城市内河表层沉积物氮形态及影响因素--以许昌清潩河为例

摘要

The amounts of nitrogen forms in 10surface sediments of Qingyi River in Xuchang City were determined by the sequential extraction technique and 4forms of extractable nitrogen (TTN) including ion exchangeable form (IEF-N), weak acid extractable form (WAEF-N), strong alkali extractable form (SAEF-N), and strong oxidant extractable form (SOEF-N) and non-extractable form (NTN) were found. The distribution characteristics, influence factors and potential risks of nitrogen forms to the river environment were also discussed. The results indicated that the concentration of total nitrogen (TN) was in the range of 2140~9470mg/kg, and had the similar distribution trend with the sediment organic matter (OM) along the mainstream. The dominant form of TTN changed from IEF-N to SAEF-N and then to SOEF-N from upstream to downstream, finally tended to be stable. IEF-N content in the sediment was influenced by sediment OM, pH value, and the amount of ammonia and suspended solid in the overlying water, and was significantly related to TN, which showed that TN can be used as an important indicator for judging the endogenous pollution risk of Qingyi River. In addition, in the overlying water high COD concentration had great effect on the sediment of SAEF-N and NTN, high content of ammonia intensified the release of IEF-N and TN, and TP influenced the activity of NTN. Therefore, the interaction of the overlying water and the sediment must be taken into account during the practical river improvement, and the regulation of water body and sediment. This study could provide important guidance to the water environment comprehensive improvement of Qingyi River and the other similar rivers.%采用连续分级提取法对许昌市清潩河河道10个表层沉积物样品中氮形态含量进行测定,分别得到离子交换态氮(IEF-N)、弱酸可提取态氮(WAEF-N)、强碱可提取态氮(SAEF-N)、强氧化剂可提取态氮(SOEF-N)和非可转化态氮(NTN),探讨了不同形态氮分布特征、影响因素及其对河道水环境潜在的风险。结果表明,沉积物中总氮(TN)含量为2140~9470mg/kg,与沉积物有机质含量沿河道变化趋势基本一致；可转化态氮(TTN)的优势形态从上游至下游逐渐由IEF-N向SAEF-N再向SOEF-N转化,逐渐趋于稳定；IEF-N含量受沉积物有机质、pH值及上覆水体氨氮和悬浮物含量影响,且与TN极显著相关,说明清潩河沉积物TN含量可以作为河道内源污染风险判断的重要指标；此外上覆水体较高的COD含量对SAEF-N和NTN的沉积、较高的氨氮含量对IEF-N和TN的释放以及总磷含量对 NTN 活性的增强等都产生影响。因此,在开展清潩河水环境综合整治时,需考虑水相与沉积物相的相互作用,同步开展治理工作。