Purpose

Soil loss by rainfall is a serious problem in civil and environmental engineering. In this study, microbially induced calcite precipitation (MICP) was applied to reduce rainfall-induced soil loss. Furthermore, the effects of particle size and organic matter content were investigated.

Materials and methods

A mixture of Sporosarcina pasteurii, 450 mM urea, and 450 mM calcium ions was introduced to sand and sandy loam with 2.6% organic matter content to induce MICP. Artificial rainfall and penetrometer tests were conducted to analyze the soil loss and surface strength, respectively, of the MICP-applied soils.

Results

As MICP was applied, the concentration of CaCO₃ precipitates increased linearly (9.8 mg CaCO₃/g-soil/application), but the strength of the soil reached a plateau of 23.9 ± 1.2 N/mm after five repeated applications (54.5 ± 3.6 mg CaCO₃/g-soil). Only after two repeated MICP applications, up to 84% of reduction in loss rate was accomplished in sand under the worst conditions (rainfall intensity of 75 mm/h, slope of 15°), while only 58% of reduction was obtained after five repeated applications in sandy loam with 2.6% organic matter. For the same amount of CaCO₃ precipitates, the strength was higher in sand with larger particle size. Lower organic matter content led to the higher strength. SEM revealed that larger CaCO₃ precipitates were obtained in sand with lower organic matter content.

Conclusion

Our results indicate that the effect of MICP on the prevention of rainfall-induced soil loss is promoted when the particle size is larger and organic matter content is lower.

中文翻译：

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微生物诱导方解石沉淀在防止降雨造成土壤流失中的应用：粒径和有机质含量的影响

目的

降雨造成的土壤流失在土木和环境工程中是一个严重的问题。在这项研究中，微生物诱导的方解石沉淀（MICP）被用于减少降雨引起的土壤流失。此外，研究了粒径和有机物含量的影响。

材料和方法

将巴氏孢子菌，450 mM尿素和450 mM钙离子的混合物引入有机质含量为2.6％的沙壤土和沙质壤土中，以诱发MICP。进行了人工降雨和渗透计测试，分别分析了使用MICP的土壤的土壤流失和表面强度。

结果

使用MICP时，CaCO ₃沉淀物的浓度线性增加（9.8 mg CaCO ₃ /克土壤/施用），但经过五次重复施用（54.5±3.6）后，土壤强度达到了23.9±1.2 N / mm的平稳状态。毫克CaCO ₃ /克土壤）。仅在重复使用两次MICP之后，在最恶劣的条件下（降雨强度为75 mm / h，斜度为15°），沙子中的损失率最多降低了84％，而重复5次后，损失率仅降低了58％含2.6％有机物的沙壤土中的有机肥料。对于相同量的CaCO ₃析出物，在粒径较大的砂中强度较高。较低的有机物含量导致较高的强度。SEM显示较大的CaCO ₃ 在具有较低有机物含量的沙子中获得沉淀。

结论

我们的结果表明，当粒径较大而有机物含量较低时，MICP可以防止降雨引起的土壤流失。