Effect of environmental changes on nitrogen release from sediments in polluted urban river
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摘要: 以苏州市古城区劣Ⅴ类水体为研究对象,利用模拟试验方法,研究和探讨了水体环境条件(DO、Eh、pH值、温度)变化和疏浚深度对河道底泥氮释放的影响.底泥供试样中NH4+-N与NO3--N含量一般为0.277 g/kg与0.0012g/kg,上覆水体NH4+-N与NO3--N含量一般为6.743 mg/L与1.500 mg/L.试验结果表明:厌氧环境(DO<0.5 mg/L)、强还原环境(Eh<-108 mV)、酸性环境(pH<6.0)及温度升高均有利于底泥中NH4+-N的释放,NO3--N的迁移转化规律则相反;供试样控制疏浚深度5 cm、10 cm、15 cm、20 cm,当疏浚深度15 cm时,泥-水界面向上覆水体中扩散的氮通量最小;疏浚深度、DO和Eh对底泥NH4+-N释放程度的影响大于pH和温度,通过曝气等方式保持水体中适当的溶解氧或使底泥保持较强的氧化电位环境可以有效抑制底泥中NH4+-N的释放.Abstract: Water and sediment samples were collected from a polluted river in the old town of Suzhou City.The water in the river is classified as poor quality V according to the National Surface Water Quality Standard of China.We examine the regularity of nitrogen release from sediments under different environmental conditions such as the dissolved oxygen(DO) level,the redox potential status measured as Eh level,the pH value,the temperature,and the dredging depth,using the indoor experimental method.The results show that the contents of ammonia-nitrogen and nitrate materials in sediment samples are 277.03 mg/kg and 1.22 mg/kg,respectively,and these contents are 6.743 mg/L and 1.500 mg/L in the overlying water.The experiments reveal that the favorable conditions for the ammonia-nitrogen release from sediments include the anaerobic environment of DO < 0.5 mg/L,the strong reducing environment of Eh <-108 mV,and the acidic environment of pH < 6.0,as well as the high temperatures; while the opposite behaviors in these conditions are observed for the migration and transformation of NO3--N.The analysis of sediment samples collected at different dredging depths of 5 cm,10 cm,15 cm,and 20 cm indicates that the minimum release of nitrogen nutrient is found from the sample of 15 cm depth.The effects of dredging depth,DO,and Eh on the ammonia-nitrogen release in sediments are found to be greater than that of pH and temperatures.Our experimental study show that the ammonia-nitrogen release from sediments will be effectively inhibited if high dissolved oxygen levels in the overlying water as well as strong oxidizing potential status in the sediment can be properly maintained.
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Key words:
- sediments /
- release of nitride /
- environmental condition /
- main control factors
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