Impacts of Holocene Peat Deposits on Nearshore Biogeochemical Processes and Trace Gas Production

Impacts of Holocene Peat Deposits on Nearshore Biogeochemical Processes and Trace Gas Production Monographische Dissertation zur Erlangung des akademischen Grades doctor rerum naturalium (Dr. rer. nat.) der Mathematisch-Naturwissenschaftlichen Fakultät der Universität Rostock vorgelegt von Matthias Kreuzburg Geboren am 03. November 1985 in Heidelberg Rostock den 24. Mai 2019 Thou canst not stir a flower, without troubling of a star. Francis Thompson, The Mistress of Vision I Table of contents Table of contents .............................................................................................................. II Eigenständigkeitserklärung ............................................................................................. VI Abstract ......................................................................................................................... VII Zusammenfassung ....................................................................................................... VIII Curriculum Vitae ............................................................................................................. IX Publications ..................................................................................................................... X Articles in peer-reviewed journals ................................................................................. X Conferences, workshops and presentations ................................................................. X Research stays abroad .............................................................................................. XII Grant .......................................................................................................................... XII Acknowledgement ........................................................................................................ XIII List of abbreviations, symbols and variables ................................................................. XIV List of Figures ............................................................................................................... XVI List of Tables .............................................................................................................. XVIII Motivation ..................................................................................................................... XIX 1. Introduction ................................................................................................................ 1 1.1. Climate relevant trace gases in coastal zones .................................................... 1 1.1.1. Methane ...................................................................................................... 1 1.1.2. Nitrous oxide ............................................................................................... 2 1.2. Geology and physical processes in coastal regions ............................................ 3 1.3. Hydrological processes across the terrestrial marine interface ........................... 5 1.3.1. Coastal interactions with peatlands ............................................................. 6 1.4. Study site ........................................................................................................... 7 1.4.1. Onshore area .............................................................................................. 7 1.4.2. Waterline and offshore area ........................................................................ 9 1.4.3. Warnow-river ............................................................................................... 9 2. Methods .................................................................................................................. 10 2.1. Geochemical field surveys ................................................................................ 10 2.1.1. Offshore water sampling ............................................................................ 10 2.1.1.1. Water column characteristics ................................................................. 10 2.1.1.2. Mini chamber lander system .................................................................. 11 2.1.2. Shoreline field campaigns.......................................................................... 12 2.1.3. Investigations of the Warnow-river system ................................................ 12 2.1.4. Analytical methods used for samples from the field campaigns ................. 12 II 2.1.4.1. Gas Chromatography ............................................................................. 12 2.1.4.2. Nutrients ................................................................................................ 14 2.2. Geophysical surveys ........................................................................................ 15 2.2.1. Geophysical data ....................................................................................... 15 2.2.2. Ground-truthing ......................................................................................... 16 2.2.3. Grain size distribution ................................................................................ 16 14 2.2.4. Geochemical sediment analysis and C age-determination ...................... 17 2.3. Column experiment study ................................................................................. 17 2.3.1. Column experiment and instrumentation ................................................... 18 2.3.2. Ground and seawater flow regimes ........................................................... 20 2.3.3. Analytical methods .................................................................................... 22 2.3.3.1. Gas fluxes among the air-water interface ............................................... 22 2.3.3.2. Porewater geochemical analysis ............................................................ 23 2.3.3.3. Monitoring of dissolved oxygen .............................................................. 24 2.3.3.4. Solid phase geochemistry ...................................................................... 25 2.3.3.5. Quantification of methanogens and sulfate reducers .............................. 25 3. Results .................................................................................................................... 27 3.1. Trace gas investigation within the study site ..................................................... 27 3.1.1. Offshore concentrations of CH4 and N2O ................................................... 27 3.1.2. Trace gas concentrations along the waterline ............................................ 30 3.1.3. Flux measurements from chamber lander incubations ............................... 31 3.1.4. Impacts of the Warnow-river on trace gas distribution ............................... 32 3.2. Geological surveys ........................................................................................... 34 3.2.1. Onshore .................................................................................................... 34 3.2.2. Bathymetry ................................................................................................ 35 3.2.3. Seafloor composition ................................................................................. 36 3.2.4. Sediment cores ......................................................................................... 38 3.2.5. Subsurface structure ................................................................................. 40 3.3. Column experiment .......................................................................................... 42 3.3.1. Aqueous phase geochemistry ................................................................... 42 3.3.1.1. Salinity ................................................................................................... 42 3.3.2. Porewater chemistry .................................................................................. 44 3.3.3. CO2 and CH4 fluxes ................................................................................... 45 3.3.4. Abundances of methanogenic archaea and sulfate reducing bacteria ....... 46 3.3.5. Solid phase geochemistry.......................................................................... 46 III 4. Discussion ............................................................................................................... 48 4.1. Hydrodynamics and trace gas distribution ........................................................ 48 4.1.1. Baltic Sea water ........................................................................................ 48 4.1.2. Warnow-river water ................................................................................... 50 4.1.3. Submarine groundwater discharge ............................................................ 51 4.2. Coastal development and geomorphology ........................................................ 52 4.2.1. Peatland formation and sea level rise ........................................................ 54 4.2.2. Submerged peat deposits in marine sediments ......................................... 56 4.3. Experimental investigation of the interaction of submerged peat with advective groundwater and seawater flow................................................................................... 58 4.3.1. Advective flow and solute transport ........................................................... 58 4.3.2. Solid phase geochemistry.........................................................................

Load more