腐殖酸在水土流失固液界面的迁移行为研究-以云南楚雄龙川江流域为例

Soil humus is one important indicators of soil fertility, has a significant influence on the physical, chemical, and biological properties of the soil. Loss of soil humic acid in soil humus is the key issues of the soil nutrients loss and soil fertility declined by water erosion caused. On the one hand, early research achievements about the soil erosion subject are mainly concerned on the sediment transport processes, the relationship between sediment transport and the flood, the forecast of the soil erosion and its control; on the other hand, the achievements about the humic acid are focused on the formation, determination, group, content changes of humic acid in the soil, and the relationship between the content changes and the plant stress resistance, and the soil pollutants degradation. So, it is very important to the land resources fertility loss caused by water erosion, that research on the regulation about dissolution, transport and deposition of the humic acid in the process of water erosion in the soil. In present research, we will firstly study the loss features of the soil humic acid in the process of water erosion, controlled by different land uses way in the field. Secondly, the dissolved, transport and deposition mechanisms of the humic acid effected by different water erosion intensity will be further studied by indoor simulation. Lastly, the features of the humic acid dissolved in the liquid phase, deposited on the solid phase and transported by the water flow will be elucidated in a natural geographic unit composed by the land use type, water erosion intensity and terrain. The results will provide valuable information to the rational use of soil and water conservation measures in the practice of soil and water loss controlled.

腐殖质对土壤的物理、化学、生物学性质有重要影响，是土壤肥力的重要指标。土壤腐殖质中腐殖酸的流失是水力侵蚀导致土壤养分流失和土壤肥力下降的关键问题。前期工作对土壤侵蚀的关注主要体现在输沙过程、水沙关系、侵蚀预报与调控上；对土壤腐殖酸的关注则体现在腐殖酸的形成、测定与分组、含量变化及其与植物抗逆性和土壤污染物降解的关系上。而研究水力侵蚀过程土壤中腐殖酸的溶解、搬运和沉积规律，对研究和调控因土壤侵蚀导致的土地肥力缺失具有重要意义。本研究首先通过野外观测，研究水力侵蚀过程中不同土地利用方式下土壤腐殖酸的流失特征；其次，进行室内模拟，研究腐殖酸在不同水力侵蚀强度下的溶解、搬运与沉积规律；最后，以土地利用方式、水力侵蚀强度以及地形等因子组合建立自然地理单元，明确水力侵蚀过程中土壤腐殖酸在液相和固相中的溶解与沉积规律，及其随水流搬运过程中的变化特征，为在水土流失治理实践中合理采用水土保持措施提供依据。

土壤中以腐殖酸流失为代表的土壤养分及生产力降低是区域社会发展面临的主要问题之一。项目选择了研究区有代表性的紫色土、红壤和黄棕壤等3种土壤类型，分别以各土壤类型上覆的植被为对象建立研究样地，以有机质、腐殖酸、pH值等肥力指标为表征，获取土壤样品144个，完成区域土壤肥力水平及基础地理数据库、2期植被数据库建设。选择紫色土和黄棕壤为供试土壤，以地表覆盖类型、pH值、生物炭、氧化还原电位、坡度为观测因子，以中雨、大雨和暴雨3种降雨强度为水力侵蚀因子，收集土壤侵蚀液，研究了降雨过程中土壤腐殖酸的淋溶、空间转移以及异地沉积、附着等侵蚀特征，分析了以生物炭为主要改善措施对土壤腐殖酸流失控制的主要机理。主要研究结果为：（1）研究区紫色土除常绿阔叶林覆盖下为酸性外，其余盖状态下呈弱酸或中偏碱性；黄棕壤和红壤均为酸性土壤。土壤腐殖质与全磷、全钾、速效钾之间呈极显著正相关，与土壤pH呈显著负相关，胡敏酸（HA）含量与土壤全磷呈显著负相关，与土壤氧化还原电位呈显著正相关，而富里酸（FA）只与高程有关。（2）自然植被覆盖下土壤中的腐殖酸含量与土壤类型相关性不大，而与植被类型和高程分布有关。0-30cm耕作层中HA含量、HA/FA值以灌木林地最高，草地最低；乔木林地在0-10cm土层中FA含量小于10-20cm土层，灌木林地在0-10cm与10-20cm土层的FA含量无显著性差异；草地0-10cm土层FA含量显著高于10-20cm土层，草地对预防土壤表层FA流失有明显作用。落叶阔叶林对腐殖酸流失有最好的控制作用。（3）紫色土土柱模拟降雨显示，随降雨强度增加HA侵蚀速率加快，最高侵蚀浓度出现的时间大雨比中雨快，但暴雨呈现不同特征；FA侵蚀速率和侵蚀浓度随降雨强度的变化差异不明显；HA和FA溶出浓度和溶出速率随着pH值的增大而增大；还原状态的土壤中，FA的溶出浓度和溶出速率要高于HA；坡度≤10°可以有效增加淋溶腐殖酸的沉积与附着；土壤中添加10%600℃制备的牛粪生物炭，配以适量NaCl有利于土壤吸附 HA 和 FA，可以减少腐殖酸流失，保持肥力。