The release and oxidation of NH4+-N in the intertidal sediments is a critical process of the nitrogen biogeochemical cycle in the estuarine wetland ecosystems. This study investigated the release and oxidation mechanisms of NH4+-N at the sediment-water interface of two kinds of Jiulong River Estuary Wetland sediments under four dissolved oxygen conditions (saturated, aerobic, anoxic and anaerobic). The results showed that the ways of NH4+-N release and oxidation in two sediments with different vegetation were significantly different under four dissolved oxygen conditions. Firstly, the release of NH4+-N from mangrove sediment to overlying water was 0.9～3.5 times than mudflat sediments, and the release of NH4+-N from mangrove sediments to overlying water were 1.64 mg (saturated), 2.07 mg (aerobic), 3.47 mg (anoxic) and 3.20 mg(anaerobic), respectively;while from mudflat sediments they were 0.85 mg, 1.00 mg, 0.77 mg and 1.27 mg, respectively. The amount of sediment NH4+-N release was low at high DO condition, but high at low DO condition. Secondly, the release rate and oxidation rate of NH4+-N in the mangrove sediments were 43.73～48.51 mgN·m-2-d·-1 and 26.19～40.68 mgN·m-2·d-1, respectively, which were higher than that (14.50～19.22 mgN·m-2·d-1 and 8.35-22.53 mgN·m-2·d-1) in the mudflat sediments. The reason was possibly that the microorganism species in mangrove sediments were richer than mudflat sediments, resulting in the higher degree of the mineralization and nitrification in mangrove sediments. This study revealed the transfer and transformation of NH4+-N in two sediments under different gradients of dissolved oxygen, which would benefit the decision-making process for the protection of coastal wetlands and the control of coastal water eutrophication.%沉移物中氨氮( NH4+-N)的释放与氧化是河口湿地生态系统氮素生物地球化学循环的关键过程.本文通过室内模拟,构建饱和(BH)、好氧(HY)、缺氧(QY)和厌氧(YY)等四种上覆水溶氧(DO)条件,研究九龙江口湿地两种沉积物(红树林、光滩)中NH4+-N在沉积物-水界面的释放与氧化规律.结果表明,不同溶氧条件下,两种沉积物氨氮的释放、氧化存在显著差异.首先,红树林沉积物上覆水NH4+-N的累积释放量是光滩沉积物的1.9～4.5倍,其中红树林沉积物上覆水NH4+-N释放量分别达到1.64 mg( BH)、2.07 mg (HY)、3.47 mg( QY)和3.20 mg (YY),而光滩沉积物则分别为0.85mg (BH)、1.00 mg( HY)、0.77 mg( QY)和1.27 mg( YY).在较高DO条件下两种沉积物NH4+-N均呈低释放状态,而在较低DO条件下则呈高释放状态.另外,四种溶氧条件下红树林沉积物NH4+-N的释放速率(N 43.73～78.51 mg.m2.d-1)和氧化速率(N 26.19～40.68 mg.m-2.d-1)均高于光滩(分别为N 14.50～19.22 mg·m-2·d-1和N 8.89～22.53 mg.m-2.d-1),原因可能是红树林沉积物微生物种类丰富,群落多样性更高,矿化和硝化作用强烈.本文明晰了不同溶氧条件下河口红树林湿地沉积物NH4+-N的迁移转化过程,可促进滨海湿地的生态保护以及近海水域富营养化的控制.
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