1. Department of Soil and Crop
Sciences, Colorado State University, Fort
Collins, Colorado 80523-1170, United States
2. National Water Quality Laboratory, U.S. Geological Survey, Denver Federal Center, Denver,
Colorado 80225-0046, United States
3. Institute for Livestock and the
Environment, Colorado State University,
Fort Collins, Colorado 80523-1170, United States
4. Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523-1872,
United States