生物质炭对苏打盐碱土土壤结构的调控机制及其对水力特性的影响

The excessive of exchangeable Na+ lead to poor physical and chemical properties, soil structure degradation and low permeability of saline-sodic soil, which seriously adversely affect the management and utilization of saline-sodic soil in Songnen plain. Biochar have the potential of improving poor structure of saline-sodic soil because of its good micropore structure, and physical and chemical properties. In this study, the typical saline-sodic in Songnen Plain is selected as the research object. Through Field and simulation experiment, this study would analyze quantitatively the relationship in biochar, soil structure, hydraulic properties, and salinization-alkalization parameters by combining uses of physical fraction of aggregate, Synchrotron based X-ray micro-CT, scanning electron microscopy (SEM) and ∂13C stable isotope technique, et al. The aims of this study are to (1) evaluate the relative contribution of physiochemical and biological factors in ameliorating saline–sodic soil aggregate, soil pore structure with biochar; (2) elucidate how particle size, shape, and porosity act together to influence soil aggregate and pore structure by changing pore space between particles (interpores) and by adding pores; (3) to reveal the evolution mechanism of soil structure effected with biochar coupling irrigation leaching/washing; (4) to detect the influence law and mechanism of biochar on soil hydraulic characteristics. This study would further discuss the mechanism of the effects of biochar on the coupled transport of soil water and salt, and provide the theoretical basis and data for remediation of saline-sodic soil.

松嫩平原苏打盐碱土交换性Na+含量高致土壤理化性质恶劣、结构差、渗透性低，降低了盐分洗脱效果，严重影响盐碱土的治理和利用。生物质炭以良好的微孔结构和理化性质，有改良苏打盐碱土不良结构的潜力。本项目拟选取松嫩平原典型的苏打盐碱土为研究对象，通过室内模拟和田间定位试验，应用团聚体物理分级、同步辐射微CT、扫描电镜、∂13C 稳定同位素示踪技术等分析生物质炭-土壤结构-水力特性-盐碱化参数之间的关系。研究目的：（1）明确生物质炭对苏打盐碱土土壤结构的物理化学和生物学因子影响的相对贡献；（2）阐释不同粒径大小生物质炭通过改变生物质炭-土壤间孔隙及其内部孔隙调控苏打盐碱土团聚体和孔隙结构的机理；（3）揭示生物质炭耦合灌溉淋洗对苏打盐碱土土壤结构的调控机制；（4）探明生物质炭对苏打盐碱土水力特性的影响规律及机理。本研究有助于深入探讨生物质炭对苏打盐碱土水盐耦合运移的调控机理，为苏打盐碱土障碍消减提供依据。

松嫩平原苏打盐碱土交换性Na+含量高致土壤理化性质恶劣、结构差、渗透性低，降低了盐分洗脱效果，严重影响盐碱土的治理和利用。生物质炭以良好的微孔结构和理化性质，有改良苏打盐碱土不良结构的潜力。本项目拟选取松嫩平原典型的苏打盐碱土为研究对象，通过室内模拟和田间定位试验，应用团聚体物理分级、同步辐射微CT、扫描电镜、∂13C 稳定同位素示踪技术等分析生物质炭-土壤结构-水力特性-盐碱化参数之间的关系。结果表明：生物炭显著降低了苏打盐碱土的容重、pH 和EC，同时显著增加了土壤饱和含水率，但改良前后土壤质地没有明显变化。生物炭对中度苏打盐碱土改良作用最明显，容重下降了25.62%，饱和含水量增加了40.26%，pH 下降了12.13%，EC 下降了27.94%；生物炭提高了大团聚体含量，团聚体稳定性也得到显著提高，其中以中度苏打盐碱土处理变化最大，≥0.25mm 水稳性团聚体含量为39.96%，MWD、GWD 分别为0.57 mm 和0.59 mm；生物炭显著增加了苏打盐碱土的CEC、K+、Ca2+、Mg2+，同时也显著降低了土壤钠吸附比、碱化度、Na+、全盐量，降低了土壤盐碱化程度。其中K+含量增加59.80%～136.78%，Ca2+含量增加8.99%～71.77%之间，Mg2⁺含量增加3.39%～178.45%，Na+含量降低-12.44%～45.35%；生物炭提高了中度苏打盐碱土微生物活性，显著增加了土壤中细菌和真菌群落的物种多样性和均匀性，其中以中度苏打盐碱土改良效果最明显；生物炭显著地改变了土壤孔隙结构，总孔隙度显著增长，相比对照处理最高涨幅为438.55%，大孔隙度占比也有明显提升，同时孔隙形状更偏向于瘦长型，极大地提高了土壤孔隙结构的复杂性和连通性，提高了土壤入渗性。综上所述，生物炭提高了苏打盐碱土的质量，改善了土壤结构，提高了土壤入渗性，有利于盐分淋洗，减缓了苏打盐碱土中的钠毒害作用。本研究有助于深入探讨生物质炭对苏打盐碱土水盐耦合运移的调控机理，为苏打盐碱土障碍消减治理和改良利用提供了理论依据和技术指导。