efficient expression of metal-chelating proteins (MCP) in microorganisms can enhance microbial remediation of Cd. In this study, a heterologous expression system (GEM01) of MCP encoded by the mcp gene in E. coli was constructed, and the adsorption effect and potential mechanism on Cd were explored. The results indicated that Cd²⁺ significantly enhanced the abundance of mcp gene in GEM01, thus increasing the Cd²⁺ biosorption capacity (8.09 mg/g, 2.32 times higher than the control). The retention of Cd²⁺ during the autolysis of GEM01 was 87.87%. Fluorescence spectroscopy and molecular dynamics simulations demonstrated that there was a strong interaction between Cd²⁺ and MCP. FT-IR demonstrated that some functional groups (e.g., carboxyl group and methyl group) in MCP were involved in the interaction between MCP and Cd²⁺. Molecular docking further demonstrated that polar and hydrophilic residues (e.g., aspartic acid, glutamic acid, serine, and histidine) on the surface of MCP bound to Cd²⁺ via electrostatic attraction. These findings offer new insights into Cd²⁺ bioremediation by MCP and genetic resources for microbial remediation of heavy metal pollution.

Biochar has been considered as a promising material for soil remediation, particularly for its ability to reduce the bioavailability of cadmium (Cd) in soil through sorption. However, long-term remediation may cause Cd to be released from a fixed state, making the recovery of biochar as an adsorbent for Cd removal an area of increasing interest. The study aims to synthesize biochar with magnetic properties using petroleum sludge containing iron in one-step, and investigate their adsorption efficiency and passivation mechanism for Cd in liquid-solid phase, as well as ecological risks. The results indicate that the petrochemical sludge waste can be directly resourced into magnetic biochar (PSMBCs) using hypoxic pyrolysis, and that it exhibits good recycling performance in water/soil. Specifically, the obtained biochar showed strong sorption capacity for Cd (18.4 to 29.8 mg/g) due to surface mineralization and cation-π coordination, which played a critical role. After applying 1.5% of PSMBCs for 30 d in paddy soil, the bioavailable content of Cd was decreased by 85.0%. Importantly, the biochar leachates did not have any toxic effects on wheat root elongation. Therefore, this study presents a promising strategy for the benign disposal of petrochemical sludge and their utilization for the remediation of Cd-contaminated soil.

Uranium tailings discharged into uranium tailings ponds could generate environmental pollution issues. Microbial-induced phosphate mineralization could reduce the release of uranium, in turn effectively managing pollution. However, it is unclear that how the phosphorus additives affect the microbial structure of uranium tailings under biomineralization. Herein, we evaluate the microbial community succession during Bacillus spp. remediation of uranium tailings, when adding hydroxyapatite (HS) and β-glycerol phosphate pentahydrate (GP). The results show that phosphorus additives effectively changed pH and uranium leaching concentration, significantly increased bacterial richness, and promoted microbial community succession, whilst promoting actinobacteria to Firmicutes and Proteobacteria populations. The two additives influenced the bacterial community succession patterns differently, with GP eliciting the greater enhancement. Additionally, GP enhanced the growth of core species and recognized the phylum firmicutes as a crucial taxon. The abundance of Bacillus, Pseudomonas, Desulfotomaculum, and Clostridium_sensu_stricto_12 was higher in GP treatments, indicating the substantial roles played by these genera in the microbial community. The results provide evidence of the involvement of the two phosphorus additives in bioremediation and bacterial community perturbations and thus provide new insights into the biomineralization technologies for uranium tailings.

Opal (amorphous silica, SiO₂·nH₂O), a solid waste byproduct of the alkaline extracting alumina from coal fly ash, exhibits strong adsorption properties and is a secondary/clay mineral in the soil. Combining opal with sand to construct opal/sand aggregates for desertification soil remediation holds the potential for large-scale ecological disposal. Unfortunately, the aggregate structure still gaps from natural soil aggregates resulting from inorganic mineral deficiencies. Herein, the effects of five inorganic mineral amendments, limestone (CaCO₃), desulphurization gypsum (CaSO₄·2H₂O), hematite (Fe₂O₃), tricalcium phosphate (Ca₃(PO₄)₂) and gibbsites (Al(OH)₃), on aggregate formation, stabilization, and pore characteristics without the organic matters were investigated in short-term cultivation experiments. Meanwhile, associated adsorption mechanisms were elucidated. Results indicated only gypsum effectively reduced the aggregate’s pH, most enhanced water-holding capacity, albeit increased electrical conductivity. All amendments facilitated aggregate formation and mechanical-stability, with gypsum, CaCO₃, and Fe₂O₃ improving water stability. Various analysis techniques, including XRD, SEM, nano-CT, FT-IR, and XPS, provided insights into the physisorption and chemisorption of minerals onto sand/opal, generating interfaces conducive to aggregation. Compared to CK (control check, without amendment addition), amended macroaggregates demonstrated increased porosity, reduced pore quantity and mean pore diameter (MPD), denser pore structure, improved interpore connectivity, and more complex pore networks, dominated by <80 µm diameters and boundary pores. Notably, desulphurization gypsum elicited the most significant variations, increasing MPD of microaggregates and 2–5 nm mesopores, and decreasing total pore volume and 0–2 nm micropores, while Ca₃(PO₄)₂ and Al(OH)₃ improved >15 nm mesopores. Overall, inorganic minerals, the “skeleton” of soil, effectively upgraded opal/sand aggregates’ physical structure and accelerated aggregate formation quickly. Therein, desulphurization gypsum optimized macroaggregate formation and stability. Desulphurization gypsumamended aggregates serve as soil-like substrates to accelerate the ecological reconstruction of desertification areas.

This paper aims to explore the ability of genetic programming (GP) to achieve the intelligent prediction of tunnelling-induced building deformation considering the multifactor impact. A total of 1099 groups of data obtained from 22 geotechnical centrifuge tests are used for model development and analysis using GP. Tunnel volume loss, building eccentricity, soil density, building transverse width, building shear stiffness and building load are selected as the inputs, and shear distortion is selected as the output. Results suggest that the proposed intelligent prediction model is capable of providing a reasonable and accurate prediction of framed building shear distortion due to tunnel construction with realistic conditions, highlighting the important roles of shear stiffness of framed buildings and the pressure beneath the foundation on structural deformation. It has been proven that the proposed model is efficient and feasible to analyze relevant engineering problems by parametric analysis and comparative analysis. The findings demonstrate the great potential of GP approaches in predicting building distortion caused by tunnelling. The proposed equation can be used for the quick and intelligent prediction of tunnelling induced building deformation, providing valuable guidance for the practical design and risk assessment of urban tunnel construction projects.