Direct use of naturally occurring microbes for soil improvement has recently gained attention due to their ubiquitous and versatile characteristics in subsurface soil. Microbes produce soft and sticky extracellular polymeric substances (or biopolymers) that are known to alter the hydrological characteristics of soils; however, the mechanisms and extent of such soft biopolymers in altering soil erosion resistance remain scarcely explored. This study explored the role of microbial biopolymers in soil erosion resistance. The surface erosion resistance of sandy soils was evaluated by using a hybrid erosion function apparatus, in which the model bacteria Leuconostoc mesenteroides were stimulated to produce an insoluble biopolymer. The results revealed that the microbial biopolymer formation increased the critical shear stress and surface erosion resistance, which the researchers attributed to the increased cohesion by grain-coating biopolymer slimes and the reduced seepage flows due to pore clogging. This study provides baseline but promising results on how microbially grown biopolymers can be used to improve soil erosion resistance.

Exocultured biopolymers are ecofriendly soil-stabilisation agents with superior particle bonding, hydrogel-formation characteristics and zero endoculture duration. However, the use of exocultured biopolymers for enhancing soil resistance against surface erosion by water flow is yet to be investigated. Using erosion function apparatus (EFA) in combination with an ultrasonic P-wave reflection monitoring device, the effect of exocultured biopolymers on the erosion parameters of critical shear stress and the erodibility coefficient was examined in this study in soils with different particle distributions. In this way, biopolymer soil treatment showed a ten-fold increase in critical shear stress along with a 90% reduction in erodibility coefficient; results which could be attributed to enhanced particle-to-particle contact and increased pore-fluid viscosity and pore clogging. The results of this study demonstrate the feasibility of using exocultured biopolymers in mitigating surface erosion of erosion-prone soils.

Natural and artificial gas hydrates with internal pores of nano to centimeters and weak grain-cementation have been widely reported, while the detailed formation process of grain-cementing hydrates remains poorly identified. Pore-scale morphology of carbon dioxide (CO₂) hydrate formed in a partially brine-saturated porous medium was investigated via X-ray computed microtomography (X-ray CMT). Emphasis is placed on the pore-scale growth patterns of gas hydrate, including the growth of dendritic hydrate crystals on preformed hydrate and water-wetted grains, porous nature of the hydrate phase, volume expansion of more than 200% during the water-to-hydrate phase transformation, preference of unfrozen water wetting hydrophilic minerals, and the relevance to a weak cementation effect on macroscale physical properties. The presented pore-scale morphology and growth patterns of gas hydrate are expected in natural sediment settings where free gas is available for hydrate formation, such as active gas vents, gas seeps, mud volcanoes, permafrost gas hydrate provinces, and CO₂ injected formation for the sake of geologic carbon storage; and in laboratory hydrate samples synthesized from partially brine-saturated sediments or formed from water-gas interfaces.