Ancillary Variables, N2O Concentrations, and N2O Diffusive Fluxes in the Subtropical Mariculture Ponds in Southeast China

We examined the plot-scale spatial variations of dissolved N2O concentrations in water and N2O fluxes across the water-air interface in the subtropical shrimp ponds in southeast China using the headspace equilibration and the gas transfer methods. Our results showed that the dissolved concentrations and diffusive fluxes of N2O in the shrimp ponds ranged from 2.26 to 19.20 nM and from 16.43 to 589.65 nmol m-2 h-1, respectively, over the culture period. Significant variations of N2O concentrations and fluxes were observed within ponds, with higher values being observed in the aeration area that could be attributed to the enhanced nitrification and denitrification. Also, N2O concentrations and fluxes varied significantly among the three studied ponds as a result of the difference in N-NO3- and N-NH4+ concentrations in water. The large fine-scale spatial variations of N2O concentrations and fluxes in our aquaculture ponds suggest that management practices such as aeration and bait feeding could greatly affect the influence of aquaculture activity on N2O emissions and climate change

本研究采用顶空平衡法与气体传输法，探究了中国东南部亚热带虾塘水体中溶解态氧化亚氮（N₂O）浓度及水-气界面氧化亚氮扩散通量的样地尺度空间变异特征。研究结果显示，养殖周期内虾塘内溶解态氧化亚氮浓度与扩散通量范围分别为2.26~19.20 nM以及16.43~589.65 nmol·m⁻²·h⁻¹。单塘内部亦存在显著的氧化亚氮浓度与通量变异，曝气区域的相关数值更高，这可归因于硝化与反硝化作用的强化。此外，3个研究虾塘间的氧化亚氮浓度与通量亦存在显著差异，其成因在于水体中硝态氮（N-NO₃⁻）与氨态氮（N-NH₄⁺）浓度的差异。本研究养殖塘内显著的精细尺度空间变异特征表明，曝气与投饵等养殖管理措施，可极大影响水产养殖活动对氧化亚氮排放及气候变化的作用效应。