杭州西湖底泥氮释放通量及影响因素研究

Study on Release of Nitrogen from Sediment and its Influencing Factors in Hangzhou West Lake

通过采集杭州西湖表层底泥,在实验室静态模拟底泥氨氮(NH_4^+-N)和硝态氮(NO_3^--N)的释放,同时研究了DO、温度和pH值对底泥N释放的影响。结果表明,西湖底泥NH_4^+-N主要呈现出正释放,而NO_3^--N则主要为负释放。NH_4^+-N的正释放速率随溶解氧增大而减小,NO_3^--N仅在好氧条件下呈现出正释放。温度通过改变微生物的活性,使底泥NH_4^+-N的正释放速率随温度的升高而增大,NO_3^--N的负释放速率也随温度的升高而增大。不同pH值条件下,NH_4^+-N的正释放速率表现为6.5 mg/(m^2·d)>7.5 mg/(m^2·d)>8.5 mg/(m^2·d)。根据模拟实验数据计算得到西湖全年可溶性无机氮(DIN)的释放量为14.603 t,说明西湖底泥已被严重污染,成为营养元素的释放源。

The release of NH4^＋-N and NO3^--N to the overlying water and the influences of DO, temperature and pH on the release rate were probed into through a series of large static simulating experiments. The result showed that NH4^＋-N is the main nitrogen form released from sediment in West Lake, and NO3^--N always spread from overlying water to sediment. The release rate of NH4^＋-N increased with the increase of dissolved oxygen, but NO3^--N can only spread from overlying water to sediment in aerobic conditions. Both of the positive release rate of NH4^＋-N and negative release rate of NO3^--N increased with the temperature. The influence of pH on release rate of NH4^＋-N manifest as 6.5〉 7.5〉 8.5. Based on the simulation experiments,the release of inorganic dissolved nitrogen is 14.603 t per year. It illustrated that the sediment in West Lake has been seriously polluted and has became the source of nutrient element.