大亚湾滨海湿地沉积物间隙水无机氮分布特征及其沉积物-水界面交换通量

为探讨大亚湾滨海湿地沉积物间隙水中无机氮的时空分布规律及其环境效应，于2017年3月（枯水期）和8月（丰水期）分别采集了大亚湾湿地3个断面的沉积柱，测定了间隙水中无机氮含量并对其在沉积物-水界面交换进行了实验室培养实验。结果发现，滨海湿地近岸上覆水中氮营养盐含量远高于大亚湾水体平均值，说明近岸人类活动对湿地生态系统中氮含量的影响较为严重，河流输送是其来源的主要途径。间隙水中NH₄-N、NO₃-N和NO₂-N的平均含量分别为:770.60、7.63和7.39 μmol/L，其中NH₄-N是DIN的主要组分，约占DIN的85.82%~99.67%。室内培养实验发现，NH₄-N、NO₃-N和NO₂-N的界面交换通量平均值分别为0.09、-0.18和0.36 mmol/（m2·d），不同断面下DIN的交换速率存在明显差异。整体上，DIN的交换通量在枯水期约为0.41 mmol/（m2·d），湿地沉积物表现为上覆水DIN的源；而丰水期沉积物则成为DIN的汇，其平均通量约为-0.23 mmol/（m2·d）。对照实验结果表明，灭菌之后NH₄-N、NO₃-N和NO₂-N的平均交换通量均有所降低，相比于原始组分别降低了76.5%、23.7%和50.3%，说明微生物在氮的转化中起到了非常重要的作用。

Distribution characteristics of the porewater inorganic nitrogen and their benthic exchange fluxes in coastal wetlands of Daya bay

In order to study the spatial distribution of the inorganic nitrogen in the sediment and their environmental effects, the contents and the exchange fluxes of DIN at sediment-water interface have been studied during March (dry season) and August (wet season) in 2017 in coastal wetland in Daya bay.The results showed that the average nitrogen content of overlying water near coastal wetland was far higher than that in Daya bay offshore water, which indicated the influence of human activities on the wetland was relatively serious.The river runoff is the main channel of nitrogen input.The average contents of nutrients (NH₄-N、NO₃-N and NO₂-N) were 770.60、7.63 and 7.39 μmol/L in the sediment porewater, respectively.NH₄-N was the major component and accounted for 85.82%~99.67% of DIN. The estimation of the sediment-water exchange fluxes indicated that the average fluxes of NH₄-N、NO₃-N and NO₂-N were 0.09、-0.18 and 0.36 mmol/(m2·d), respectively.Generally, the average exchange flux was 0.41 mmol/(m2·d) in dry season, as the source of DIN providing a lot of nitrogen into the overlying water.The sediment became the sink of DIN in wet season, with average flux of -0.23 mmol/(m2·d).Comparing with the original experiment group, it was found that the average exchange fluxes of NH₄-N、NO₃-N and NO₂-N in the sterilized group decreased by 76.5%, 23.7% and 50.3%, respectively.This indicates that microorganism plays a very important role in nitrogen transformation.