Patrick L. Brezonik is Professor Emeritus in the Department of Civil, Environmental, and Geo- Engineering at the University of Minnesota. His research interests have included various surface water quality issues, nutrient chemistry, natural organic matter, and applications of satellite imagery to analyze large-scale patterns in surface water quality. William A. Arnold is the Distinguished McKnight University and Joseph T. Rose S. Ling Professor in the Department of Civil, Environmental, and Geo- Engineering at the University of Minnesota. His research interests include transformation and remediation of anthropogenic chemicals in the environment, photochemistry, and surface-mediated redox processes.