1. Department of Geology & Planetary Science, 4107 O'Hara Street; University of Pittsburgh; Pittsburgh PA 15260 USA
2. USDA-ARS, Hydrology and Remote Sensing Laboratory; Beltsville MD 20705 USA
3. USDA-ARS; Environmental Management and Byproducts Utilization Laboratory; Beltsville MD 20705 USA
4. Electric Power Research Institute; 3420 Hillview Avenue Palo Alto CA 94304 USA