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Dust is an environmental and health hazard. In this study, a new technology for dust suppressant is introduced using soybean urease with an optimal cementing solution. Calcium carbonate is produced by soybean urease and cementing solution, which bonds the soil particles towards a dust suppressant. A laboratory wind tunnel test is carried out to examine its effectiveness and discover possible optimization solutions. Several factors, including soybean meal concentration, cementing solution concentration, and volume of solution per unit area, are examined to quantify their influences on soil transport mass, evaporation ratio, evaporation rate, surface strength, water retention ratio, and infiltration rate of soil treated by different dust suppressants. Field tests are conducted to explore the performance of this method in the natural environment. The results show that compared with other dust suppressants, the optimized soybean urease has the smallest evaporation rate, a moderate infiltration rate, the largest water retention ratio and surface strength. The indexes of soybean urease for dust suppressant are found to be better than traditional materials. In the natural environment, soybean urease has a stronger anti-disturbance ability. This study concludes that soybean urease dust suppressant has great application potential as a cheap and green method. [ABSTRACT FROM AUTHOR]

Wind-induced soil erosion is a major global misfortune, which obliterates nearly one-third of worldwide soil. The windswept sand particles cover large areas including highways, and make the visibility vague. This results in accidents, damaged infrastructure, delayed flights, and various health issues. The erosive impact of the wind can be minimized by enhancing the intactness of the soil surface. There is a prerequisite to adopt viable measures to strengthen soil against wind erosion. There are certain nature-based solutions that can fortify soil against wind erosion and the application of biopolymers is one of them. The objective of this study is to examine the viability of non-toxic biopolymers for stabilizing desert sand by improving its erosion resistance property and strength. In the present experiment, three biopolymers, sodium alginate (SA), pectin (P), and acacia gum (AG), were used with 1, 2, and 3% concentrations for 1 and 0.75 PV as stabilizing agents. The treatment with biopolymers was performed either by surficial treatment (spraying or pouring of solution) or by mixing and compact method based on the viscosity of prepared biopolymer solutions. The biotreated sand samples were tested in a wind tunnel at varying wind speeds of 10, 20, and 30 m/s to assess sand erosion. Surface strengths were assessed by measuring compressive strength using a pocket penetrometer. Crust thickness measurement was performed to check the penetration depth of biopolymer solution and binding of sand particles. All three biopolymers with 1% concentration gave a feasible solution for erosion against wind and binding of particles through SEM analysis. SA and P could not be sprayed for 2 and 3% concentrations due to high viscosity. This solution is also not feasible for the field application. Simultaneously, AG with 2 and 3% concentration was highly soluble, less viscous, and gave more surface strength due to higher percentage of biopolymer concentration. [ABSTRACT FROM AUTHOR]

Enzyme-induced carbonate precipitation (EICP) is a promising technique for soil reinforcement. To select a suitable calcium source and a suitable solution amount for aeolian sand stabilization using EICP, specimens treated with different solution amounts (1.5, 2, 2.5, 3, and 3.5 L/m2). Surface strength, crust thickness, calcium carbonate content (CCC) and water vapor adsorption tests were performed to evaluate the effect of two calcium sources (calcium acetate and calcium chloride) on aeolian sand solidification. The plant suitability of solidified sand was investigated by the sea buckthorn growth test. The suitable calcium source was then used for the laboratory wind tunnel test and the field test to examine the erosion resistance of solidified sand. The results demonstrated that Ca(CH 3 COO) 2 -treated specimens exhibited higher strength than CaCl 2 -treated specimens at the same EICP solution amount, and the water vapor equilibrium adsorption mass of Ca(CH 3 COO) 2 -treated specimens was less, indicating that Ca(CH 3 COO) 2 -solidified sand was more effective and had better long-term stability. In addition, plants grown in Ca(CH 3 COO) 2 -treated sand had greater seedling emergence percentage and higher average height, which indicated that calcium acetate is a more suitable calcium source for EICP treatment. Furthermore, the surface strength and crust thickness of solidified sand increased with increasing the solution amount. For sand treated with 3 L/m2 of solution, the excessive strength and thickness of the crust made plants growth difficult, and the performance of sand treated with more than 2 L/m2 of solution significantly improved. Thus, the solution amount of 2–3 L/m2 is suggested for engineering applications. The sand solidified using EICP in the field could effectively mitigate wind erosion and facilitate the growth of native plants. Therefore, EICP can be combined with vegetative method to achieve long-term wind erosion control in the future. • Calcium acetate is a more suitable calcium source for aeolian sand solidification using EICP. • The EICP solution amount of 2–3 L/m2 is suggested for engineering applications. • EICP can be combined with vegetative method to achieve long-term wind erosion control. [ABSTRACT FROM AUTHOR]

Microbial-induced calcium carbonate precipitation (MICP) is a new technology used for reinforcing soils through microbial mineralization. However, the existing MICP treatment technology is more suiTable for deeper soils due to its high permeability. In this study, HPMC, a cohesive material combined with Sporosarcina pasteurii-induced calcium carbonate precipitation was used to improve the surface layer of the soil. It was also tested in different contents of bacterial solutions and cementation solutions and with a different number of MICP treatments, and was analyzed and discussed by measuring the surface layer strength, calcium carbonate content generated in the crust, rainfall erosion resistance, wind erosion resistance, and ammonia retention rate of the specimens. The microstructure of the samples was investigated by XRD and SEM. It was shown that the addition of HPMC and increasing the number of MICP treatments were effective in the increase in the calcium carbonate content in the surface crust, but had no effect on the total amount of induced calcium carbonate. The combination of HPMC addition and MICP technology can effectively reduce rainwater scour loss and wind erosion loss, and increase its rainfall erosion resistance and wind erosion resistance. Rainfall losses were reduced by up to 30% in specimens treated with HPMC for MICP technology. When the wind speed was 12 m/s, the maximum mass loss rate of the specimens treated with HPMC for MICP was only 0.828%. The addition of HPMC can effectively improve the ammonia absorption rate and reduce the release of ammonia in the process of MICP technology, which is of great significance for environmental protection. The microstructure showed that the addition of HPMC and the increase in the number of treatments using MICP technology can make the surface structure of the specimens more compact, and the calcium carbonate can more effectively fill the pores and cement the soil particles, while the addition of HPMC may not change the calcium carbonate crystal type. [ABSTRACT FROM AUTHOR]

• Jack bean and soybean crude ureases were used for topsoil stabilization. • Organic matter in crude urease affected soil mechanical properties markedly. • Jack bean presented a greater potential in topsoil stabilization than soybean. • Optimum bean dosages were proposed at 40 g/L jack bean and 80 g/L soybean. • The cost of using crude ureases was greatly reduced compared to commercial urease. Enzyme-induced carbonate precipitation (EICP) is a prominent biogeotechnical technique for soil stabilization to address desert invasion and dust emission issues. This study investigates the bio-cementation efficacy of EICP mediated by jack bean crude urease (JCU) and soybean crude urease (SCU) on surface stabilization of aeolian sand from Tengger Desert. Topsoil properties of the EICP-treated sand including CaCO 3 , organic matter content, surface strength, and wind erosion resistance were evaluated. The urease activity of JCU was 3.4 times higher than SCU, resulting in a higher CaCO 3 content and surface strength of JCU-treated topsoil. The optimum bean dosages were observed at 40 g/L jack bean and 80 g/L soybean for achieving maximum CaCO 3 content and surface strength, respectively. EICP-treatments with excessive bean dosages would decrease the surface strength due to the interference of organic matter precipitation on effective bridging between the generated CaCO 3 crystals and the sand particles. Wind erosion resistance was evaluated under wind-sand flow condition at a wind speed of 13.8 m/s, which was positively correlated with surface strength. JCU presented an overall greater stabilization potential of topsoil than SCU. Additionally, the urease costs of EICP-treatments with JCU and SCU were reduced by about 380–1400 times compared with commercially available ureases. [ABSTRACT FROM AUTHOR]

Mine tailings, or mill tailings (MTs), are highly susceptible to wind erosion (dust) and have brought about different environmental and safety concerns. Many efforts have been attempted to stabilize MTs for dust control, but all have drawbacks. The current study investigates the feasibility of using two natural and renewable biopolymers, xanthan gum and guar gum, to stabilize MTs for dust control. Moisture retention and wind tunnel tests were performed to evaluate, respectively, the enhancement of water retention capacity and the improvement of resistance to wind dispersal after MTs were treated with biopolymer solutions of different concentrations. Because the resistance to the formation of dust is closely related to how easy the particles can be detached from the surface, a flat-ended cylindrical penetrometer was manufactured and used to evaluate the surface strength (maximum penetration force) of dry MT specimens treated with biopolymer solutions of different concentrations. Scanning electron microscopy imaging was also performed to investigate the evolvement of the microstructure of MTs after biopolymer treatment. The results indicate that both xanthan gum and guar gum are effective in enhancing the moisture retention capacity, improving the dust resistance, and increasing the surface strength of MTs beyond that of water wetting. This is mainly because the biopolymers form coatings on MT particles and create bonding between them. The results also demonstrate that the flat-ended cylindrical penetrometer is a promising technique for characterizing the dust resistance of MTs. [ABSTRACT FROM AUTHOR]

Sand erosion due to wind is a serious problem in the relatively arid and semiarid areas. A new organic polymer sand-fixing agent (PVIN), polymerized by the monomer of vinyl acetate, initiator and cross-linking agent, is introduced in this study. To understand the effect of PVIN on sand fixation, the strength test, water-retaining test and wind erosion test were performed. The results indicated that the presence of PVIN could improve the structural strength, water retaining and anti-wind erosion ability. When the sand-fixing agent was applied on the sand surface, the crust in surface layer was produced. The structural strength variations determined by micropenetrometer indicated that the specimens treated with concentrations of 1, 3, 5, 10, and 20% PVIN have produced the crusts with thickness being approximately 1, 2, 4-5, 5, and 5-6 mm and the strength being around 1, 4.5, 18, 26 and 41, respectively. This crust has a good water-absorption, water-retaining and anti-evaporation properties. It can also improve the anti-wind erosion ability, and also prevent the loose sand surface from forming a sand dune in the wind erosion conditions. Additionally, this sand-fixing agent has a low cost, it is easier to produce and apply and also produces no additional pollution. Therefore, this can be considered as an ideal soil-fixing agents to control sand erosion in the relatively arid and semiarid areas. [ABSTRACT FROM AUTHOR]