1. Columbia Environmental Research Center, U.S. Geological Survey, Columbia, Missouri 65201, United States
2. National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, United States
3. Leetown Science Center, U.S. Geological Survey, Kearneysville, West Virginia 25430, United States
4. Central Midwest Water Science Center, U.S. Geological Survey, Iowa City, Iowa 52240, United States
5. Oregon Water Science Center, U.S. Geological Survey, Portland, Oregon 97201, United States
6. New Jersey Water Science Center, U.S. Geological Survey, Lawrenceville, New Jersey 08648, United States
7. National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Duluth, Minnesota 55804, United States
8. South Atlantic Water Science Center, U.S. Geological Survey, Columbia, South Carolina 29210, United States