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

Abstract

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 diffraction 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 affect the fate of U along the Rio Paguate. Solid analyses using X-ray fluorescence determined that sediments located in the Jackpile Mine contain ranges of 320 to 9200 mg kg U. The presence of coffinite, a U(iv)-bearing mineral, was identified by X-ray diffraction 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 μg L) compared with those at a wetland 4.5 kilometers downstream of the mine (5.77 to 110 μg L). 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) compared to concentrations in wetland sediments with higher organic matter (14-15%) and U concentrations (2-21 mg kg). 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 findings from this study provide new insights about how hydrologic events may affect the reactivity of U present in mine waste solids exposed to surface oxidizing conditions, and the influence of organic-rich sediments on U accumulation in the Rio Paguate.

Effect of Calcium on the Bioavailability of Dissolved Uranium(VI) in Plant Roots under Circumneutral pH

“…The sampling sites of plants were colocated with water and stream bank sediment samples that were studied by Blake et al during the same time period (Table S1). 14 Regional plants (grass, willow ( Salix ), and cattail ( Typha latifolia L. )), which are abundant at the site and may be used as cattle fodder or for ceremonial traditions, were sampled (Table S1). Detailed information for the sites and laboratory plant preparation is presented in the Supporting Information.…”

A Review of Metal Exposure Studies Conducted in the Rural Southwestern and Mountain West Region of the United States

“…Chemical concentrations were measured using Inductively Coupled Plasma (ICP) – Optical Emissions Spectroscopy [15, 16, 19–21], ICP – Atomic Emissions Spectroscopy [15, 16, 19, 20], ICP – Mass Spectroscopy [13, 15–17, 19–24], or Graphite Furnace Atomic Absorption Spectroscopy [18]. Additionally, concentrations of As, U, chromium (Cr), lead (Pb), iron (Fe), and vanadium (V) were measured in mine waste, soil, sediment and other solid material using x-ray fluorescence [21, 22], X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy [21]. ICP-MS was also used to measure As, U, Cd, selenium (Se), Pb, and molybdenum (Mo) was measured in soil and uptake in grasses consumed by sheep [25].…”

“…Minimal seasonal/temporal variability was reported for As and U measured in UWSs in the Arizona portion of Navajo Nation [23], and UWSs across the Navajo Nation [19]. Blake et al (2017) observed As concentrations less than 10 μg/L in replicate surface water sources located downstream of a U mine in New Mexico [22]. In the same samples however, U concentrations ranged between <LOD and >700 μg/L and exhibited a strong season effect.…”

“…Samuel-Nakamura et al (2017) reported Cd concentrations ranging from 0.03 to 0.65 μg/L for eight water sources used by sheep in a Navajo community in New Mexico [25]. Four studies reported concentrations of other metals in UWSs (Table 4) including iodine in groundwater in west TX [14, 29]; V [21], Al, Fe, Mn, Pb, Se, Mo, and other metals [20–22, 25]. …”

Development of electrospun polymer nanofiber mats for removal of uranium from aqueous systems

“…where the solubility constant (K sp ) is related to the soluble species activity raised to the power of their molar coefficient. 27 This is compared to that of groundwater near Shiprock, NM that had concentrations of HCO 3 between ~100-1500 mg/L (pH's between 6.4 and 7.7) 6 where CO 3 2would be at ~ 0.5% of these concentrations (0.5-7 mg/L). At such high concentrations in surface waters and ground waters, carbonates can compete with uranium hydrolysis products, creating highly soluble uranyl carbonate species and contributing to enhanced mobility of uranium in the environment.…”