Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong SAR, China; Southern Federal University, Rostov-on-Don, Russian Federation.
Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong SAR, China.
Chemosphere. 2024 Jun;358:142134. doi: 10.1016/j.chemosphere.2024.142134. Epub 2024 Apr 25.
Soil cracking can significantly alter the water and nutrient migration pathways in the soil, influencing plant growth and development. While biochar usage has effectively addressed soil cracking, the feasibility of using less energy-intensive hydrochars in desiccating soils remains unexplored. This study investigates the impact of wood and peanut shell hydrochars on the desiccation cracking characteristics of clayey soil. A series of controlled environmental laboratory incubations with regular imaging was conducted to determine crack development's dynamic in unamended and hydrochar-amended soils. The results reveal that the addition of wood hydrochar at 2% and 4% dosage reduced the crack intensity factor (CIF) by 22% and 43%, respectively, compared to the unamended control soil. Similarly, the inclusion of peanut shell hydrochar at 2% and 4% lowered the CIF by 22% and 51%, respectively. The presence of hydrophilic groups on the surface of hydrochars, such as O-H, CH, and C-O-C, enhanced the water retention capacity, as confirmed by Fourier-transform infrared analysis. The CIF decrease is attributed to mitigated water evaporation rates, enabled by enhanced water retention within the hydrochar pore spaces. These findings are supported by scanning electron microscopy analyses of the hydrochar morphology. Despite CIF reduction with hydrochar incorporation, the crack length density (CLD) increased across all hydrochar-amended series. In contrast to unamended soil which exhibited pronounced widening of large cracks and extensive inter-pore voids, the incorporation of hydrochar resulted in higher CLD due to the formation of finer interconnecting crack meshes. Consequently, the unamended control soil suffered greater water loss due to heightened evaporation rates. This study sheds new light on the potential of hydrochars in addressing desiccation-induced soil cracking and its implications for water conservation.
土壤开裂会显著改变土壤中的水分和养分迁移途径，从而影响植物的生长和发育。虽然生物炭的使用有效地解决了土壤开裂问题，但在干燥土壤中使用能源消耗较少的水热炭的可行性仍未得到探索。本研究调查了木屑和花生壳水热炭对粘性土干燥开裂特性的影响。通过一系列带有定期成像的受控环境实验室孵育，确定了未改良和水热炭改良土壤中裂缝发展的动态。结果表明，与未改良对照土壤相比，添加 2%和 4%剂量的木屑水热炭分别使裂缝强度因子（CIF）降低了 22%和 43%。同样，添加 2%和 4%的花生壳水热炭使 CIF 分别降低了 22%和 51%。水热炭表面的亲水性基团，如 O-H、CH 和 C-O-C，增强了水保持能力，傅里叶变换红外分析对此进行了证实。CIF 的降低归因于水蒸发速率的减缓，这是由于水在水热炭孔隙中的保留能力增强所致。水热炭形态的扫描电子显微镜分析支持了这一发现。尽管水热炭的加入降低了 CIF，但所有水热炭改良系列的裂缝长度密度（CLD）都有所增加。与未改良土壤相比，后者表现出大裂缝明显变宽和广泛的孔隙间空隙，而水热炭的加入导致了更高的 CLD，因为形成了更细的相互连接的裂缝网。因此，由于蒸发速率升高，未改良的对照土壤损失了更多的水分。本研究为水热炭在解决干燥引起的土壤开裂问题及其对节水的影响方面提供了新的思路。
