Chris Sommerfield, University of Delaware (IMAGE) University of Delaware Caption Chris Sommerfield is tracking radioactive iodine, used in medical treatments, through waterways to learn how substances travel along rivers to the ocean. Credit Bob Bowden Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.