太湖流域上游东苕溪干流沉积物和悬浮物的氮形态分布及影响因素

Distribution of nitrogen forms in suspended sediments and surface sediments of East Tiaoxi River,upper reaches of Taihu Basin and their influence factors

氮是影响和控制水体富营养化的重要因素,不同形态的氮对水体富营养化贡献不同.使用连续提取法对东苕溪干流悬浮物、表层沉积物样品中各形态氮含量进行测定,探讨各形态氮的分布特征及其影响因素.结果表明,东苕溪水体氮污染严重,总氮浓度均值为4.48 mg/L.悬浮物中各形态氮含量均高于沉积物,其中悬浮物中铁锰氧化态氮(IMOF-N)含量所占比例最大,均值为1506.94 mg/kg;沉积物中有机硫化物结合态氮(OSF-N)含量最高,均值为625.31 mg/kg.IMOFN、OSF-N含量受阳离子交换量、粒径影响显著,均与总氮浓度显著相关.相关性分析表明水体的性质对IMOF-N及OSF-N含量影响较显著,并且总体上对悬浮物的影响强于沉积物.另外,悬浮物有助于水体中的氮发生硝化反应向硝态氮转化,沉积物则有助于水体的氮发生还原作用向氨氮转化.在一定程度上,水体中的悬浮物对藻类具有抑制作用.

Nitrogen is a dominant nutrient influencing and controlling eutrophication, and different nitrogen forms can make diverse contributions to water quality. The contents of different nitrogen forms in suspended sediments and surface sediment of East Tiaoxi River were determined by sequential extraction procedure. In addition, their distribution characteristics and influence factors were discussed. The results showed that the nitrogen pollution in East Tiaoxi River were serious with an average concentration of 4.48 mg/L, and the water quality in the middle reach of East Tiaoxi River was better than that in the upper and lower reaches. The a- mounts of four nitrogen forms in suspended sediments were significantly higher than those in surface sediment, in addition, the per- centage of iron-manganese oxides bound nitrogen （IMOF-N） with the mean concentration of 1506.94 mg/kg were higher than that of other three nitrogen forms in suspended sediment. The percentage of organic matter-sulfide bound nitrogen （OSF-N） with the mean of 625.31 mg/kg was highest in surface sediment. IMOF-N and OSF-N contents were significantly affected by cation exchange capacity and particle size in both suspended sediments and surface sediments, and they were also significantly correlated with total nitrogen（TN） ,indicating that IMOF-N and OSF-N were the main fractions of TN. The correlation results showed that the water quality had significant influence on IMOF-N and OSF-N, and the influence of water on suspended sediments was stronger than that on surface sediments. Furthermore, suspended particulates were beneficial to produce nitrate nitrogen in water. In contrast, sedi- ments were available for generating ammonia nitrogen in water, and to some extent, suspended sediments has inhibitory effect on algae.