1. Office of Research and Development, National Exposure Research Laboratory, US Environmental Protection Agency, Cincinnati, Ohio 45268 USA
2. Region 4, Watershed Protection Division, US Environmental Protection Agency, Atlanta, Georgia 30303 USA
3. Department of Forestry, University of Kentucky, Lexington, Kentucky 40546 USA
4. Department of Biology, University of Louisville, Louisville, Kentucky 40292 USA
5. Office of Research and Development, National Exposure Research Laboratory, US Environmental Protection Agency, Athens, Georgia 30605 USA