城市重污染河道上覆水氮营养盐浓度及DO水平对底质氮释放的影响

利用模拟试验方法, 研究和探讨了苏州市古城区重污染河道上覆水的氮营养盐浓度及DO水平对河道底泥内源氮释放的影响.结果表明:① 上覆水体的氮营养盐水平可对底泥中氮营养盐的释放程度(即释放速率和释放量)产生影响,氮营养盐含量低的上覆水体有利于底泥中氮特别是氨氮的释放(外城河与苗家河２种处理的累积释放量差值可达6 mg/kg),相反,则不利于氨氮的释放.故当氮营养盐含量较低的外城河水进入古城区河道时,有可能引起内城河道中底泥氨氮的大量释放,这种情况在调水过程中更为明显；②溶解氧是控制底泥氮释放规律的重要因素，其对氨氮和硝态氮释放的影响呈非线性,厌氧条件能加速底泥氨氮的释放,好氧则对其释放产生抑制，故保持河道水体中适当的溶解氧可有效抑制底泥中氨氮等释放造成的污染.

Effects of Nutrient Concentration and DO Status of Heavily Polluted Urban Stream Water on Nitrogen Release from Sediment

The release of nitrogen compounds from river sediment with different nutrient levels and dissolved oxygen (DO) statuses of overlying water that sampled from the Suzhou City were studied by simulative method. The results indicate that: (1) The nutrient status of overlying water may affect the release degree (release velocity and amount) of nutrient in sediment. The release of nitrogen compounds from sediment becomes easier with the decreasing of nutrient concentration in overlying water (the difference between the accumulated release amounts of sediment from outer moat and Miaojia River reached 6mg/kg), while it becomes difficult when nutrient concentration is increasing. Therefore, when the water from the outer moat with low nutrient concentration flowing into the inner channels, it can induce the rapid release of nutrients from sediment. This situation is more significant during water diversion process. (2) DO is an important factor that affected the release rules of nitrogen compounds from sediment. The effects of DO on the release of ammonium and nitrate showed non-linear characteristics. The release amount of ammonium was increased under anaerobic condition and decreased under aerobic condition. Therefore, maintaining appropriate DO level of overlying water may effectively control the release of the organic matter and nitrogen compounds, such as ammonium.