Insights into transport velocity of colloid-associated plutonium relative to tritium in porous media

Abstract

Although faster transport velocities of colloid-associated actinides, bacteria, and virus than nonreactive solutes have been observed in laboratory and field experiments, some questions still need to be answered. To accurately determine the relative velocity (UPu/UT) of 239Pu and tritium representative of the bulk water, a conceptual model of electrostatic interactions coupled with the parabolic water velocity profile in pore channels is developed. Based on the expression for UPu/UT derived from this model, we study the effects of water flow rates and ionic strengths on the UPu/UT. Also, the velocity relationship between Pu, tritium and Sr2+ is explored. The results show that UPu/UT increased fairly linearly with decreasing water flow rates; UPu/UT declined approximately exponentially with increasing Na+ concentrations; the charge properties of colloid-associated Pu (negative), tritium (neutral) and Sr2+ (positive) had a close association with their transport velocities as UPu : UT : USr2+ = 1.41 : 1 : 0.579.

Continuum-based models and concepts for the transport of nanoparticles in saturated porous media: A state-of-the-science review

“…Mechanistic models focus on the individual particles by considering the forces, torques, and energy of particle and interacting media [30,36,[47][48][49][50][51][52][53][54]. These models become more difficult to apply when several phenomena occur simultaneously during transport of NP in porous media [21,31,33,48,[55][56][57][58][59][60][61][62][63][64]. Moreover, the intrinsic complexities and heterogeneities prevalent in real environmental conditions, such as surface roughness [65][66][67][68], natural organic matter (NOM) [32,47,69], iron oxyhydroxide coating [70][71][72], silylation [73], extracellular polymeric substance, and biofilm [74][75][76] make it unfeasible to use models such as classical colloid filtration theory (CFT) [65][66][67][68], Derjaguin-Landau-Verwey-Overbeek (DLVO) theory [47,77], and Maxwell model…”

“…Significance for NPThe importance of size exclusion was elucidated in considering the reasons for unexpected large migration distances of solute contaminants, such as radionuclides, in the subsurface because of their association with groundwater colloids,[59,61,[274][275][276][277][278][279][280][281]. Size exclusion, also known in a more general concept as hydrodynamic chromatography, has been recognized as an underlying phenomenon for faster migration of particles compared to non-reactive solute in porous or fractured media[58-61, 100, 108, 117, 142, 151, 153, 280, 282-285].…”

Trace-level plutonium(IV) polymer stability and its transport in coarse-grained granites

“…A model of the electrostatic interaction coupled with a parabolic water velocity profile in pore channels was developed in our recent study (Xie et al, 2014c). The velocity relationships between negatively charged colloid-associated Pu, uncharged 3 H 2 O, and positive ion Sr…”