流域磷输入对河流磷输出的滞后效应定量研究

The excessive input of phosphorus (P) has been the major reason for ecosystem degeneration in many rivers and eutrophication in downstream waters. The riverine P export is the function of current P input, legacy P, land-to-water transport and in-stream decay conditions, and the quantitative recognition the influence of these factors is essential to optimize the source-sink prevention and control strategies for P pollution. However, the quantitative recognition the contributions of these factors to riverine P export is still difficult based on current models or methods. Choosing 14 tributaries and their catchments in Shanxi Water Source as study area, the major aims of this project are 1) to integrate a spatial reference regression model to quantify the response of riverine P export to Net Anthropogenic Phosphorus Inputs (NAPI), Legacy P, land-to-water transport and in-stream decay conditions by means of the integration of the kernel function function/module of NAPI algorithm, LOADEST model and SPARROW model, and the introduction of soil P environmental sensitive index; and then 2) to solve the key scientific issues of the quantification the contributions of current P input and legacy P to riverine P export, as well as the influences of anthropogenic and natural factors to the transport of current P input and legacy P. The outcome of the proposed research can establish a innovated quantitative research method for lag effect of watershed P input to riverine P export, which is able to further reveal the lag effect of P at watershed scale, and to provide decision basis for watershed phosphorus management and water pollution control.

磷过剩已成为许多河流生态系统功能退化以及下游水体富营养化的重要原因。河流磷输出是当前磷输入、遗留磷、陆地–河流迁移和河流滞留条件的函数，定量识别这些因素的影响对优化磷的源汇控制策略具有重要现实意义。然而，现有模型和方法尚很难定量区分它们对河流磷输出变化的贡献。本项目以浙江省珊溪水源地的14条支流及其集水区为研究区域，将NAPI算法、LOADEST模型和SPARROW模型的核心功能/模块有机整合，引入土壤磷环境敏感指标，建立河流磷输出对NAPI、遗留磷、陆地–河流迁移和河流滞留条件的空间参照回归模型；解决当前磷输入和遗留磷对河流磷输出的贡献定量、人为和自然因素对当前磷输入和遗留磷迁移过程的影响分析这两个关键科学问题。完成本研究，将有望建立定量研究流域磷输入对河流磷输出的滞后效应的新方法，加深我们对流域尺度磷滞后效应的了解，为流域磷管理和水污染控制供决策依据。

磷过剩已成为许多河流生态系统功能退化以及下游水体富营养化的重要原因。河流磷输出的时空变化是当前磷输入、遗留磷、陆地-河流迁移和河流滞留条件的函数，定量识别这些因素的影响对优化磷污染的源汇控制策略具有重要现实意义。然而，现行的模型和方法尚很难定量识别它们各自对河流磷通量变化的贡献。本项目以浙江省珊溪水源地的14条支流及其集水区为研究对象，引入土壤磷环境敏感指标，解决当前磷输入和遗留磷对河流磷输出的贡献定量、陆地–河流输移和河流滞留条件对当前磷输入和遗留磷入河过程的影响分析这两个关键科学问题。结果发现，珊溪水源地土壤中TP的含量处于0.02~2.76 g kg-1之间，其均值为0.50g kg-1；AP的含量处于0.005~561.42 mg kg-1之间，均值为53.89 mg kg-1。耕地、建设用地和园地的土壤AP含量平均值分别为54.57mg kg-1、46.53mg kg-1和39.96mg kg-1，土壤有效磷含量超出了临界值。与其他流域相比，珊溪水源地土壤AP含量偏高。将耕地、建设用地和土壤AP含量作为解释变量，分别对不同水文季节的河流TP浓度建立多元线性回归模型。平水期、梅汛期和台汛期的模型拟合得都比较好，R2分别为0.761、0.770和0.728。河流磷浓度模拟模型的建立，将为流域磷污染控制措施的制定提供了科学依据。根据非点源污染的产生和迁移过程，从“源头控制”、“过程拦截”和“末端治理”三个方面提出水源地磷污染控制措施。主要措施包括调整农业种植结构、推广测土配方施肥技术、建设植被缓冲带、进一步控制生活污水、巩固畜禽养殖综合整治成果和建立和完善水源地保护机制。情景模拟结果表明，通过“退耕还林”、“侧推配方施肥”“植被缓冲带”途径使农业污染的贡献度削减50%，同时通过加大农村生活污水收集和处理力度使生活污染的贡献度削减50%，各支流TP浓度模拟值将会进一步下降，水质稳定符合II类水质的要求。本项目建立了流域磷输入对河流磷输出滞后效应的定量研究方法，揭示河流磷输出变化特征及影响因素，为流域磷管理和水污染控制供决策依据。