title: Sources and ages of fine-grained sediment to streams using fallout radionuclides in the Midwestern United States.
abstract: Fallout radionuclides,7Be and210Pbex, sampled in bed sediment for 99 watersheds in the Midwestern region of the United States and in 15 samples of suspended sediment from 3 of these watersheds were used to partition upland from channel sources and to estimate the age or the time since the surface-derived portion of sediment was on the land surface (0-∼1 year). Channel sources dominate: 78 of the 99 bed material sites (79%) have >50% channel-derived sediment, and 9 of the 15 suspended-sediment samples (60%) have >50% channel-derived sediment.7Be was detected in 82 bed sediment samples and all 15 suspended-sediment samples. The surface-derived portion of 54 of the 80 (68%) streams with detectable7Be and210Pbexwere ≤ 100 days old and the surface-derived portion of all suspended-sediment samples were ≤ 100 days old, indicating that surface-derived fine-grained sediment moves rapidly though these systems. The concentrations of two hydrophobic pesticides-DDE and bifenthrin-are correlated with the proportion of surface-derived sediment, indicating a link between geomorphic processes and particle-associated contaminants in streams. Urban areas had the highest pesticide concentrations and the largest percentage of surface-derived sediment. Although the percentage of surface-derived sediment is less than channel sources at most of the study sites, the relatively young age of the surface-derived sediment might indicate that management actions to reduce sediment contamination where the land surface is an important source could have noticeable effects.
authors: U.S. Geological Survey, Maryland-Delaware-DC Water Science Center, Baltimore, MD 21228 USA. Electronic address: agellis@usgs.gov.
authors: Allen C
authors: AC
authors: Gellis
authors: U.S. Geological Survey, National Research Program, Menlo, Park, CA 94025 USA.
authors: Christopher C
authors: CC
authors: Fuller
authors: U.S. Geological Survey, Texas Water Science Center, Austin, TX 78754 USA.
authors: Peter C
authors: PC
authors: Van Metre
mesh_terms: D004784:Environmental Monitoring; D019015:Geologic Sediments / Q000737:chemistry*; D015146:Midwestern United States; D011868:Radioisotopes; D045483:Rivers / Q000737:chemistry*; D014874:Water Pollutants, Chemical
chemical_list: D011868:Radioisotopes; D014874:Water Pollutants, Chemical
keywords: Midwest United States; Radionuclides; Sediment sources