Nitrification amplifies the decreasing trends of atmospheric oxygen and implies a larger land carbon uptake
Nitrification amplifies the decreasing trends of atmospheric oxygen and implies a larger land carbon uptake
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硝化作用加剧了大气中氧气的减少趋势，意味着陆地碳吸收量更大
DOI：
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发表时间：
2007
期刊：
影响因子：
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通讯作者：
Laurent Bopp
中科院分区：
文献类型：
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作者：
P. Ciais;Andrew C. Manning;M. Reichstein;S. Zaehle;Laurent Bopp
大气O2趋势测量用于划分全球海洋和陆地生物碳汇在多年的基础上。其基本原理是，陆地吸收或释放CO2伴随着相反的O2通量。在不考虑其他元素的情况下，CO2和O2的陆地通量的摩尔比应为1。然而，人类活动产生的活性氮（例如，肥料，氮沉积）也被纳入植物组织。陆地氮循环的各种反应途径导致大气O2通量。因此，氮、碳和氧的循环必须联系在一起。我们在这里报告了以前未考虑的影响大气O2趋势的人为氮相关机制，从而推导出全球碳汇。特别是，我们推测人为驱动的变化正在推动全球氮循环进入更氧化的状态，主要是通过硝化作用，硝酸盐肥料工业生产，化石燃料燃烧和人为生物质燃烧。这些与氮相关的过程的总和会额外减少大气中的O2，并略微增加大气中的CO2。我们已经计算出，在1993-2003年期间，有效的陆地生物O2：CO2摩尔比范围在0.76和1.04之间，而不是1.10（每摩尔CO2消耗产生的O2摩尔数），这取决于四个对比的氮氧化和还原途径的情况下使用。使用我们最有信心的情景，这意味着对1993-2003年最新报告的全球陆地生物和海洋碳汇的0.23 PgC yr-1修正，陆地生物碳汇变大，海洋碳汇变小。我们将100%的不确定性归因于所有与氮相关的O2和CO2通量，这相当于全球碳汇不确定性增加±0.09 PgC/年。因此，在1993-2003年的十年间，考虑到与人类活动有关的氮的陆地O2通量，陆地生物汇增加了45%，为0.74 ± 0.78 PgC yr−1，海洋汇略小，为2.01 ± 0.66 PgC yr−1。
Atmospheric O2 trend measurements are used to partition global oceanic and land biotic carbon sinks on a multiannual basis. The underlying principle is that a terrestrial uptake or release of CO2 is accompanied by an opposite flux of O2. The molar ratio of the CO2 and O2 terrestrial fluxes should be 1, if no other elements are considered. However, reactive nitrogen produced by human activities (e.g., fertilizers, N deposition) is also being incorporated into plant tissues. The various reaction pathways of the terrestrial nitrogen cycle cause fluxes of atmospheric O2. Thus the cycles of nitrogen, carbon, and oxygen must be linked together. We report here on previously unconsidered anthropogenic nitrogen‐related mechanisms which impact atmospheric O2 trends and thus the derived global carbon sinks. In particular, we speculate that anthropogenic‐driven changes are driving the global nitrogen cycle to a more oxidized state, primarily through nitrification, nitrate fertilizer industrial production, and combustion of fossil fuels and anthropogenic biomass burning. The sum of these nitrogen‐related processes acts to additionally decrease atmospheric O2 and slightly increase atmospheric CO2. We have calculated that the effective land biotic O2:CO2 molar ratio ranges between 0.76 and 1.04 rather than 1.10 (moles of O2 produced per mole of CO2 consumed) over the period 1993–2003, depending on which of four contrasting nitrogen oxidation and reduction pathway scenarios is used. Using the scenario in which we have most confidence, this implies a 0.23 PgC yr−1 correction to the global land biotic and oceanic carbon sinks of most recently reported estimates over 1993–2003, with the land biotic sink becoming larger and the oceanic sink smaller. We have attributed large uncertainties of 100% to all nitrogen‐related O2 and CO2 fluxes and this corresponds up to ±0.09 PgC yr−1 increase in global carbon sink uncertainties. Thus accounting for anthropogenic nitrogen‐related terrestrial fluxes of O2 results in a 45% larger land biotic sink of 0.74 ± 0.78 PgC yr−1 and a slightly smaller oceanic sink of 2.01 ± 0.66 PgC yr−1 for the decade 1993–2003.