1. Tracing the Sulfur Cycle

4. Sulfate reduction 2CH 2 O + SO 4 2–  H 2 S + 2HCO 3 – SO 4 2– + 8e – + 9H +  HS – + 4H 2 O  G° r = –192.36 kJ/mol log K = 33.7 33.7 = log a HS– – log a SO42– – 8 log a e– – 9 log a H+ For a SO 4 /HS activity ratio = 1: pe = 4.21 – 9/8 pH

9. -10 -5 0 5 10 1520 051015202530 Devonian marine evaporite Sulphide oxidation 2300 Level 3500 Level 4500 Level 49-5300 Level Tailings water SO 4 (mg/L) 200 500 700 1000  34 S ‰ CDT  18 O sulphate ‰ VSMOW Brine Con Mine, Yellowknife

11. Sulfur systematics in the Waterloo Aquifer Ramon Aravena

13.  34 S Data in Groundwater Kitchener-Waterloo Aquifer

25. Sulfate Reduction 2CH 2 O + SO 4 =  H 2 S + 2HCO 3 - -27 ‰ -27 ‰ Methanogenesis CH 3 COOH  CH 4 + CO 2 CO 2 + H 2 O  CH 4