Coincident Biogenic Nitrite and pH Maxima Arise in the Upper Anoxic Layer in the Eastern Tropical North Pacific
Coincident Biogenic Nitrite and pH Maxima Arise in the Upper Anoxic Layer in the Eastern Tropical North Pacific
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DOI：
10.1029/2022gb007470
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发表时间：
2022-12
影响因子：
5.2
通讯作者：
Timur Cinay;Diana Dumit;R. Woosley;Elisabeth L. Boles;Jarek V. Kwiecinski;Susan Mullen;T. Tamasi;M. Wolf;Colette L. Kelly;N. M. Travis;K. Casciotti;A. R. Babbin
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作者：
Timur Cinay;Diana Dumit;R. Woosley;Elisabeth L. Boles;Jarek V. Kwiecinski;Susan Mullen;T. Tamasi;M. Wolf;Colette L. Kelly;N. M. Travis;K. Casciotti;A. R. Babbin
东热带北太平洋（ETNP），像其他海洋缺氧区（ODZs），其特征是缺氧水柱，亚硝酸盐积累在缺氧核心，并通过亚硝酸盐还原为N2O和N2气体的固定氮损失。在这里，我们约束的相对贡献的可观察到的功能，如二次亚硝酸盐最大值（SNM）和当地的pH值最大值的无机氮和碳物种的同时测量的地球化学过程。在水柱顶部1公里范围内的高分辨率采样揭示了该地区以前未观察到的一致化学特征，包括三级亚硝酸盐最大值。溶解无机碳的测量表明，pH值随着深度的增加，在ODZ的顶部，峰值在SNM的电位密度为σθ = 26.15 ± 0.06（1 s.d.）。我们开发了一种新的方法来确定厌氧氨氧化（anammox），反硝化，亚硝酸盐氧化，异化硝酸盐还原为亚硝酸盐，和碳酸钙溶解的亚硝酸盐循环在缺氧ODZ核心的相对贡献。每个反应的计算相对贡献是稍微敏感的假定C：N：P比和碳的氧化态下沉通过ODZ的有机物。此外，我们确定的来源的pH值增加的顶部ODZ作为质子的净消耗通过亚硝酸盐还原成N2的反硝化过程。由于反硝化作用引起的pH值的增加影响了溶解在ETNP中的方解石和文石的缓冲效果。
The Eastern Tropical North Pacific (ETNP), like the other marine oxygen deficient zones (ODZs), is characterized by an anoxic water column, nitrite accumulation at the anoxic core, and fixed nitrogen loss via nitrite reduction to N2O and N2 gases. Here, we constrain the relative contribution of biogeochemical processes to observable features such as the secondary nitrite maximum (SNM) and local pH maximum by simultaneous measurement of inorganic nitrogen and carbon species. High‐resolution sampling within the top 1 km of the water column reveals consistent chemical features previously unobserved in the region, including a tertiary nitrite maximum. Dissolved inorganic carbon measurements show that pH increases with depth at the top of the ODZ, peaking at the potential density of the SNM at σθ = 26.15 ± 0.06 (1 s.d.). We developed a novel method to determine the relative contributions of anaerobic ammonium oxidation (anammox), denitrification, nitrite oxidation, dissimilatory nitrate reduction to nitrite, and calcium carbonate dissolution to the nitrite cycling in the anoxic ODZ core. The calculated relative contributions of each reaction are slightly sensitive to the assumed C:N:P ratio and the carbon oxidation state of the organic matter sinking through the ODZ. Furthermore, we identify the source of the pH increase at the top of ODZ as the net consumption of protons via nitrite reduction to N2 by the denitrification process. The increase in pH due to denitrification impacts the buffering effect of calcite and aragonite dissolving in the ETNP.