1. Acid Mine Drainage : Metals in Water and Sediment Upper Lefthand Creek, Northwestern Boulder County 2003 REU Program – August 7, 2003 Roshan Cholas, University of California at Berkeley Joe Ryan, Alice Wood and Lily Isenhart, University of Colorado at Boulder

2. Upper Lefthand Creek

3. Mines Affecting Lefthand Creek

4. Acid Mine Drainage Sulfuric acid is produced from the interaction of sulfide minerals in rocks with water and air. The acidic conditions leach metals from mine tailings. The metal rich water drains into nearby streams.

5. Acid Mine Drainage Big Five Pond 2 FeS 2 (s) + 7 0 2 + 2 H 2 O  2 Fe 2+ (aq) + 4 SO 4 2- + 4 H + Fe 2+  Fe 3+ + e - FeS 2 (s) + 14 Fe 3+ + 8 H 2 O  15 Fe 2+ +2 SO 4 2- + 16H + Fe 3+ + 3 OH -  Fe(OH) 3 (s)

6. Problem Statement Inputs of metals from mines enter the creek but do not remain in the water column. A major flood could pose a risk to drinking water by carrying metal rich sediment to the water intake of the Left Hand Water District.

7. Objectives Since the metals do not remain in the water column we hypothesize that they are ending up in the sediment through adsorption, settling or precipitation. Zn, Cu and Pb have different tendencies to adsorb so differences should be seen in their locations in the stream. A comparison of metal loadings in the water with concentrations in the sediment gives a better understanding of the fate of metals in the creek.

8. Sediment Sample Sites

9. Methods ~1 L of Sediment per site Dried at 100°C Sieved 20 min. Used particles < 63 µ m

10. Methods ACID DIGESTION 1 gram sediment 20 mL HCl (~1.5 M) 0.2 mL H 2 O 2 (30%) Shaking water bath: 3 hrs 55-60°C 120 rpm

11. Methods Samples centrifuged Liquid extracted using syringe Inductively coupled plasma – atomic emission spectrophotometry (ICP-AES) used to analyze for Zn, Cu, Pb, Al, Fe, and Mn

12. Results

13. Results

14. Results

15. Results

16. Conclusion Higher concentrations of Zn, Cu, and Pb in the Sediment correspond to higher concentrations in the water. Pb has a higher tendency to adsorb to the sediment than Zn or Cu.

17. Acknowledgements National Science Foundation Joe Ryan Alice Wood Lily Isenhart JoAnn Silverstein Joy Jenkins John Drexler and Fred Luiszer, Laboratory for Environmental and Geological Studies, for ICP-AES analysis