梯级水库建设对怒江与澜沧江沉积物氮形态分布的影响

为探究梯级水库建设对沉积物氮形态分布的影响，通过分级浸取方法得到沉积物的离子交换态氮（IEF-N）、弱酸提取态氮（WAEF-N）、强碱提取态氮（SAEF-N）以及强氧化剂提取态氮（SOEF-N），对比研究了有梯级水库建设的澜沧江和干流无水电站建设的怒江沉积物中氮形态的分布特征，分析了可转化态氮的主要影响因素.结果表明，两条流域沉积物赋存环境存在差异，进而使沉积物的理化性质呈现明显的差异，最终导致沉积物可转化态氮的含量及空间分布也不同，澜沧江沉积物可转化态氮的含量高于怒江，且澜沧江的空间变化也大于怒江，怒江IEF-N、WAEF-N、SAEF-N与SOEF-N含量范围分别为1.56~2.55，16.91~46.42，1.83~10.66，486.61~719.27mg/kg，澜沧江IEF-N、WAEF-N、SAEF-N与SOEF-N含量范围分别为1.55~14.35，20.77~83.08，1.36~92.15，562.61~1404.82mg/kg.两条河流的可转化态氮含量大小排列顺序一致，均为SOEF-N > WAEF-N > SAEF-N > IEF-N，怒江与澜沧江上游自然河段可转化态氮含量及空间分布基本一致，但在澜沧江的梯级水库段上，4种可转化态氮空间分布特征发生了较明显的变化，产生这种现象的原因主要是水库的建设导致了沉积物理化性质的改变，总有机碳、粒度、氧化还原电位对可转化态氮的影响不同.

Effect of cascade reservoir construction on nitrogen distribution in sediments of Nujiang River and Lancang River

In order to investigate the effect of cascade reservoir construction on the distribution of nitrogen forms in sediments, the ion exchangeable nitrogen (IEF-N), the weak acid extractable nitrogen (WAEF-N), the strong alkaline extractable nitrogen (SAEF-N) and the strong oxidant extractable nitrogen (SOEF-N) of sediments were obtained by the sequential extraction method, and were compared to study the distribution characteristics of nitrogen forms in the sediments of Lancang River with cascade reservoir construction and Nujiang River with no hydropower station in the main stream. The main influencing factors of convertible nitrogen were analyzed. The results showed that there were differences in the occurrence environment of sediments between the two basins, and the physical and chemical properties of sediments were obviously different, and the content and spatial distribution of converted nitrogen in sediments were also different. The content of transformed nitrogen in the sediments of Lancang River were greater than that of Nujiang River, and the spatial variation of Lancang River were also greater than that of Nujiang River. The contents of IEF-N, WAEF-N, SAEF-N and SOEF-N in Nujiang River were 1.56~2.55mg/kg and 16.91~46.42mg/kg, respectively. The contents of IEF-N, WAEF-N, SAEF-N and SOEF-N in Lancang River were 1.55~14.35mg/kg, 20.77~83.08mg/kg, 1.36~92.15mg/kg and 562.61~1404.82mg/kg, respectively, and the contents of Lanchang River were 1.55~14.35mg/kg, 1.36~92.15mg/kg, 562.61~1404.82mg/kg, 20.77~8.08mg/kg, 1.36~92.15mg/kg and 562.61~1404.82mg/kg, respectively. The order of convertible nitrogen content between the two rivers were the same, which were SOEF-N>WAEF-N>SAEF-N>IEF-N, Nujiang River and the upper reached of Lancang River. The content and spatial distribution of convertible nitrogen were basically the same, but on the cascade reservoir section of Lancang River, The spatial distribution characteristics of four kinds of converted nitrogen have changed obviously. The main reason for this phenomenon was that the construction of reservoir leads to the change of physical and chemical properties of sediments, total organic carbon and particle size. The effect of redox potential on convertible nitrogen were different.