南京河流夏季水-气界面N2O排放通量

利用静态箱-气相色谱法对南京4条河流(内秦淮河、外秦淮河、金川河、团结河)和1座水库(金牛湖)的夏季水-气界面N2O气体通量进行24 h连续观测.结果表明,4条河流24 h内均为N2O的排放源,而金牛湖作为本底对照则表现为N2O的吸收汇.受水利条件变化的影响内秦淮河N2O在20:00达到排放峰值.金川河和团结河N2O排放通量均在夜间水中溶解氧饱和度极低的时候达到最低值.外秦淮白天的硝化作用和夜间的反硝化作用导致其N2O呈现出双峰的排放趋势.金牛湖N2O的排放量主要受风速影响,呈现出夜高昼低的排放趋势.在常规观测中,团结河、金川河、外秦淮河及金牛湖这4种水体能代表全天平均值的采样时间段均在08:00~12:00之间,但对于受外界影响较大的内秦淮其适宜的时间段则为14:00~16:00.

Nitrous Oxide Flux at the Water-Air Interface of the Rivers in Nanjing During Summer

Employing floating static chamber-chromatography method, the N₂O diurnal fluxes at the water-air interface of four rivers(Tuanjie River, Jinchuan River, Inner and Outer Qinhuai River)and Jinniu Lake were monitored in Nanjing during summer. The results show that four rivers act as the sources of N₂O emission, but Jinniu Lake is characterized by the absorption of N₂O. The highest N₂O flux from Inner Qinhuai presented at 20:00 because of the changing of hydrodynamic conditions. Both Jinchuan and Tuanjie rivers' minimum N₂O fluxes were detected when the content of dissolved oxygen was extremely low. The tendency of N₂O from Outer Qinhuai showed a double-peak because of its daytime nitrification and nocturnal denitrification. The flux of N₂O from Jinniu Lake had been noted as being generally higher at night than that during light hours due to the effect of wind. For natural rivers, the proper sampling period is from 08:00 to 12:00, but for the river subjected to interference, the sampling period is different.