海水反硝化和厌氧氨氧化速率同步测定的^(15)N示踪法及其应用

Simultaneous determination of denitrification and anammox rates in seawater using ^(15)N tracer assay and its application

反硝化与厌氧氨氧化作用是海洋结合态氮迁出的主要途径,15N示踪法是定量反硝化和厌氧氨氧化作用的新方法,它具有灵敏度高、可同步测量反硝化与厌氧氨氧化速率的优点.本研究开展了一系列方法学实验,以确定高纯氦气驱赶水样所含气体的时间、超声赶气时间、同位素比值质谱仪测量N2含量的精度、N2含量及其同位素组成测定的工作曲线以及示踪剂的最佳添加量等,从而确立起15N示踪同步测定海水反硝化和厌氧氨氧化速率的方法.所建立方法测量N2含量的相对标准偏差小于8%,可满足海洋反硝化与厌氧氨氧化速率测定的需要.应用该方法实测了厦门筼筜湖富氧与缺氧水体的反硝化与厌氧氨氧化速率,结果表明,缺氧底层水的反硝化速率[4.10~5.47μmol/(dm3·d)]比富氧表层水[0.43~0.46μmol/(dm3·d)]明显来得高,但缺氧底层水的厌氧氨氧化速率[0.00~0.12μmol/(dm3·d)]则比富氧表层水的速率[0.52~0.67μmol/(dm3·d)]低得多.

Denitrification and anammox are two pathways for removal of fixed nitrogen from marine environments.15N tracer assay was a new method for simultaneously measuring denitrification and anammox rates in seawater with high sensitivity. In this study,a series of experiments were conducted to assess the purge time for removing natural dissolved N2,the blowing time for N2concentrated in bottle headspace,the measurement accuracy of N2determination,the standard curve for calculation of N2content,and the effect of tracer amounts on the measured denitrification rate. The established method measured N2content with an accuracy of less than 8%,which met the need for measurements of denitrification and anammox rates. The measured denitrification and anammox rates in the Yundang lagoon,Xiamen,indicated that the denitrification rates in the anoxic bottom water[4. 10 ～ 5. 47 μmol /（dm3·d）] were much higher than those in the aerobic surface water[0. 43 ～ 0. 46 μmol /（dm3·d）],while the anammox rates in the bottom water[0. 00 ～ 0. 12 μmol /（ dm3·d）]were lower than those in the surface water[0. 52 ～ 0. 67μmol/（dm3·d）].