环境因子对密云水库消落带沉积物-水界面氮交换通量的影响研究

Effects of environmental factors on nitrogen exchange flux at the sediment-water interface in the water level fluctuation zone of Miyun reservoir

为探究不同环境因子对水库消落带沉积物中氮迁移释放的影响,以密云水库消落带为研究对象,采用原状泥柱静态培养实验,并通过单一影响因素法,开展了温度、上覆水pH、溶解氧对沉积物-水界面氮交换通量的影响研究。结果表明:消落带上覆水和沉积物中无机氮含量在夏季(落干期)和秋季(淹水期)存在明显的差异,其中沉积物中NH_(4)^(+)-N含量变化最大,秋季较夏季下降80.4%,NO_(3)-N含量下降59.7%,淹水期间三态氮(NH_(4)^(+)-N、NO_(2)-N、NO_(3)-N)由沉积物释放到水中。温度、pH和溶解氧对消落带沉积物-水界面氮的迁移转化作用存在差异,升温促进NH_(4)^(+)-N释放并抑制NO_(3)-N释放,偏酸和偏碱条件会促进NH_(4)^(+)-N的释放,有氧条件会加剧沉积物-水界面三态氮的交换,促进三态氮的释放。密云水库消落带沉积物C/N为7.51~9.35,其表层水体中的有机质主要来源于水体内部生物残体。因此,未来应关注密云水库消落带沉积物内源释放风险,同时完善消落带湿地建设,减少消落带氮流失对水体的污染。

To investigate the response of nitrogen at the sediment-water interface in the water level fluctuation zone under different environmental conditions(e.g.,temperature,pH,and dissolved oxygen),a static culture experiment was conducted in an undisturbed mud column using sediment and water samples collected from the Miyun reservoir.The results were as follows:the inorganic nitrogen content of the sediment and overlying water in the fluctuation zone was significantly different in summer(dry period)and autumn(flooded period).Among them,the NH_(4)^(+)-N content of the sediment showed the greatest change,decreasing by 80.4%in autumn compared with summer,while the NO_(3)-N content decreased by 59.7%in autumn.Tri-state nitrogen(NH_(4)^(+)-N,NO_(2)-N,NO_(3)-N)was released into the water from the sediment during flooding.Temperature,pH,and dissolved oxygen had different effects on the migration and transformation of nitrogen at the sediment-water interface in the fluctuation zone.Increasing the temperature promoted the release of NH_(4)^(+)-N and inhibited the release of NO_(3)-N.Acidic and alkaline conditions promoted the release of NH_(4)^(+)-N.Aerobic conditions intensified the exchange of tri-state nitrogen at the sediment-water interface and aggravated the release of three-state nitrogen.The C/N ratio(7.51~9.35)of sediment indicates that organic matter in the surface water is mainly derived from biological residues in the water.Therefore,attention should be paid to the risk of endogenous release by sediments in the fluctuation zone of the Miyun reservoir in the future,and the construction of wetlands should be improved to reduce the pollution caused by nitrogen loss in the fluctuation zone.