长江口现代水下三角洲沉积物的 210 Pb垂向剖面特征及其沉积动力影响因素
发布时间：2024-04-21 17:37
长江河口细颗粒物质来源丰富、水动力作用活跃,近年来又受到三峡大坝等流域大型工程的影响,因此其水下三角洲沉积层序对自然过程(物源变化、潮汐水道地形调整、风暴潮事件等)和人类活动(航道疏浚等)的响应成为一个重要的科学问题。 本研究对覆盖长江口水下三角洲的31个站位的沉积物柱状样进行了粒度分析和210Pb测定。所获2468个子样的粒度分析结果表明,长江水下三角洲表层底质的平均粒径一般细于4Φ,只有CJ03和CJ09站位的表层沉积物为极细砂(3Φ<平均粒径<4Φ)。长江河物质主要是来源于现代流域供给,少数站位的砂质沉积则代表海底侵蚀。柱样的平均粒径有四类垂向分布趋势：向上细化、垂向稳定、垂向波动式变化、向上粗化,分别对应于不同的地貌部位和冲淤动态。沉积物粒度参数的变化主要受物源丰富程度、沉积过程和流域输入悬沙物质组成等因素的影响。向上变粗类型的沉积物柱样主要来自南槽口门附近以及北槽挖沙水道附近。向上变细和垂向均一类型的柱样采集地均为研究区内距河口较远处。此外,在南支北槽挖沙水道外和在南支北港口门外获取的柱样粒度分选极差(2<分选系数<4),指示长江口南支口门的沉积水动力...
【文章页数】：282 页
【学位级别】：博士
【文章目录】：
摘要
Abstract
Acknowledgements
Notations
Chapter 1 Introduction
1.1 The Scientific Problem
1.2 Purpose of the stuay
1.3 Hypothesis
1.4 Themes of research
1.4.1 Grain size analysis of sediment cores
1.4.2 Factors affecting grain size distribution
1.4.3 210Pb dating for sedimentation rates
1.4.4 Factors affecting the 210Pbex activities of sediments
1.4.5 210Pbex patterns in relation to sediment dynamics
1.4.6 Tidal cycle measurements
1.4.7 Observed variations in relation to sediment dynamical changes
Chapter 2 Literature Review
2.1 Estuarine processes
2.1.1 River discharges of freshwater and sediment
2.1.2 Tides and tidal currents in estuaries
(a) Tides and tidal currents
(b) Tidal limit and tidal current limit
2.1.3 Estuarine circulations
2.1.4 Formation of turbidity maxima
2.1.5 Sediment transport patterns
(a) Sediment resuspension
Initiation of sediment motion
Shields curve
(b) Bottom boundary layer
Bottom shear stress
Bottom roughness length
(c) Sediment transport rate
Estimation of suspended sediment flux
Calculation of resuspended flux
(d) Gravity currents
Gravity current
Turbidity current
Hyperpycnal plume
Fluid mud
2.2 River deltas
2.2.1 Types of river deltas
2.2.2 Evolution of river deltas
2.2.3 Sedimentary facies and sequences
2.2.4 Sediment budget
2.3 210Pb in deltaic sedimentation
2.3.1 Analytical techniques
2.3.2 Spatial distribution patterns
2.3.3 Vertical distribution in relation to accumulation rate
2.3.4 Sediment dynamic factors affecting the burial of 210Pb
Chapter 3 The Study Area
3.1 Regional geology and geomorphology
3.1.1 Geological background
3.1.2 Geomorphological features
3.1.3 Estuary and delta evolution
(a) Evolution under sea level rise
(b) Land progradation since 2000BP
(c) Development in the last 100 years
3.1.4 Holocene sediment systems
3.2 Hydrodynamics
3.2.1 Freshwater discharges
3.2.2 Tides and tidal currents
3.2.3 Waves
3.2.4 Estuarine and shelf circulations
3.2.5 Modern events
(a) Floods
(b) Typhoon
3.3 Sedimentation
3.3.1 Sediment supply
3.3.2 Variations of sediment supply
(a) Mass flux change,in response to natural oscillations
(b) Sediment flux change,in response to deforestation
(c) Sediment flux change,in response to dam constructions
(d) Sediment flux change,in response to dredging navigation channels
3.3.3 Surficial sediment types and distributions
3.3.4 Suspended sediment and turbidity maxima
3.3.5 Sediment transport patterns
3.3.6 Depocenter and sedimentation rates
3.4 Biotic influence
Chapter 4 Material and Methods
4.1 Sampling and sample treatment
4.1.1 Sampling locations
4.1.2 Software utilization for geomorphology maps
4.1.3 Core sample recovery
4.1.4 Sub-sampling and core description
4.2 Grain size analysis
4.2.1 Sample preparetion for grain size analysis
4.2.2 Measurements of grain size distribution
4.2.3 Calculation of grain size parameters
4.2.4 The grading and classification of sediments
4.3 Water content analysis
4.3.1 Water content calculation
4.3.2 Data precision of water content
4.4 Determination of sedimentation rates
4.4.1 Sample pretreatment for 210pb dating
4.4.2 210Pb activity and sedimentation rates
4.4.3 Sediment flux estimations
4.4.4 Error correction of accumulation rates
(a) Grain size correction of accumulation rates
(b) Compaction correction of accumulation rates
Approach Ⅰ:Standard layer method
Approach Ⅱ:Removing of compact effecf
4.5 Fine grain sediment resuspension and transport
4.5.1 Tidal cycle measurements
4.5.2 Laboratory analysis and data processing
(a) SSCs data analysis
SSCs data analysis of in situ water samples
SSCs data analysis of calibrated ADCP echo intensity information
Figure producing of SSCs profile
(b) Data analysis of bottom boundary layer parameters
(c) Estimation of sediment re-suspension
(d) Estimation of suspended sediment flux
Chapter 5 Results
5.1 Seafloor morphology of the study area
5.2 Sediment types and distributions
5.2.1 Description of sediment cores
5.2.2 Vertical distribution patterns of sediment grain size
5.2.3 Spatial distribution of vertical patterns
5.2.4 Sub-sample selection,for 210Pb dating
5.3 Water content and compaction effects
5.3.1 Water content precision in relation to sub-sampling duration
5.3.2 Distributions of compaction effects on core lengths
5.3.3 Compaction effects on core lengths in relation to water content
5.4 Distribution patterns of 210pb activities
5.4.1 Vertical distribution patterns of 210Pb activities
5.4.2 Horizontal distributions of 210Pb decay profile types
5.4.3 Horizontal distributions of 210pb activities
5.5 Distribution patterns sedimentation rates
5.5.1 Detailed analysis results of each core sample
(a) Sediment cores with normal 210Pbex decay profile
Core CJ06
Core CJ08
Core CJ12
(b) Sediment cores with unique total 210Pb activity profile
Core CJ01
Core CJ04
Core CJ09
Core CJ15
(c) Sediment cores with sectional 210Pbex decay profile
Core CJ02
Core CJ05
Core CJ07
Core CJ11
Core CJ14
Core CJ16
Core CJ19
Core CJ23
Core CJ24
Core CJ25
(d) Sediment cores with topsy-turvy 210Pb activity profile(sectional 210pbex decay and inverse 210Pbex decay profile)
Core CJ13
Core CJ17
Core CJ18
Core CJ20
Core CJ21
Core CJ22
Core CJ26
Core CJ27
Core CJ28
Core CJ29
5.5.2 Horizontal distributions of sedimentation rates
5.6 Profiles of hydrodynamic observations
5.6.1 Distribution of SSCs and current velocity components
5.6.2 Distribution of bottom boundary layer parameters
Chapter 6 Discussion
6.1 210pb profiles in relation to catchments changes
6.1.1 Catchment changes over the Changjiang Estuary
(a) Mass discharge changes
(b) Deltaic Processes
6.1.2 210Pb profiles in relation to catchments changes
(a) 1980s(first period in Fig.3.10)
(b) After 2003 (third period in Fig.3.10)
(c) Years in between (second period in Fig.3.10)
6.2 210Pb distribution patterns in relation to sedimentary processes
6.2.1 Surficial 210Pb in relation to turbidity maximum
6.2.2 Sedimentary processes represented by 210Pb patterns
(a) Sedimentary processes of Pattern 2
(b) Sedimentary processes of Pattern 3
(c) Possible sedimentary processes of Pattern 4
6.3 Sedimentation rate variations in response to catchments changes
6.3.1 Variations in sedimentation rates
(a) Sedimentation rate variations over modern subaqueous delta
(b) Sedimentation rates over the old Changjiang Delta
(c) Sedimentation rates over the delta front-transition region
6.3.2 Sedimentation rates in relation to turbidity maxima
6.3.3 Sedimentation rates in relation to mass discharge
6.3.4 Relationships between sedimentation rates and 210Pbex
6.3.5 Distribution of sedimentation rates affected by evolution of biological communities
6.4 Conditions for the formation of hyperpycnal flow
6.4.1 Conditions for the generation of hyperpycnal flow
6.4.2 Possibility of hyperpycnal flow induced by the increase in SSCs within the bottom boundary layer
6.4.3 Relationship between seabed morphology and sediment gravity flow
6.5 Factors affecting the distribution of sediment grain size
6.5.1 Locations on different deltaic facies
6.5.2 Material source affecting the distribution of sediment grain size
6.5.3 Possible sedimentation process affecting the distribution of sediment grain size
(a) Hyperpycnal depositional sequence
(b) Turbidity currents
6.5.4 Variation in hydrodynamics affecting the distribution of sediment grain size
(a) Variation over time
Hydrodynamic events
Channel evolution at the Changjiang River mouth
(b) Variation over the estuary (horizontal hydrodynamic distribution)
6.5.5 Human activities affecting the distribution of sediment grain size
6.6 Future sediment retention
6.7 Hydrodynamics data analysis
6.7.1 Analyzing parameters of the bottom boundary layer at estuary
6.7.2 Validity of SSCs data calibrated from echo intensity recorded by ADCP
Chapter 7 Conclusion
Basic characteristics of sediment core samples
Vertical distribution patterns
Distribution of sedimentation rates
Catchments changes
Factors affecting the distributions
Further research in need
References
Appendices
Appendix 1: Results of regression analyses on excess 210Pb activity against depth
Appendix 2: Sub-sampling duration effects on the precision of the water content data(2009)
Appendix 3: Relative water content(dimensionless ratio)of sediment cores(2009)(note:Locations shown in Figure 3.7-1)
Appendix 4: Research articles completed during 2009-2013
本文编号：3961227
【文章页数】：282 页
【学位级别】：博士
【文章目录】：
摘要
Abstract
Acknowledgements
Notations
Chapter 1 Introduction
1.1 The Scientific Problem
1.2 Purpose of the stuay
1.3 Hypothesis
1.4 Themes of research
1.4.1 Grain size analysis of sediment cores
1.4.2 Factors affecting grain size distribution
1.4.3 210Pb dating for sedimentation rates
1.4.4 Factors affecting the 210Pbex activities of sediments
1.4.5 210Pbex patterns in relation to sediment dynamics
1.4.6 Tidal cycle measurements
1.4.7 Observed variations in relation to sediment dynamical changes
Chapter 2 Literature Review
2.1 Estuarine processes
2.1.1 River discharges of freshwater and sediment
2.1.2 Tides and tidal currents in estuaries
(a) Tides and tidal currents
(b) Tidal limit and tidal current limit
2.1.3 Estuarine circulations
2.1.4 Formation of turbidity maxima
2.1.5 Sediment transport patterns
(a) Sediment resuspension
Initiation of sediment motion
Shields curve
(b) Bottom boundary layer
Bottom shear stress
Bottom roughness length
(c) Sediment transport rate
Estimation of suspended sediment flux
Calculation of resuspended flux
(d) Gravity currents
Gravity current
Turbidity current
Hyperpycnal plume
Fluid mud
2.2 River deltas
2.2.1 Types of river deltas
2.2.2 Evolution of river deltas
2.2.3 Sedimentary facies and sequences
2.2.4 Sediment budget
2.3 210Pb in deltaic sedimentation
2.3.1 Analytical techniques
2.3.2 Spatial distribution patterns
2.3.3 Vertical distribution in relation to accumulation rate
2.3.4 Sediment dynamic factors affecting the burial of 210Pb
Chapter 3 The Study Area
3.1 Regional geology and geomorphology
3.1.1 Geological background
3.1.2 Geomorphological features
3.1.3 Estuary and delta evolution
(a) Evolution under sea level rise
(b) Land progradation since 2000BP
(c) Development in the last 100 years
3.1.4 Holocene sediment systems
3.2 Hydrodynamics
3.2.1 Freshwater discharges
3.2.2 Tides and tidal currents
3.2.3 Waves
3.2.4 Estuarine and shelf circulations
3.2.5 Modern events
(a) Floods
(b) Typhoon
3.3 Sedimentation
3.3.1 Sediment supply
3.3.2 Variations of sediment supply
(a) Mass flux change,in response to natural oscillations
(b) Sediment flux change,in response to deforestation
(c) Sediment flux change,in response to dam constructions
(d) Sediment flux change,in response to dredging navigation channels
3.3.3 Surficial sediment types and distributions
3.3.4 Suspended sediment and turbidity maxima
3.3.5 Sediment transport patterns
3.3.6 Depocenter and sedimentation rates
3.4 Biotic influence
Chapter 4 Material and Methods
4.1 Sampling and sample treatment
4.1.1 Sampling locations
4.1.2 Software utilization for geomorphology maps
4.1.3 Core sample recovery
4.1.4 Sub-sampling and core description
4.2 Grain size analysis
4.2.1 Sample preparetion for grain size analysis
4.2.2 Measurements of grain size distribution
4.2.3 Calculation of grain size parameters
4.2.4 The grading and classification of sediments
4.3 Water content analysis
4.3.1 Water content calculation
4.3.2 Data precision of water content
4.4 Determination of sedimentation rates
4.4.1 Sample pretreatment for 210pb dating
4.4.2 210Pb activity and sedimentation rates
4.4.3 Sediment flux estimations
4.4.4 Error correction of accumulation rates
(a) Grain size correction of accumulation rates
(b) Compaction correction of accumulation rates
Approach Ⅰ:Standard layer method
Approach Ⅱ:Removing of compact effecf
4.5 Fine grain sediment resuspension and transport
4.5.1 Tidal cycle measurements
4.5.2 Laboratory analysis and data processing
(a) SSCs data analysis
SSCs data analysis of in situ water samples
SSCs data analysis of calibrated ADCP echo intensity information
Figure producing of SSCs profile
(b) Data analysis of bottom boundary layer parameters
(c) Estimation of sediment re-suspension
(d) Estimation of suspended sediment flux
Chapter 5 Results
5.1 Seafloor morphology of the study area
5.2 Sediment types and distributions
5.2.1 Description of sediment cores
5.2.2 Vertical distribution patterns of sediment grain size
5.2.3 Spatial distribution of vertical patterns
5.2.4 Sub-sample selection,for 210Pb dating
5.3 Water content and compaction effects
5.3.1 Water content precision in relation to sub-sampling duration
5.3.2 Distributions of compaction effects on core lengths
5.3.3 Compaction effects on core lengths in relation to water content
5.4 Distribution patterns of 210pb activities
5.4.1 Vertical distribution patterns of 210Pb activities
5.4.2 Horizontal distributions of 210Pb decay profile types
5.4.3 Horizontal distributions of 210pb activities
5.5 Distribution patterns sedimentation rates
5.5.1 Detailed analysis results of each core sample
(a) Sediment cores with normal 210Pbex decay profile
Core CJ06
Core CJ08
Core CJ12
(b) Sediment cores with unique total 210Pb activity profile
Core CJ01
Core CJ04
Core CJ09
Core CJ15
(c) Sediment cores with sectional 210Pbex decay profile
Core CJ02
Core CJ05
Core CJ07
Core CJ11
Core CJ14
Core CJ16
Core CJ19
Core CJ23
Core CJ24
Core CJ25
(d) Sediment cores with topsy-turvy 210Pb activity profile(sectional 210pbex decay and inverse 210Pbex decay profile)
Core CJ13
Core CJ17
Core CJ18
Core CJ20
Core CJ21
Core CJ22
Core CJ26
Core CJ27
Core CJ28
Core CJ29
5.5.2 Horizontal distributions of sedimentation rates
5.6 Profiles of hydrodynamic observations
5.6.1 Distribution of SSCs and current velocity components
5.6.2 Distribution of bottom boundary layer parameters
Chapter 6 Discussion
6.1 210pb profiles in relation to catchments changes
6.1.1 Catchment changes over the Changjiang Estuary
(a) Mass discharge changes
(b) Deltaic Processes
6.1.2 210Pb profiles in relation to catchments changes
(a) 1980s(first period in Fig.3.10)
(b) After 2003 (third period in Fig.3.10)
(c) Years in between (second period in Fig.3.10)
6.2 210Pb distribution patterns in relation to sedimentary processes
6.2.1 Surficial 210Pb in relation to turbidity maximum
6.2.2 Sedimentary processes represented by 210Pb patterns
(a) Sedimentary processes of Pattern 2
(b) Sedimentary processes of Pattern 3
(c) Possible sedimentary processes of Pattern 4
6.3 Sedimentation rate variations in response to catchments changes
6.3.1 Variations in sedimentation rates
(a) Sedimentation rate variations over modern subaqueous delta
(b) Sedimentation rates over the old Changjiang Delta
(c) Sedimentation rates over the delta front-transition region
6.3.2 Sedimentation rates in relation to turbidity maxima
6.3.3 Sedimentation rates in relation to mass discharge
6.3.4 Relationships between sedimentation rates and 210Pbex
6.4 Conditions for the formation of hyperpycnal flow
6.4.1 Conditions for the generation of hyperpycnal flow
6.4.2 Possibility of hyperpycnal flow induced by the increase in SSCs within the bottom boundary layer
6.4.3 Relationship between seabed morphology and sediment gravity flow
6.5 Factors affecting the distribution of sediment grain size
6.5.1 Locations on different deltaic facies
6.5.2 Material source affecting the distribution of sediment grain size
6.5.3 Possible sedimentation process affecting the distribution of sediment grain size
(a) Hyperpycnal depositional sequence
(b) Turbidity currents
6.5.4 Variation in hydrodynamics affecting the distribution of sediment grain size
(a) Variation over time
Hydrodynamic events
Channel evolution at the Changjiang River mouth
(b) Variation over the estuary (horizontal hydrodynamic distribution)
6.5.5 Human activities affecting the distribution of sediment grain size
6.6 Future sediment retention
6.7 Hydrodynamics data analysis
6.7.1 Analyzing parameters of the bottom boundary layer at estuary
6.7.2 Validity of SSCs data calibrated from echo intensity recorded by ADCP
Chapter 7 Conclusion
Basic characteristics of sediment core samples
Vertical distribution patterns
Distribution of sedimentation rates
Catchments changes
Factors affecting the distributions
Further research in need
References
Appendices
Appendix 1: Results of regression analyses on excess 210Pb activity against depth
Appendix 2: Sub-sampling duration effects on the precision of the water content data(2009)
Appendix 3: Relative water content(dimensionless ratio)of sediment cores(2009)(note:Locations shown in Figure 3.7-1)
Appendix 4: Research articles completed during 2009-2013
本文编号：3961227
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