九龙江流域典型汇水区地表径流氮磷流失特征分析

选取九龙江流域5个典型汇水区,通过流域主要雨季天然降雨径流过程监测,对所获得的氮磷营养盐的监测数据进行归纳与分析,着重探讨了暴雨事件下径流氮磷流失及其形态的变化规律。结果表明:暴雨事件下农业汇水区地表径流氮输出以水溶态为主,磷以泥沙结合态为主,天然林地为主的汇水区则相反,前者以泥沙结合态为主,后者以水溶态为主;5个汇水区暴雨事件中总氮最高浓度值为日常采样浓度值的2.9～11.3倍,暴雨事件中总磷最高浓度值为日常采样浓度值的2.9～20.5倍;氮磷输出量均值的差异反映氮磷输出量大小受土壤质地、施肥量、土壤氮磷含量、土壤保水保肥性能等因素的综合影响。整个径流过程中水量和氮磷浓度随时间变化幅度较大,且2者变化呈大体相同的趋势。氮磷及其各形态的浓度多数在相同时间内达到峰值。泥沙结合态氮、水溶态磷变化幅度较小,水溶态氮和泥沙结合态磷浓度变化幅度较大。统计各汇水区雨量不同的降雨事件下氮磷流失负荷表明,特大暴雨对汇水区氮磷负荷的贡献非常显著。

Characteristics of nitrogen and phosphorus losses with surface runoff in typical sub-watersheds of Jiulong River watershed

Five typicl sub-watersheds in the Jiulong River watershed were chosen for monitoring nitrogen and phosphorus losses.Results of the monitoring and analysis show that in the event of storms in agriculture-based watersheds,the N loss with the runoff is dominated with soluble N and the P loss with P combined with silt whereas in natural-forest-based ones,the situation is completely different.Under storms,the maximum total N concentration in the runoff is 2.9-11.3 times as much as that in the runoff normal and the maximum total P concentration 2.9-20.5 times as much.Throughout the entire course of runoff,water volume and N & P concentration vary sharply with the time,showing a similar trend.The concentrations of total N & P and their various forms come up to their respective peaks almost at the same time.The contents of silt N and soluble P fluctated within a limited range whereas those of soluble N and silt P do within a large one.