We investigated the uranium (U) uptake mechanisms by Salt Cedars growing along the Rio Paguate, which flows throughout the abandoned U mine, Jackpile Mine, in Laguna Pueblo, New Mexico. Salt cedar plants growing next to the river adjacent to the mine showed U accumulation in their roots ranging from 25.2 – 58.9 mg kg-1, while the U concentration in their aerial parts ranged from 1.4 – 3.1 mg kg-1. Synchrotron based micro X-ray fluorescence analysis of the plant roots indicates that the U accumulation occurs in the inter-phase between the epidermis and the cortex. The mechanisms for U accumulation in the salt cedar roots were further investigated in controlled-laboratory experiments were the roots were exposed to a solution containing 100 µM U. The roots were then examined with microprobe and SEM/TEM and the U appears to be entrapped in the cell walls of the tracheids near secondary xylem vessels in the roots. This preferable binding of U to the root cell walls may explain the retention of U in the roots and thus its weak translocation toward salt cedars leaves. This study contributes to better understand the physicochemical mechanisms for U uptake and accumulation by plants growing in the vicinity of contaminated sites.

Investigation of uranium uptake mechanisms by plants from abandoned mine lands in the Southwestern United States

253rd National Meeting (2017)

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