Three-Component Storm Hydrograph Separation of a Karst Spring Contaminated by Polychlorinated Biphenyls in Central Indiana

Abstract

Abstract Hydrogen and carbon isotopes were used to infer the sources of spring discharge at Illinois Central Emergence during a major storm event. The stable isotopes of hydrogen allowed for the separation of pre-storm groundwater from storm water across a storm hydrograph. The carbon isotopes were then used to separate further the pre-storm water into epikarst and phreatic storage. The two component hydrograph separation using hydrogen isotopic data indicates that the pre-storm water (epikarst and phreatic) constitute a higher percentage of the total discharge than storm water for the duration of the storm event. The three component separation using carbon isotopic data indicates that the Illinois Central Emergence draws heavily from the epikarst zone throughout the storm event. For the May/June 1997 storm event at Illinois Central Emergence, the relative percentages of storm, epikarst, and phreatic water were 5, 90, and 5%, respectively. This information aids in the investigation of the storage and transport of subsurface contaminants and also may be used to develop and implement a remediation plan to address the contaminants present at the site.