Pore-Scale Colloid Retention Processes in the Vadose Zone: A Statistical Analysis
Abstract
It is well accepted that colloid and nanoparticle transport processes in porous media differ substantially between water saturated and unsaturated conditions. Differences are frequently ascribed to particle immobilization by association with interfaces with the gas, as well as to restrictions of the liquid medium. Yet, the current understanding of the importance of particle retention in any given region of the pore is based on observations of single pores or two-dimensional pore network representations. This raises concerns regarding the statistical significance of the numerous processes suspected to dominate retention and their consideration in mechanistic models. We perform column experiments in which a suspension of silver colloids is injected at varying moisture content and water chemistry to modify the availability and affinity of colloid deposition at different pore-scale locations. Subsequent imaging by X-ray microtomography is used to gain detailed information of the location of colloid deposits along the column. The data are used to: i) evaluate the relative contribution of commonly implicated pore-scale retention sites toward retention, ii) determine if and how colloid retention changes with depth, and iii) revise a nonequilibrium transport model with verified kinetic terms.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.H51E..02M
- Keywords:
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- 1843 Land/atmosphere interactions;
- HYDROLOGY;
- 1847 Modeling;
- HYDROLOGY;
- 1865 Soils;
- HYDROLOGY;
- 1875 Vadose zone;
- HYDROLOGY