DOI: 10.1002/2014GB005001
Scopus记录号: 2-s2.0-84947128528
论文题名: N-loss isotope effects in the Peru oxygen minimum zone studied using a mesoscale eddy as a natural tracer experiment
作者: Bourbonnais A ; , Altabet M ; A ; , Charoenpong C ; N ; , Larkum J ; , Hu H ; , Bange H ; W ; , Stramma L
刊名: Global Biogeochemical Cycles
ISSN: 8866236
出版年: 2015
卷: 29, 期: 6 起始页码: 793
结束页码: 811
语种: 英语
英文关键词: isotope effects
; mesoscale eddy
; N-loss
Scopus关键词: biogenic deposit
; biogeochemical cycle
; concentration (composition)
; isotopic composition
; mesoscale eddy
; nitrous oxide
; nutrient budget
; oxidation
; oxygen minimum layer
; tracer
; Peru
英文摘要: Mesoscale eddies in Oxygen Minimum Zones (OMZs) have been identified as important fixed nitrogen (N) loss hotspots that may significantly impact both the global rate of N-loss as well as the ocean's N isotope budget. They also represent "natural tracer experiments" with intensified biogeochemical signals that can be exploited to understand the large-scale processes that control N-loss and associated isotope effects (ε; the ‰ deviation from 1 in the ratio of reaction rate constants for the light versus heavy isotopologues). We observed large ranges in the concentrations and N and O isotopic compositions of nitrate (NO3 -), nitrite (NO2 -), and biogenic N2 associated with an anticyclonic mode-water eddy in the Peru OMZ during two cruises in November and December 2012. In the eddy's center where NO3 - was nearly exhausted, we measured the highest δ15N values for both NO3 - and NO2 - (up to ∼70‰ and 50‰) ever reported for an OMZ. Correspondingly, N deficit and biogenic N2-N concentrations were also the highest near the eddy's center (up to ∼40 μmol L-1). δ15N-N2 also varied with biogenic N2 production, following kinetic isotopic fractionation during NO2 - reduction to N2 and, for the first time, provided an independent assessment of N isotope fractionation during OMZ N-loss. We found apparent variable ε for NO3 - reduction (up to ∼30‰ in the presence of NO2 -). However, the overall ε for N-loss was calculated to be only ∼13-14‰ (as compared to canonical values of ∼20-30‰) assuming a closed system and only slightly higher assuming an open system (16-19‰). Our results were similar whether calculated from the disappearance of DIN (NO3 - + NO2 -) or from the appearance of N2 and changes in isotopic composition. Further, we calculated the separate ε values for NO3 - reduction to NO2 - and NO2 - reduction to N2 of ∼16-21‰ and ∼12‰, respectively, when the effect of NO2 - oxidation could be removed. These results, together with the relationship between N and O of NO3 - isotopes and the difference in δ15N between NO3 - and NO2 -, confirm a role for NO2 - oxidation in increasing the apparent ε associated with NO3 - reduction. The lower ε for N-loss calculated in this study could help reconcile the current imbalance in the global N budget if representative of global OMZ N-loss. © 2015. American Geophysical Union. All Rights Reserved. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/78003
Appears in Collections: 气候变化事实与影响
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作者单位: School for Marine Science and Technology, University of Massachusetts Dartmouth, New Bedford, MA, United States; Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, United States; Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, United States; GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
Recommended Citation:
Bourbonnais A,, Altabet M,A,et al. N-loss isotope effects in the Peru oxygen minimum zone studied using a mesoscale eddy as a natural tracer experiment[J]. Global Biogeochemical Cycles,2015-01-01,29(6)