降雨-径流条件下库岸带农业非点源氮磷运移定量研究

Lakeside Zone, as a natural ecological barrier of a reservoir, where is exposed in flood Season and submerged in dry season, has the unique environmental factors, ecological processes and vegetation characteristics that are different from those of rivers and lakes. Rainfall-runoff process is the main driving force and carrier of soil erosion and contaminant transport, and it is important for non-point source pollution control to understand nitrogen and phosphorus transport path. In this study, field experiments would be conducted in the Danjiangkou reservoir that is the source of water for the Middle Route project which is part of the South-to-North Water Transfer Scheme. Field surveys together with in situ observation and simulated experiment would be employed. Temporal and spatial distribution characteristics of soil and plants would be surveyed and studied in order to divide Lakeside Zone. Based on this mentioned above, with a dye tracer and 15N-isotope dilution technique, under rainfall and flow scouring, chemical form, content of nitrogen and phosphorus and their temporal and spatial distribution would be studied in the lakeside zone and Landscapes; and nitrogen, phosphorus transport path and the internal mechanism in different types of reservoir banks would be explored; and coupling effect of lakeside zone and farmland, woodland, citrus orchards and other landscapes on nonpoint source pollution and its mechanism. The research results would provide a theoretical basis for agricultural non-point source pollution prevention of and a technological support for rational planning for land use of lakeside zone which would be very important for protecting the water quality security in the Danjiangkou Reservoir.

库岸带是水库的天然生态屏障，由于经受着丰水期暴露和枯水期淹没的反季节性变化，有着与河流湖泊明显不同的环境因子、生态过程和植被特征。降雨径流过程是土壤侵蚀、污染物运移的主要驱动力和载体，弄清降雨条件下土壤中氮磷养分输运路径是有效控制非点源污染的重要内容。本研究以南水北调中线水源地--丹江口水库典型库岸带为研究对象，采用野外调查、定点观测和模拟控制试验相结合的方法，研究库岸带背景景观土壤、植被特性及时空分布特征，并划分库岸带类型；在此基础上，借助土体染色示踪法和元素示踪技术，通过降雨和径流冲刷试验，研究库岸带和背景景观中氮、磷赋存形态、含量及时空变化，探讨不同类型库岸带氮、磷运移路径及内在机理，揭示库岸带与林地、农田、园地等背景景观耦合对非点源氮磷截留去除的作用机制，为丹江口库区农业非点源污染防控提供理论依据，为库岸带土地利用合理规划提供技术支撑，对保障丹江口水库水质安全有重要意义。

库岸植被缓冲带是截留陆域面源污染物、改善水库水质的有效手段。对现有库岸带开展系统调查，构建适宜的河岸植被缓冲带，使之具有拦蓄泥沙、截留氮磷污染物的最佳生态效益，保障水质安全已成为丹江口库区生态环境建设与保护所面临的最紧迫的任务。本研究针对种典型库岸植被缓冲带，开展野外模拟径流冲刷实验，通过室外试验和室内测量分析相结合的方式来进行缓冲带对陆源污染物阻控能力的研究，初步明确了库岸植被缓冲带对农业面源污染的净化机理，并探讨了丹江口库区不同立地条件下的植被缓冲带最佳宽度配置。.研究结果表明，不同植被类型缓冲带在不同流量和营养浓度条件下对氮磷污染物有较好去除效果，总体而言对氮的去除能力略高于磷，随着污染负荷的增加，各种库岸植被缓冲带对NO3-、TP和SRP的净化率有降低趋势，对TN的净化率却有相反趋势。随着流量增大，各植被缓冲带在不同污染负荷条件下对各污染物质的净化率均呈现下降趋势。地表径流和壤中流中各污染物的浓度存在一定的差异，壤中流的污染物浓度要低于地表径流，壤中流的净化率高于地表径流。径流中各污染物质相关性分析结果表明，除了各形态磷素之间、各形态氮素之间呈极显著相关外，径流中泥沙含量与全磷含量呈极显著的正相关性。分别对不同坡度、不同污染物浓度和不同流量的情景模式，各情景模式中总磷去除效率达到80%的植被缓冲带宽度在6.6-43.5m之间，总氮的去除效率达到50%的植被缓冲带宽度在13.7-58.2m之间。.本研究运用景观生态学、水文学、统计学及GIS技术等理论基础与研究方法，研究库岸植被缓冲带对于污染物阻控机理与效率，分别探讨了不同立地条件下的植被缓冲带最佳宽度配置，为丹江口库区农业非点源污染防控提供理论依据，对丹江口库区植被缓冲带的空间优化配置具有一定现实指导意义。