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Response to Comment on “A Polymer Membrane Containing Fe0 as a Contaminant Barrier” We thank Benson and Edil (1) for pointing out the shortcoming in the Introduction of our paper (2), which we should have corrected. In response to their comment, we provide the following revised passage: In the past, leakage from landfills and contaminant containment sites was a common source of sediment and groundwater contamination (3, 4). For example, contamination associated with unlined landfills accounts for 15% of the National Priority List (NPL) sites (5). Current technologies have reduced such contamination significantly (6). In modern landfills, membranes composed of high-density polyethylene (HDPE) or poly(vinyl chloride) (PVC) are often used (4, 7). Even these polymer barriers, however, cannot completely prevent leakage. The leakage may be caused by physical failure, improper installation of the barrier, or diffusion of contaminants through the barrier material (8-12). Our intent was not to misrepresent the performance of current waste containment systems. We are seeking methods to further improve the performance by slowing one of the possible leakage pathways.
Literature Cited (1) Benson, C. H.; Edil, T. B. Environ. Sci. Technol. 2004, 38, 5263. (2) Shimotori, T.; Nuxoll, E. E.; Cussler, E. L.; Arnold, W. A. Environ. Sci. Technol. 2004, 38 (7), 2264-2270. (3) National Research Council. Alternatives for Ground Water Cleanup; National Academy Press: Washington, DC, 1994. (4) LaGrega, M. D.; Buckingham, P. L.; Evans, J. C. Environmental Resources Management. Hazardous Waste Management; McGraw-Hill: New York, 2001.
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(5) U.S. Environmental Protection Agency. Final National Priorities List (NPL) Sites; http://www.epa.gov/superfund/sites/query/ queryhtm/nplfin1.htm (accessed May 2003). (6) Bonaparte, R.; Daniel, D.; Koerner, R. Assessment and Recommendations for Improving the Performance of Waste Containment Systems; EPA/600/R-02/099; U.S. Environmental Protection Agency: Cincinnati, OH, 2002. (7) Koerner, R. M. Designing with Geosynthetics; Prentice Hall: Upper Saddle River, NJ, 1998. (8) Workman, J. P.; Keeble, R. L. In Sanitary Landfilling: Process, Technology and Environmental Impact; Christensen, T. H., Cossu, T. H., Stegmann, R., Eds.; Academic Press Inc.: San Diego, CA, 1989; pp 301-309. (9) Rowe, R. K.; Fraser, M. J. Proceedings of the Geoenvironment 2000; American Society of Civil Engineers: Reston, VA, 1995; pp 270-284. (10) Hsuan, G. Y. Geotext. Geomembr. 2000, 18 (1), 1-22. (11) Akgu ¨ n, H. Environ. Geol. 1997, 30 (3/4), 209-214. (12) Foose, G.; Benson, C.; Edil, T. J. Geotech. Geoenviron. Eng. 2002, 128 (5), 391-403.
T. Shimotori and W. A. Arnold* Department of Civil Engineering University of Minnesota 500 Pillsbury Drive SE Minneapolis, Minnesota 55455
E. E. Nuxoll and E. L. Cussler Department of Chemical Engineering and Materials Science University of Minnesota 421 Washington Avenue SE Minneapolis, Minnesota 55455 ES040490L
10.1021/es040490l CCC: $27.50
2004 American Chemical Society Published on Web 08/28/2004
