人工湿地污水处理系统中氧化亚氮的释放规律研究

利用静态箱-气相色谱法研究了潜流和表面流人工湿地系统中N2O的释放规律和相关的氨氧化细菌.结果表明,潜流和表面流人工湿地的N2O平均通量分别为296.5μg.(m2.h)-1和28.2μg.(m2.h)-1,总体上均表现为大气N2O的排放源,前者的N2O平均释放通量高于农田、森林、草原和沼泽湿地等生态系统,潜流方式促进了N2O的释放.潜流和表面流人工湿地N2O通量有较大的月份差异和明显的日变化特征,最高值出现在7月,分别为(762.9±239.3)μg.(m2.h)-1和(91.9±20.3)μg.(m2.h)-1,一天中的极大值和极小值分别出现在中午和凌晨.温度和芦苇的生长情况对N2O通量有一定的影响.人工湿地系统进水端,较高浓度的污水和充足的碳、氮源,促进了硝化和反硝化过程,使得N2O通量均高于出水端.克隆结果表明,人工湿地污水处理系统中与N2O产生相关的氨氧化细菌主要为Nitrosomonas和Nitrosospira.

Nitrous Oxide Fluxes of Constructed Wetlands to Treat Sewage Wastewater

The nitrous oxide fluxes and ammonia-oxidizing bacterium in two typical constructed wetlands, i.e. subsurface flow(SF) and free water surface (FWS) were studied by the method of static chamber-gas chromatography. The results showed that the mean N_2O fluxes were 296.5 μg·(m~2·h)~(-1) and 28.2 μg·(m~2·h)~(-1) respectively, and two typical wetlands were all the sources of atmosphere nitrous oxide as a whole. SF wetland exhibited a higher risk of N_2O emissions, and the mean N_2O flux in this system was higher than the values reported in the literature for ecosystems, e. g. farmland, forest, grassland and marsh. The nitrous oxide fluxes in test wetlands presented obvious seasonal and diurnal variation, and the highest N_2O emission flux was in July. The highest flux was(762.9 ± 239.3) μg·(m~2·h)~(-1) and(91.9 ±20.3) μg·(m~2·h)~(-1) in SF and FWS wetlands, respectively. The peak flux mostly occurred around midday, whereas the minimum flux likely occurred in the early morning. The results indicated that the growth of Phragmites australis and temperature were the key factors controlling the variation of N_2O fluxes. The average N_2O emission from the microsites above the inflow zones was higher than that above the outflow microsites. High influent strength promoted nitrification and denitrification, and high fluxes were obtained. The clone results showed that Nitrosomonas and Nitrosospira were the main ammonia-oxidizing microorganisms contributing to N_2O production in constructed wetlands.