长江下游干流水体中氮的空间分布特征

为全面了解长江下游干流氮素的含量水平，于2014年6月对长江下游干流表层、中层和底层水体中总氮（TN）、溶解性氮（TDN）、氨氮（NH4＋-N）的含量进行检测，分析了氮素的空间分布特征。研究结果表明：TDN是氮在长江下游干流水体中的主要形态，而且表层、中层、底层水体中氮素含量均不相同；长江下游干流水体中TN的含量范围为0．85～2．46 mg／L，表层和底层水体中TN平均含量均高于中层水体中TN的平均含量；水体中TDN的含量范围为0．72～2．08 mg／L，表层水体中TDN平均含量相对较高；水体中NH4＋-N的含量范围为0．13～0．75 mg／L，表层、中层和底层水体中NH4＋-N的含量相近；从研究区域上游至下游，TN和TDN的平均含量呈现上升的趋势；不同城市间的NH4＋-N平均含量波动较大。通过相关性分析还发现，TDN与叶绿素a （Chl-a）呈显著负相关，水温（T）与叶绿素a （Chl-a）呈显著正相关，其它形态氮与水的理化性质无明显相关关系。此研究结果可作为控制长江下游干流水体中氮素污染的基础数据。

Spatial Distribution Characteristics of Nitrogen in Mainstream Lower Yangtze River

In order to obtain the nitrogen concentration in mainstream lower Yangtze river and provide basic data for controlling nitrogen pollution,in June 2014 we detected the concentrations of TN,TDN and NH4+-N in surface, middle and bottom waters of lower Yangtze River,and analysed the spatial distribution characteristics of nitrogen. Results reveal that TDN is the main form of nitrogen in the mainstream of lower Yangtze River,and the concentra-tion of nitrogen varies with the depth of water.The range of TN concentration was 0.85-2.46 mg/L and the average concentrations of TN in surface and bottom waters were higher than that in middle water.The range of TDN concen-tration was 0.72-2.08 mg/L,and the average concentration of TDN in surface was much higher.The range of NH4+-N concentration was 0.13-0.75 mg/L,and the average contents of NH4+-N were similar from the bottom to the surface waters.The average contents of TN and TDN present ascendant trend,and the average content of NH4+-N varies greatly between different cities from upstream to downstream in the study area.Through correlation analysis we also found that TDN is in significant negative correlation with chlorophyll-a (Chl),water temperature (T)is significantly positively correlated with chlorophyll-a (Chl),but the other forms of nitrogen have no obvious correla-tion with water’s physicochemical property.