冰期-间冰期和千年尺度上氧化亚氮排放途径和源区的变化

IF 5.4 2区 地球科学 Q1 ENVIRONMENTAL SCIENCES
J. A. Menking, J. E. Lee, E. J. Brook, J. Schmitt, L. Soussaintjean, H. Fischer, J. Kaiser, A. Rice
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引用次数: 0

摘要

末次盛冰期(LGM)向全新世过渡期间,大气N2O摩尔分数增加了80 nmol mol−1。通过对N2O同位素比率的冰芯测量,我们发现这种增加是由硝化和反硝化作用的增加所驱动的,两种生产途径之间的相对分配取决于假设的同位素端元源特征。同样,我们还将Heinrich Stadial 4/Dansgaard Oeschger 8 (HS4/DO8)千年事件中35 nmol mol−1 N2O摩尔分数的增加归因于两种N2O生成途径的增加。相比之下,新仙女木时期25 nmol mol−1 N2O摩尔分数的减少几乎完全是由硝化作用的减少所驱动的。在海洋和陆地环境中,N2O产量的消冰和HS4/DO8增加都发生了,其中陆地源对变暖的响应要快约两个世纪。对硝化和反硝化排放变化的限制是强有力的,并且与先前显示N2O排放对北半球突变变暖的敏感性的研究一致。这项研究首次证明了反硝化和硝化途径在驱动源变化中的重要性。由于源同位素体特征的不确定性,绝对排放量更不确定。例如,考虑到反硝化过程中N2O部分还原为N2导致的同位素富集,反硝化对LGM排放的贡献从(65±10)%转变为(91±6)%。减少源特征的不确定性将增加冰芯N2O同位素记录推断环境变化的能力。
本文章由计算机程序翻译,如有差异,请以英文原文为准。

Glacial-Interglacial and Millennial-Scale Changes in Nitrous Oxide Emissions Pathways and Source Regions

Glacial-Interglacial and Millennial-Scale Changes in Nitrous Oxide Emissions Pathways and Source Regions

During the transition from the Last Glacial Maximum (LGM) to the Holocene, the atmospheric N2O mole fraction increased by 80 nmol mol−1. Using ice core measurements of N2O isotopomer ratios, we show that this increase was driven by increases in both nitrification and denitrification, with the relative partitioning between both production pathways depending on the assumed isotopic end-member source signatures. Similarly, we also attribute a 35 nmol mol−1 N2O mole fraction increase during the Heinrich Stadial 4/Dansgaard Oeschger 8 (HS4/DO8) millennial-scale event to increases in both N2O production pathways. In contrast, the 25 nmol mol−1 N2O mole fraction decrease during the Younger Dryas was driven almost exclusively by a decrease in nitrification. The deglacial and HS4/DO8 increases in N2O production occurred in both marine and terrestrial environments, with the terrestrial source responding faster to warming by about two centuries. Constraints on changes in nitrification and denitrification emissions are robust and consistent with previous studies showing the sensitivity of N2O emissions to abrupt Northern Hemisphere warming. This study demonstrates for the first time the importance of both denitrification and nitrification pathways in driving source changes. Absolute emissions are more uncertain due to uncertainty about source isotopomer signatures. For instance, the contribution of denitrification to emissions at the LGM shifts from (65 ± 10) % to (91 ± 6) % when factoring in isotope enrichment due to partial reduction of N2O to N2 during denitrification. Reducing uncertainty in source signatures will increase the power of ice core N2O isotope records in deducing environmental change.

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来源期刊
Global Biogeochemical Cycles
Global Biogeochemical Cycles 环境科学-地球科学综合
CiteScore
8.90
自引率
7.70%
发文量
141
审稿时长
8-16 weeks
期刊介绍: Global Biogeochemical Cycles (GBC) features research on regional to global biogeochemical interactions, as well as more local studies that demonstrate fundamental implications for biogeochemical processing at regional or global scales. Published papers draw on a wide array of methods and knowledge and extend in time from the deep geologic past to recent historical and potential future interactions. This broad scope includes studies that elucidate human activities as interactive components of biogeochemical cycles and physical Earth Systems including climate. Authors are required to make their work accessible to a broad interdisciplinary range of scientists.
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