Uptake of Lead by Iron Corrosion Scales: Effects of Iron Mineralogy and Orthophosphate A thesis submitted to the Graduate School of the University of Cincinnati in partial fulfillment of the requirements for the degree of Master of Science in the Department of Geology of the College of Arts and Sciences by Lauren W. Wasserstrom B.A. University of Cincinnati 2014 Committee Chair: J. Barry Maynard, Ph.D. I ABSTRACT Owing to its toxic nature, lead (Pb) in tap water (released from pipes, solder, and brass fittings) poses an important risk to human health. High concentrations of lead have recently been found to accumulate in iron corrosion scales formed in galvanized iron pipes in household plumbing, but the interaction between iron and lead in this situation is not well understood. Therefore, a model system of simulated iron-bearing corrosion scales in household plumbing was devised to isolate the variables that influence lead uptake. Continuous flow experiments were performed to test the interaction of lead with the iron minerals in corrosion scales in household plumbing, and to assess the influence of changing orthophosphate concentration on lead previously accumulated in the analog iron corrosion scales. Serving as laboratory analogs for the capture of lead by iron corrosion products, sediment filters impregnated with various iron oxy-hydroxides that represent actual iron corrosion scale solids were synthesized and tested in a laboratory apparatus. Water quality was monitored and the analog iron corrosion scales were analyzed. A mass balance was performed on lead to evaluate the effectiveness of the iron filter. Results showed that the presence of iron greatly enhances lead uptake by the sediment filter compared to the control containing no iron. Filter efficiency was evaluated using normalized ratios of lead, phosphorous, and copper uptake to the mass of iron (Fe) in the sediment filter. This revealed very different behaviors for the iron minerals. Lead uptake by the filter was highest with feroxyhyte (0.02 mg of Pb per mg of Fe), followed closely by lepidocrocite (0.01), and then by goethite (0.003), magnetite (0.002), and ferrihydrite (0.002). Variable uptake of phosphorous and copper was also observed. Phosphorous was most strongly associated with lepidocrocite, followed by ferrihydrite, feroxyhyte, and magnetite, but did not bind to goethite. Copper was taken up more by feroxyhyte and lepidocrocite with some uptake by goethite and magnetite, but II did not bind to ferrihydrite. Feroxyhyte and lepidocrocite appear to be the most effective scavengers for lead and copper, whereas phosphorous uptake is highest with lepidocrocite. Although lead uptake was highest for feroxyhyte it has not been reported in drinking water corrosion scales. Based on these findings, lepidocrocite was chosen as the most appropriate model corrosion scale. Lepidocrocite-impregnated filters were used in the final stage of the study to evaluate the impact of varying orthophosphate concentrations on lead previously accumulated in the iron-bearing filter. Increasing the orthophosphate levels suppressed the release of lead. However, the effect was only noticeable at 3.5 mg/L as PO4 or higher. These findings confirm the suggestion that galvanized pipes in household plumbing have the ability to trap lead from upstream sources, and emphasize the need to consider galvanized pipes as a significant source of lead in tap water. Furthermore, typical orthophosphate dosing used in the U.S. (< 3.0 mg/L as PO4) will not be sufficient to prevent lead release from galvanized pipes. III IV ACKNOWLEDGEMENTS Foremost, I would like to express my sincere gratitude to my advisor Dr. Barry Maynard for his continuous guidance, support, and patience through every step of my thesis. To my other committee members, Michael Schock, Philip Hart, and Dr. Warren Huff, thank you for your invaluable advice, expertise, and encouragement. I am honored to have had the opportunity to work with this team of extraordinarily talented, dedicated, and inspiring individuals. I thank Keith Kelty and Maily Pham for water quality analyses, and Stephan Harmon from the U.S. Environmental Protection Agency for assisting in SEM analysis. To Dawn Webb and Jeff Swertfeger at the Cincinnati Water Works, thank you for lending laboratory equipment and other supplies, as well as your willingness to help in any way possible. I also thank Nicholas Sylvest with Pegasus Technical Services for helping with laboratory experiments. I am indebted to the Department of Geology for providing support and equipment, and to the Environmental Protection Agency, Office of Research and Development, for which funding for this research via the UC-USEPA Research Traineeship Program was awarded. Last, but certainly not least, thank you to my parents (Jon Wasserstrom; Jayne and Rick Nathans), siblings (Cara and Bryan), and grandparents (Dr. Herbert and Marilyn Bell) for your constant love, support, and encouragement in everything I do. V TABLE OF CONTENTS ABSTRACT ..................................................................................................................... II ACKNOWLEDGEMENTS ............................................................................................ V LIST OF FIGURES ..................................................................................................... VII LIST OF TABLES ...................................................................................................... VIII LIST OF SYMBOLS ..................................................................................................... IX LIST OF APPENDICES ............................................................................................... XI CHAPTER 1: INTRODCUTION ................................................................................... 1 Background ...................................................................................................................... 1 Importance of Iron ........................................................................................................... 3 Motivation ....................................................................................................................... 5 Approach ......................................................................................................................... 6 CHAPTER 2: METHODS AND MATERIALS ........................................................... 9 Study Design.................................................................................................................... 9 Carbon Block Filters ........................................................................................................ 9 Sediment Filters ............................................................................................................. 12 Water Analyses ............................................................................................................. 16 Water Quality Parameters .............................................................................................. 16 Metal Analyses .............................................................................................................. 17 General Protocol ............................................................................................................ 18 CHAPTER 3: RESULTS AND DISCUSSION ........................................................... 26 Stage 1 ........................................................................................................................... 26 Stage 2 ........................................................................................................................... 32 Stage 3 ........................................................................................................................... 38 CONCLUSIONS ............................................................................................................ 59 REFERENCES ............................................................................................................... 63 APPENDIX ..................................................................................................................... 72 VI LIST OF FIGURES Figure 1 Images of sediment filter from field studies ........................................................ 7 Figure 2 Labeled photograph of laboratory apparatus ....................................................... 8 Figure 3 Configuration of laboratory apparatus ............................................................... 20 Figure 4 Sediment filter fabrication process .................................................................... 22 Figure 5 Diagram of the sampling points on the apparatus ............................................. 23 Figure 6 Comparison of metal concentrations in water from both sides of apparatus ..... 43 Figure 7 Total lead accumulated in the Fe1 sediment filter ............................................. 44 Figure 8 Correlation of Pb added to the tank and Pb measured in the tank by ICP......... 45 Figure 9 SEM images of sediment filters from Stage 1 ................................................... 47 Figure 10 Photographs of sediment filters used in Stage 2 .............................................. 48 Figure 11 X-ray diffractograms of iron minerals used in Stages 2 and 3 ........................ 49 Figure 12 Efficiency of iron filters from Stage 2 ............................................................. 50 Figure 13 SEM images