title: Isotopic mapping of groundwater perchlorate plumes.
abstract: Analyses of stable isotope ratios of chlorine and oxygen in perchlorate can, in some cases, be used for mapping and source identification of groundwater perchlorate plumes. This is demonstrated here for large, intersecting perchlorate plumes in groundwater from a region having extensive groundwater perchlorate contamination and a large population dependent on groundwater resources. The region contains both synthetic perchlorate derived from rocket fuel manufacturing and testing activities and agricultural perchlorate derived predominantly from imported Chilean (Atacama) nitrate fertilizer, along with a likely component of indigenous natural background perchlorate from local wet and dry atmospheric deposition. Most samples within each plume reflect either a predominantly synthetic or a predominantly agricultural perchlorate source and there is apparently a minor contribution from the indigenous natural background perchlorate. The existence of isotopically distinct perchlorate plumes in this area is consistent with other lines of evidence, including groundwater levels and flow paths as well as the historical land use and areal distribution of potential perchlorate sources.
authors.affiliation: Department of Earth and Environmental Sciences, University of Illinois at Chicago (MC-186), 845 West Taylor Street, Rm. 2442, Chicago, IL 60607-7059, USA. sturchio@uic.edu
authors.forename: Neil C
authors.initials: NC
authors.lastname: Sturchio
authors.forename: John R
authors.initials: JR
authors.lastname: Hoaglund
authors.forename: Roy J
authors.initials: RJ
authors.lastname: Marroquin
authors.forename: Abelardo D
authors.initials: AD
authors.lastname: Beloso
authors.forename: Linnea J
authors.initials: LJ
authors.lastname: Heraty
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Bortz
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Patterson
mesh_terms: D002140:California; D002713:Chlorine / Q000032:analysis; D060587:Groundwater / Q000032:analysis*; D009566:Nitrates / Q000032:analysis; D010103:Oxygen Isotopes / Q000032:analysis; D010472:Perchlorates / Q000032:analysis*
chemical_list: D009566:Nitrates; D010103:Oxygen Isotopes; D010472:Perchlorates; D002713:Chlorine; C494474:perchlorate