Denitrification in the water column of the central Baltic Sea
Denitrification in the water column of the central Baltic Sea
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DOI：
10.1016/j.gca.2012.12.038
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发表时间：
2013-04-01
影响因子：
5
通讯作者：
Hall, Per O. J.
中科院分区：
文献类型：
--
作者：
Dalsgaard, Tage;De Brabandere, Loreto;Hall, Per O. J.
在2008年9月和2010年8月的两次航行中，研究了波罗的海中部哥特兰盆地东部水柱中固定氮的去除情况。水柱分层，缺氧的硫化物底层水在氧-缺氧界面处与含氧硝酸盐的水相遇。厌氧氨氧化从来没有检测到，而反硝化作用被发现在所有的培养从缺氧深度，并立即低于缺氧-缺氧界面发生。硫化物（H2S + HS- + S2-）在大多数情况下是唯一的电子供体的反硝化作用，但在以前的研究结果相反，反硝化作用是在某些情况下由有机物单独驱动。随着硫化物浓度的增加，一氧化二氮（N2 O）成为反硝化作用越来越重要的产物，在10 μ M硫化物时，N2 O占总氮气体形成量的80%以上。使用测得的水柱浓度的NO3-和硫化物和NO3-和硫化物的浓度和反硝化速率之间的实际测量的关系，在升高的NO3-或硫化物浓度的孵育中测得的反硝化的潜在速率转换为原位速率。原位反硝化作用范围为0.24至15.9 nM N-2 h（-1）。假设这些速率在整个含NO3缺氧区都是有效的，则深度综合原位反硝化速率估计为0.06-2.11 mmol N m（-2）d（-1）。这一区域的厚度一般为3-6米，这可能是通过在好氧-缺氧界面处内波引起的规则湍流混合所能维持的厚度。然而，高达55米厚的低O-2水层（
Removal of fixed nitrogen in the water column of the eastern Gotland Basin, central Baltic Sea, was studied during two cruises in September 2008 and August 2010. The water column was stratified with anoxic sulfidic bottom water meeting oxic nitrate containing water at the oxic-anoxic interface. Anammox was never detected whereas denitrification was found in all incubations from anoxic depths and occurred immediately below the oxic-anoxic interface. Sulfide (H2S + HS- + S2-) was in most cases the only electron donor for denitrification but, in contrast to previous findings, denitrification was in some situations driven by organic matter alone. Nitrous oxide (N2O) became an increasingly important product of denitrification with increasing sulfide concentration and was >80% of the total N gas formation at 10 mu M sulfide. The potential rates of denitrification measured in incubations at elevated NO3- or sulfide concentrations were converted to in situ rates using the measured water column concentrations of NO3- and sulfide and the actual measured relations between NO3- and sulfide concentrations and denitrification rates. In situ denitrification ranged from 0.24 to 15.9 nM N-2 h(-1). Assuming that these rates were valid throughout the anoxic NO3- containing zone, depth integrated in situ denitrification rates of 0.06-2.11 mmol N m(-2) d(-1) were estimated. The thickness of this zone was generally 3-6 m, which is probably what can be maintained through regular turbulent mixing induced by internal waves at the oxic-anoxic interface. However, layers of up to 55 m thickness with low O-2 water (