氮元素作為海洋環(huán)境中的重要生源要素之一，通常被認(rèn)為是初級生產(chǎn)力的限制因子，加之全球氮循環(huán)與碳循環(huán)在氣候變化中的密切耦合以及人類活動對于氮元素排放的逐漸增加，海洋氮循環(huán)也就成為整個海洋生物地球化學(xué)循環(huán)中最為關(guān)鍵的一環(huán)。海洋中化合態(tài)氮的收支取決于游離態(tài)氮氣的固定和化合態(tài)氮的丟失(N-loss)，前者主要由固氮生物執(zhí)行，而后者主要由反硝化細(xì)菌和厭氧銨氧化細(xì)菌所實現(xiàn)。由于海洋氮循環(huán)受到多種過程的控制以及在量化各種過程速率方面存在很大的不確定性，全球氮的收支是否處于平衡仍然存在很大的爭議。海洋沉積物是化合態(tài)氮丟失的一個重要場所，約50⁷0%的化合態(tài)氮在此被移除，而其中50%以上的氮丟失又發(fā)生在陸架海沉積物中(Bohlen et al.2012; Gruber2008)，盡管該區(qū)域只占全球海洋面積的7.5%(Menard&Smith1966)。由此可見陸架海沉積物在全球海洋氮循環(huán)中所起的關(guān)鍵性作用。 反硝化、厭氧銨氧化和異化硝酸鹽還原為銨(DNRA)是沉積物厭氧環(huán)境中氮循環(huán)的三種關(guān)鍵過程。前兩個過程控制著沉積物中化合態(tài)氮的丟失，而DNRA則將NO₃

【文章頁數(shù)】：171 頁

【學(xué)位級別】：博士

【文章目錄】：
摘要 Abstract 1 Introduction
1.1 Nitrogen cycle in marine environment
    1.1.1 Nitrogen composition
    1.1.2 Nitrogen budget in marine environments
    1.1.3 Marine nitrogen transformation processes
    1.1.4 Methods in determining nitrogen transformations
1.2 N-loss in continental shelf sediments
1.3 Introduction to the East China Sea
    1.3.1 General description
    1.3.2 Nitrogen budget in the East China Sea
1.4 Aims of this thesis 2 Application of the isotope pairing technique in sediments where anammox, denitrification and DNRA coexist
Abstract
2.1 Introduction
2.2 Materials and procedures
    2.2.1 Assumptions
    2.2.2 Revised equations for calculations of anammox and denitrification rates after DNRA intrusion
    2.2.3 Quantification effects of DNRA on anammox, denitrification and total benthic N2production
    2.2.4 Revised procedure for estimating actual anammox, denitrification and DNRA rates in slurry incubation
2.3 Assessment
2.4 Discussion
2.5 Comments and recommendations 3 Anaerobic ammonium oxidation, denitrification and dissimilatory nitrate reduction to ammonium in the East China Sea sediment
Abstract
3.1 Introduction
3.2 Materials and methods
    3.2.1 Sample collection and preparation
    3.2.2 15N slurry incubations
    3.2.3 Chemical analysis
    3.2.4 Rate calculations
3.3 Results
    3.3.1 Water column and sediment characteristics
    3.3.2 15N slurry incubations
    3.3.3 Nitrate storage and release in the sediment
    3.3.4 N-loss and nitrate reduction in slurry incubation
3.4 Discussion
    3.4.1 The influence of nitrate release and DNRA on anammox and denitrification rates calculation with isotope pairing method
    3.4.2 Distribution and regulation of anammox, denitrification and DNRA in ECS sediments
    3.4.3 Biogeochemical significance of anammox, denitrification and DNRA in the ECS sediments
3.5 Conclusions 4 Direct measurements of benthic N-loss and DNRA in the East China Sea
Abstract
4.1 Introduction
4.2 Methods
    4.2.1 Sample collection and preparation
    4.2.2 General sediment characteristics
    4.2.3 Net fluxes of O₂and dissolved inorganic nitrogen
    4.2.4 Core incubation for benthic N-loss
    4.2.5 Slurry incubation for tracking anammox, denitrification and DNRA
    4.2.6 Chemical analysis
4.3 Results
    4.3.1 General characteristics of the investigation sites
    4.3.2 Pore water nitrogen species profiles
    4.3.3 Oxygen and nutrients net fluxes
    4.3.4 Slurry incubation
    4.3.5 Concentration series test for core incubation
    4.3.6 N-loss from core incubation
    4.3.7 DNRA from core incubation
4.4 Discussion
    4.4.1 Isotope pairing technique testing with¹⁵NO3
- concentration and time series when anammox and denitrification co-exist
    4.4.2 Underestimation of N-loss by¹⁵NO3
- diffusion limitation
    4.4.3 Other evidence for supporting underestimation of benthic N-loss by IPT
    4.4.4 A revised procedure for estimating benthic N-loss
    4.4.5 DNRA and its effect on benthic nitrogen cycle
    4.4.6 Global significance of the additional N-loss 5 Response of benthic nitrogen cycle to hypoxia of the Changjiang estuary
Abstract
5.1 Introduction
5.2 Materials and Methods
    5.2.1 Sites description
    5.2.2 Sediment and water sampling
    5.2.3 Sediment characteristics
    5.2.4 Sediment oxygen profiles
    5.2.5 Track anammox, denitrification and DNRA with slurry incubations
    5.2.6 Measuring oxygen uptake and nutrient fluxes with intact core incubations
    5.2.7 Measuring anammox, denitrification and DNRA with intact core incubation
    5.2.8 Rates calculations
5.3 Results
    5.3.1 General characteristics
    5.3.2 Pore water profiles of oxygen and nitrate
    5.3.3 Sediment oxygen uptake (SOU)
    5.3.4 Partitioning of anammox, denitrification and DNRA
    5.3.5 Benthic N-loss and DNRA from core incubation
    5.3.6 Nutrients net fluxes, nitrification and mineralization
    5.3.7 Correlation of measured benthic nitrogen transformation rates with bottom water oxygen
5.4 Discussion
    5.4.1 Response of SOU to reduced oxygen
    5.4.2 Response of nutrient fluxes to reduced oxygen
    5.4.3 Response of anammox, denitrification and DNRA to reduced oxygen
    5.4.4 Integrated response of benthic nitrogen cycle to reduced oxygen
    5.4.5 The fate of organic nitrogen 6 Conclusions and Prospect Reference Acknowledgements Supplementary Material 1 for Chapter 3 Supplementary Material 2 for Chapter 3 個人簡歷 發(fā)表的學(xué)術(shù)論文



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