三江平原农田渠系中氮素的时空变化

以三江平原开发强度不同的浓江上游段和别拉洪河中游段的农田排水渠系为研究对象,根据毛、农、斗、支、干5个渠道级别设采样点,分析TN、NH⁺₄-N和NO^-₃-N在渠系中的时空变化规律及其影响机制.结果表明,别拉洪河中游段渠系中的TN、NH⁺₄-N和NO^-₃-N浓度大于浓江上游段;TN、NH⁺₄-N、NO^-₃-N的浓度峰值沿着渠系从低级向高级移动,浓江上游段峰值出现的最高级别是干渠,而别拉洪河中游段是斗渠;多等级的排水渠系对氮素起到了一定的截留作用,且别拉洪河中游段渠系对氮素的截留大于浓江上游段;2个渠系中的TN、NH⁺₄-N的季节变化趋势相一致,6～9月逐月减少,而NO^-₃-N的季节变化不明显且没有规律;TN与NH⁺₄-N、NO^-₃-N呈显著性正相关,浓江上游段TN与NH⁺₄-N、NO^-₃-N之间的关系适合幂函数模型,而别拉洪河中游段适合三次曲线模型;通过多元回归分析得到别拉洪河中游段渠系中的TN浓度与NH⁺₄-N、NO^-₃-N之间的关系模型可以解释78%的TN浓度.

Spatio-temporal Dynamics of Nitrogen in Agricultural Ditch Systems in Sanjiang Plain

Agricultural drainage water sampling was conducted along ditch systems from 1^st order to 5^th order in Nongjiang River and Bielahonghe River during June to September, 2005. The spatio-temporal dynamics of nitrogen concentrations in agricultural ditch systems were analyzed. Results showed that there were higher concentrations of nitrogen in Bielahonghe ditch system. Peak values of TN, NH⁺₄-N and NO^-₃-N moved from 1^st order to 3^rd and 5^th order in Nongjiang and Bielahonghe ditch systems respectively. The retention of nitrogen in Bielahonghe ditch system was more than Nongjiang ditch system. The temporal dynamics of TN and NH⁺₄-N were parallel in the two ditch systems, which decreased from June to September. But the temporal dynamics of NO^-₃-N had no obvious trend. The relationships between TN and NH⁺₄-N and NO^-₃-N were positively correlated in both Nongjiang and Bielahonghe ditch systems, fitting for Power model and Cubic model respectively. The relationships between TN and NH⁺₄-N and NO^-₃-N can be described by multi-variance linear regression, which explained 78% of TN concentration in Bielahonghe ditch system.