Biochar as a soil amendment can influence the physical and solute transport properties of soils and, thus, provide a means to improve soil fertility. However, the use of different sized biochar particles down to the nano-scale has revealed inconsistent results, with the mechanisms poorly understood owing to a lack of experimental data. This study investigated the effects and mechanisms of nano-sized biochar particles (NBC) applied to a sandy loam soil with regard to impacts on the hydraulic characteristics and soil structure. Column experiments were carried out with NBC application rates of 0.0%, 0.3%, 0.5%, 0.7% and 1.0% (by weight). It was found that the NBC changed the distribution of the soil pore structure and affected the degrees of anisotropy, fractal dimension, soil porosity and stability of soil aggregates. NBC applications also increased the water repellency of the soil and reduced the surface energy of soil particles. Regarding soil hydraulic properties, NBC applications increased the saturated hydraulic conductivity of the soil and decreased soil water retention. Increasing the amount of NBC applied to the mixing-layer decreased cumulative infiltration values (reduced by 3.75%–13.75%). The above results reveal how NBC affects the soil pore structure and soil hydraulic characteristics, which provides a theoretical basis for the systematic evaluation of soil improvement and environmental effects of nano-sized biochar.

中文翻译：

---

纳米生物炭作为土壤改良剂对砂壤土结构和水力特性的影响

生物炭作为土壤改良剂可以影响土壤的物理和溶质运输特性，从而提供一种提高土壤肥力的方法。然而，使用不同尺寸的生物炭颗粒直至纳米级显示出不一致的结果，由于缺乏实验数据而对其机制知之甚少。本研究调查了将纳米级生物炭颗粒 (NBC) 应用于砂壤土对水力特性和土壤结构的影响及其机制。在 0.0%、0.3%、0.5%、0.7% 和 1.0%（按重量计）的 NBC 施用率下进行柱实验。结果表明，NBC改变了土壤孔隙结构的分布，影响了各向异性程度、分形维数、土壤孔隙度和土壤团聚体的稳定性。NBC 应用还增加了土壤的斥水性并降低了土壤颗粒的表面能。关于土壤水力特性，NBC 应用增加了土壤的饱和导水率并降低了土壤保水性。增加应用于混合层的 NBC 量会降低累积入渗值（降低 3.75%–13.75%）。以上结果揭示了 NBC 对土壤孔隙结构和土壤水力特性的影响，为系统评价纳米生物炭的土壤改良和环境效应提供了理论依据。增加应用于混合层的 NBC 量会降低累积入渗值（降低 3.75%–13.75%）。以上结果揭示了 NBC 对土壤孔隙结构和土壤水力特性的影响，为系统评价纳米生物炭的土壤改良和环境效应提供了理论依据。增加应用于混合层的 NBC 量会降低累积入渗值（降低 3.75%–13.75%）。以上结果揭示了 NBC 对土壤孔隙结构和土壤水力特性的影响，为系统评价纳米生物炭的土壤改良和环境效应提供了理论依据。