京杭运河常州段氮形态的时空分布特征研究

对京杭运河常州段8个研究点位水体中的氮形态（TN、NH4＋-N、NO2--N和NO3--N）和环境因子（pH、T和DO）进行了连续9个月的动态监测,全面研究了各氮形态的随时间和空间的动态变化规律,并对各氮形态及环境因子进行了相关性分析。常州段水体月平均NH4＋-N变化范围为（0.589±0.351）～（3.148±1.178）mg.L-1,TN变化范围为（3.373±1.379）～（7.373±2.307）mg.L-1,枯水期到丰水期各氮形态整体表现出波动性下降趋势,其中出境断面NH4＋-N下降趋势平稳,NO3--N则是主导出境断面TN含量的主要形态。各点位NH4＋-N的平均浓度范围为（1.202±0.492）～（2.813±1.566）mg.L-1,TN范围为（3.520±0.504）～（8.349±3.679）mg.L-1,各形态氮含量基本呈现出上游段（S）〈新运河（G）〈老运河（L）〈下游（X）的空间分布特征,其中下游段存在一个重要的氮素上升突变段,NO3--N是对TN的贡献率（43.8%～57.4%）最大的无机态氮,其次是NH4＋-N、ON、NO2--N,其中有机氮对TN的贡献率（13.3%）则以老河段最高。NH4＋-N和NO3--N、TN、pH相关系数分别为0.397＊＊、0.932＊＊、0.261＊,与DO相关系数为-0.344＊＊,陆源输入及DO不足是京杭运河常州段氮污染严重的重要原因。

Spatio-tempo Distribution of Different Nitrogen Forms in Changzhou Segment of Grand Canal

Different nitrogen forms（TN、NH4＋-N、NO2-N,NO3-N） and environmental factors at 8 sampling sites in Changzhou Segment of the Grand Canal had been monitored for 9 months to study the spatio-tempo distribution characteristics of various nitrogen forms,as well as the correlation between different phosphorus fractions and environmental factors.Results showed that the monthly average contents of NH4＋-N ranged from（0.589 ± 0.351） mg.L-1 to（3.148 ± 1.178） mg.L-1,while TN were in the range of（3.520 ± 0.504） mg.L-1 ～（7.373 ± 2.307） mg.L-1.Different nitrogen forms experienced a volatility decrease process from low flow period to high flow period,a steady decline of NH4＋-N levels occurred in the river boundary section,while NO3--N might be the dominant specie affecting the TN.Spatially,the average contents of NH4＋-N changed from（1.202 ± 0.492） mg.L-1 to（2.813 ± 1.566） mg.L-1,while TN varied from（3.520 ±0.504） mg.L-1 to（8.349 ± 3.679） mg.L-1.The contents of various N forms in each segment occurred in the order： downstream,（OH）3old canal,（OH）3new canal （OH）3 upstream,a sharp increase of all nitrogen forms occurred in downstream.The NO3-N form on the contribution of TN was highest（43.8% ～ 57.4%）,followed by NH4＋-N,ON（organic nitrogen）,NO2-N,and the old canal contributed most TN of 13.3%.A significant positive correlation between NH4＋-N and NO3 N,TN,pH,DO was observed with the correlation coefficients of 0.397＊＊,0.932＊＊,0.261＊ and-0.344＊＊,terrigenous input and oxygen starvation may explain the serious nitrogen pollution in Changzhou Segment.