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University of New Mexico: Dataset Details, ID=doi:10.6073/pasta/e96864d4ade2a90397dcff0b8ce75645

Superfund Research Program

Immobilization of U, As, and Co-occurring Metals in Mine Wastes

Project Leader: Jose Manuel Cerrato
Co-Investigators: Scott Fendorf (Stanford University), Christopher L. Shuey (Southwest Research and Information Center), Juan Lezama Pacheco (Stanford University), Jorge Gonzalez-Estrella
Grant Number: P42ES025589
Funding Period: 2017-2022

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Title: Uranium mobility and accumulation along the Rio Paguate, Jackpile Mine in Laguna Pueblo, NM

Accession Number: doi:10.6073/pasta/e96864d4ade2a90397dcff0b8ce75645

Link to Dataset: https://portal.edirepository.org/nis/mapbrowse?packageid=edi.450.2

Repository: EDI Data Portal (Environmental Data Initiative)

Data Type(s): Environmental Science Data

Summary: The mobility and accumulation of uranium (U) along the Rio Paguate, adjacent to the Jackpile Mine, in Laguna Pueblo, New Mexico was investigated using aqueous chemistry, electron microprobe, X-ray di raction and spectroscopy analyses. Given that it is not common to identify elevated concentrations of U in surface water sources, the Rio Paguate is a unique site that concerns the Laguna Pueblo community. This study aims to better understand the solid chemistry of abandoned mine waste sediments from the Jackpile Mine and identify key hydrogeological and geochemical processes that a ect the fate of U along the Rio Paguate. Solid analyses using X-ray uorescence determined that sediments located in the Jackpile Mine contain ranges of 320 to 9200 mg kg-1 U. The presence of co nite, a U(IV)-bearing mineral, was identi ed by X-ray di raction analyses in abandoned mine waste solids exposed to several decades of weathering and oxidation. The dissolution of these U-bearing minerals from abandoned mine wastes could contribute to U mobility during rain events. The U concentration in surface waters sampled closest to mine wastes are highest during the southwestern monsoon season. Samples collected from September 2014 to August 2016 showed higher U concentrations in surface water adjacent to the Jackpile Mine (35.3 to 772 mg L-1) compared with those at a wetland 4.5 kilometers downstream of the mine (5.77 to 110 mg L-1). Sediments co-located in the stream bed and bank along the reach between the mine and wetland had low U concentrations (range 1 5 mg kg-1) compared to concentrations in wetland sediments with higher organic matter (14 15 ) and U concentrations (2 21 mg kg-1). Approximately 10 of the total U in wetland sediments was amenable to complexation with 1 mM sodium bicarbonate in batch experiments; a decrease of U concentration in solution was observed over time in these experiments likely due to re-association with sediments in the reactor. The ndings from this study provide new insights about how hydrologic events may a ect the reactivity of U present in mine waste solids exposed to surface oxidizing conditions, and the in uence of organic-rich sediments on U accumulation in the Rio Paguate. Environmental impact: Uranium mobility and accumulation in the environment can a ect surface water and sediment chemistry. Here, we investigated the mobility of uranium in water and accumulation on sediments along the Rio Paguate and within a wetland and reservoir 5 km south of the Jackpile Mine. Main findings of the study suggest that ore and mine waste from surficial locations of the Jackpile Mine are the source of uranium in the surface water. Additionally, the concentration of uranium in the Rio Paguate varies seasonally, with higher concentrations during the southwestern monsoon season. The uranium concentration in surface water decreases downstream of the mine and adsorption of uranium to organic-containing sediments in a wetland 5 km downstream contributes to this decrease. These results have important implications to better understand the mobility and accumulation of uranium in the environment.

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