This study investigated background levels and uptake rates of organophilic metals, particularly selenium, in ten streams draining portions of the Yukon-Tanana Terrane and Cassiar Platform between Ross River and Watson Lake, Yukon. The study area is suspected to have elevated background metals concentrations and is of interest for mineral exploration and development due to high mineralization. Information on natural metals levels is lacking for this region and for the Yukon in general. Water, sediments, benthic invertebrates and fish (slimy sculpin; Cottus cognatus) were sampled and analyzed for metals concentrations. Benthic invertebrates were identified to genus and percent composition of each species in each stream was calculated. The lack of anthropogenic activity in the area indicates that selenium concentrations found in all sample media and natural, background concentrations. Of all the sample media, concentrations of selenium were highest in sediment; however, sediment selenium concentrations were found to be in a range similar to levels documented at the Kudz Ze Kayah and Viceroy Brewery Creek mines in other regions of the Yukon. Selenium concentrations in water generally exceeded CCME guidelines, but also fell within a range similar to the Kudz Ze Kayah and Viceroy Brewery Creek mines. These findings with respect to selenium levels in water and stream sediments highlight the importance of developing site-specific selenium guidelines for management of aquatic systems. The rate of uptake of selenium in benthic invertebrate and fish tissues was greater than that of the other organophilic metals investigated. Selenium concentrations were generally higher in benthic invertebrates than in fish, likely owing to the detritus-feeding and bottom-dwelling life history of these invertebrates. Weak positive trends were noted in the relationship between selenium concentrations in fish and benthic invertebrates, and between fish and the water column. A significant positive relationship was noted between selenium concentrations in fish and stream sediments. These findings are consistent with past studies documenting dietary sources as the most common uptake pathways for selenium, with water comprising a secondary source. Examination of benthic invertebrate community composition revealed commonly abundant species and species typical of fast-flowing streams with high water quality, which is characteristic of the streams in the study area. The findings of this study provide valuable baseline information on background concentrations of metals, particularly selenium, as well as documentation of benthic invertebrate community composition, in an aquatic system that may experience resource development in the future.

not_specified

At present, little metal speciation information exists for most parts of the Yukon. The current database of knowledge is largely based on research from southern stream environments which tend to be warmer than Yukon streams. This presents a challenge for regulators and practitioners interpreting data from northern systems using guidance that is developed and defined by southern baseline data and effects. This study was designed using a preliminary approach to assist in filling the current information gap. The Selwyn Basin in the Yukon has natural elevated concentrations of metals including arsenic, mercury and selenium (EDI 2008, Gartner Lee 2007). Water quality studies that have been conducted within the Selwyn Basin have not considered the importance of metal speciation and changes in mobility and exposure to aquatic organisms inhabiting lotic watercourses likely impacted by both naturally elevated and anthropogenic (mining related) metal input sources. The objective of this project was to increase the understanding of metal speciation in relation to surface water and sediment metal concentrations within the Selwyn Basin at six discrete lotic watercourse sites over two seasons.

Pollutant loads have been increasing over time in the Elk River, B.C. due to coal mining operations and runoff from associate spoil piles. The Elk River is a tributary to the Kootenay/Kootenai River and Lake Koocanusa. Extensive water chemistry monitoring has been conducted in Lake Koocanusa to assess the impacts from the Elk River, however, this is not the case for the Kootenai River downstream of Lake Koocanusa, downstream of Libby Dam (http://deq.mt.gov/DEQAdmin/LakeKoocanusa). This study generated data on selenium and nutrient concentrations and loads in the Kootenai River (Libby Dam to Canadian border), which will help to differentiate between local loads and loads transported via Lake Koocanusa. Working in cooperation with the U.S. Environmental Protection Agency (USEPA), the U.S. Geological Survey (USGS) collected and analyzed water-column samples in the Kootenai River watershed downstream of Libby Dam. Field data collection also included discharge measurements. The following are key design components of water quality sample collection in the Kootenai River watershed downstream of Libby Dam: Sampling locations: (1) USGS gages on the mainstem Kootenai River: Kootenai River below Libby Dam, MT (USGS site identification number 12301933), Kootenai River at Leonia, ID (12305000), Kootenai River at Tribal Hatchery near Bonners Ferry, ID (12310100), and Kootenai River at Porthill, ID (12322000); (2) USGS gages on tributaries to the Kootenai River: Fisher River near Libby MT (12302055), Yaak River near Troy MT (12304500); (3) Ungaged tributaries: Moyie River near the mouth (12307750). Water quality analyses: (1) Low-level nutrients, total water (3 sampling events) (2) Total selenium, dissolved water (3 sampling events) (3) Selenium speciation, dissolved water (2 events): selenite, Se(IV); selenate, Se(VI); selenocyanate, SeCN; selenomethionine, SeMet; and methylseleninic acid, MeSe(IV). Total dissolved selenium and selenium speciations analyses were performed by Brooks Applied Labs, Bothell, WA. The nutrient samples were analyzed by the USGS National Water Quality Laboratory (NWQL), Lakewood, CO. Secondary, total dissolved selenium analyses were also conducted by the NWQL for a subset of samples for interlaboratory comparisons. The three sampling events were: (1) September 2018, a period of low and stable flows in both the Kootenai River and tributaries; (2) December 2018, a period of low, stable winter flows in the tributaries but unstable and increasing flows in the Kootenai River due to dam releases in preparation for spring runoff (3) May 2019, a period close to annual peak runoff from snowmelt in tributaries plus high dam releases of snowmelt originating in the Canadian Rockies. Results: Results of the selenium sampling are compiled and summarized in this data release. These data and the nutrient data are separately published through the USGS National Water Information System (https://doi.org/10.5066/F7P55KJN). No samples exceeded USEPA’s national recommended aquatic life criteria for selenium, expressed as a water concentration, of 3.1 µg/L. Selenium concentrations in the four mainstem Kootenai River sites had low variability across sites and sampling events, ranging from 0.628 to 1.17 µg/L for the 12 samples, for an average concentration of 0.91 µg/L (± 0.17 µg/L, standard deviation). In all measured concentrations, selenate was the dominant chemical species, accounting for 87% of the total selenium, on average (range 79-94%). Selenium concentrations were less than the detection limit of 0.037 µg/L in all of the tributary samples, indicating that selenium concentrations in the Kootenai River cannot be attributed to tributary sources. Daily average selenium loads in the Kootenai River were estimated by assuming that the width and depth integrated water samples collected were representative of average conditions for that day and were multiplied by daily average discharge volumes of the Kootenai River at those locations. In

Yuma Ridgway’s rail (Rallus obsoletus yumanensis, hereafter, rail) are an endangered species for which patches of emergent marsh within the Salton Sea watershed comprise a substantial portion of habitat for the species’ disjointed range in the southwestern United States. These areas of emergent marsh include: 1) marshes managed by federal (particularly the U.S. Fish and Wildlife Service’s Sonny Bono Salton Sea National Wildlife Refuge (SBSSNWR), state (California Department of Fish and Wildlife), and local (Imperial Irrigation District) resource agencies that are sustained by direct deliveries of Colorado River water; and 2) unmanaged marshes sustained by agricultural drainage water. Management of rail habitat in this arid environment is complicated by increasingly limited availability of unimpaired freshwater owing by recent water management decisions associated with the Quantification Settlement Agreement, and risks posed by potentially harmful concentrations of selenium (Se) found in agricultural drainage water that can readily bioaccumulate in aquatic food webs. To provide timely science for managers, the selenium concentrations in this data release are the basis for summary statistics reported in Ricca et al. 2022. These data comprise selenium concentrations and associated locations and dates of the following matrices sampled to describe pathways of selenium exposure to rails occupying managed and unmanaged marshes: 1) unfiltered surface water, midge larvae (Chironomidae), water boatmen (Corixidae), mosquitofish (Gambusia spp.) and crayfish (Astacidae). Selenium samples were collected from 15 fixed sampling points each in managed and unmanaged marshes during late February, April, and June of 2016, which corresponded to rail pre-nesting, nesting, and fledgling reproductive life-stages, respectively. Two areas within the two treatment types (managed vs. unmanaged marsh) were of particular interest to help assess risks associated with changing Sea dynamics and different water management strategies: 1) a large unmanaged marsh (Morton Bay) unintentionally created in approximately 2008 when it became separated from the Salton Sea as water inflows began to drop and a berm formed from accumulated sediment; and 2) a restored marsh (HZ-9A) managed by the SBSSNWR, which is currently supplied with Colorado River water, but may be sustained in the future by a blend of clean (that is, low Se) Colorado River and agricultural drainage water with higher Se from the Alamo River.

A stream sediment and water survey was carried out in the Coal River area of southeastern Yukon during the summer of 2005. This survey was carried out under a Joint Research Agreement between the Yukon Government (Oil & Gas and Mineral Resources Division of the Department of Energy, Mines and Resources) and the Federal Government, acting through the Earth Science Sector's Metals in the Environment Program. Analytical data accompany this document for 50 elements in stream sediments and 60 variables in waters from a total of 174 sites sampled in 2005. National Geochemical Reconnaissance protocol was used for the collection, preparation and analysis of waters and silts. Samples were collected in the Yukon Territory portion of NTS map sheet 95E, west of the height of land that marks the boundary between Yukon and Northwest Territories and separates the Coal River and Flat River drainage basins.

This Data Release presents multi-agency data for selenium concentrations in ecosystem media that includes water column, suspended particulate material, zooplankton, invertebrates, and fish. Because the data are compiled from multiple sources, the significant figures used to report contaminant concentrations and other metrics may not be internally consistent. These data will serve as the basis for ecosystem-scale modeling of Lake Koocanusa, a bi-national reservoir in Montana and British Columbia. Spreadsheets are ordered in a food-web format to facilitate modeling that emphasizes spatially and temporally paired data. Selenium concentrations are species-specific for fish and taxa-specific for invertebrates to address required specificity for biodynamic dietary modeling. Phytoplankton, zooplankton, and invertebrate densities or biomass are compiled, in addition to fish catches, to help elucidate productivity and identify which groups, taxa, or species are abundant on a seasonal basis. For water quality context, the historical record of selenium concentrations is given, with emphasis on the primary selenium loading site near where the Elk River enters Lake Koocanusa. Spreadsheets with the term "annex" in their file name address a competing toxin, mercury, for fish. Recent high frequency monitoring of selenium concentrations at the international border and at a gaging station below Libby Dam provide a perspective on future selenium data availability. Methodologies are described as federal, provincial, and state agencies transition to a consistent set of protocols to ensure consistency in monitoring for locations on both sides of the border.

This Data Release presents multi-agency data for selenium concentrations in ecosystem media that includes water column, suspended particulate material, zooplankton, invertebrates, and fish. Because the data are compiled from multiple sources, the significant figures used to report contaminant concentrations and other metrics may not be internally consistent. These data will serve as the basis for ecosystem-scale modeling of Lake Koocanusa, a bi-national reservoir in Montana and British Columbia. Spreadsheets are ordered in a food-web format to facilitate modeling that emphasizes spatially and temporally paired data. Selenium concentrations are species-specific for fish and taxa-specific for invertebrates to address required specificity for biodynamic dietary modeling. Phytoplankton, zooplankton, and invertebrate densities or biomass are compiled, in addition to fish catches, to help elucidate productivity and identify which groups, taxa, or species are abundant on a seasonal basis. For water quality context, the historical record of selenium concentrations is given, with emphasis on the primary selenium loading site near where the Elk River enters Lake Koocanusa. Spreadsheets with the term "annex" in their file name address a competing toxin, mercury, for fish. Recent high frequency monitoring of selenium concentrations at the international border and at a gaging station below Libby Dam provide a perspective on future selenium data availability. Methodologies are described as federal, provincial, and state agencies transition to a consistent set of protocols to ensure consistency in monitoring for locations on both sides of the border.

Due to declining water levels and increasing salinity in the Salton Sea which may increase the hazards to wildlife, the U.S. Geological Survey and U.S. Bureau of Reclamation are re-evaluating selenium concentrations in the region. As part of this work, selenium concentrations in water and sediment samples and selected other inorganic constituents were compiled from published reports, public databases, and unpublished archives into a tabulated spreadsheet. This spreadsheet represents a rapid synthesis of available data on selenium concentrations in water and sediment in the region surrounding the Salton Sea, however it does not include all data ever published in the region. Additionally, the data compilation was done with an emphasis on selenium concentrations measured after 2005, therefore earlier selenium data may be under-represented.

Till geochemistry includes copper, lead, zinc, gold, silver, chromium, nickel, mercury, antimony, and arsenic.