Molybdenum and arsenic behavior in a limestone aquifer in Central Florida Dissertation Zur Erlangung des Doktorgrades der Naturwissenschaften (Dr. rer. nat.) am Fachbereich Geowissenschaften der Universität Bremen Vorgelegt von Ali Mozaffari Bremen, November 2016 2 Gutachter: Prof. Dr. Thomas Pichler I Erklärung Hiermit versichere ich, dass ich i.die Arbeit ohne unerlaubte fremde Hilfe angefertigt habe, ii. keine anderen als die von mir angegebenen Quellen und Hilfsmittel benutzt haben und iii.die den benutzten Werken wörtlich oder inhaltlich entnommen Stellen als solche kenntlich gemacht habe. ___________________ ,den ________________ II ______________________________ (Unterschrift) III Table of Contents Abstract .............................................................................................................................. IX Kurzzusammenfassung ..................................................................................................... XI Chapter 1. Introduction ....................................................................................................... 1 1.1 Problem statement ...................................................................................................... 1 1.2 Research objectives .................................................................................................... 2 1.3 Research outlines ....................................................................................................... 3 1.4 Site description ............................................................................................................ 4 1.4.1 Location ................................................................................................................ 4 1.4.2 Concentration of Mo and As in groundwater and sediments/rocks ........................ 7 1.5 Geology and Hydrogeology ......................................................................................... 9 1.5.1 Regional geology of Central Florida ...................................................................... 9 1.5.2 Local geology of the study area .......................................................................... 10 1.5.3 Floridan Aquifer System ..................................................................................... 11 Chapter 2. Literature review ............................................................................................. 12 2.1 Geochemistry, biochemistry and applications of Mo .................................................. 12 2.2 Natural reserves of Mo .............................................................................................. 14 2.3 Importance of Mo in the biogeochemical cycle of nitrogen......................................... 15 2.4 Molybdenum geochemistry in marine environments .................................................. 17 2.4.1 Molybdenum behavior in oxic conditions ............................................................ 17 2.4.2 Molybdenum enrichment in anoxic/sulfidic conditions ......................................... 19 2.5 Molybdenum in groundwater ..................................................................................... 21 2.5.1 Molybdenum sorption ......................................................................................... 22 2.5.1.1 Molybdenum sorption on hydrous ferric oxide and goethite .......................... 24 2.5.1.2 Molybdenum sorption on iron, aluminum, titanium, and manganese oxides .. 26 2.5.1.3 Clay minerals ................................................................................................ 28 2.5.1.4 Pyrite ............................................................................................................ 28 2.5.1.5 Organic matter .............................................................................................. 29 2.5.2 Competitive impacts of anion effect on Mo adsorption ........................................ 30 2.6 Sedimentary As ......................................................................................................... 31 2.7 Geochemistry of aqueous As .................................................................................... 34 Chapter 3. Chemical fractionation of molybdenum and arsenic ................................... 36 Abstract ............................................................................................................................. 36 3.1 Introduction ............................................................................................................... 38 3.2 Materials and methods .............................................................................................. 39 3.2.1 Materials and reagents ....................................................................................... 39 3.2.2 Sample selection, preparation and analytical methods ....................................... 39 IV 3.2.3 Sequential extraction procedure ......................................................................... 42 3.2.4 Powellite precipitation ......................................................................................... 43 3.2.5 Mobilization test for weakly bound Mo and As .................................................... 44 3.3 Results ...................................................................................................................... 44 3.3.1 Sequential extraction procedure results .............................................................. 44 3.3.1.1 Molybdenum ................................................................................................. 45 3.3.1.2 Arsenic ......................................................................................................... 48 3.3.2 Dissolving aquifer matrix samples in groundwater and DDI water ....................... 51 3.4 Discussion ................................................................................................................. 56 3.4.1 Estimation of the potential mobility of Mo and As ................................................ 56 3.4. 2 Exchangeable phase of Mo and As ................................................................... 61 3.5 Conclusions............................................................................................................... 62 Chapter 4. Primary sources of molybdenum and arsenic .............................................. 64 Abstract ............................................................................................................................. 64 4.1 Introduction ............................................................................................................... 65 4.2 Materials and methods .............................................................................................. 67 4.2.1 Selection and preparation of samples for CRS method ...................................... 67 4.2.2 Chromium-reducible sulfur method ..................................................................... 68 4.2.3 Quantification of CRS ......................................................................................... 71 4.2.4 Powellite ............................................................................................................. 71 4.3 Results ...................................................................................................................... 72 4.3.1 Chromium reduction sulfur results ...................................................................... 72 4.3.2 Comparing the results obtained by CRS method with SEP ................................. 76 4.3.3 Dissolving the synthesized powellite in groundwater and DDI water ................... 78 4.4 Discussion ................................................................................................................. 79 4.4.1 Possible sources of Mo and As in sedimentary rocks ......................................... 79 4.4.2 Pyrite .................................................................................................................. 80 4.4.3 Organic matter .................................................................................................... 83 4.4.4 Powellite ............................................................................................................. 84 4.5 Conclusions............................................................................................................... 84 Chapter 5. Impact of adsorption (hydrous ferric oxides and humic acid) and desorption (hydrous ferric oxides) reactions on the mobilization of molybdenum and arsenic from the aquifer matrix .............................................................................................. 86 Abstract ............................................................................................................................. 86 5.1 Introduction ............................................................................................................... 87 5.2 Materials and methods .............................................................................................. 89 5.2.1 Reagents, sample selection and analytical methods ........................................... 89 5.2.2 Preparation of HFO ............................................................................................ 90 V 5.2.3 Batch experiments .............................................................................................. 90 5.2.4 Sorption type of Mo and As onto HFO ...............................................................