1. Ground Water

2. Kristina Loen Wei Zheng

3.  Groundwater important of drinking  Pollution industry/agriculture: near surface abandoned, obtained from deeper anoxic aquifers.  Anoxic redox processes important for water quality in deep aquifers  Anoxic RØMØ aquifer: inorganic geochemical processes+microbiologically mediated redox processes+thermodynamics

4.  This Study  Focus: geochemistry of Fe-oxide reduction/sulfate reduction/methanogenesis mediated by microorganisms.  Shallow marine sand rather dune sand of RØmØ  High flow rate, different infiltration composition, lithologically less homogeneous  Useful interpreting other anaerobic aquifer

5.  Northern Zealand, Denmark  10m deep phreatic postglacial sandy aquifer, lower 7-8m occasional gravely, with pebbles; upper 2-3m homogeneous eolian sand with occasional paleosols.  Porosities 25-30%, Hydraulic conductivity 1.3×10 -4 m/s  Groundwater table 1.2mbs (meter below surface)

7.  Groundwater: stainless steel drive point piezometers  H 2 sampling: a bundle of 10mm PVC with 20mm disc-shape 20μm nylon screen, field measure: bubble stripping (Chapelle & McMahon 1991)  Methane: syringe, injected pre-weighted 13ml evacuated blood vial, frozen below -18°C  Others(anions, acetate,formate): filtered anaerobically through 0.2μm filter, 5ml polypropylene vials, frozen below -18°C  pH, O 2, conductivity: field measured.  Alkalinity: Gran titration  Fe 2+, H 2 S: spectrophotometric  In Lab: Cation-AAS; Anion-ion chromatography; methane-gas chromatography; acetate/formate: ion exclusion chromatography

8.  Radiotracer Rate: 50mmID, 1.5mm thick, stainless steel tubing ; After retrieval core, 1mm holes and 12.5~25uL radiotracer injected, interval of 10~12cm. Incubation  CO 2 reduction-H 14 CO 3 - 22h  Acetate - 14 CH 3 COONa 14h  Sulfate reduction-H 2 35 SO 4 18h  incubation ended by freezing cores to -50°C

9.  α=1.06 (SRR-Sulfate Reduction Rate) (Jakobsen&Postma 1994)  α=1.08 (Hansen, 1998)  (CO 2 Reduction Rate)  α=1.08 (Acetate Turnover Rate) 

10.  Sediment Parameters: Fe, Organic and Inorganic carbon, Sulfide as AVS (Acid Volatile) and CRS (Chromium Reducible)  Sediment bound organic carbon: non acid desorbable sedimentary organic carbon (NADSOC) Inorganic carbon=TC-NADSOC-ADSOC

11. Inorganic compounds /shell With increase Ca, Mg Reduction of Fe- oxides

12. Dry Deposition /Earlier Inundation

13. Dry Deposition in Pyrite Oxidation Fe-oxide reduction/sulfate reduction/ increase in methane

15. Degrade/Oxidation Organic Matter release

16. Transport organic matter from surface to aquifer

18.  Na + slightly delayed in terms of vertical transportation  Ion exchange affect cations, also affect Ca 2+, Mg 2+, K +  Mg 2+ displace Ca 2+  Ca 2+ affected by dissolution of calcite, ion exchange release Ca 2+, precipitate Ca 2+  Al 3+ not affected by ion exchange

19.  Sulfate reduction rate highly correlated with where sulfide found in sediment  AVS (Acid Volatile Sulfur) only in 5~6 mbs, transform of AVS to CRS (Chromium Reduced Sulfur)  Sulfate reduction rate extremely small, sulfate input higher, so sulfate reduction took place in large volume of sediment.  Organic matter low

21. Average - 4.5kJ/mol, adequate for ATP synthesis High Low

22. Similar to RØmØ aquifer, but 1) No pool AVS below sulfate reducing zone, indicating enough sulfide for conversion, related to higher measurable sulfide concentration 2) H 2 level high enough to sustain methanogenesis, removing need for stagnant microniches. 3) Data indicating influx organic matter from soil, sustaining redox processes in system

23. Questions?