Costa Rica Water (IMAGE) University of Texas at Arlington Caption In each water sample, researchers examined nitrate isotopes, which are unique, allowing the team to trace the water sample back to where it originated. Credit Photo courtesy Ricardo Sánchez-Murillo Usage Restrictions Photo credit License Original 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.