DOI: 10.1002/2013GB004642
Scopus记录号: 2-s2.0-84924570950
论文题名: Close coupling of N-cycling processes expressed in stable isotope data at the redoxcline of the Baltic Sea
作者: Frey C ; , Dippner J ; W ; , Voss M
刊名: Global Biogeochemical Cycles
ISSN: 8866236
出版年: 2014
卷: 28, 期: 9 起始页码: 974
结束页码: 991
语种: 英语
英文关键词: Baltic Sea
; denitrification
; hypoxia
; nitrate isotopes
; nitrification
; nitrogen cycle
Scopus关键词: anoxic conditions
; denitrification
; diffusion
; eutrophication
; nitrogen cycle
; pollutant removal
; Rayleigh number
; reaction kinetics
; redox conditions
; stable isotope
; transformation
; water mass
; Atlantic Ocean
; Baltic Sea
; Gotland Basin
英文摘要: Over the past decades, the hypoxic state of the central Baltic Sea has deteriorated because of eutrophication, but little is known about the extent to which related factors such as nitrogen removal have been altered. The Baltic Sea is a stratified semi-enclosed basin with a large, anoxic bottom water mass in its central Gotland Basin and highly active microbial nitrogen transformation processes at the redoxcline, the interface between oxic and anoxic waters. In this study, we identified and quantified the dominant transformation processes of reactive nitrogen by exploiting fine resolution profiles of δ15NNO3 , δ18ONO3 , and δ15NNH4 through the pelagic redoxcline between 60 and 140 m. Our results showed increasing δ15NNO3 and δ18ONO3 values with decreasing nitrate concentrations, but the associated low apparent isotope effect (ε = ∼5%), as inferred from a closed system Rayleigh model, was not consistent with the high ε (∼25%) characteristic of denitrification in the water column. These findings could be explained by substrate limitation. The observed δ18ONO3 :δ15NNO3 ratio of 1.38:1 rather than the usual 1:1 ratio typical for denitrification-dominated systems could be explained by the occurrence of both nitrification and denitrification. We then developed a numeric reaction-diffusion model, according to which a realistic denitrification rate of 14 nmol N L-1 d-1 was estimated, and a nitrification rate of 6.6 nmol N L-1 d-1 confirmed. Our study not only demonstrates the value of stable isotope data for investigating nitrogen transformation processes but also highlights that care is needed in interpreting systems with closely coupled processes such as those at ocean redoxclines. ©2014. 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/77457
Appears in Collections: 气候变化事实与影响
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作者单位: Leibniz Institute for Baltic Sea Research Warnemünde, Rostock, Germany
Recommended Citation:
Frey C,, Dippner J,W,et al. Close coupling of N-cycling processes expressed in stable isotope data at the redoxcline of the Baltic Sea[J]. Global Biogeochemical Cycles,2014-01-01,28(9)