低溶解氧状态下河网区不同类型沉积物的氮释放规律

采集浙江温州温瑞塘河河网中4个受不同人类行为干扰的沉积物样品,分别代表受河道上游来水、制革厂排水、建筑垃圾和生活污水排放的影响,研究了低溶解氧(DO)状态下不同类型沉积物各形态氮(N)的释放规律.结果表明,低DO状态下,不同上覆水条件能明显影响沉积物-水系统中N迁移转化.上覆水污染越重越不利于沉积物中N释放,水质改善后易促进沉积物中N的释放.屿田河高营养盐水平的上覆水中的N仍能在扩散作用下进入沉积物,并导致已严重污染的沉积物中总氮(TN)和硝酸盐氮(NO3--N)含量增加,控制河流外源N持续输入利于沉积物污染负荷的降低.低DO状态下各类沉积物中氨氮(NH4+-N)均会释放进入上覆水,而NO3--N则迁至沉积物中,并在反硝化作用下脱离系统.NH4+-N的释放量取决于其在沉积物中的含量.低DO状态下NO3--N释放的风险小于NH4+-N.

Regularity of nitrogen release under low oxygen conditions from various sediments in a river network

Four sediment samples affected by different human activities were collected from the Wenzhou Wenruitanghe River network, Zhejiang Province. They represented upriver water, tannery drainage, construction waste and municipal drainage. The characteristics of release of various nitrogen (N) forms from the different sediments were investigated under low dissolved oxygen (DO) conditions. The transformation of N in the sediment-water system was significantly affected by the conditions of the overlying water. It was disadvantageous for N release if the overlying water was seriously contaminated, and it was advantageous for N release when the condition of the overlying water was improved. The N in the overlying water, highly contaminated in the Yutianhe River, could be transferred into the seriously polluted sediment by diffusion, leading to an increase of TN and nitrate nitrogen (NO-3-N) in the sediments. Input control of external N could decrease the potential load of contamination. Ammonia nitrogen (NH+4-N) was released into the overlying water from all kinds of sediments while NO-3-N was transferred into them. The quantities of NH+4-N released from sediments were higher than those of NO-3-N transferred into the sediments. The risk of NO-3-N release was lower than that of NH+4-N under low oxygen conditions.