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Compared to traditional biochar (BC), nano-biochar (NBC) boasts superior physicochemical properties, promising extensive applications in agriculture, ecological environments, and beyond. Due to its strong adsorption and migration properties, NBC may carry nutrients or pollutants to deeper soil layers or even groundwater, causing serious environmental risks. Nevertheless, the migration rules and mechanisms of NBC in soil are still unclear. Therefore, this study employed soil column migration experiments to systematically explore the migration rules and mechanisms of NBC under various flow rates, initial soil water contents, soil depths, and soil textures. The results showed that regulated by smaller particle size differences and greater surface charges, NBC exhibited a stronger migration ability compared with traditional BC. As the soil texture transitioned from fine to coarse, the migration capability of NBC significantly improved, driven by both pore structure and interaction forces as described by the DLVO theory. The migration ability of NBC was also greatly boosted as the soil transitioned from saturated to unsaturated conditions, primarily because of preferential flow. When the flow rate increased from 70% KS to 100% KS and 130% KS, the migration ability of NBC also increased accordingly, as changes in injection flow rates altered the velocity distribution of pore water. NBC in 25 cm soil columns was more prone to shallow retention compared with 10 cm soil columns, resulting in weaker overall migration ability. In addition, through fitting of the two-site kinetic model and related parameters, the penetration curves of NBC under various variable conditions were effectively characterized. These findings could offer valuable insights for NBC's future efficient, rational, and sustainable utilization, facilitating the evaluation and mitigation of its potential environmental risks. [ABSTRACT FROM AUTHOR]

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Since waste residues of antimony ores are piled in a disorderly way long-term, heavy metal elements of the residues are dissolved and precipitated under the eluviation effect of snow and rain, causing serious pollution to the surrounding soil. This paper takes the antimony ore of Hunan stannary as the research area, and the surrounding soil of the storage yard of antimony ores as the research object, and carries out research on the migration rules of Sb in the leachate of waste residues of antimony ores in soil by means of spot sampling, lab analysis, and test and simulation, and simulates the migration of Sb in the surrounding soil of mining areas. The results show that through the dynamic penetration experiment of indoor soil columns, the hydrodynamic dispersion coefficient (D = 2.485 cm2 /h), adsorption distribution coefficient (Kd = 48.826 cm3/g), retardation factor (Rd = 78.50), and other parameters of Sb migrating in soil are obtained; the study makes use of the HYDRUS-1D model to conduct dynamic simulation of Sb in the soil nearby the antimony mine areas on the stannaries of Hunan Province, and the results indicate that the measured value is quite close to the fitted value, and in the correlation analysis of double variables, R is equal to 0.986, indicating that the simulation effect is fairly good. This study aims to provide a theoretical foundation and scientific basis for evaluating, controlling, curbing, and repairing the surrounding ecological environment of antimony mine areas. [ABSTRACT FROM AUTHOR]