酸化驱动的黑土土壤团聚体破碎机制研究

Soil acidification results in base cation leaching and aggregate structure damaging. But the main control factors related to change in soil colloid, cementing material during the soil acidification process and the quantitative characteristics of aggregate crushing and reassembling are still needed to be further researched. The project takes the black soil and red soil of which are important to grain production as the research objects, collects soil under different use way (cultivated land, woodland, protected land) and long-term different fertilization way, uses chemical selective dissolution technology and ultrasonic which energy can be measured to disperse and crack soil. Our study will use technologies of X ray fluorescence (XRF), X ray diffraction (XRD), infrared spectroscopy (FTIR), scanning electron microscopy (SEM/EDS), transmission electron microscopy (TEM/EDS) and high resolution transmission electron microscopy (HRTEM), with the method of combining field long term experiment and indoor simulation experiment，then start from the composition characteristics and main controlling factors of aggregates colloidal substances and cementing material, take the scientific problem of identity of "acid" material and cementing material as breakthrough point, and study the progress of aggregate crushing by different acidification ways, reveal the main controlling factors of aggregate crushing by soil acidification and critical characteristics of aggregate crushing, and clarify the molecular level mechanism of the soil structure degradation driven by acidification. This project will help to give basic data and scientific basis to sustainable utilization of soil, soil erosion control, global carbon cycle, environmental restoration and other fields.

土壤酸化导致盐基离子淋失，土壤团聚结构破坏。但土壤酸化过程中团聚体的胶体物质、胶结物质变化的主控因素还不清楚，团聚体的破碎过程的数量特征还有待进一步研究。本项目选择对我国粮食生产占重要地位的黑土为研究对象，采集不同利用方式（耕地、林地、保护地）和长期不同施肥土壤，采用化学选择性溶提技术、能量可测超声波分散破碎土壤，应用XRF、 XRD、FTIR、SEM/EDS、TEM/EDS 、HRTEM 等先进的测试手段，以野外长期定位试验和室内模拟实验相结合的方法，从团聚体胶体物质和胶结物质的组成特征和主控因素入手，以“抗酸”物质与胶结物质同一性的科学问题为切入点，研究不同酸化原因土壤团聚体破碎过程，揭示土壤酸化驱动下团聚体破碎的主控因素和团聚体破碎过程的临界特征，阐明土壤酸化驱动的结构体退化的作用机制。为土壤可持续利用、土壤侵蚀防治、全球碳循环、环境修复等领域提供基础数据和科学依据。

黑土酸化导致土壤养分淋失、团聚体稳定性变差，土壤肥力退化，对粮食生产和农田生态系统的稳定性造成严重威胁。基于此，采用模拟试验和长期施肥定位试验相结合的方法，研究了酸化驱动下，黑土胶体物质数量稳定性变化、有机无机复合体数量稳定性的变化、主要胶结物质变化对团聚体稳定性的影响，揭示黑土酸化过程中团聚体破碎的主控因素和团聚体稳定性破坏的临界酸度特征。研究结果如下：.1．长期施肥和不同利用方式下土壤胶体的CEC8.2与土壤酸度显著相关。酸化降低了土壤胶体的CEC8.2、CECP、CECV、CECV/CEC8.2、CECm、净土壤酸化降低了土壤胶体的比表面。土壤酸度增加，pH值的降低，负电荷密度降低，导致胶体负电荷间的静电排斥力降低，胶体趋向不稳定。土壤胶体稳定性的主控因素胶体的CEC8.2和表面电荷密度。.2．长期施肥土壤pH值的下降，同时伴随Ca2+的流失和胡敏酸的老化，进而导致黑土胶散复合体总量的下降，土壤结构和稳定性变差。Ca2+的减少和HA的老化是影响黑土土壤酸化和土壤团聚体稳定性的主要驱动因素。玉米秸秆和NPK肥的适量配施能够有效提高黑土胶散复合体和Ca2+的含量，减缓HA的老化。.3．黑土和玉米带黑土团聚体的机械稳定性和水稳性均随土壤pH的降低而显著下降。pH平均每下降0.1个单位，破碎能分别降低14.04J g-1和8.4J g-1；黑土持续酸化下，粉粒稳定能降低幅度小于砂粒。团聚体稳定能和粉粒临界破碎能下降的主要因素为土壤中CaCO3和Ca-SOC含量的下降，导致玉米带黑土团聚体稳定能和粉粒临界破碎能下降的主控因素均为土壤中CaCO3含量的下降。.4．土壤pH由5.81降低到5.43阶段，Ca2+离子淋失速率最大，该阶段水稳性微团聚体稳定能临界破碎能下降幅度亦最大。pH由5.81降低到5.43阶段，ka差值最大， pH由5.43降低到5.22阶段，kc迅速提升，此时砂粒和粉粒的破碎速度加快。.综上，黑土酸化的降低了土壤胶体的稳定性、增加了主要胶结物质CaCO3的淋失，促进了胡敏酸的老化，导致团聚体稳定性下降。pH由5.43降低到5.22阶段为砂粒和粉粒的加速破碎的临界值。