Uranium Redistribution Due to Water Table Fluctuations in Sandy Wetland Mesocosms

Environ Sci Technol. 2015 Oct 20;49(20):12214-22. doi: 10.1021/acs.est.5b02957. Epub 2015 Oct 2.

Abstract

To understand better the fate and stability of immobilized uranium (U) in wetland sediments, and how intermittent dry periods affect U stability, we dosed saturated sandy wetland mesocosms planted with Scirpus acutus with low levels of uranyl acetate for 4 months before imposing a short drying and rewetting period. Concentrations of U in mesocosm effluent increased after drying and rewetting, but the cumulative amount of U released following the dry period constituted less than 1% of the total U immobilized in the soil during the 4 months prior. This low level of remobilization suggests, and XANES analyses confirm, that microbial reduction was not the primary means of U immobilization, as the U immobilized in mesocosms was primarily U(VI) rather than U(IV). Drying followed by rewetting caused a redistribution of U downward in the soil profile and to root surfaces. Although the U on roots before drying was primarily associated with minerals, the U that relocated to the roots during drying and rewetting was bound diffusely. Results show that short periods of drought conditions in a sandy wetland, which expose reduced sediments to air, may impact U distribution without causing large releases of soil-bound U to surface waters.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Autoradiography
  • Desiccation
  • Geologic Sediments / chemistry
  • Plant Roots / chemistry
  • Radioactivity
  • Uranium / analysis*
  • Water Pollutants, Radioactive / analysis*
  • Wetlands*

Substances

  • Water Pollutants, Radioactive
  • Uranium