1. U.S. Geological Survey, 4821 Quail Crest Place, Lawrence, Kansas 66049, Department of Chemistry, The University of Kansas, Lawrence, Kansas 66045, U.S. Geological Survey, 401 Hardin Road, Little Rock, Arkansas 72211, U.S. Geological Survey, 956 National Center, 12201 Sunrise Valley Drive, Reston, Virginia 22192, and U.S. Geological Survey, 408 Federal Center, Denver, Colorado 80225-0046