白洋淀沉积物氨氮释放通量研究

白洋淀沼泽化趋势不断加重,本文分析了沉积物氨氮释放风险与水质效应,评估沉积物中氨氮交换通量对上覆水体水质产生的重要影响.结果表明:白洋淀淀区表层水氨氮(NH_4~+-N)平均浓度在0.0~0.49 mg·L~(-1)之间,硝氮(NO_3~--N)平均浓度维持在0.09~0.20 mg·L~(-1),总氮(TN)浓度范围为1.40~4.52 mg·L~(-1),淀区水质在V类水平和劣V类水平.沉积物NH_4~+-N的平均含量在61.1~160.6 mg·kg~(-1),NO_3~--N含量整体平均值较低,范围在4.3~9.0 mg·kg~(-1),TN含量平均值在1555~4400 mg·kg~(-1)之间.整个白洋淀淀区表层沉积物孔隙水中NH_4~+-N浓度明显高于上覆水浓度,NH_4~+-N存在从沉积物向上覆水释放的风险.淀区沉积物-水界面潜在NH_4~+-N扩散通量范围为-9.3~38.3 mg·m~(-2)·d~(-1),NH_4~+-N潜在内源释放风险非常高.烧车淀区、南刘庄区、圈头区的潜在NH_4~+-N平均释放通量达到10.0 mg·m~(-2)·d~(-1)以上.为了避免白洋淀沼泽化过程加快,水质氮污染需要采取相应措施进行有效控制,而控制沉积物NH_4~+-N的内源释放是其中的关键环节.

Study on ammonia nitrogen release flux in the sediment-water interface of Baiyangdian Lake

The swamping trend of Baiyangdian Lake is increasing. This paper investigated the risk of ammonia nitrogen release from sediments and its water quality effect, and assessed the impact posed by exchange flux of ammonia nitrogen in sediments to the overlying water. The results showed that the mean NH₄⁺-N concentration in surface water was from 0.03 to 0.49 mg·L^-1, mean NO₃^--N concentration was from 0.09 to 0.20 mg·L^-1 and mean TN concentration was from 1.40 to 4.52 mg·L^-1. Water quality in Baiyangdian Lake were belonged to grade V and below grade V. NH₄⁺-N in surface sediments of Baiyangdian Lake ranged from 61.0 to 160.6 mg·kg^-1, the average value of NO₃^--N content was relative low, which was from 4.3 to 9.0 mg·kg^-1. TN concentrations ranged from 1555 to 4400 mg·kg^-1. For all sampling sites, NH₄⁺-N concentrations were higher in the pore water than that in the overlying water. The releasing of NH₄⁺-N from sediments to overlying water clearly revealed the releasing risk of internal nutrient in Baiyangdian Lake. The NH₄⁺-N influxes across the sediment-water interface varied from -9.3 to 38.3 mg·m^-2·d^-1. In Shaochedian Area, Nanliuzhuang Area and Quantou Area, the NH₄⁺-N fluxes across the sediment-water interface reached up to 10.0 mg·m^-2·d^-1. Appropriate measures should be taken to effectively control the nitrogen pollution in the water of Baiyangdian Lake, among which, the controlling of endogenous release of NH₄⁺-N in sediments is the key step.