Application of biocementation technique using Bacillus sphaericus for stabilization of soil surface and dust storm control

Dust emission and wind erosion are widespread phenomena in arid and semi-arid regions, which have far-reaching harmful effects to the environment. This study aimed to use microbial induced carbonate precipitation (MICP) method with Bacillus sphaericus to reduce soil losses that occur in a dust-producing area due to wind erosion in the Ilam Province, Iran. Soil samples at the 0-30 cm depth were used and sterilized in an autoclave for 2 h at 121°C and 103 kPa. Approximately 3 kg soils were weighed and poured in the 35 cm×35 cm×3 cm trays. Different treatments included two levels of B. sphaericus (0.0 and 0.5 OD), three levels of suspension volume (123, 264, and 369 mL), two levels of urea-chloride cementation solution (0.0 and 0.5 M), and two levels of bacterial spray (once and twice spray). After 28 d, soil properties such as soil mass loss, penetration resistance, and aggregate stability were measured. The results showed a low soil mass loss (1 g) in F₁₄ formulation (twice bacterial spray+264 mL suspension volume+without cementation solution) and a high soil mass loss (246 g) in F₅ formulation (without bacteria+264 mL suspension volume+0.5 M cementation solution). The highest (42.55%) and the lowest (19.47%) aggregate stabilities were observed in F₁₆ and F₇ formulations, respectively, and the highest penetration resistance (3.328 kg/cm²) was observed in F₁₈ formulation. According to the final results, we recommended the formulation with twice bacterial spray, 0.5 M cementation solution, and 269 mL suspension volume as the best combination for soil surface stabilization. Furthermore, this method is environmentally friendly because it has no adverse effects on soil, water, and plants, thus, it would be an efficient approach to stabilize soil surface.     

褐土碳酸钙结核的胶体特性研究

碳酸钙是黄土母质发育土壤的重要胶结物质，对土壤团粒结构的形成具有重要作用。本文采集了碳酸盐褐土中的碳酸钙结核，采用物理分散法和化学分散法分别提取得到褐土碳酸钙结核纳米颗粒和褐土碳酸钙结核胶体，并以工业纳米碳酸钙作为对照对其胶体特性进行研究。采用X射线衍射仪、zeta电位仪和动态光散射仪对褐土碳酸钙结核胶体和工业纳米碳酸钙的矿物组成、zeta电位和胶体稳定性进行了表征。结果表明：褐土碳酸钙结核胶体、褐土碳酸钙结核纳米颗粒和工业纳米碳酸钙的初始颗粒直径分别为224.24、88.01和98.50 nm，而褐土碳酸钙结核胶体和褐土碳酸钙结核纳米颗粒的多分散度高于工业纳米碳酸钙。褐土碳酸钙结核胶体中方解石含量为70.3%，其次含有石英、长石和伊利石等矿物；褐土碳酸钙结核纳米颗粒主要含有方解石和伊利石，含量分别为48%和45%。3种碳酸钙胶体表面均带负电荷，其zeta电位绝对值均随着溶液pH的增大而增大。褐土碳酸钙结核胶体在NaCl和CaCl₂溶液中的临界聚沉浓度分别为538.01 mmol/L和2.08 mmol/L，褐土碳酸钙结核纳米颗粒在NaCl和CaCl₂溶液中的临界聚沉浓度为82.18 mmol/L和1.11 mmol/L，而工业纳米碳酸钙的临界聚沉浓度为80.37 mmol/L和1.59 mmol/L。3种碳酸钙胶体的矿物组成差异是引发其凝聚行为差别的内在原因，化学分散剂的表面修饰作用、颗粒直径大小和溶液化学条件也是影响胶体稳定性的重要因素。本文研究结果表明，碳酸钙胶体的可变电荷特性可能是其具有胶结特性的本质原因，其对石灰性土壤团聚体结构的影响还需要进一步深入研究。     

昆明地区碳酸盐岩发育红土载磁矿物的提取与鉴定

利用重液分离工艺对昆明地区磁化率最高的碳酸盐岩发育的红土进行载磁矿物的分离提取,并对提取出的样品进行X射线衍射(XRD)鉴定,结果显示碳酸盐岩发育红土的主要载磁矿物为磁赤铁矿(γ-Fe₂O₃)、赤铁矿(α-Fe₂O₃)和针铁矿(α-FeOOH),它们占总载磁矿物的半定量比例分别为30%、37%和33%,这些测定结果大体上与传统的磁学参数测定方法推测的结果吻合,但在准确鉴定、识别和半定量分析上明显优于前者。