| 九龙江河口区夏季反硝化作用初探 |
| 摘要点击 3874 全文点击 2812 投稿时间：2011-01-06 修订日期：2011-03-14 |
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| 中文关键词 反硝化 N2:Ar 法 氮 水气通量 九龙江河口 |
| 英文关键词 denitrification N2:Ar method nitrogen air-water fluxes Jiulong River Estuary |
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| 中文摘要 |
| 河口反硝化是削减入海河流氮污染的重要途径，为探明地处亚热带的九龙江河口混合区的反硝化作用，于2010年7月开展13个站位的面上调查，利用N2:Ar 法和膜进样质谱分析仪（MIMS）直接测定反硝化产物溶解N2浓度，用吹扫捕集-气相色谱法测定溶解N2O浓度，并估算二者净增量和水气交换通量.结果表明，溶解N2和N2O净增量有明显的区域变化，从淡水端向海域减少，N2净增量为-9.9～66.8 μmol·L-1，N2O净增量为4.3～31.5 nmol·L-1；N2O饱和度为170%～562%，平均352%；N2水气通量为-2.9～53.2 mmol·（m2 ·d）-1，N2O水气通量为5.2～23.9 μmol·（m2 ·d）-1，N2O通量占总通量的0.03%～1.2%（平均0.25%）.温度和营养盐（氮、 磷）是影响九龙江河口区反硝化作用的重要因子；淡水端（盐度<0.5）反硝化作用及其空间分布主要受硝酸盐含量控制，海水端溶解N2与N2O的增加主要来自淡水端的输送，并受盐度梯度（混合作用）影响. |
| 英文摘要 |
| Denitrification is an important process mitigating nitrogen (N) pollution in aquatic systems. Water samples in 13 sites throughout the Jiulong River Estuary were collected in July, 2010 in a preliminary investigation of the denitrification rate in this area. As end-products of denitrification, dissolved N2 was measured by determining N2:Ar ratios using MIMS (HPR-40), while the concentration of nitrous oxide (N2O) dissolved in water was determined by Purge and Trap-Gas Chromatography. The results showed significant spatial variance of net increase of dissolved N2 (ranging between -9.9 and 66.8 μmol·L-1) and N2O (ranging between 4.3 and 31.5 nmol·L-1) in the Jiulong River Estuary. The net increase of dissolved N2 and N2O declined gradually from river sites to sea sites. Dissolved N2O was supersaturated by 170%-562%. The air-water fluxes of N2 ranged between -2.9 and 53.2 mmol·(m2 ·d)-1, and N2O between 5.2 and 23.9 μmol·(m2 ·d)-1. The N2O yield shared only 0.03%-1.2% (average 0.25%) of total N air-water flux. The results suggested that water temperature and nutrient (N and P) were the key factors influencing denitrification. The denitrification rate is controlled by nitrate level at fresh-water sites with salinity <0.5‰. However, in salty waters, net increase in N2 and N2O mainly originated from denitrification occurring upstream of the estuary, and was dominated by the salinity gradient due to tidal mixing. |
