Analysis of Dissolved Selenium Loading for Selected Sites in the Lower Gunnison River Basin, Colorado, 1978-2005

Thomas, Judith C.; Leib, Kenneth J.; Mayo, John W.

doi:10.3133/sir20075287

Cited by 2 publications

(1 citation statement)

References 9 publications

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“…Contaminants of major interest that are released from the Mancos include nitrate, selenium, sulfate, and uranium. Contamination of surface drainages by salts and selenium released from the Mancos is well established; − however, little is known about concentrations in groundwater and few data are available for uranium . Because Mancos Shale contains constituents similar to those in uranium mill tailings, differentiating the natural (Mancos-derived) component from the anthropogenic (mill-derived) component in proximal groundwater is problematic.…”

Section: Introductionmentioning

confidence: 99%

Naturally Occurring Contamination in the Mancos Shale

Morrison

Goodknight

Tigar

et al. 2012

Environ. Sci. Technol.

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Some uranium mill tailings disposal cells were constructed on dark-gray shale of the Upper Cretaceous Mancos Shale. Shale of this formation contains contaminants similar to those in mill tailings. To establish the contributions derived from the Mancos, we sampled 51 locations in Colorado, New Mexico, and Utah. Many of the groundwater samples were saline with nitrate, selenium, and uranium concentrations commonly exceeding 250, 000, 1000, and 200 μg/L, respectively. Higher concentrations were limited to groundwater associated with shale beds, but were not correlated with geographic area, stratigraphic position, or source of water. The elevated concentrations suggest that naturally occurring contamination should be considered when evaluating groundwater cleanup levels. At several locations, seep water was yellow or red, caused in part by dissolved organic carbon concentrations up to 280 mg/L. Most seeps had (234)U to (238)U activity ratios greater than 2, indicating preferential leaching of (234)U. Seeps were slightly enriched in (18)O relative to the meteoric water line, indicating limited evaporation. Conceptually, major ion chemical reactions are dominated by calcite dissolution following proton release from pyrite oxidation and subsequent exchange by calcium for sodium residing on clay mineral exchange sites. Contaminants are likely released from organic matter and mineral surfaces during weathering.

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Section: Introductionmentioning

confidence: 99%

Naturally Occurring Contamination in the Mancos Shale

Morrison

Goodknight

Tigar

et al. 2012

Environ. Sci. Technol.

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Salinity and selenium yield maps derived from geostatistical modeling in the lower Gunnison River Basin, western Colorado, 1992–2013

Williams¹,

Gidley²,

Stevens³

2023

Scientific Investigations Report

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Vertical coordinate information is referenced to the North American Vertical Datum of 1988 (NAVD88).Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD83).Elevation, as used in this report, refers to distance above the vertical datum. Supplemental InformationConcentrations of chemical constituents in water are given in either milligrams per liter (mg/L) or micrograms per liter (µg/L).As used in this report, load relates the mass of a constituent for a specified unit of time. Load is specified for annual or seasonal time periods and reported as the mean in tons per day for salinity (total dissolved solids) and pounds per day for selenium.As used in this report, yield is mass per time per unit of area. Yield of salinity (total dissolved solids) is in units of tons per year per acre, and selenium yield is in units of pounds per day per acre.The water year is defined as the 12-month period from October 1 through September 30. The water year is designated by the calendar year in which it ends. Thus, the year ending

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Analysis of Dissolved Selenium Loading for Selected Sites in the Lower Gunnison River Basin, Colorado, 1978-2005

Cited by 2 publications

References 9 publications

Naturally Occurring Contamination in the Mancos Shale

Naturally Occurring Contamination in the Mancos Shale

Salinity and selenium yield maps derived from geostatistical modeling in the lower Gunnison River Basin, western Colorado, 1992–2013

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