1. Department
of Animal and Avian Sciences, University of Maryland, College Park, Maryland 20742, United States
2. Organic
Geochemistry Research Laboratory, U.S. Geological Survey, 4821 Quail Crest
Place, Lawrence, Kansas 66049, United States
3. Iowa
Water Science Center, U.S. Geological Survey, 400 S. Clinton Street, Iowa City, Iowa 52240, United States
4. Columbia
Environmental Research Center, U.S. Geological Survey, 4200 New Haven
Road, Columbia, Missouri 65201, United States