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(204) Selenium uptake by vegetation from the Southeast Idaho phosphate mines region.
Mackowiak, Cheryl*,1, Amacher, Michael1, Herring, James2, 1 USDA-FS, Rocky Mountain Research Station, Logan, UT2 US Geological Survey, Denver, CO
ABSTRACT- As part of a series of geoenvironmental studies on the mobilization and fate of selenium (Se) in the Permian Phosphoria Formation of Southeast Idaho and the Western U.S., vegetation samples were collected along transects established at the Idaho Wooley Valley (WV) units 1, 3, and 4 waste rock dumps and compared with undisturbed locations at Dairy Syncline, Deer Creek, Dry Valley, Maybe Canyon, and Rasmussen Ridge. Additionally, plant samples were collected from wetlands associated with waste rock dumps and compared with samples collected from a reference wetland. Transect vegetation samples were collected from both reclamation forages and native plant species. The oven-dried tissue was analyzed for Se using hydride generation followed by atomic absorption spectroscopy. The wetland vegetation had mean tissue Se above 10 mg kg-1, whereas tissue Se from the reference wetland was an order of magnitude less. Vegetation sampled near a seep contained an order of magnitude more Se than vegetation sampled 160 m from the seep, suggesting some Se immobilization may have occurred along the flow path. The mean Se concentration in vegetation from WV unit 4 was approximately 30 mg kg-1, while reference locations (excluding Maybe Canyon) were below 2 mg kg-1. Legumes tended to contain the most (65 mg kg-1) Se of all sampled lifeforms. Additionally, wetland grasses and trees sampled at waste rock dumps also had higher Se levels than other lifeforms. Deeply rooted vegetation such as legumes and trees may act as a bioindicator of Se availability and help predict Se leaching potentials within waste rock dumps.
Key words: selenium, phosphoria, vegetation, bioindicator
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