Biochar has been used as an eco‐friendly enhancer to alter soil microstructure and improve the mechanical and hydraulic properties of soil. Recent studies observed that variation in biochar particle size can affect its ability to alter soil microstructures. This poses a challenge to select the proper biochar particle size to manipulate soil properties to favor agricultural applications including crop cultivation or engineering design, such as landfill cover. This study experimentally investigated the influence of biochar particle size on soil microstructures and its effects on water retention and gas permeability (k_g) of a repacked biochar‐amended soil (BAS). Peanut shell biochar with four different sizes, ranging from finer than 0.25 to >2 mm, was amended into silty sand. Change in microstructure of BAS was observed using a mercury intrusion porosimeter. Results indicated that the particle size of biochar played a significant role in altering soil microstructures. The addition of smaller biochar particles (i.e., <0.25 mm) decreased soil mesopores and macropores by ∼19%, resulting in greater water retention and reduction of k_g by ∼31% at ∼0.35 air‐filled porosity. However, the mesopores and macropores of soil amended with larger biochar particles (i.e., >2 mm) increased threefold. This resulted in a reduction of water retention at low matric potential (i.e., lower than −3 kPa) and increased k_g by up to 93% at ∼0.35 air‐filled porosity. These findings indicate that application of smaller biochar particles can enhance the water retention ability of the silty sand and reduce soil k_g, which is beneficial to the water and air management of the biochar‐amended soil layers (i.e., as an aeration layer or sealing layer).

中文翻译：

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用不同粒径的花生壳生物炭修正的重新包装的粉质砂的透气性和保水性

生物炭已被用作生态友好的增强剂，可改变土壤的微观结构并改善土壤的机械和水力性质。最近的研究发现，生物炭粒径的变化会影响其改变土壤微观结构的能力。这对于选择合适的生物炭颗粒尺寸来控制土壤特性，从而有利于农业应用（包括农作物种植或工程设计，如垃圾掩埋场）提出了挑战。本研究实验研究生物炭颗粒尺寸对土壤的微结构的影响及其对保水性和透气性的影响（ķ_克）重新包装的生物炭改良土壤（BAS）。将四种尺寸从0.25毫米到大于2毫米的花生壳生物炭修改为粉砂。使用压汞仪测量了BAS的微观结构。结果表明，生物炭的粒径在改变土壤微观结构中起着重要作用。添加较小的生物炭颗粒（即<0.25 mm）可使土壤中孔和大孔减少约19％，从而在约0.35充气孔隙率下具有更大的保水性，并使k _g减少约31％。但是，用较大的生物炭颗粒（即> 2 mm）修正的土壤中孔和大孔增加了三倍。这导致在低基质电势下（即低于-3 kPa）保水量减少，k增加在约0.35空气孔隙率下，_g最多可提高93％。这些发现表明较小的生物炭颗粒的应用可增强粉砂的保水能力和减少土壤ķ_克，这是生物炭修订的土壤层（即水和空气管理有益的，因为曝气层或密封层）。