大型湖库型水源保护区氮素污染景观源-汇机制及空间优化调控

Human impacts on the nitrogen (N) cycle have profoundly affected the natural functioning of earth’s ecosystems in modern times. Anthropogenic activities have greatly increased watershed export of N and detrimental impacts on functions and values of the receiving water bodies. Water environmental problems due to N enrichment continue to threat the safety of human drinking water. There are still.many of the urgent needs to solve these basic science issues further, including how to identify accurately N sources-sinks pattern at the watershed scale? What are the mechanisms of N sources-sinks exchange conversion? How to regulate the N sources-sinks relations by landscape spatial optimization? and so on. This project will take water resource protection area of Hun river upstream of Dahuofang reservoir as a case, from the perspective of landscape ecology, using remote sensing and GIS, field positioning monitoring, statistical analysis, simulation modeling, to achieve the following objectives: 1) to discriminate and improve identification methods of N sources-sinks pattern; 2) to clarify the spatial relationships and conversion mechanisms of N sources-sinks; and 3) to seek landscape regulation strategies for spatial optimization of N sources-sinks. The findings will be helpful for environmental management of headwater area of large lakes and reservoirs, and also could provide new ideas for the development of landscape optimization theories.

近代以来，人类活动增加的N素输入严重干扰了自然生态系统N循环。流域尺度上N素的输出深刻影响着下游受纳水体的功能和价值。N富集诱发的水环境问题不断威胁着人类的饮用水安全。人类干扰下N源-汇关系及空间优化调控技术等还存在着诸多急需进一步深入探讨的科学问题，包括：流域N源-汇格局如何准确识别？N源-汇转换的规律和机制是什么？有怎样的景观空间优化途径？等。本项目以大伙房水库浑河支流水源保护区流域为案例区，采用遥感和GIS分析、定位监测、野外采样与测试分析、经典统计和地统计、模型模拟等手段，从景观生态学的视角：1）辨析和改进流域尺度N源-汇识别方法；2）阐明N源-汇空间关系及转换机制；3）寻求N源-汇调控的景观空间优化策略，为大型湖库型水源区流域水环境管理实践奠定扎实的科学基础，为基于格局—过程的景观源汇优化理论发展研究提供新的思路。

大型湖库型水源保护区普遍存在非点源污染的问题，氮、磷超标的问题一致没有有效解决。尤其是流域尺度上活性氮引起水质退化的源汇识别、源汇转换机制、空间防控途径等基础研究还较为薄弱。本项目针对以上科学问题，选择辽宁大伙房水库上游清原流域为案例区，开展了流域N 源-汇斑块空间分布识别、流域N 源-汇空间关系及转换机制、流域N 源-汇空间优化调控技术研究。（1）阐明了流域河流氮素时空分布特征及其与土地利用的关系，该地区的氮素污染属于中等污染水平，硝态氮的浓度在枯水期最高，铵态氮含量在丰水期最高，从上游到中、下游三种形态氮素含量指标均为逐渐升高，河流氮素含量与旱田、建设用地和水域面积有显著正相关性；（2）阐明了流域N素收支时空动态，整个流域氮盈余均值为33.65 kgN/hm2，主要的氮输入是化肥施用占60%，四个季节的氮盈余斑块时空分布差异较大，与土地利用和覆被类型及物候关系较大；（3）通过氮传输比和负荷量的空间和季节性变化研究，揭示出降雨产生的径流是驱动潜在N传输的主要动力，通过地表径流和亚表层径流在水田、旱田和水域间的输移是主要的机制；（4）非点源污染优先控制区是解决水质和径流管理问题的一种低成本方案，借鉴Mauri模型框架开发的小流域非点源污染治理优先顺序土地评分系统，具有良好的成本效益和可行性。研究成果为指导水库型水源保护区非点源污染氮素的源汇作用研究和治理策略制定提供了科学依据。