1. Departments of Chemistry and Physical and Environmental Sciences, University of Toronto at Scarborough, 1265 Military Trail, Toronto, Ontario, Canada M1C 1A4, Aquatic Ecosystem Protection Research Division, Environment Canada, 867 Lakeshore Road, Burlington, Ontario, Canada L7R 4A6, and Instituto Regional de Estudios en Sustancias Toxicas, Campus Omar Dengo, Universidad Nacional, Heredia, Costa Rica