[Remediation Mechanism of Chitosan-modified Biochar on Cd-contaminated Farmland Soil and Its Effect on Bacterial Community].

To explore the remediation mechanism of chitosan-modified biochar （passivator） on Cd-contaminated farmland soil, pot experiments were conducted to determine the effects of passivator on soil physical and chemical properties, ryegrass biomass, enzyme activity, and the response of soil bacterial diversity and structure. The results showed that when the amount of passivating agent was increased from 0.5% to 3%, the content of available Cd in soil was significantly decreased compared with that in the control, and the above-ground and subsurface biomass of ryegrass was increased by 1.08-1.56 times and 1.00-1.68 times, respectively. The enrichment and running coefficients were reduced by 6.15%-30.00% and 10.42%-31.25%, respectively. The correlation analysis results showed that soil pH, CEC, SOM, AN, AP, and AK were significantly negatively correlated with DTPA-Cd, indicating that the application of a passivating agent promoted the passivation of Cd in soil by changing the physical and chemical properties of soil. High-throughput sequencing results showed that the application of the inactivation agent changed the structure and diversity of the soil bacterial community, which was manifested as a significant decrease in α diversity, significant isolation of bacteria between different treatment groups, and an increase in the relative abundance of beneficial bacteria such as Sphingomonas and Blastococcus. Moreover, the activities of soil urease and cellulase increased, whereas the activities of sucrase and catalase decreased with the addition of a passivator. This study provides a theoretical basis and technical reference for the application of modified biochar in the remediation of Cd-contaminated farmland soil.

[Preparation of Chitosan-modified Biochar and Its Adsorption Mechanism for Cd2+ in Aqueous Solution].

Chitosan-modified biochar （CBC） was prepared as a low-cost and highly efficient adsorbent for Cd2+ in aqueous solutions. Batch adsorption experiments were conducted to evaluate the adsorption performance. Characterization experiments with SEM-EDS， FTIR， and XPS were used to analyze the surface microstructure and chemical composition of the adsorbent. The results showed that the adsorption performance of CBC was remarkably improved by the introduction of surface functional groups （-OH， -C=O， and -NH2）. The pseudo-second-order kinetic model and Langmuir model were better for describing the kinetics and isotherms for Cd2+ adsorption onto CBC， indicating that the adsorption rate was determined by the active sites and controlled by monolayer chemisorption. The adsorption process was endothermic spontaneous， and the key mechanisms involved complexation， precipitation， cation exchange， and cation-π bonds. After five instances of adsorption-desorption cycles， the adsorption capacity of CBC for Cd2+ still remained above 80% of the initial adsorption capacity， indicating that CBC had a favorable recyclability. The current work embodies the concept of green chemistry， and the prepared chitosan-modified biochar was a promising adsorbent for the removal of Cd2+ in wastewater and soil.

Virgibacillus kekensis sp. nov., a moderately halophilic bacterium isolated from a salt lake in China.

A Gram-positive, moderately halophilic, motile, strictly aerobic, endospore-forming, oxidase- and catalase-positive, rod-shaped bacterium, strain YIM kkny16(T), was isolated from a saline mud sample collected from the Keke salt lake in the Qaidam Basin, north-west China. This isolate grew in the presence of 0-25 % (w/v) NaCl and at pH 6.0-10.0 and 10-50 degrees C; optimum growth was observed with 10 % (w/v) NaCl and at pH 7.0 and 37 degrees C. Strain YIM kkny16(T) had meso-diaminopimelic acid as the diagnostic diamino acid, MK-7 as the predominant respiratory quinone, with a significant amount of MK-6, and anteiso-C(15 : 0), iso-C(14 : 0) and C(16 : 1)omega7c alcohol as major fatty acids. Major polar lipids were diphosphatidylglycerol and phosphatidylglycerol. The DNA G+C content was 41.8 mol%. Phylogenetic analysis based on 16S rRNA gene sequences confirmed that strain YIM kkny16(T) was a member of the genus Virgibacillus, exhibiting sequence similarities of 94.9-97.3 % to the type strains of recognized Virgibacillus species. Strain YIM kkny16(T) could be differentiated from recognized Virgibacillus species based on phenotypic characteristics, chemotaxonomic differences, phylogenetic analysis and DNA-DNA hybridization data. On the basis of evidence from this polyphasic study, strain YIM kkny16(T) is considered to represent a novel species of the genus Virgibacillus, for which the name Virgibacillus kekensis sp. nov. is proposed. The type strain is YIM kkny16(T) (=DSM 17056(T)=CGMCC 1.6298(T)).