Global oceanic emission of ammonia: Constraints from seawater and atmospheric observations
Global oceanic emission of ammonia: Constraints from seawater and atmospheric observations
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DOI：
10.1002/2015gb005106
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发表时间：
2015-08
影响因子：
5.2
通讯作者：
F. Paulot;D. Jacob;Martin Johnson;T. Bell;A. Baker;W. Keene;I. Lima;S. Doney;C. Stock
中科院分区：
文献类型：
--
作者：
F. Paulot;D. Jacob;Martin Johnson;T. Bell;A. Baker;W. Keene;I. Lima;S. Doney;C. Stock
目前全球氨排放清单确定海洋是最大的自然来源。这一来源取决于海水pH值、温度和海水总氨浓度（NHx（sw）），这反映了有机物的矿化、浮游生物的吸收和硝化作用之间的平衡。在这里，我们比较[NHX（SW）]从两个全球海洋地球化学模式（BEC和COBALT）对广泛的海洋观测。模拟的[NHx（sw）]通常偏高。通过在观测范围内增加浮游生物对NHx的亲和力，可以在COBALT中实现改进的模拟。由此得出的全球海洋排放量为2.5 TgN a−1，远低于当前文献值（7-23 TgN a−1），包括广泛使用的全球排放倡议（GEIA）清单（8 TgN a−1）。这样一个弱的海洋源意味着大陆源贡献了超过一半的大气NHx在北方半球的大部分海洋。从海洋源排放的氨不足以中和硫酸盐气溶胶的酸度，与观测结果一致。在赤道太平洋上空有证据表明，大气氨的来源可能是海洋有机氮在海洋表面或大气中的光解所致。排除这一可能的缺失来源，得出全球海洋氨排放量在2-5 TgN a−1之间，与其他来自明火和土壤的自然来源相当。
Current global inventories of ammonia emissions identify the ocean as the largest natural source. This source depends on seawater pH, temperature, and the concentration of total seawater ammonia (NHx(sw)), which reflects a balance between remineralization of organic matter, uptake by plankton, and nitrification. Here we compare [NHx(sw)] from two global ocean biogeochemical models (BEC and COBALT) against extensive ocean observations. Simulated [NHx(sw)] are generally biased high. Improved simulation can be achieved in COBALT by increasing the plankton affinity for NHx within observed ranges. The resulting global ocean emissions is 2.5 TgN a−1, much lower than current literature values (7–23 TgN a−1), including the widely used Global Emissions InitiAtive (GEIA) inventory (8 TgN a−1). Such a weak ocean source implies that continental sources contribute more than half of atmospheric NHx over most of the ocean in the Northern Hemisphere. Ammonia emitted from oceanic sources is insufficient to neutralize sulfate aerosol acidity, consistent with observations. There is evidence over the Equatorial Pacific for a missing source of atmospheric ammonia that could be due to photolysis of marine organic nitrogen at the ocean surface or in the atmosphere. Accommodating this possible missing source yields a global ocean emission of ammonia in the range 2–5 TgN a−1, comparable in magnitude to other natural sources from open fires and soils.