title: The seasonal fluctuations and accumulation of iodine-129 in relation to the hydrogeochemistry of the Wolf Creek Research Basin, a discontinuous permafrost watershed.
abstract: The long lived radioisotope (129)I is a uranium fission product, and an environmental contaminant of the nuclear age. Consequently, it can trace anthropogenic releases of (129)I in watersheds, and has been identified as a potential means to distinguish water sources in discharge (Nimz, 1998). The purpose of this work was to identify the sources and mass input of (129)I and trace the transport, partitioning and mass balance of (129)I over time in a remote watershed. We monitored (129)I and other geochemical and isotope tracers (e.g. δ(14)CDIC, δ(13)CDIC, δ(2)H, δ(18)O, etc.) in precipitation and discharge from the Wolf Creek Research Basin (WCRB), a discontinuous permafrost watershed in the Yukon Territory, Canada, and evaluated the use of (129)I as a water end-member tracer. Radiocarbon and geochemical tracers of weathering show that discharge is comprised of (i) groundwater baseflow that has recharged under open system conditions, (ii) spring freshet meltwater that has derived solutes through closed-system interaction with saturated soils, and (iii) active layer drainage. The abundance of (129)I and the (129)I/(127)I ratio correlated with geochemical tracers suggests varying contributions of these three water end-members to discharge. The (129)I concentration was highest at the onset of freshet, reaching 17.4×10(6) atoms/L, and likely reflects the lack of interaction between meltwater and organic matter at that time. This peak in (129)I was followed by a decline over the summer to its lowest value. Mass balance calculations of the (129)I budget show that the input to the watershed via precipitation is nearly one order of magnitude higher than the output suggesting that such arctic watersheds accumulate nearly 90% of the annual input, primarily in soil organic matter. Temporal variations in discharge (129)I concentrations correlated with changes in discharge water sources suggesting that (129)I is a promising hydrologic tracer, particularly when used in concert with other stable and radioisotopes.
authors.affiliation: André Lalonde AMS Lab, Department of Earth and Environmental Science, University of Ottawa, 25 Templeton St., Ottawa, ON K1N 6N5, Canada. Electronic address: mattherod@gmail.com.
authors.forename: Matthew N
authors.initials: MN
authors.lastname: Herod
authors.affiliation: André Lalonde AMS Lab, Department of Earth and Environmental Science, University of Ottawa, 25 Templeton St., Ottawa, ON K1N 6N5, Canada.
authors.forename: Tianjiao
authors.initials: T
authors.lastname: Li
authors.affiliation: Center for Geomicrobiology, Department of Bioscience, Aarhus University, Ny Munkegade 116, 8000 Aarhus C, Denmark.
authors.forename: André
authors.initials: A
authors.lastname: Pellerin
authors.affiliation: André Lalonde AMS Lab, Department of Earth and Environmental Science, University of Ottawa, 25 Templeton St., Ottawa, ON K1N 6N5, Canada.
authors.forename: William E
authors.initials: WE
authors.lastname: Kieser
authors.affiliation: André Lalonde AMS Lab, Department of Earth and Environmental Science, University of Ottawa, 25 Templeton St., Ottawa, ON K1N 6N5, Canada.
authors.forename: Ian D
authors.initials: ID
authors.lastname: Clark
mesh_terms: D062070:Hydrology; D007457:Iodine Radioisotopes / Q000032:analysis*; D065946:Permafrost; D011834:Radiation Monitoring; D045483:Rivers / Q000737:chemistry*; D012621:Seasons; D014875:Water Pollutants, Radioactive / Q000032:analysis*; D015874:Yukon Territory
chemical_list: D007457:Iodine Radioisotopes; C000614963:Iodine-129; D014875:Water Pollutants, Radioactive
keywords: Accelerator mass spectrometry; Hydrologic tracers; Iodine isotopes; Iodine-129; Mass balance; Radiocarbon; Radioisotope tracers; Stable isotopes; Watershed hydrology