title: Reconstructing the history of mining and remediation in the Coeur d'Alene, Idaho Mining District using lake sediments.
abstract: Mining that began in the late 1800s intensified during World War II contaminating Lake Coeur d'Alene sediments with potentially toxic elements. We used 80y of the sediment record to reconstruct metal(loid) loadings to the lake and quantitatively evaluate the effectiveness of tailings management. Sediment core analysis for pollen, chronological markers, and metal(loid)s permitted stratigraphic reconstruction showing that contaminant loading decreased after tailings pond construction, but that most metal(loid) concentrations exceed recommended limits. Arsenic concentrations (250-450 mg kg(-)(1)) at the sediment-water interface are potentially toxic; however, low P concentrations in recent sediments (1.0-1.4 mg kg(-)(1)) inhibit eutrophication and the concomitant release of soluble As. Zinc (3 g kg(-)(1)), Cd (10 mg kg(-)(1)), Ag (10 mg kg(-)(1)), and Cu (90 mg kg(-)(1)) concentrations are now lower than in sediments deposited during active mining, but remain an environmental concern. Sedimentary Cr and Pb concentrations have not changed in the last 50y, because tailings continue to enter the lake. Although modern Cr concentrations (40 mg kg(-)(1)) are unlikely to cause toxicity, current Pb concentrations (4 g kg(-)(1)) exceed acceptable limits, creating challenges for remediation. Strategies to manage other mining-contaminated watersheds should include consideration of elemental differences when evaluating remediation effectiveness.
authors.affiliation: Division of Soil & Land Resources, 875 Perimeter Drive, MS 2339, University of Idaho, Moscow, ID 83844-2339, USA. Electronic address: mmorra@uidaho.edu.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Morra
authors.affiliation: Division of Soil & Land Resources, 875 Perimeter Drive, MS 2339, University of Idaho, Moscow, ID 83844-2339, USA. Electronic address: meghan.carter@gmail.com.
authors.forename: Meghan M
authors.initials: MM
authors.lastname: Carter
authors.affiliation: Department of Geological Sciences, 875 Perimeter Drive, MS 3022, University of Idaho, Moscow, ID 83844-3022, USA. Electronic address: rember@uidaho.edu.
authors.forename: William C
authors.initials: WC
authors.lastname: Rember
authors.affiliation: Geology Department, 217 McGlothlin Street Hall, The College of William & Mary, Williamsburg, VA 23187, USA. Electronic address: jmkaste@wm.edu.
authors.forename: James M
authors.initials: JM
authors.lastname: Kaste
mesh_terms: D001151:Arsenic / Q000032:analysis; D004784:Environmental Monitoring / Q000379:methods*; D019015:Geologic Sediments; D007061:Idaho; D060106:Lakes / Q000737:chemistry*; D008906:Mining; D015032:Zinc / Q000032:analysis
chemical_list: D015032:Zinc; D001151:Arsenic
keywords: Lake sediments; Metal contamination; Metals; Mine tailings; Mining