Marine biogenic source of atmospheric organic nitrogen in the subtropical North Atlantic
Marine biogenic source of atmospheric organic nitrogen in the subtropical North Atlantic
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DOI：
10.1073/pnas.1516847113
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发表时间：
2016-01-26
影响因子：
11.1
通讯作者：
Hastings, Meredith G.
中科院分区：
文献类型：
--
作者：
Altieri, Katye E.;Fawcett, Sarah E.;Hastings, Meredith G.
全球模型估计，大气氮 (N) 沉积到海洋的人为成分占海洋外部氮供应的三分之一和人为二氧化碳吸收的 10%。然而，很少有来自海洋大气环境的观测限制来验证这些发现。由于大气有机氮数据的缺乏，与大气氮沉降相关的最大不确定性是有机氮的来源和循环，有机氮占总氮沉降的20-80%。我们研究了 18 个月以来在北大西洋西部百慕大岛上收集的雨水和气溶胶有机氮的浓度和化学成分。在这里，我们发现海洋气溶胶中的水溶性有机氮浓度（[WSON]）与海洋表面初级生产力和风速密切相关，表明气溶胶 WSON 是海洋生物源。高[WSON]气溶胶的化学成分也表明其主要来源是海洋。我们发现海洋降雨中的 WSON 在成分上与同时收集的气溶胶中的 WSON 不同，这表明云内清除（而不是云下“冲刷”）是降雨 WSON 的主要贡献者。我们得出的结论是，尽管来自北美大型污染源的顺风输送，但人类活动并不是北大西洋海洋大气中有机氮的重要来源。结合之前对铵和硝酸盐的研究，得出这样的结论：全球海洋沉积的氮总量中只有 27% 是人为造成的，而之前估计的 80% 是人为造成的。
Global models estimate that the anthropogenic component of atmospheric nitrogen (N) deposition to the ocean accounts for up to a third of the ocean's external N supply and 10% of anthropogenic CO2 uptake. However, there are few observational constraints from the marine atmospheric environment to validate these findings. Due to the paucity of atmospheric organic N data, the largest uncertainties related to atmospheric N deposition are the sources and cycling of organic N, which is 20-80% of total N deposition. We studied the concentration and chemical composition of rainwater and aerosol organic N collected on the island of Bermuda in the western North Atlantic Ocean over 18 mo. Here, we show that thewater-soluble organic N concentration ([WSON]) in marine aerosol is strongly correlated with surface ocean primary productivity and wind speed, suggesting a marine biogenic source for aerosol WSON. The chemical composition of high-[WSON] aerosols also indicates a primary marine source. We find that the WSON in marine rain is compositionally different from that in concurrently collected aerosols, suggesting that in-cloud scavenging (as opposed to below-cloud "washout") is the main contributor to rain WSON. We conclude that anthropogenic activity is not a significant source of organic N to the marine atmosphere over the North Atlantic, despite downwind transport from large pollution sources in North America. This, in conjunction with previous work on ammonium and nitrate, leads to the conclusion that only 27% of total N deposition to the global ocean is anthropogenic, in contrast to the 80% estimated previously.