
OPTICAL OBSERVATIONS OF SUSPENDED PARTICLE DYNAMICS IN A TIDAL WETLAND John Franco Saraceno B.S., University of California, Davis, 2006 THESIS Submitted in partial satisfaction of the requirements for the degree of MASTER OF SCIENCE in GEOLOGY at CALIFORNIA STATE UNIVERSITY, SACRAMENTO SUMMER 2011 © 2011 John Franco Saraceno ALL RIGHTS RESERVED ii OPTICAL OBSERVATIONS OF SUSPENDED PARTICLE DYNAMICS IN A TIDAL WETLAND A Thesis by John Franco Saraceno Approved by: __________________________________, Committee Chair David Evans, Ph.D. __________________________________, Second Reader Brian Bergamaschi, Ph.D. __________________________________, Third Reader Scott Wright, Ph.D. ____________________________ Date iii Student: John Franco Saraceno I certify that this student has met the requirements for format contained in the University format manual, and that this thesis is suitable for shelving in the Library and credit is to be awarded for the thesis. __________________________, Department Chair ___________________ David Evans, Ph.D. Date Department of Geology iv Abstract of OPTICAL OBSERVATIONS OF SUSPENDED PARTICLE DYNAMICS IN A TIDAL WETLAND by John Franco Saraceno Suspended particulate matter (SPM) plays an important role in the biogeochemistry of estuaries and wetlands. Recent wetland restoration efforts have targeted tidal wetlands; yet, many questions pertaining to SPM dynamics s remain. A paired in situ optical and acoustical sensor package was deployed for several weeks during the winter in the main channel at Browns Island, CA, in order to identify processes controlling estuarine and marsh sediment dynamics. Turbidity, particle volume concentration and particulate attenuation were employed as surrogates of SPM concentration. The slope of the particulate attenuation spectra, γ, and laser diffraction were used to study particle size dynamics and flocculation processes. Water samples were collected hourly over one tidal cycle at the end of the study period for SPM concentration and organic content in support of optical measurements. Together these observations helped elucidate the role of tidal wetlands in the cycling of estuarine particles. Tidal action was a driving force of particle dynamics at Browns Island, as fluctuations in tidal water levels controlled wetland inundation and current velocity. SPM surrogates were maximum at the height of the higher high (HH) flood tide and minimum at lower low (LL) tide water level, consistent with the loss of SPM through deposition v and/or flocculation due to the interaction of estuarine water with the island. Following HH slack tide, particles smaller than 133 µm flocculated into larger particle aggregates. The largest aggregates reached a maximum size of 150 µm during the ebb tide. The controlling mechanism for flocculation was likely particle to particle collisions and differential settling in the presence of organic rich pore waters draining from the marsh. The transport of organic rich flocs could be an important mechanism for the export of contaminants and organic matter off of the island and into the estuary. _______________________, Committee Chair David Evans, Ph.D. _______________________ Date vi ACKNOWLEDGEMENTS I thank my committee members Dave Evans, Brian Bergamaschi and Scott Wright for guidance and helpful suggestions. I am appreciative of Bryan Downing for his role in attaining high quality data and for stimulating insightful discussions. I could not have completed this work without the help and expert advice of Emmanuel Boss. I wish to thank the University of Maine at Orono In Situ Sound and Color Lab and the USGS California Water Science Center for the use of the equipment used in this study. I express thanks to Neil Ganju and many other USGS personnel for the collection and processing of hydrodynamic and sediment data. I express the deepest gratitude to my dear old friend Calvin Kenney for nudging me to pursue a graduate degree and in part making it possible through a gracious scholarship. Lastly, I extend my sincere appreciation to my wife, Stacy, for lending her ear, critical eye, and inexhaustible support. The CALFED drinking water program funded this work. vii TABLE OF CONTENTS Page Acknowledgements ........................................................................................................... vii List of Tables .......................................................................................................................x List of Figures .................................................................................................................... xi Chapter 1. INTRODUCTION .........................................................................................................12 1.1 The Ecological and Societal Importance of Estuaries and Tidal Wetlands ............ 12 1.2 Suspended Particulate Matter Biogeochemistry ..................................................... 13 1.2.1 Size ................................................................................................................... 14 1.2.2 Flocculation...................................................................................................... 15 1.2.3 Settling Velocity .............................................................................................. 16 1.2.4 Contaminate Transport..................................................................................... 17 1.2.5 Optical Properties............................................................................................. 17 1.3 Particle Cycling in Tidal Wetlands ......................................................................... 18 1.4 Previous Work ........................................................................................................ 19 2. SITE DESCRIPTION ....................................................................................................22 2.1 Geologic Setting ..................................................................................................... 22 3. METHODS ....................................................................................................................24 3.1 Sampling Procedure and Instrumentation ............................................................... 24 3.2 Turbidity ................................................................................................................. 25 3.3 Attenuation and Absorption .................................................................................... 25 3.4 ac9 Data Treatment ................................................................................................. 26 3.5 cp Spectra and Particle Size .................................................................................... 28 3.6 In Situ Particle Size Distributions ........................................................................... 29 3.7 Discrete Measurements ........................................................................................... 31 3.7.1 Sample Collection ............................................................................................ 31 3.7.2 SPM Concentration .......................................................................................... 31 3.7.3 Particle Organic Content .................................................................................. 31 viii 3.8 Time Series Analysis .............................................................................................. 32 4. RESULTS ......................................................................................................................33 4.1 Hydrodynamics ....................................................................................................... 33 4.2 Wind Velocity ......................................................................................................... 34 4.3 SPM Concentration Surrogates ............................................................................... 35 4.3.1 Turbidity .......................................................................................................... 35 4.3.2 Particulate Beam Attenuation .......................................................................... 36 4.3.3 Volume Concentration ..................................................................................... 37 4.4 SPM, POM Concentration and Organic Content .................................................... 38 4.5 Particle Size ............................................................................................................ 39 4.5.1 cp Slope ............................................................................................................ 39 4.5.2 Mean and Median Particle Size ....................................................................... 39 4.5.3 Particle Size Distributions................................................................................ 39 5. INTERPRETATION......................................................................................................42 5.1 Hydrodynamics ....................................................................................................... 42 5.2 Drivers of SPM Concentration ............................................................................... 43 5.2.1 Precipitation ..................................................................................................... 43 5.2.2 Wind ................................................................................................................. 44 5.2.3 Tidal forcing....................................................................................................
Details
-
File Typepdf
-
Upload Time-
-
Content LanguagesEnglish
-
Upload UserAnonymous/Not logged-in
-
File Pages79 Page
-
File Size-