1. Iron Oxidation Kinetics Denae Athay Working with Jessica Brumley, Danette Miller, Emily Spargo, Kim Wahnee, Dr. Nairn and Dr. Strevett REU 2000

2. Introduction to the site… Mayer Ranch Volunteer wetland Cattail marsh receiving metal rich mine discharge Two upwelling rich in alkalinity and CO 2 Proposed site for remediation

4. Introduction to the Experiment… Iron is discharged in reduced form Immediately begins to oxidize Abiotic: oxygen from the atmosphere Biotic: iron oxidizing bacteria Thiobacillus ferrooxidans, Metallogium, Leptothrix Fe +2 + ¼ O 2 + H + = Fe 3+ + ½ H 2 O Fe 3+ + 3H 2 O = Fe(OH) 3 (s) + 3H +

5. What we know… Time Fe+2 Biotic Abiotic

6. What we don’t know… Which process is dominant Biotic oxidation normally dominates in acid mine drainage Conditions not ideal for bacteria Mayer is net alkaline with neutral pH Why we care Remediation design to enhance natural oxidation process

7. Our Hypothesis... The dominant iron oxidation process is abiotic

8. How we wanted to test this… Sample mine drainage as a function of time to measure decrease in ferrous iron Bacteria removed from one microcosm via 0.2  m filter Comparison of iron oxidation rates indication dominant reaction

9. The field design… Filter Seep Unfiltered Microcosm Filtered Microcosm

10. The field design… Step 1: pump mine drainage into microcosms (1 filtered to remove bacteria) Step 2: microcosms placed in marsh to keep temperature constant Step 3: samples taken from each at regular intervals (acidified) In-situ measurements to monitor reactions T, Alkalinity, Conductivity, Turbidity, DO, Salinity Performed at both seeps and middle of marsh

13. Back in the lab… Samples analyzed Ferrous iron concentration Total iron concentration

14. Back in the lab… This involved… 126 ferrous iron titrations 23 hours hot acid digestions 57 atomic absorption spectrophotometer analysis

20. Conclusions… Our data supports our hypothesis Abiotic oxidation is dominant Biotic oxidation is minimal Remediation of the site Aeration can drive the reaction to precipitate out the iron

21. If I knew then what I know now... Contamination is important to prevent Pumping aerates the sample Filter the samples Take an initial sample Avoid long periods without sampling Plan ahead on sleeping arrangements

22. Acknowledgement… Dr. Nairn

24. Acknowledgement… Dr. Nairn Dr. Strevett

26. Acknowledgement… Dr. Nairn Dr. Strevett NSF REU Sharon & Janna Robbins Rebecca Jim Carrie Evenson Jane Sund Erin Breetzke Lisa Hare Todd Wolfard Jake Manko Danette Miller Jessica Brumley

28. Acknowledgement… Dr. Nairn Dr. Strevett NSF REU Sharon & Janna Robbins Rebecca Jim Carrie Evenson Jane Sund Erin Breetzke Lisa Hare Todd Wolfard Jake Manko Danette Miller Jessica Brumley Kim Wahnee

30. Acknowledgement… Dr. Nairn Dr. Strevett NSF REU Sharon & Janna Robbins Rebecca Jim Carrie Evenson Jane Sund Erin Breetzke Lisa Hare Todd Wolfard Jake Manko Danette Miller Jessica Brumley Kim Wahnee Emily Spargo

32. Any Questions?