太湖地区入湖小流域河岸带土壤水文过程及其环境效应研究

The spatial location, hydrological characteristics and soil environmental characteristics of the different level rivers in the basin are different, which leads to the difference of the master factors that affect the migration and transformation of the nutrients in the soil in the corresponding riparian zone. The thickness of unsaturated zone soil which is in the riparian zone of plain river network region is thinner, the level of phreatic water is higher. The interaction of the precipitation, phreatic water and river water has a significantly effect on the unsaturated zone soil, soil microorganism and the nutrients dynamic interaction in the interface of the riparian zone soil and river water. In addition, excessive use of the riparian zone in plain river network region caused that the destruction and degradation of the Riparian zone ecosystem were very serious. Based on these, the riparian zones of the different level rivers of the sub-basin of Tai Lake were chosen to as the research object and the research method that combines indoor experimental and field observation was used in the project. the rule of moisture movement which is in the riparian zone soil profile, the characteristics of the soil/microorganism in the riparian zone and its purification mechanism under the pattern of "dry-wet alternation", the nutrient dynamic interaction process in the interface of "soil - water" of the riparian zone, and the key technology of the riparian zone ecological restoration will be discussed. The project will reveal the riparian zone soil hydrological processes and its environmental effects of sub-basin of Tai Lake, and construct the ecological restoration technology system which is suitable for the region, and furthermore to provide the theoretical basis for the comprehensive prevention of the non-point source pollutants in the region.

流域内不同级别河流的空间位置、水文特征以及土壤环境特征不同，导致影响营养物质在相应河岸带土壤中迁移转化的主控因素不同。平原河网地区河岸带土壤非饱和带厚度较薄，潜水水位较高，降水、潜水、河水三者之间的相互作用对非饱和带土壤、土壤微生物、以及河岸带陆域与河水界面营养物质的动态交互过程影响显著。另外，人类通常对平原河网地区河岸带利用强度较大，河岸带生态系统破坏和退化现象十分严重。基于此，本项目以太湖地区典型入湖小流域内不同级别河流河岸带为研究对象，采用现场观测、室内实验相结合的研究方法，探讨河岸带土壤剖面水分运动规律，寻求"干湿交替"模式下河岸带土壤/微生物特性及其截污净污机制，剖析河岸带"陆域-河水"界面营养物质的动态交互过程，研发河岸带基质生态修复关键技术，从而揭示太湖地区入湖小流域河岸带土壤水文过程及其环境效应，构建该地区河岸带基质生态修复技术体系，为该地区非点源污染综合治理提供理论依据。

太湖河网地区河岸带土壤水文过程、生源要素迁移转化复杂。同时，该地区河岸带利用强度较大，河岸带生态系统破坏和退化现象严重。本项目以太湖地区殷村港小流域不同级别河岸带为研究对象，采用野外观测、室内实验相结合的研究方法，探讨河岸带土壤剖面水分运动机理，寻求“干湿交替”模式下河岸带土壤/微生物特性及其截污净污机制，剖析河岸带“土-水”界面营养物质的动态交互过程。研究结果发现：(1)研究区各月份降雨量差异较大，河水水位和地下水位随降雨量的变化而变化。年内河水与地下水之间存在一定的相互补排关系，夏秋季节地下水补给河水；冬春季节河水补给地下水。(2) 河岸植物银杏根系的二态分布特点影响河岸带土壤剖面的水分分布。三大初始水源中，与河水和地下水相比较，降雨是决定该研究区内河岸植物吸水的关键因素。雨季银杏优先选择降雨和受降雨直接补给的浅层土壤水作为其稳定的水分来源；而在降雨量较少的旱季，银杏选择地下水作为其主要水分来源。（3）河岸带0-15cm浅土壤层的有机碳含量随水位变化波动较大，但均出现随着水位降低有机碳含量下降的现象，并且在低水位时达到最低值，而在雨季水位升高时呈现含量上升趋势。（4）干湿交替条件下，河岸带0-15cm土层β-D葡糖苷酶、多酚氧化酶和过氧化物酶活性均表现为高水位最高，中水位次之，低水位最低，在雨季含量均出现上升趋势。同时，地下水位的涨跌对土壤酶的空间分布有一定影响。（5）河岸带土壤对磷具有吸附截留作用，近水岸域地下水中磷含量较低。当河岸土壤对磷的截留效果达到饱和，开始解吸释放磷。（6）受河水水位变化的影响，河岸近水0-30cm土壤层的总氮、氨氮和硝氮含量均高于中层和深层土壤，且0-30cm土壤层的各形态氮素的四季变化波动更大。磷素有类似的变化规律。另外，探讨了平原河网地区不同级别河流河岸带基质生态修复的有效途径，研发基于基质的河岸带生态修复技术。项目成果可为该地区非点源污染综合防治和河岸带生态修复提供理论依据和技术支撑。