Application of microbially induced calcite precipitation to prevent soil loss by rainfall: effect of particle size and organic matter content

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 ofSporosarcina 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 CaCO(3)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 degrees), while only 58% of reduction was obtained after five repeated applications in sandy loam with 2.6% organic matter. For the same amount of CaCO(3)precipitates, the strength was higher in sand with larger particle size. Lower organic matter content led to the higher strength. SEM revealed that larger CaCO(3)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.