| Autor: |
Zavarin, M., Maxwell, R. M., Kersting, A. B., Zhao, P., Sylwester, E. R., Allen, P. G., Williams, R. W. |
| Předmět: |
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| Zdroj: |
AIP Conference Proceedings; 2003, Vol. 673 Issue 1, p102, 5p |
| Abstrakt: |
Natural inorganic colloids (< 1 micron particles) found in groundwater can sorb low-solubility actinides and may provide a pathway for transport in the subsurface. For example, Kerting et al. found that Pu, associated with colloids fraction of the groundwater, was detected over 1 km away from the underground nuclear test at the Nevada Test Site (NTS) where it was originally deposited 28 years earlier. However, laboratory experiments have not identified the mechanisms by which Pu may sorb to colloids or exist as its own colloid and travel relatively unimpeded in the subsurface. Some data suggest that Pu sorption to colloids is a very fast process while desorption is very slow or simply does not occur. Slow desorption of Pu from colloids could allow Pu sorbed to a colloid to travel much farther than if sorption were an equilibrium process. However, Pu sorption (and particularly desorption) data in the literature are scant and sometimes contradictory. In some cases, Pu desorption is rather fast, with rates dependent on colloid mineralogy. Moreover, the effect of sorption and desorption kinetics (as well as other mechanisms) on colloid-facilitated transport at the field scale has not been thoroughly evaluated. This is, in part, due to limitations in colloid transport as well as sorption/desorption models. In an effort to better understand the dominant mechanisms that control colloid-facilitated Pu transport, we have performed a series of sorption/desorption experiments using mineral colloids and Pu(IV) and Pu(V). We focused on natural colloidal minerals present in water samples collected from both saturated and vadose zone waters at the NTS. These colloid minerals include zeolites, clays, silica, Mn-oxides, Fe-oxides, and calcite. X-ray absorption fine-structure spectroscopy (XAFS) was performed to characterize the speciation of sorbed plutonium. We applied both surface complexation modeling and particle-tracking reactive transport codes to better understand the... [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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