Dr. Matt Helmers, Iowa State University (IMAGE) Iowa State University Caption Nitrates that leach into the soil can affect communities that depend on the rivers for clean drinking water. They can leach into the soil and are carried downstream. These nitrates are believed to contribute to a dead zone in the Gulf of Mexico where few plants or animals survive. Credit ISU photo by Bob Elbert. 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.