Biomineralization technology is a promising method for soil cementation, enhancing its mechanical properties. However, its application in mitigating slope surface erosion caused by rainfall has not been fully explored. This study experimentally examined the feasibility of using plant-based enzyme-induced carbonate precipitation (PEICP) to reduce slope surface rainfall erosion through simulated rainfall tests. The effects of biotreatment cycles (N) and rainfall intensity (Ri) on erosion resistance were evaluated. The results demonstrated that increasing the biotreatment cycles improved the bio-cementation level, as evidenced by enhanced surface strength, increased calcium carbonate content (CCC) and thicker crust layers. Specifically, as the biotreatment cycles (N) increased from 2 to 6, the crust layer thickness expanded from 5.2 mm to 15.7 mm, with surface strength rising from 38.3 kPa to 244.3 kPa. Likewise, the CCC increased significantly from 1.09% to 5.32%, further reinforcing the soil structure and enhancing erosion resistance. Slopes treated with six biotreatment cycles exhibited optimal erosion resistance across rainfall intensities ranging from 45 to 100 mm/h. Compared to untreated slopes, biotreated slopes showed significant reductions in soil loss, with a decrease to below 10% at N = 4 and near-complete erosion resistance at N = 6. These findings highlight the potential of PEICP technology for improving slope stability under rainfall conditions.

Natural cementation of rock debris is a spontaneous geochemical process that plays an important role in geotechnical stabilization. The focus of this study is to analyze the natural cementation phenomenon in mudslide-prone areas using mineralogical and biological methods. We analyzed the formation of the natural cementation phenomenon by studying its mineral composition, elemental endowment distribution, mechanical properties, and community structure. Similarly, simulated cementation experiments of rock debris by carbonate mineralizing bacteria were carried out in the laboratory to assess the feasibility of biomineralization in the stabilization of rock and soil. The results show that the natural cementation of rock debris in mudslide-prone areas is caused by the formation of calcite under chemical action, and microorganisms also contribute to it; this cementation has multiple environmental protection significance, including improving the compressive properties of rock debris (up to 2.58 Mpa), slowing down or preventing the occurrence of geologic hazards such as slumps, landslides, etc., and significantly decreasing the migratory properties of heavy metal ions and its ecological risks. Laboratory simulation conditions showed that carbonate mineralizing bacteria were enabled to utilize the Ca2+ provided by weathering to achieve rapid cementation of the rock debris, which played an important role in the increase of their compressive strength and the improvement of their pore parameters. This study provides a theoretical basis for future engineering applications of biomineralization technology.

To improve the reinforcement effect of MICP technology on fine-grained soil, and consider the fine particle size and activity characteristics of red mud, the experiment of red mud strengthening MICP solidified fine-grained soil was designed and carried out. Combined with mechanical test and microstructural analysis, the enhancing mechanism of red mud on microbial solidified fine-grained soil was comprehensively evaluated. The results show that: (1) Red mud can significantly improve the production of cement during microbial reinforcement of fine-grained soils; the optimal dosage of red mud is 20 %, which increases the strength by 34.6 % and the production of cement by 42.9 %, compared with conventional MICP. (2) After red mud was incorporated into the soil, the pore volume and pore diameter of the treated soil were significantly reduced, and the overall compactness was further improved. (3) The enhancement mechanism of microbial consolidation of fine-grained soils by red mud is mainly due to the presence of chemically active b-C2S and calcium oxide in red mud. These active calcium-based components undergo hydration and carbonation reactions under the action of microbial mineralization, generating calcium carbonate and hydrated calcium silicate, which improves the cement yield and enhances the intergranular bond strength, compactness and overall reinforcement effect of the treated soil. (c) 2025 Production and hosting by Elsevier B.V. on behalf of The Japanese Geotechnical Society. This is an open access article under the CC BY- NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

A range of fungal species showed variable abilities to colonize and penetrate a mortar substrate. Calcium biomineralization was a common feature with calcium-containing crystals deposited in the microenvironment or encrusting hyphae, regardless of the specific mortar composition. Several species caused significant damage to the mortar surface, exhibiting burrowing and penetration, surface etching, and biomineralization. In some cases, extensive biomineralization of hyphae, probably by carbonatization, resulted in the formation of crystalline tubes after hyphal degradation on mortar blocks, including those amended with Co or Sr carbonate. Ca was the only metal detected in the biomineralized formations with Co or Sr undetectable. Aspergillus niger, Stemphylium sp. and Paecilomyces sp. could penetrate mortar with differential responses depending on the porosity. Fluorescent staining of thin sections recorded penetration depths of similar to 530 um for A. niger and similar to 620 um for Stemphylium sp. Penetration depth varied inversely with porosity and greater penetration depths were achieved in mortar with a lower porosity (lower water/cement ratio). These results have provided further understanding of biodeteriorative fungal interactions with cementitious substrates that can clearly affect structural integrity. The potential significance of fungal colonization and such biodeteriorative phenomena should not be overlooked in built environment contexts, including radionuclide storage and surface decontamination.

This study aims to solidify sodium sulfate saline loess by biomineralization of reactive magnesium oxide (MgO) binder. The impact of Na2SO4 concentration on the viability and urease activity of S. pasteurii, the mechanism and products of biomineralization of MgO, and the effectiveness of the biomineralization-MgO binder in solidifying saline loess with varying salt content (1%, 3%, and 5%) were investigated. Results showed that low and moderate concentrations of Na2SO4 favored bacterial proliferation. However, the presence of Na2SO4 inhibited bacterial urease activity, and the inhibition was more significant at higher Na2SO4 concentrations. In addition, low and moderate concentrations of Na2SO4 decreased the specific urease activity, whereas high concentrations of Na2SO4 significantly increased specific urease activity. S. pasteurii was able to use carbonate ions formed by urea hydrolysis for the mineralization of MgO and to form magnesium carbonate minerals dominated by rosettelike dypingite and hydromagnesite crystals. The primary mechanism involves microbial cells and extracellular polymeric substances leading to partial dehydration of Mg2+ ions from the Mg2+-H2O complex and allowing for further association with carbonate anions to from Mg-bearing carbonates. Unconfined compressive strength tests conducted on the saline loess samples after 7 days of curing revealed a significant influence of urea concentration on the strength of the solidified soil. The optimal urea concentration to obtain a better 7-day UCS ranged from 4 mol/L to 5 mol/L. Furthermore, solidified soil with 5% salinity yielded the highest 7-day UCS and soil with 3% salinity exhibited the lowest 7-day UCS at the same urea concentration. XRD and SEM analysis of the solidified soil samples indicated that the formation of magnesium carbonate minerals in the soil matrix by the biomineralization-MgO binder was responsible for the UCS enhancement. The remarkable 7-day UCS of saline loess solidified with biomineralization-MgO binder demonstrates the effectiveness of this material in curing saline loess.

Lead (Pb) is a hazardous heavy metal that accumulates in many environments. Phytoremediation of Pb polluted soil is an environmentally friendly method, and a better understanding of mycorrhizal symbiosis under Pb stress can promote its efficiency and application. This study aims to evaluate the impact of two ectomycorrhizal fungi (Suillus grevillei and Suillus luteus) on the performance of Pinus tabulaeformis under Pb stress, and the biomineralization of metallic Pb in vitro. A pot experiment using substrate with 0 and 1,000 mg/kg Pb2+ was conducted to evaluate the growth, photosynthetic pigments, oxidative damage, and Pb accumulation of P. tabulaeformis with or without ectomycorrhizal fungi. In vitro co-cultivation of ectomycorrhizal fungi and Pb shots was used to evaluate Pb biomineralization. The results showed that colonization by the two ectomycorrhizal fungi promoted plant growth, increased the content of photosynthetic pigments, reduced oxidative damage, and caused massive accumulation of Pb in plant roots. The structural characteristics of the Pb secondary minerals formed in the presence of fungi demonstrated significant differences from the minerals formed in the control plates and these minerals were identified as pyromorphite (Pb-5(PO4)(3)Cl). Ectomycorrhizal fungi promoted the performance of P. tabulaeformis under Pb stress and suggested a potential role of mycorrhizal symbiosis in Pb phytoremediation. This observation also represents the first discovery of such Pb biomineralization induced by ectomycorrhizal fungi. Ectomycorrhizal fungi induced Pb biomineralization is also relevant to the phytostabilization and new approaches in the bioremediation of polluted environments.